How to Read a Supplement Facts Label

Two bottles of the same vitamin can look almost identical on a shelf and still differ in dose, in form and in what else is inside. Most of those differences are printed on the label, in the box headed Supplement Facts. This guide walks through it line by line.

It follows the US format. Supplements sold in other countries are labelled under local rules, so the layout and terms you see may differ.

Start with the serving size

The serving size sits at the top of the panel, and every number below it depends on it. Under FDA rules, one serving is the maximum amount the label recommends taking at one time. If the label gives no recommendation, a serving is one unit: one tablet, one capsule, one scoop.

So if the serving size is two capsules, the amounts listed are for two capsules. That matters when you compare prices: a bottle of 60 capsules with a two-capsule serving lasts 30 days, not 60.

Amount per serving and %DV

Next to each nutrient you’ll see the amount per serving and, usually, a %DV: the percentage of the Daily Value that one serving provides. The FDA’s rule of thumb is simple:

• 5% DV or less per serving is considered low.
• 20% DV or more per serving is considered high.

Check the units as well as the numbers. Current US labels use these units for some common vitamins:

The mineral, not the compound

Minerals come attached to something else: calcium as calcium carbonate, magnesium as magnesium citrate, and so on. The FDA requires the panel to state the weight of the mineral itself, not the weight of the whole compound. Manufacturers may name the source on the panel too, and labels often show it in brackets, for example “Magnesium (as magnesium citrate)”.

This is why a label can say 200 mg of magnesium while the capsule holds a much heavier amount of powder. How much heavier depends on the form, which we explain in our guide to comparing magnesium supplement labels.

More isn’t automatically better

A %DV and an upper limit are different things. The %DV compares one serving with the Daily Value, a reference amount used on nutrition labels. An upper limit is a separate figure that health authorities set for some nutrients: the most that is considered unlikely to cause harm. So a %DV above 100 isn’t necessarily a problem in itself, but for nutrients with an upper limit, the total amount matters. Vitamin D is one example: NHS guidance states that adults should not take more than 100 micrograms (4,000 IU) a day, as it could be harmful.

Upper limits are easy to lose track of when several products contain the same nutrient. A multivitamin plus a separate vitamin D, or a “hair, skin and nails” blend plus a multivitamin, can overlap, so the total across all of them is what counts.

Ingredients without a Daily Value

Many ingredients, such as herbal extracts and amino acids, have no Daily Value. On the panel they are followed by a symbol that points to the footnote “Daily Value Not Established.”

That is normal and not a warning sign in itself. It does mean the label can’t tell you whether the amount is meaningful. For that, you need to know what doses have actually been studied for that ingredient. Fish oil is a good example of reading amounts without a %DV to lean on: our guide to comparing omega-3 supplements shows how to work with EPA and DHA figures.

Proprietary blends

Some labels group ingredients under a name such as “Proprietary Blend” or a branded term. The rules for blends are different from the rules for single ingredients:

A blend isn’t automatically a bad sign, but it makes products hard to compare. If one ingredient is the reason you’re buying, a product that lists its exact amount is easier to judge.

The “Other ingredients” list

Below the panel is the ingredient statement, which lists everything that isn’t a dietary ingredient: capsule shells, fillers, binders, colours, flavourings. It’s worth a look if you avoid gelatin, particular additives or certain allergens.

Claims on the bottle

Phrases like “supports bone health” are called structure/function claims. They are not pre-approved by the FDA. Instead, the manufacturer must have substantiation that the claim is truthful and not misleading, and must notify the FDA of the claim no later than 30 days after the product goes on the market. The label must also carry a disclaimer saying the FDA has not evaluated the claim and that the product is not intended to diagnose, treat, cure or prevent any disease. Dietary supplements cannot claim to diagnose, treat, cure or prevent disease unless they are regulated as drugs.

It also helps to know that the FDA is not authorised to approve dietary supplements for safety and effectiveness before they are sold. A claim on the label tells you what the manufacturer is allowed to say, not what has been shown to work.

“Verified” and “certified”

Words like standardized, verified or certified, when used by the manufacturer itself, don’t necessarily guarantee quality or consistency. A seal from an independent testing organisation can tell you more, but only if you check it: look the product up on the certifier’s own website to see what was tested and whether that product is actually listed. A quality seal is about what is in the bottle, not about whether the supplement will help you.

A quick label checklist

1. Serving size: how many units make one serving, and what does one serving cost?
2. Amount and units: what does the label state per serving, and how does that compare with the Daily Value?
3. Overlap: does the same nutrient appear in other products as well?
4. Blends: is the amount of each ingredient disclosed, or only the blend’s total weight?
5. Other ingredients: are there any capsule materials, additives or allergens that matter to you?
6. Medicines and health conditions: some supplements interact with medicines. St. John’s wort, for example, can reduce the effectiveness of many medicines and can cause other clinically important interactions. This is a question worth taking to a pharmacist or doctor.