How to read a supplement label (and a lab certificate)

The front of a supplement pack does the selling: a big number, a leaf, a badge, sometimes a lab coat in silhouette. The useful part is on the back, in smaller type. This guide walks through that small type in the order that clears up the most confusion, and then through the one document that often sits behind the badge, the certificate of analysis.

In a nutshell: check the daily portion first, then how much of the nutrient that portion provides, then the full ingredient list and warnings. Treat claims and "lab tested" badges as questions to ask, not as answers. We focus on food supplements sold in the EU, with the Netherlands as our reference point. A US "Supplement Facts" panel follows different rules and is not a template for a European pack.

What the law says must be on the back

EU supplement labelling comes from several layers. Directive 2002/46/EC covers food supplements specifically, and the general food-information rules (Regulation (EU) No 1169/2011) apply on top. Here are the main pieces, with the article that requires each (legal text read on 8 October 2026):

• What you should find: The name "food supplement"; Where the rule comes from: Directive 2002/46/EC, Article 6(1)
• What you should find: The names of the nutrient categories or substances that characterise the product; Where the rule comes from: Directive 2002/46/EC, Article 6(3)(a)
• What you should find: The portion recommended for daily consumption, and a warning not to exceed it; Where the rule comes from: Directive 2002/46/EC, Article 6(3)
• What you should find: A statement that supplements should not replace a varied diet, and that the pack should be kept out of reach of young children; Where the rule comes from: Directive 2002/46/EC, Article 6(3); also listed on the Your Europe labelling page
• What you should find: The amount of each nutrient per recommended daily portion, in numbers, with vitamins and minerals also shown as a percentage of the reference value; Where the rule comes from: Directive 2002/46/EC, Article 8
• What you should find: Ingredients, allergens, storage conditions, a durability date and the name and address of the food business operator; Where the rule comes from: Regulation (EU) No 1169/2011, Article 9(1)

The articles are in the Directive on EUR-Lex and Regulation 1169/2011. Law changes, so check the current consolidated text if a decision depends on it.

Two Dutch details are worth knowing. The Dutch business portal says that mandatory label information on food must be in Dutch (Ondernemersplein, read 8 October 2026); how that works for orders shipped from other countries is a separate question. And the Dutch food authority, the NVWA, says there is no notification obligation for supplements in the Netherlands (NVWA). Businesses do have to register with the NVWA; they just don't notify each product. The Dutch medicines board adds that herbal supplements fall under food law and do not need approval before sale, unlike herbal medicines (CBG-MEB). In plain terms: a supplement label is a manufacturer's statement under food law, and no authority approves the product itself before it goes on sale (individual health claims are a different matter, as the next sections explain).

Start with the portion, because the numbers hang on it

The nutrient amounts on a pack are given per recommended daily portion. That portion might be one capsule, three capsules or a scoop. Before comparing anything, find out which it is.

Here is a fictional example. Tub A says "Magnesium 200 mg per daily portion" and the portion is two capsules. Each capsule therefore holds about 100 mg, if the capsules are identical. Tub B says "Magnesium 150 mg per capsule" and the portion is also two capsules, so a portion gives 300 mg. The two numbers on the front, 200 and 150, look as if A is stronger. They are measured against different things.

Now add a price. Say Tub A has 60 capsules for €12 and Tub B has 90 capsules for €15, both with a two-capsule portion:

• : Capsules; Tub A: 60; Tub B: 90
• : Days per tub (two capsules a day); Tub A: 30; Tub B: 45
• : Nutrient per daily portion; Tub A: 200 mg; Tub B: 300 mg
• : Price per day; Tub A: €0.40; Tub B: €0.33
• : Price per 100 mg of the nutrient; Tub A: €0.20; Tub B: €0.11

This is arithmetic for comparing labels, not a dose suggestion. Whether 200 or 300 mg suits anybody is a separate question, and a bigger number is not a better result. What the arithmetic does show is that "cost per tub" and "number on the front" both mislead, while "cost per stated portion" does not.

Is that the nutrient, or the whole ingredient?

Minerals come bound to something else: magnesium to citrate, zinc to gluconate and so on. A label can show the weight of the whole compound or the weight of the mineral in it, and the two are not the same number. Our fictional label reads "Magnesium compound 1,000 mg, providing magnesium 150 mg (40% NRV)". The mineral is the 150 mg, and how much of a compound is mineral depends on the compound. If a label shows only the compound weight, ask the manufacturer for the mineral content before you calculate anything. Our magnesium forms guide explains why compound weight, absorption and benefit are three separate questions.

What that percentage is a percentage of

For vitamins and minerals the label also gives a percentage of a reference value. These are the nutrient reference values (NRVs) in Annex XIII of Regulation 1169/2011. Annex XIII sets magnesium at 375 mg, vitamin C at 80 mg and vitamin D at 5 µg (Annex XIII). So "150 mg magnesium" is 40% of 375 mg, which is where the "(40% NRV)" in our example comes from. A pack showing "vitamin D 25 µg (500% NRV)" is simply 25 divided by 5.

The NRV is a labelling yardstick, not your personal requirement and not a treatment dose. It also isn't a safety limit in either direction. EFSA keeps those jobs separate: dietary reference values describe the amount of a nutrient needed to maintain health in a healthy individual or group, while a tolerable upper intake level is the maximum amount that can be consumed daily over a lifetime (EFSA). A percentage on a pack tells you neither whether you need the nutrient nor how much is too much.

Small print, big difference: ingredients and herbs

Read the full ingredient list, not just the headline ingredient. Look for allergens, the storage instructions and the date marking. The same brand can sell several formulations, so check the pack in your hand, not the one in last year's review.

For herbal products, a name like "ashwagandha" or "ginkgo" is a starting point. Ask which plant part is used, whether it is a powder or an extract, and what the extract is standardised to, if anything. Research on one preparation does not automatically transfer to another.

Claims: what the pack is allowed to say

Health claims on food are regulated by Regulation (EC) No 1924/2006. Its basic rule (Article 10(1)) is that a health claim is prohibited unless it has been authorised and listed, and the European Commission keeps a register of authorised health claims together with their conditions of use and any restrictions (EU register of health claims). The conditions matter: an authorised wording belongs to a particular nutrient or substance, so it does not travel to any product that merely mentions it.

Three limits apply on top, all from Directive 2002/46/EC:

• Article 6(2): labelling, presentation and advertising must not attribute to food supplements the property of preventing, treating or curing a human disease, or refer to such properties.
• Article 7: they must not state or imply that a balanced and varied diet cannot provide appropriate quantities of nutrients in general.
• Article 6(3): the pack carries the reminder that supplements are not a replacement for a varied diet.

That is why supplement packs tend to use wording of the "contributes to the normal function of…" kind rather than promising to fix anything, and why a pack that promises to treat a condition is worth a raised eyebrow. Our reading, as an editorial point rather than a legal ruling: a claim on a pack is a statement to check, not independent evidence.

Two phrases deserve a second look. "Clinically studied ingredient" tells you something about an ingredient, not necessarily the finished product, dose or outcome that the study used. And "better absorbed" is a statement about how much of a substance reaches the bloodstream, which is different from whether anything improves for the person taking it. A doubling in a blood measurement isn't a doubling of any effect, and it can't tell you the product suits you. Ask what was compared, in whom and what was measured.

Behind the badge: reading a certificate of analysis (COA)

A certificate of analysis reports laboratory results for a sample. Brands often mention one, sometimes behind a QR code. It can tell you something useful, as long as you know what you are looking at. A fictional, simplified example:

• Field: Product and batch; Example entry: "Oil 10%, batch 24-0187"; What to ask: Is this the same product and batch number as the one on my pack?
• Field: Sample type; Example entry: "Finished product" or "raw material"; What to ask: A raw-ingredient result does not describe the finished capsule, gummy or oil
• Field: Laboratory and date; Example entry: Named lab, report date; What to ask: Is the lab named, and does its stated scope cover this test?
• Field: Analyte and method; Example entry: "Lead, ICP-MS"; What to ask: Which substances were looked for, and with what method?
• Field: Result; Example entry: "< LOQ" or "ND"; What to ask: What do the abbreviations mean in this report?
• Field: Unit; Example entry: "mg/kg", "mg/mL", "mg per serving"; What to ask: Can I convert this to the portion on the label?
• Field: Limit or specification; Example entry: "Max 3.0 mg/kg"; What to ask: Where does the limit come from, and is it the one that applies?

Does it match your product? The first check is boring and decisive: product name, formulation and batch. A QR code is a route to a document; it does not prove the document describes the batch you hold. If a report is for a different batch or a raw material, ask for the right one.

What was actually measured? A potency panel (how much of the active ingredient is in the product) and a contaminant panel (metals, microbes, residues) answer different questions. "Pass" only means something once you know the tests and the limit. A report that tested potency alone says nothing about contaminants, and vice versa.

What "not detected" means. Labs use two related ideas. The limit of detection (LOD) is the lowest concentration a method can detect at a stated level of confidence, and the limit of quantification (LOQ) is the lowest level at which the method performs well enough for typical use. A result under the LOQ can mean "something may be there, but too little to measure reliably", which is different from zero. The Eurachem laboratory guide notes that terminology varies between sectors (Eurachem, The Fitness for Purpose of Analytical Methods, 3rd edition, 2025), so look for the report's own definition and its numeric limit rather than reading "ND" or "<LOQ" as "none".

Units. A concentration in mg/mL is not the amount in a bottle or a serving. To compare it with the label you need the volume, the density or the serving size. If you cannot do the conversion, ask the supplier to show it.

The laboratory. Accreditation is about a laboratory's competence for defined activities. Accreditation bodies publish a schedule of each lab's scope (UKAS, the UK accreditation body, does, for example; UKAS). In the Netherlands, accreditation is granted by the Raad voor Accreditatie (RvA). A logo on a report is a prompt to look the lab up and check the relevant test is in its scope; it is not a product certificate.

Who hosts it. A report on the seller's own site is not automatically unreliable and not automatically trustworthy. The laboratory's name, the batch identifiers and a way to contact the lab are what let you check.

Why the questions are worth asking

A 2026 analysis of 186 CBD and related cannabinoid oils collected over about a decade in Europe found that 49% of the products (86 of 181) did not contain the CBD amount declared on the label. Several contained THC variants beyond the usual measured one. Polycyclic aromatic hydrocarbons turned up in every sample, and 54% (101 of 186) exceeded the EU maximum limits for oil-based food supplements (Binova et al. 2026, Analytical and Bioanalytical Chemistry). That is a snapshot of the oils sampled over those years, not a current failure rate for all European CBD products, and it does not describe supplements in other categories. What it does show is that the label and the contents can differ and that a test panel which looks only at one thing can miss another.

The US National Center for Complementary and Integrative Health puts the general point plainly: what is on the label may not be what is in the product, and a "standardized" or "certified" wording does not necessarily guarantee product quality or consistency (NCCIH).

What a good COA still cannot tell you

A COA is a quality document. A clean, well-matched report can show that a sample contained roughly what was declared and none of the tested contaminants above the stated limits. It cannot tell you:

• that the product works for what you want it for;
• that it suits you, or is compatible with your medicines;
• that other batches look the same;
• anything about substances the lab did not test for.

"Third-party tested" can be a useful sign that a company is willing to show its homework. It is a prompt to read the document, not the end of the research. If you use a product, keep the report and the packaging together; the batch number helps if a professional ever needs to look into a reaction.

The checklist to take to the shelf

• What is the daily portion, and how many capsules, scoops or millilitres is it?
• How much of the nutrient (not the compound) is in that portion, and what does that cost per day?
• What is the full ingredient list, including allergens, and does it match the pack you will receive?
• Which preparation do the ingredient names refer to?
• If there is a COA, does it name the same batch, the finished product, the tests you care about and a laboratory you can check?
• What does the claim actually say, and is it a claim about a nutrient or about this product?

When the label can't answer the question

A label is product information, not a personalised safety assessment. If you take medicines, are pregnant or breastfeeding, or are choosing for a child, take the exact pack to a pharmacist. Our guide to supplements, herbs and medication shows what to bring and what to ask. For the wider picture of where supplements fit, see our introduction.

Three quick questions

Is 100% NRV the amount I personally need? No. It is a labelling reference value. Your own needs depend on your diet, circumstances and health, and a pharmacist, dietitian or doctor is the person to ask.

Is "lab tested" on the pack enough? It is a starting point. Ask which tests, which lab and which batch, and read the report itself if the brand offers it.

What if the label is unclear? Ask the manufacturer for the missing information. If you cannot work out what a portion contains, you cannot make a useful comparison, and that is itself information.

Written by Smart Supplements with AI assistance from the sources linked in the text. It has not been reviewed by a clinician.

Last updated: 12 October 2026

This article is for informational purposes only and is not intended as medical advice. Always consult a healthcare professional before starting any new supplement, especially if you take prescription medication.