A supplement label contains a surprising amount of useful information, arranged in a way that makes it easy to skip. Reading it in a specific order takes about ninety seconds and answers the two questions that actually matter: how much of the ingredient you care about is in one dose, and what evidence exists that the product contains it.
The order to read a label in
- Serving size. At the top. “2 capsules” means every number below is for two capsules, and a 60-capsule bottle is a 30-day supply — not 60.
- The ingredient you came for. Find it and note the amount. If it is inside a proprietary blend, you cannot determine the dose at all.
- The form of the ingredient. “Magnesium oxide 500 mg” and “magnesium 500 mg” are different statements, and so are folic acid and methylfolate. The compound weight is not the same as the active weight.
- Other ingredients and allergens. Below the actives. Look for the allergen statement, and for anything you react to.
- The small print. Batch number, expiry, storage conditions, warnings, and the name of the company responsible for the product in your market.
What the percentages really mean
The “% NRV” or “% Daily Value” column tells you what share of a labelling reference value one serving provides. Those references — the EU NRV and the US Daily Value — exist so that packaging can use phrases like “a source of” or “high in” consistently. They are not personal targets and not upper limits.
Two practical consequences:
- A very large percentage is not a quality signal. For water-soluble vitamins, a 1,000% figure often reflects the fact that absorption falls sharply at high intakes. It is cheaper to print than to justify.
- For some nutrients, the reference value and the upper limit are not far apart. Selenium, zinc and vitamin B6 are the clearest examples; more is genuinely not better, and sustained high intakes are where regulators publish limits.
Our ingredient index lists the EU NRV and the US Daily Value for each vitamin and mineral, alongside the amounts commonly seen on labels and the caution that travels with the ingredient — including biotin's interference with common laboratory tests and vitamin K's interaction with anticoagulants.
The two places a label can hide a small dose
1. Proprietary blends
A blend declares a single total weight for a group of ingredients without disclosing individual amounts. It is lawful in many markets and almost always signals that at least one ingredient is present in a small amount. If you are buying for one specific ingredient, this is the label pattern to avoid — a product that declares that ingredient separately, with its amount, has told you more.
2. Compound weight instead of active weight
A label can legally declare the weight of the compound — for example a mineral salt — while you are trying to judge the elemental mineral content. Magnesium glycinate and magnesium oxide contain very different proportions of elemental magnesium, so comparing the headline numbers on two products can be genuinely misleading. Check whether the label says “magnesium” or “magnesium citrate”, and multiply if you care about equivalence.
Testing marks: what the front of the pack is promising
| Mark on the pack | What it covers | How to check it |
|---|---|---|
| GMP / cGMP | The manufacturing facility's processes and documentation | It is about the factory. It says nothing about this bottle's contents. |
| Product verification programmes | The finished product's contents against its own label: identity, strength, purity, contaminants | Look the exact brand and product up in the programme's own public list — certification is product-specific. |
| Banned-substance programmes | A defined list of prohibited substances, tested by batch | Look up the batch number. Batch-level verification is the entire point. |
| Certificate of analysis | What a named laboratory found in a named batch | Check the batch number against the pack, and confirm the laboratory is accredited for that test. |
| “Lab tested”, “verified”, “clinically studied” | Often nothing specific, unless a named programme or study is identified | Ask which laboratory, which batch, which study. A specific answer is easy for an honest seller. |
The certification decoder covers each of these in more detail, including the ones that look like product quality marks but only cover a company or a factory.
Four things worth checking before you buy again
- Does the pack declare the ingredient you want, with an amount? If it is hidden in a blend, you are buying a hope rather than a dose.
- Does the expiry date leave you enough time? Potency falls over time, and products bought near end of life are often close to the limit of their shelf life on the day they arrive.
- Is the responsible company identified in your market? The name and address on the pack is who you complain to and who a regulator can pursue.
- Can the seller produce a batch document on request? A supplier with real documentation answers in one message; the one that cannot will tell you something by avoiding the question.
Frequently asked questions
What do the percentages on a supplement label mean?
They are the share of a labelling reference value — the EU NRV or the US Daily Value — supplied by one serving. They are not a measure of quality and not a dose recommendation. A product with 1,000% of a vitamin is not ten times better than one with 100%; for several nutrients, a large multiple of the reference value is simply absorbed less efficiently, and for a few it is a reason to check the upper limit.
What is a proprietary blend and why does it matter?
A proprietary blend lists total milligrams for a group of ingredients without saying how much of each. You cannot tell whether the ingredient you wanted is 500 mg or 5 mg. It is legal in many markets and it is the single most common way a label hides a small dose. If you are buying for a specific ingredient, buy a product that declares it separately.
Does “GMP certified” mean the product works?
No. GMP is about how the product is made — hygiene, documentation, batch records, quality control. It says nothing about whether the ingredients are present at the declared strength or whether the product does anything. Product-level certification, such as a verification programme that tests the finished product against its label, is a stronger claim; a batch test report matched to the batch number is stronger still.
How can I check that a supplement actually contains what the label says?
Ask for, or look for, a batch-specific certificate of analysis from an accredited laboratory, and check that the batch number matches the pack. Where a product carries a verification programme mark, look the product up in that programme's own public list rather than trusting the logo on the bottle. Our certification decoder explains which marks test the product and which only audit the factory.
Are supplements regulated before they are sold?
Mostly not, and this surprises people. In the United States supplements are regulated as a category of food with no pre-market approval, and in the EU the permitted vitamin and mineral forms are harmonised but maximum levels and notification duties are set nationally. Australia has a listed route that is largely self-assessed. Responsibility for compliance usually sits with the company whose name is on the pack, which makes the label and the documentation worth reading.