How to read a supplement label: what to look for

General information, not medical advice. If you have symptoms or take medication, talk to your GP or pharmacist.

In short

• Read the active substance per daily portion first, not the advertising on the front.
• The % RI helps you compare. A very high percentage does not automatically mean the product is better or safer.
• A hidden blend without a dose per ingredient makes fair comparison hard.
• In the EU, health claims are regulated. Vague promises such as detox or hormone balance are not among the authorised wordings.
• In Belgium, a supplement must be notified to the FPS Public Health before sale. The FASFC checks the market.

You are in the pharmacy or scrolling past jars of magnesium online. The front sounds confident. The back lists milligrams, a % RI and sometimes a blend without clear doses. This article helps you with how to read a supplement label: what the portion really is, what % RI means and how to judge the promises. Supplements add to a varied diet; they do not replace it. If you train a lot, you may first benefit from enough protein from ordinary food and enough sleep, before another jar joins the shelf.

How to read a supplement label: portion and % RI

Look at the recommended daily portion and how many capsules or scoops that is. If it says 200 mg per capsule but the portion is three capsules, you take 600 mg a day according to the label. Check that sum and ask whether that portion fits your routine.

% RI means the percentage of the European reference intake per day, fixed for labelling in Annex XIII of Regulation (EU) No 1169/2011. For magnesium, 100% RI is for example 375 mg. Handy for comparing products. A high percentage says nothing about whether you need that amount. For many vitamins and minerals, the European Food Safety Authority (EFSA) has established a tolerable upper intake level. Taking more than that limit over time can be harmful.

Which form and how much of the nutrient?

“Magnesium” or “zinc” alone says little: oxide, citrate or bisglycinate are different salts. The label should show the amount of the nutrient itself, in milligrams per daily portion, not only the weight of the whole salt. For omega-3, look for EPA and DHA amounts, not only “fish oil 1000 mg”.

Hidden blends

Sometimes one total weight is listed for a mix with a fancy name, without a dose per ingredient. In English that is often called a proprietary blend, a hidden mix. Then you cannot compare the amount with what research used. For vitamins and minerals, EU rules require a numerical amount per substance per daily portion (Directive 2002/46/EC). If that clarity is missing, be careful with the promise on the front.

Claims on the pack

Food supplements may not cure, treat or prevent disease: that is in Directive 2002/46/EC and in Regulation (EU) No 1169/2011. Regulation (EC) No 1924/2006 lays down which nutrition and health claims are allowed, with fixed wording and conditions. An authorised example is that a nutrient “contributes to the normal function of the immune system”, not “supports immunity” or “never get sick again”. Promises such as detox or hormone balance are not standard authorised claims. Check doubtful wording in the EU Register of nutrition and health claims. Before-and-after photos or claims about disease are not evidence.

Belgium: notification and checks

In Belgium, a food supplement must be notified to the FPS Public Health before sale. You then get a notification number. That number is not proof that the product fully complies. The Federal Agency for the Safety of the Food Chain (FASFC) checks products on the market, including online. Prefer a recognised seller and be extra critical of offers from outside the EU.

Independent tests

A lab report or seal about content and purity can be a quality signal, especially for sports supplements. Not every seal is equal. A test says nothing about whether you need the product, and marketing can sell seals hard. Ask where possible: tested for what, by whom, and for which batch?

When to see a doctor or pharmacist?

If you take medication, are pregnant, have an illness or doubt a high dose, ask your GP or pharmacist. Do not casually combine supplements with medicines.

Sources

• European Parliament and Council (2002). Directive 2002/46/EC on the approximation of the laws of the Member States relating to food supplements. Official Journal of the European Union.
• European Parliament and Council (2011). Regulation (EU) No 1169/2011 on the provision of food information to consumers (incl. Art. 7 and Annex XIII, reference intakes). Official Journal of the European Union.
• European Parliament and Council (2006). Regulation (EC) No 1924/2006 on nutrition and health claims made on foods. Official Journal of the European Union.
• European Commission. EU Register of nutrition and health claims (accessed October 2026).
• EFSA (2025). Overview on Tolerable Upper Intake Levels (version 11, August 2025). European Food Safety Authority.
• FPS Public Health, Food Chain Safety and Environment. Food supplements and fortified food (accessed October 2026).