Guide · 5 min read

How to read a supplement label

Short answer

A label tells you what the maker says is in the product. It does not prove the product works, and in the US and the UK/EU supplements are regulated as foods, so nobody approves them for effect before sale [2][5]. Look for the form and amount of extract (not just "herb"), whether the amounts are shown per capsule or per serving, whether a blend hides its doses, and whether an independent programme has tested the contents. Then compare that against the form and dose actually studied.

A supplement bottle on a kitchen counter next to reading glasses

What the label must show, and what it doesn't prove

The rules differ by country, but the common point is that a supplement label is a manufacturer's statement, not a regulator's verdict. NCCIH puts it plainly: what is listed on a supplement label may not be what is in the product, and the FDA is not authorised to review supplements for safety and effectiveness before they are marketed [3].

United StatesFood rules, not drug rulesThe FDA regulates supplements under a different set of rules from conventional foods and drugs, and can act against an unsafe or misbranded product only after it is on sale [1]. It has no authority to approve a supplement before it is marketed [2]. A label may describe how an ingredient affects the structure or function of the body, but then it must carry: "This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease" [2].

UK and EU: food supplementA food, not a medicineUK guidance says food supplements are meant to supplement the normal diet, are not medicinal products and are regulated as food. Labels must give a recommended daily dose with a warning not to exceed it, a statement that the product is not a substitute for a varied diet, and a warning to keep it out of reach of young children [5]. Health claims on food need authorisation, and the EU keeps a register of authorised and non-authorised claims [6].

UK: THR markA registered herbal medicineA herbal product can instead be registered with the MHRA as a traditional herbal medicine. The THR mark means it meets required standards for quality, safety and evidence of traditional use [8]. The NHS advises looking for the THR mark and a product code, and notes that herbal medicines are not tested in the same way as standard medicines to see how well they work [7]. Registration is only for minor conditions that do not need medical supervision, and rests on at least 30 years of traditional use rather than trials showing it works [15].

Extract or raw herb?

Four lines that look similar and mean different things.

On the label	What it means	What to check
Amount of extract, e.g. "300 mg root extract"	The weight of the concentrated extract in one serving. It is not the weight of herb it was made from.	Which extract? Trial doses are for a named extract, so compare like with like.
"Equivalent to 3,000 mg dried herb"	How much raw herb was used to make the extract. Useful, but it is a different quantity from the extract weight.	Is the dose I am comparing quoted as extract or as herb?
Drug-extract ratio, e.g. "4:1"	Roughly how many parts of dried herb went into one part of extract. A higher ratio means a more concentrated extract.	The ratio depends on the solvent and method, so two "4:1" extracts are not guaranteed to match.
Standardised to a marker, e.g. "95% curcuminoids"	A fixed share of one compound (or group of compounds) in the extract. It shows consistency for that marker, not that the marker is what does the work.	Is this the same standardisation the trials used? NCCIH cautions that "standardized" on a label does not necessarily guarantee quality or consistency [3].

This matters because trials test one named preparation at one dose, and the result belongs to that preparation. The ingredient pages here rate each use against the form and dose that was studied, so the useful question is whether your bottle matches it. Examples from our entries:

Dry extract, ratio givenValerianThe EU monograph dose is 400–600 mg of dry extract per dose, for ethanol extracts with a drug-to-extract ratio of 3–7.4:1 [10]. A label that says "valerian root 500 mg" without saying extract or powder does not tell you whether you are near that dose.Named branded extractLavenderThe anxiety trials tested Silexan, a specific lavender oil, at 80 mg a day [11]. Our entry notes that dose and results apply to this standardised oil, not to other lavender oil products.Absorption and formulationCurcuminIn a small study of healthy volunteers, 2 g curcumin plus 20 mg piperine gave far higher blood levels than 2 g curcumin alone [14]. NCCIH warns that liver damage has been reported with high-absorption products [13], so a label that promises more absorption is not a reason to take more.Spice vs extractTurmericThe trials mostly tested curcumin or curcuminoid extracts, not culinary turmeric or plain root powder, so they do not show that the spice works [13]. NCCIH notes that products vary in curcumin content and often add piperine from black pepper.Milligrams and release typeMelatoninIn the Cochrane review of jet lag, doses of 0.5–5 mg were similarly effective, though people fell asleep faster and slept better on 5 mg than 0.5 mg, and 2 mg slow-release was relatively ineffective [12]. Check both the dose and whether the tablet is slow-release.

Proprietary blends

A blend is listed under a name such as "Proprietary Blend", with the total weight of the blend on the same line and the ingredients indented beneath it in order from heaviest to lightest [4]. The FDA describes the label as showing amounts per serving "except for dietary ingredients that are part of a proprietary blend" [2]. So you can see the blend's total, but not how much of each ingredient it contains.

That makes a blend impossible to compare with a trial dose. If a product lists a herb in a blend of several, you cannot tell whether it reaches the amount studied, and the herb that sells the product may be the smallest part. A label that gives each amount separately is easier to check.

Serving size, per-capsule amounts and percentage values

In the US, one serving is the maximum amount the label recommends per eating occasion or, without a recommendation, one unit such as a tablet or capsule [4]. Amounts on the panel are per serving, so if the serving is "2 capsules", the figure is not per capsule. Check the servings per day too: the daily dose is the amount per serving multiplied by how many servings you are told to take.

The US percent Daily Value is required for nutrients that have an established Daily Value [4], so most herbs, which have none, show no percentage. UK labels must also give a recommended daily dose and a warning not to exceed it [5]. A high percentage on a vitamin or mineral is not a reason to take more.

Testing seals: what they check

Independent programmes, including USP Verified and NSF, test products and let passing ones carry a mark. NSF's Certified for Sport programme, for example, says it verifies that the product contains none of the banned substances on its list, that the contents match the label, that there are no unsafe levels of contaminants, and that the factory meets good manufacturing practice [9].

Notice what is missing: none of that is a test of whether the supplement improves anything. A seal answers "is what is written on the bottle inside it, and is it clean?", which is worth knowing, particularly for athletes who are drug-tested. It does not answer "does it work?" or "is it safe for me?". The wording "verified" or "certified" on its own does not necessarily guarantee quality or consistency [3], so look for the name of the programme and search its database for the product.

Warnings, dates and when to ask a pharmacist

Read the warning lines as information about the ingredient, not boilerplate. Interaction, pregnancy and children's warnings often reflect the same cautions in our ingredient entries, for example that valerian should not be combined with sedatives or alcohol, or that curcumin products need care in liver disease. If a label has no warning at all, that is not evidence that there is nothing to worry about.

Check the best-before or expiry date and the storage instructions; UK guidance requires supplements to carry a keep-out-of-reach-of-children statement [5]. Buy from a seller you can identify, and note the batch or lot number, which is what an independent programme's database or the manufacturer will ask for.

Show the bottle to a pharmacist before you start if you take any prescription or over-the-counter medicine, are pregnant or breastfeeding, are due to have surgery, or have a liver or kidney condition. The NHS advises checking with a pharmacist before taking a herbal medicine if you already take other medicine [7], and NCCIH advises telling your health care providers about every supplement you take, especially before surgery [3]. Do not stop a prescription because of something on a label.

A five-line check before you buy

1. Is the form (extract, powder, oil) and the amount named, and does it match the form studied? 2. Is each ingredient listed separately, or hidden in a blend? 3. Is the amount per capsule or per serving, and how many servings a day? 4. Is there an independent testing mark you can look up? 5. Do the warnings mention anything that applies to you or your medicines? Our methodology explains how the ingredient ratings you are comparing against are assigned.

Questions people ask

Does "third-party tested" mean a supplement works?

No. Programmes such as NSF Certified for Sport check that the contents match the label, that there are no unsafe levels of contaminants and, in that programme, that none of the listed banned substances are present [9]. That is about what is in the bottle, not whether it helps. A seal on a product with a weak evidence record is still a weak-evidence product.

Is a "natural" or "standardised" label a guarantee of quality?

No. NCCIH says natural does not always mean safe (it uses kava, which can cause liver disease, as its example) and that "standardized", "verified" or "certified" on a label does not necessarily guarantee quality or consistency [3]. NCCIH also notes that what is listed on a supplement label may not be what is in the product [3].

Who should I show the bottle to?

Any pharmacist, especially if you take other medicines. The NHS advises checking with a pharmacist before taking a herbal medicine if you already take other medicine, and lists statins, antidepressants, diabetes medicines, blood pressure medicines, blood thinners and hormonal contraception among those that do not mix safely with herbal products [7]. NCCIH advises telling all your health care providers about every supplement you take, especially before surgery [3].

Sources

Regulator U.S. Food and Drug Administration. Dietary Supplements. FDA.
Regulator U.S. Food and Drug Administration. Questions and Answers on Dietary Supplements. FDA.
Regulator/health agency NCCIH. Using Dietary Supplements Wisely. National Center for Complementary and Integrative Health.
Regulator guidance U.S. Food and Drug Administration. Dietary Supplement Labeling Guide: Chapter IV. Nutrition Labeling. FDA.
Regulator guidance Food Standards Agency. Food supplements. GOV.UK.
Regulator European Commission. Nutrition and health claims. Food Safety.
Health agency NHS. Herbal medicines.
Regulator guidance MHRA. The Traditional Herbal Registration (THR) Certification Mark: Guidance for Business. GOV.UK.
Certifier NSF. What Our Mark Means. Certified for Sport.
Regulator monograph European Medicines Agency HMPC. European Union herbal monograph on Valeriana officinalis L., radix (EMA/HMPC/150848/2015). 2016.
Randomised controlled trial Kasper S, Gastpar M, Müller WE, et al. Lavender oil preparation Silexan is effective in generalized anxiety disorder: a randomized, double-blind comparison to placebo and paroxetine. Int J Neuropsychopharmacol. 2014.
Systematic review Herxheimer A, Petrie KJ. Melatonin for the prevention and treatment of jet lag. Cochrane Database of Systematic Reviews. 2002.
Regulator/health agency NCCIH. Turmeric: Usefulness and Safety. National Center for Complementary and Integrative Health.
Pharmacokinetic study Shoba G, Joy D, Joseph T, Majeed M, Rajendran R, Srinivas PS. Influence of piperine on the pharmacokinetics of curcumin in animals and human volunteers. Planta Med. 1998.
Regulator guidance MHRA. Apply for a traditional herbal registration (THR). GOV.UK.

Draft, awaiting clinical review