How to Read a Supplement Label: Dosage and Standardization

You pick up a supplement bottle, turn it over, and read: «Dry extract of ashwagandha (Withania somnifera) standardized to 5% withanolides, 300 mg. Excipient: magnesium stearate.» Do you know exactly what each part of that sentence means? Most consumers don't, and that has real consequences: buying products with ineffective doses, confusing the weight of the extract with that of the raw powder, or overlooking excipients that can affect absorption.

Reading a supplement label is not a skill reserved for pharmacists. It's a basic competency that anyone who cares about their vitality and well-being should have. This article gives you the tools to do it with sound judgement.

Important notice: This article is for informational purposes only. The information contained here does not constitute individualized medical or pharmaceutical advice. Before starting any supplementation, especially if you take medication, have a diagnosed health condition, are pregnant or breastfeeding, consult your doctor or pharmacist.

What you'll find here: what a dose is and how it's expressed, the difference between an extract and a raw powder, what the standardization percentage means and why it matters, and the role excipients play in the final quality of the product. All of it grounded in current European regulations and the available scientific evidence.

Why a supplement label matters more than it seems

The label of a dietary supplement is not a bureaucratic formality. It's the only legal document the manufacturer is required to provide before you consume the product. In the European Union, Regulation (EU) No 1169/2011 on the provision of food information to consumers and Spain's Royal Decree 1487/2009 on dietary supplements set out what must mandatorily appear on every label and how it must be expressed.

Meeting the minimum legal requirements, however, doesn't guarantee that the information is easy to interpret. Two products can both declare «500 mg of turmeric» and contain radically different amounts of active curcuminoids, depending on whether it's raw powder or a standardized extract. The difference in active compounds can be as much as 10 to 1.

Market analyses have flagged discrepancies between the declared and actual curcuminoid content in some turmeric supplements. It's not an isolated case: the gap between what's declared and what's actually present affects multiple supplement categories.

Knowing how to read a label allows you to:

• Compare actual products, not just prices or presentations.
• Verify that the dose is clinically relevant—that is, comparable to the one used in studies with positive results.
• Identify problematic excipients for your particular case (allergies, intolerances, interactions).
• Spot misleading marketing practices that inflate the declared weight using forms with low bioavailability.

The label is your first line of defense as an informed consumer.

The legal structure of a supplement label in the EU

Before getting into the technical details, it helps to be clear about which elements are legally mandatory on a dietary supplement label in Spain and the European Union. Under Royal Decree 1487/2009 and Regulation (EU) No 1169/2011, every label must include:

1. Product name
The wording «dietary supplement» («complemento alimenticio» in Spain) must appear clearly. Not «nutritional supplement,» not «health product»: «complemento alimenticio» is the legal term in Spain.

2. Name and amount of the active substances
These must be expressed per recommended daily serving, in International System units (mg, µg, IU where applicable). If the product contains vitamins or minerals, they must also be expressed as a percentage of the Reference Intake (RI) established by EFSA.

3. Recommended daily serving and a warning not to exceed it
The label must state the daily dose recommended by the manufacturer and include the warning: «Do not exceed the expressly recommended daily dose.»

4. Warning to keep out of the reach of children
Mandatory on all dietary supplements.

5. A statement that it does not replace a varied and balanced diet
Also mandatory. If it doesn't appear, the label fails to comply with the regulations.

6. List of ingredients
Including active substances and excipients (also called «other ingredients» or «additional ingredients»). Allergens must be visually highlighted (bold, underline, or a different color).

7. Expiry date and storage conditions

8. Details of the manufacturer or the party responsible for marketing

What CANNOT appear on a supplement label

This is just as important: European regulations prohibit dietary supplements from claiming properties to prevent, treat, or cure human diseases. Only health claims that have been evaluated and authorized by EFSA, and that appear in the EU Register of authorized claims (Regulation (EC) No 1924/2006), may be used.

If a label says it «cures,» «treats,» or «prevents» a disease, it is breaking the law. If it says «contributes to the normal function of the immune system» (an authorized claim for vitamin C, for example), it is within the regulations.

Dosage: what the number on the label really means

The dose is the most visible piece of information on a label and, paradoxically, the easiest to misread. Understanding how it's expressed is the first step to comparing products with sound judgement.

Dose per capsule vs. dose per daily serving

Many manufacturers state the amount of active ingredient per capsule, but the recommended daily serving may be 2, 3, or 4 capsules. A product that declares «200 mg of magnesium per capsule» with a dose of 3 capsules a day delivers 600 mg daily. Another that declares «600 mg per capsule» with a dose of 1 capsule delivers the same amount, but may look more potent at first glance.

Rule of thumb: always look for the amount per daily serving, not per unit consumed.

Active dose vs. total dose of the ingredient

This is the most common mistake, and the one with the greatest impact on a product's real efficacy. The dose declared on the label may refer to:

• The total weight of the ingredient (including fiber, water, starch, and other non-active components).
• The weight of the extract (a concentrate of the ingredient's components).
• The weight of the active compound (the molecule or group of molecules with documented biological activity).

A concrete example: one product declares «500 mg of valerian root.» Another declares «300 mg of valerian extract standardized to 0.8% valerenic acid.» Which one delivers more active compound?

• The first: 500 mg of raw powder. The valerenic acid content of raw valerian powder ranges from 0.1% to 0.5% depending on the variety and processing. At best, 500 mg × 0.5% = 2.5 mg of valerenic acid.
• The second: 300 mg × 0.8% = 2.4 mg of valerenic acid.

They deliver similar amounts of active compound, but the first looks like «more» because the number is bigger. This kind of comparison is only possible if you know how to read the label.

Units of measurement: mg, µg, IU, and equivalents

European labels must use the International System, but some fat-soluble vitamins (A, D, E) may be expressed in International Units (IU) in addition to micrograms (µg) or milligrams (mg). The most relevant conversions:

• 1 µg of vitamin D3 = 40 IU
• 1 IU of vitamin A (retinol) = 0.3 µg of retinol
• 1 IU of vitamin E (alpha-tocopherol) = 0.67 mg of natural alpha-tocopherol

If one label expresses vitamin D in IU and another in µg, you need to convert in order to compare. A product with «1,000 IU of vitamin D3» and another with «25 µg of vitamin D3» contain exactly the same amount.

The Reference Intake (RI) and what it means

For vitamins and minerals, the label must express the amount as a percentage of the Reference Intake (RI) established by EFSA. The RI is the daily amount considered sufficient to meet the needs of most of the healthy adult population. It is not a therapeutic dose: it's a nutritional reference value.

A supplement that provides 100% of the RI of a nutrient is not necessarily the most suitable for every case. People with documented deficiencies, with greater physiological demand (athletes, pregnant women, those over 65), or with absorption problems may need higher amounts, always under the supervision of a healthcare professional.

The RI is useful for comparing products with one another, but not for determining whether a dose is clinically relevant for a specific goal.

Extract vs. raw powder: the difference that changes everything

This distinction is probably the most important thing you can learn about supplement labels. And it's the one most frequently used to create confusion in the market.

What a raw powder is

A raw powder (also called «plant powder» or «pulverized herbal drug») is simply the plant or ingredient dried and ground. It contains all the components of the original ingredient in their natural proportions: active compounds, fiber, starch, residual water, pigments, and so on.

Advantage: it's the minimal level of processing and keeps the ingredient's complete profile.
Disadvantage: the concentration of active compounds is variable and generally low.

What an extract is

An extract is the result of an extraction process that concentrates the components of interest from the original ingredient. Depending on the process (aqueous, ethanolic, supercritical CO₂ extraction, etc.) and the objective, the extract can concentrate certain active compounds while removing or reducing others.

The extraction ratio indicates how many kilograms of raw material are needed to produce 1 kilogram of extract. A 10:1 extract means 10 kg of fresh plant were used to obtain 1 kg of extract. That ratio, on its own, guarantees nothing about the concentration of active compounds: it depends on what has been extracted and on the quality of the raw material.

That's why an extraction ratio without standardization is a marketing figure, not a quality figure.

How to tell whether it's an extract or raw powder on the label

The label must specify it. Look for these expressions:

A real example: ginkgo biloba

Ginkgo biloba is one of the most studied ingredients in supplementation. Clinical trials on cognitive function have consistently used the EGb 761® extract, standardized to 24% flavonoids and 6% terpene lactones, at doses of 120–240 mg/day. The results are mixed: some studies show benefit in symptoms of already-established cognitive decline, while the GuidAge trial did not demonstrate a preventive effect on the incidence of Alzheimer's in older adults with memory complaints. What's relevant for this article is that all of these studies used the specific standardized extract, not raw leaf powder.

A product that declares «500 mg of ginkgo leaf powder» may contain between 1.2 mg and 5 mg of flavonoids (0.24%–1% natural content), compared with the 28.8–57.6 mg that the standardized extract would provide at the studied dose. The difference is 10 to 20 times in active compounds.

This is why the form of the ingredient matters as much as the declared amount.

The standardization percentage: what it guarantees and what it doesn't

The standardization percentage is the most direct indicator of the concentration of active compounds in an extract. When a label declares «extract standardized to 5% withanolides,» it means the manufacturer guarantees that every 100 mg of extract contains at least 5 mg of withanolides.

Why standardization matters

Plants are living organisms whose chemical composition varies depending on the botanical variety, geographic origin, growing conditions, harvest time, and post-harvest processing. One batch of ashwagandha grown in India may have a withanolide content of 1.5%; another batch of the same species, 4.2%.

Without standardization, the manufacturer cannot guarantee that the product has the same potency from one batch to the next. With standardization, the manufacturing process adjusts the concentration of the extract so that it always contains the declared percentage of active compounds.

A randomized clinical trial (Chandrasekhar et al., 2012, Indian Journal of Psychological Medicine) evaluated an ashwagandha extract standardized to 5% withanolides at 300 mg twice a day and observed a reduction in perceived stress versus placebo. If the product you buy doesn't specify the standardization percentage, you can't know whether the dose you're taking is comparable to the one in that study.

What gets standardized and what doesn't

Not all of a plant's active compounds are equally relevant, and not all extracts are standardized by the same markers. Some examples:

In some cases, the standardization marker is a compound that serves as an indicator of the extract's quality but isn't necessarily the sole driver of biological activity. Phytochemistry research has documented that in many cases the effect is synergistic: several compounds acting together produce a greater effect than each one separately (phytochemical synergy, or full-spectrum effect). For this reason, an extract standardized by a single marker is not automatically superior to a well-characterized full-spectrum extract.

The limitations of standardization

Standardization guarantees the concentration of the declared markers, but it does not guarantee:

• The absence of contaminants (heavy metals, pesticides, mycotoxins).
• The bioavailability of the active compound (how much is actually absorbed).
• Therapeutic equivalence with the extract used in the clinical studies (which may be a patented extract made with a specific process).

Put another way: standardization is a necessary but not sufficient condition for assessing the quality of a supplement.

The special case of proprietary blends

One of the most common ways to hide a lack of standardization is the proprietary blend, frequent in supplements of US origin marketed in Europe. The practice consists of declaring a list of ingredients with a single total amount for the blend, without specifying how much of each: «Energizing blend: 500 mg (caffeine, guarana, green tea).»

That makes it impossible to know whether any ingredient is present in a useful dose or merely in trace amounts so it can appear on the label. Although both European and US regulations require declaring the individual ingredients of a supplement, the quantification requirements differ between jurisdictions, and imported products don't always meet European declaration standards. Faced with a proprietary blend without a breakdown, it's impossible to calculate the active compound: it is, in itself, a warning sign.

Excipients: the ingredients that aren't the active ingredient

Excipients are substances added to a supplement with technological functions: to ease manufacturing, improve stability, control the release of the active compound, or improve organoleptic characteristics (taste, color, texture). They have no nutritional or pharmacological activity of their own, but they can affect the quality, absorption, and tolerability of the product.

On the label they appear under names such as «excipients,» «other ingredients,» «additional ingredients,» or are simply listed at the end of the ingredient list.

The most common excipients and what they do

Anti-caking agents
These keep the powder from clumping during manufacturing. The most common:

• Magnesium stearate: the most widely used excipient in capsules and tablets. Some in vitro studies have suggested it may slow the dissolution rate of the active compound under laboratory conditions; the clinical relevance of this effect at the amounts normally used (0.5–1% of the capsule's weight) has not been demonstrated in human studies. At those amounts, it poses no health risk.
• Silicon dioxide (colloidal silica): also an anti-caking agent, generally well tolerated.

Bulking agents (fillers)
These increase the volume of the capsule's contents to make filling easier. The most common:

• Microcrystalline cellulose (MCC): derived from plant cellulose, inert, well tolerated.
• Dicalcium phosphate: also provides calcium as a secondary nutrient.
• Maltodextrin: derived from starch; may be relevant for people with diabetes or following low-carbohydrate diets.

Coating agents
These are applied to tablets to protect the active compound, make swallowing easier, or control release. The most common:

• Hydroxypropyl methylcellulose (HPMC): of plant origin, suitable for vegans.
• Gelatin: of animal origin (bovine or porcine), relevant for vegans and people with religious dietary restrictions.
• Shellac: of animal origin (an insect secretion), relevant for vegans.

Colorants
Used in colored gelatin capsules or coated tablets. The colorants authorized in the EU for foods are listed in Regulation (EC) No 1333/2008. The most frequent in supplements:

• Titanium dioxide (E171): a whitening agent. In 2021, EFSA concluded that its genotoxicity could not be ruled out, and it was banned as a food additive in the EU from August 2022 (Regulation (EU) 2022/63). This ban applies to all foods, including dietary supplements. Only medicines, regulated by the EMA under different rules, may continue to use it under specific conditions. If it appears on the label of a current supplement, it indicates non-compliance with the regulations in force.
• Iron oxides (E172): colorants of mineral origin, generally well tolerated.

Preservatives
Less frequent in solid supplements (capsules, tablets), more common in liquids:

• Sorbic acid and sorbates (E200–E203): authorized, well tolerated at the usual doses.
• Benzoates (E210–E213): authorized. A study published in The Lancet (McCann et al., 2007) evaluated specific mixtures of azo colorants combined with sodium benzoate and found an association with hyperactivity in children. EFSA reviewed this study and concluded that the evidence was insufficient to establish a direct causal relationship with sodium benzoate in isolation. At the amounts usually present in supplements, it is not considered an established risk for the general population.

Excipients relevant for specific groups

How to read the list of excipients

1. Identify whether the capsule is gelatin or HPMC (plant-based). It's usually indicated in the ingredient list as «capsule shell: gelatin» or «capsule shell: hydroxypropyl methylcellulose.»
2. Look for declared allergens (in bold or underlined).
3. Check whether there is titanium dioxide (E171): its presence in a current supplement indicates a formulation that does not comply with the European regulations in force.
4. If you have diabetes or follow a specific diet, check whether there is maltodextrin, sucrose, or other carbohydrates among the excipients.

Special ingredients: vitamins, minerals, and molecular forms

Plant extracts aren't the only ingredients that require interpretation. With vitamins and minerals, the declared chemical form changes the dose equivalence and the bioavailability: two products can state the same amount and deliver something very different to the body.

Vitamins: active forms vs. precursors

Some vitamins can be declared in their active form or as a precursor that the body has to convert before it can use it:

• Vitamin B9: appears as folic acid (the synthetic form, which requires enzymatic conversion) or as methylfolate (L-5-MTHF, the directly usable active form). People with variants of the MTHFR gene have a reduced ability to convert folic acid into methylfolate.
• Vitamin B12: cyanocobalamin (the most stable and economical form) versus methylcobalamin or adenosylcobalamin (the active forms). Evidence on clinically relevant differences in healthy people is limited, although in older adults or those with absorption problems the active forms may be preferable.
• Vitamin D: D2 (ergocalciferol, of plant origin) versus D3 (cholecalciferol, of animal origin or from lichen), with greater efficacy of D3 in raising serum levels of 25-hydroxyvitamin D (detailed later, in the section on bioavailability).
• Vitamin E: natural tocopherol (d-alpha-tocopherol) versus the synthetic form (dl-alpha-tocopherol). The natural form has greater bioavailability, and EFSA recognizes different conversion factors for the two forms.

Minerals: inorganic vs. organic forms

Minerals come in forms with very different bioavailability. As a general rule, organic forms (chelates, citrates, malates) are absorbed better than inorganic ones (oxides, sulfates, carbonates):

Studies in animal models, such as Coudray et al. (2005) in Magnesium Research, have documented greater bioavailability of bisglycinate and citrate compared with magnesium oxide. The practical implications are developed in the bioavailability section: 100 mg of elemental magnesium as oxide is not functionally equivalent to 100 mg of elemental magnesium as bisglycinate, even though the label declares the same amount.

How to read the amount of elemental mineral

Quality labels declare both the amount of the mineral salt and the amount of elemental mineral:

«Magnesium bisglycinate 500 mg (equivalent to 50 mg of elemental magnesium).»

The relevant figure for comparing against the reference intakes (RI) established by EFSA is the elemental mineral, not the salt. The RI of magnesium for adults is around 300–375 mg/day according to EFSA. If a product provides 50 mg of elemental magnesium per capsule and the daily dose is 2 capsules, it provides 100 mg/day: roughly 27–33% of the RI.

Bioavailability: the factor the label doesn't always reveal

Bioavailability is the fraction of a nutrient or active compound that reaches the systemic circulation and is available to exert its biological effect. It's the link between what the label says and what your body actually makes use of.

Two products can declare the same dose of the same ingredient and have radically different bioavailability. The label doesn't always indicate this, but there are signals you can look for.

Forms with higher bioavailability: what to look for on the label

Magnesium
Magnesium can come in multiple forms with very different bioavailability. Comparative studies have documented that magnesium bisglycinate and magnesium citrate have significantly higher bioavailability than magnesium oxide, the cheapest and most frequent form in low-quality supplements. If you want to dig deeper into how to choose between the two most common organic forms, you can read our guide on magnesium bisglycinate vs. citrate.

*The percentages are approximations that vary with the measurement method and the population studied. Comparative studies confirm the hierarchy between forms, but the absolute values differ across investigations. Consult a healthcare professional for individualized guidance.

Curcumin
Free curcumin has very low oral bioavailability due to its poor water solubility and rapid metabolism. Several technologies have been shown to improve it significantly:

• Formulations with piperine: piperine (a black pepper extract) inhibits the hepatic metabolism of curcumin. A classic study by Shoba et al. (1998) with 8 healthy volunteers showed that adding 20 mg of piperine increased the area under the curcumin blood concentration curve by roughly 2,000%, indicating a very significant improvement in its intestinal absorption. This finding refers to plasma curcumin levels, not direct clinical effects, and has been the subject of subsequent research with variable results depending on the formulation. Even with this increase, the absolute bioavailability of curcumin remains low compared with other compounds.
• Lipid formulations (phytosomes): curcumin bound to phospholipids (Meriva®) improves intestinal absorption.
• Nanoparticles and micelles: more recent technologies with promising results in preliminary studies.

On the label, look for mentions such as «with piperine,» «phytosome,» «lipid formulation,» or the trade names of patented extracts (Meriva®, BCM-95®, Longvida®).

Vitamin D
Vitamin D3 (cholecalciferol) has greater bioavailability than D2 (ergocalciferol) for raising serum levels of 25-hydroxyvitamin D. The label should specify which of the two forms the product contains.

Iron
Heme iron (of animal origin) has a bioavailability of 15–35%, compared with 2–20% for non-heme iron (of plant or mineral origin). Ferrous bisglycinate has greater bioavailability than ferrous sulfate in absorption studies (Bovell-Benjamin et al., 2000). Some studies also suggest a lower incidence of gastrointestinal effects, although direct comparative evidence on this point is more limited.

Warning signs about bioavailability on the label

• Low-bioavailability forms in key ingredients (magnesium oxide, calcium carbonate as the sole source, elemental iron).
• No information about the chemical form of the ingredient (only the name of the mineral, without specifying the salt).
• The absence of absorption-enhancing technologies in ingredients that need them (curcumin without piperine or a lipid formulation, for example).

Warning signs and quality signals on a label

With the concepts above absorbed, it helps to have a quick checklist to assess any label in a few seconds. These signals don't replace a detailed analysis of each section, but they serve as an initial screen.

Quality signals (✓)

• Extract with a registered trade name: KSM-66®, Sensoril®, Meriva®, Phytosome®, BioPerine®, etc. These usually have their own studies and verifiable quality control.
• Standardization percentage declared with its marker compound: «standardized to 5% withanolides» is more informative than just «standardized extract.»
• Elemental mineral declared: «X mg of elemental magnesium» alongside the amount of the salt.
• Active form of vitamins: methylfolate instead of folic acid, D3 instead of D2, when there is evidence of a relevant difference.
• Dose per daily serving aligned with the clinical evidence: verifiable by looking up the reference studies.
• Precise claim language authorized by EFSA, not vague promises.
• Manufacturing information and third-party certifications: GMP by an independent body, NSF, USP (detailed later).

Warning signs (⚠)

• A dose well below those used in studies: may indicate that the ingredient is present as a «label ingredient,» without a useful dose.
• An extract without a standardization percentage: doesn't allow you to calculate the real active compound.
• An extraction ratio without standardization: a 20:1 ratio doesn't guarantee active-compound concentration; it only indicates how much plant was processed.
• Proprietary blends without a breakdown: they declare «blend of X, Y, Z: 500 mg» without specifying how much of each ingredient (described in the standardization section).
• Unauthorized claim language: «potentiates,» «activates,» «boosts,» «revitalizes» without the backing of an EFSA claim.
• Low-bioavailability chemical forms in key ingredients, or the absence of the chemical form (only the name of the mineral, without the salt).
• No manufacturer or importer details, or no expiry date: both are legally mandatory in the EU; their absence is a sign of a traceability problem.

How to compare two supplement labels step by step

Everything above has one concrete practical application: comparing two products competing for the same goal. Here is the protocol in 6 steps.

Step 1: Identify the active ingredient and its chemical form
Is it raw powder or an extract? What chemical form does it have (in the case of minerals and vitamins)? Note the form of each product.

Step 2: Compare the dose per daily serving, not per capsule
Calculate how much active compound each product provides per day. If one requires 3 capsules and another 1, the price per capsule isn't the relevant comparison: the price per daily serving is.

Step 3: Check the standardization percentage
If it's a plant extract, is it standardized? By which marker? Is the percentage comparable to the one used in the reference clinical studies?

Step 4: Calculate the actual amount of active compound
Multiply the extract dose by the standardization percentage. Example: 400 mg of extract at 5% withanolides = 20 mg of withanolides. Compare this number between products, not the total extract dose.

Step 5: Review the excipients
Is there any excipient relevant to your situation (allergens, gelatin, titanium dioxide)? Is the capsule plant-based or animal gelatin?

Step 6: Assess the additional quality signals
Does the product have third-party certifications (NSF, USP, Informed Sport, ISO 22000)? Does the manufacturer publish the certificates of analysis (COA) for its batches? Is the dose comparable to the one used in clinical trials?

A practical example: comparing two ashwagandha products

Product A looks equivalent in total dose, but it provides between 3 and 10 times less guaranteed active compound. Product B, despite having the same total extract dose, is comparable to the dose used in the reference clinical trial.

Certifications and quality seals: what they mean on the label

Beyond the data declared by the manufacturer, there are third-party certifications that independently verify the quality, purity, and labeling accuracy of a supplement. Their presence on the label is a sign of transparency and a commitment to quality.

NSF International (NSF/ANSI 173)
A US certification that verifies the product contains what the label declares, in the stated amounts, and that it contains no contaminants above the established limits. Highly valued in sports.

USP Verified
The United States Pharmacopeia verifies the identity, potency, purity, and disintegration of the product. It's one of the most rigorous certifications on the market.

Informed Sport / Informed Choice
A certification specifically for athletes that verifies the absence of substances banned by WADA (the World Anti-Doping Agency). Relevant if the consumer competes in regulated sports.

ISO 22000 / FSSC 22000
International food-safety management standards that apply to the manufacturing process, not the final product. They guarantee that the manufacturer has quality-control systems in place.

GMP (Good Manufacturing Practices)
In the EU, dietary supplement manufacturers are required to apply hygiene standards and food self-monitoring systems. That compliance is a legal minimum, not a differentiator. GMP certification by independent bodies (such as NSF GMP or NPA GMP), on the other hand, does add value.

Product-specific certifications

• Organic (EU seal): guarantees that the ingredients come from certified organic farming.
• Vegan Society / The Vegan Trademark: verifies that the product contains no ingredients of animal origin and has not been tested on animals.
• Halal / Kosher: religious certifications that verify compliance with the corresponding dietary requirements.

What to do if there are no certifications
The absence of third-party certifications doesn't necessarily mean the product is of poor quality, but it does mean there is no independent verification of the manufacturer's declarations. In that case, check whether the manufacturer publishes the Certificates of Analysis (COA) for its batches: documents issued by independent laboratories that verify the composition and purity of the product.

Frequently asked questions about how to read a supplement label

What's the difference between «extract» and «powder» on a supplement label?

Raw powder is the ingredient simply dried and ground, with the natural concentration of active compounds (generally low and variable). An extract is a concentrate obtained through an extraction process that raises the concentration of the components of interest. For most botanical ingredients, the standardized extract is the form with the most clinical evidence and the greatest reproducibility of results.

What does «standardized to X%» mean on the label?

It means the manufacturer guarantees that each unit of the extract contains at least that percentage of the declared active compound. For example, «standardized to 5% withanolides» guarantees 5 mg of withanolides per 100 mg of extract. It's the most direct indicator of the product's real potency and lets you compare products with sound judgement.

Can excipients affect the efficacy of a supplement?

In most cases, excipients at the usual amounts don't significantly affect the efficacy of the active compound. Some, however, are relevant for specific groups: gelatin for vegans, lactose for people with intolerance, maltodextrin for diabetics. Titanium dioxide (E171) was banned as a food additive in the EU in 2022, a ban that also applies to dietary supplements; its presence in a current supplement indicates non-compliance with the regulations in force.

How do I know whether a supplement's dose is clinically relevant?

Look up the clinical studies that support the ingredient (on PubMed or Google Scholar) and compare the dose and form of the ingredient used in those studies with what the product label declares. If the study used an extract standardized to 5% at 300 mg twice a day, and the product you're evaluating uses raw powder at 500 mg once a day, the comparison isn't direct.

What is the Reference Intake (RI) and what is it for?

The RI (or NRV, Nutrient Reference Value) is the daily amount of a nutrient considered sufficient to meet the needs of most of the healthy adult population, established by EFSA. It lets you compare a supplement's dose with reference nutritional needs, but it doesn't determine whether that dose is appropriate for a specific goal or for a person with particular needs.

What should I do if I have doubts about a supplement?

Consult your doctor or pharmacist before starting any supplementation, especially if you take medication, have a health condition, or are pregnant or breastfeeding. A healthcare professional can help you interpret the label in the context of your particular situation.

What's the difference between «10:1 extract» and «standardized to 10%»?

They're different concepts. A 10:1 extract indicates that 10 parts of plant were used to obtain 1 part of extract, but it says nothing about the concentration of specific active compounds. An extract standardized to 10% guarantees that 10% of the extract's weight corresponds to a specific active compound. The second figure is far more informative for assessing the product's real potency.

Does more milligrams always mean a better supplement?

No. The milligram figure only makes sense in context: of what kind of ingredient? with what percentage of active compound? is it comparable to the doses in clinical studies? An extract standardized to 95% at 200 mg can deliver more active compound than a plant powder at 1,000 mg. Comparing milligrams without context is one of the most common mistakes when choosing supplements.

What does «% RV» or «% of reference values» mean on the label?

It's the percentage of the daily reference intake established by EFSA for that nutrient that the product's dose provides. For example, if the RI of vitamin C is 80 mg and the product provides 200 mg, the label will declare «250% RV.» It's useful for vitamins and minerals with established reference intakes, but it doesn't apply to plant extracts or molecules without a defined RI.

Are supplements with standardized extracts always superior to whole-plant ones?

Not necessarily. For some ingredients the scientific evidence has been generated with standardized extracts, so the comparison with the studies is more direct. For others there is the hypothesis—with some support in the phytochemistry literature—that the synergy between multiple compounds of the plant may be relevant, and that a highly purified extract could lose part of that effect. That hypothesis is still under investigation and should not be taken as established evidence. The answer depends on the ingredient and the goal: what matters is that the form of the extract is consistent with the available evidence.

How do I know whether a health claim on a label is authorized by EFSA?

You can check it directly in the EU Register on Nutrition and Health Claims. You enter the nutrient or ingredient and you'll see which claims are authorized, which are under evaluation, and which have been rejected. It's a public, free tool.

Reading a supplement label with sound judgement doesn't require a university degree. It requires knowing the basic vocabulary and the real meaning of each piece of information. Four elements concentrate most of the useful information: the dose per daily serving, the form of the ingredient, the standardization percentage, and the excipients. Mastering them completely changes the way you evaluate a product.

A big number on the label is not synonymous with greater potency. A standardized extract at a lower dose can deliver more guaranteed active compound than a raw powder with twice the milligrams. Quality isn't measured by the size of the capsule or the length of the ingredient list, but by the form, the concentration, and the comparability with the available scientific evidence.

Every time you apply these criteria to a label, you'll make a more informed decision. Regardless of the brand.

If you have doubts about how to interpret the label of a specific supplement, or about whether a formulation is suitable for your goals, consult your doctor or pharmacist.

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References

The statements in this article are based on the available scientific literature. The references that support the main claims of this article are listed below.

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