How to Evaluate a Supplement Formula: Disclosure, Blends, Duplicates, Upper Limits and Cost

The core idea

A formula is not the sum of its studies. Finding that each ingredient has been studied does not show that the combination works, in those amounts, in a person like you. A blend can add the risks of every ingredient without adding the benefits. Reviewers of pre-workout blends, for example, said comparing formulas is "challenging and often impossible" when amounts are not disclosed. [1]

This page is the hub for the Reading Formula Labels collection. It is a checklist for asking better questions. It does not rank, recommend or name products, and it is not medical advice. FDA advises talking to a doctor, pharmacist or other health care professional before deciding to use a supplement. [2]

Step 1: Is each ingredient named, and is the amount shown?

In the US, the Supplement Facts panel must list the serving size and servings per container and declare each dietary ingredient. [2] Amounts are required except for ingredients inside a proprietary blend. [2] The details are on the Supplement Facts panel page.

Step 2: What is hiding inside a blend?

A blend must show one total weight, with its ingredients in descending order by weight. [3] You can tell which ingredient is most abundant, not how much of any single one you get. That is a disclosure limit, not proof that anything is wrong. If you cannot see the amount, you cannot compare it with a studied amount or an upper limit. See proprietary blends explained.

Step 3: Do the same nutrients appear twice?

Vitamins and minerals repeat across a multivitamin, a "hair" or "energy" formula, a single-nutrient pill and fortified foods. Add them up before comparing with any upper limit. The table shows NHS (UK) supplement cautions for several nutrients. They are advice from one country, not universal limits, and they do not cover pregnancy, children or medical conditions. Your care team can say which apply to you.

Those NHS pages were last reviewed in 2020 and listed a later review date, so check current NHS wording. US figures differ; see RDA, AI, DV and UL and doubling up across products.

Percent Daily Value (%DV) helps a little. FDA's general guide is that 5% DV or less per serving is low and 20% DV or more is high. [9] But %DV describes one serving of one product, so it does not add up across products for you. [9]

Children and iron: US labels on iron-containing supplements carry a warning that accidental overdose of iron products is a leading cause of fatal poisoning in children under 6. [10] The NHS also says very high iron doses can be fatal, particularly in children. [8] If a child swallowed an adult or children's vitamin, call Poison Help at 1-800-222-1222 (US) or 911 and do not make the child vomit. See poisoning: what to do first.

Step 4: Medicines and conditions

Herbs and other extras can change how medicines work. NCCIH gives one example: St. John's wort makes many medications less effective. [11] Tell your pharmacist about every product, bring the label, and mention kidney or liver disease, pregnancy, breastfeeding and any planned surgery. See medication interactions. Never change a prescribed medicine because of a supplement; ask the prescriber first.

Step 5: Is there evidence for the finished formula?

Ask whether this formula, or one with the same ingredients and amounts, was tested in people like you, and whether the outcome was something you can feel or only a lab marker. NCCIH notes that strong evidence behind supplement claims is often lacking. [11] In one review of 27 ingredients common in immune-support products, rigorous human evidence existed for only eight. [11] A finished blend with no published trial of its own has, in practice, only ingredient-level evidence to point to.

A claim such as "supports immune health" is usually a structure/function claim, which FDA does not pre-approve; the maker must have substantiation. [12] See structure-function claims.

Step 6: Quality and testing

FDA does not have the authority to approve dietary supplements before they are marketed. [2] It also does not test them before sale. [2] Label accuracy has been a problem in some product types. A 2017 test of 31 melatonin supplements found most did not match their labels. [13] A review of 16 studies of athletes' supplements found that labels differed from actual amounts. [14] A third-party testing mark can check things like identity and contaminants, but not whether a formula works for you. See what third-party testing can and cannot show and quality testing and certifications.

Step 7: Cost per serving

Divide the price by the servings per container, using the serving size on the panel. FDA's labeling guide says a serving is the maximum amount recommended per occasion, so "1-3 tablets" means the panel describes 3. [3] A cheaper product is not better if the amounts are not what the label says, and a dearer one is not better because of marketing. See comparing supplement labels and cost per serving.

Quick checklist

• Every ingredient named, with an amount; a large blend total is a reason to ask questions.
• Amounts added up with other products and compared with official limits for your country.
• Evidence for the same ingredients, amounts and kind of person, not only for each ingredient alone.
• A claim you can check, no "miracle" language (label red flags).
• A pharmacist or clinician has seen the full label.

More tools: the label checklist and the Supplement Formulas hub.