How to Read a Supplement Label, Line by Line

Quick answer

Start with the Supplement Facts panel: the serving size first, then the amount of each ingredient per serving, which FDA requires except for ingredients inside a proprietary blend. Percent Daily Value of 5% or less is low and 20% or more is high. Then read Other Ingredients, allergen names, the maker's address, the claims and the disclaimer.^1,2

Key facts

FDA requires five statements on a supplement label: the product name, the net quantity, the nutrition labeling, the ingredient list, and the name and place of business. An expiration date is not required.³
A serving is the largest amount the label recommends for one eating occasion, so directions of 1 to 3 tablets make the serving size 3 tablets.¹
The panel lists the weight of the nutrient itself, not of the compound that supplies it: calcium from calcium carbonate is listed as calcium, and NIH says the same of magnesium.^1,4
Percent Daily Value of 5% or less per serving is low and 20% or more is high; ingredients with no Daily Value are marked with a symbol.^1,2
A proprietary blend shows the blend's total weight and lists its ingredients in descending order by weight, without an amount for each.¹
A label states what the maker says is inside: melatonin products measured 0% to 667% of the declared amount in an FDA survey of 110 products.⁵

What does the Supplement Facts panel show?

FDA requires a Supplement Facts panel on supplement labels. It lists the serving size and the servings per container, every dietary ingredient in the product, and for most ingredients the amount per serving, by weight, as a percent of Daily Value, or both.^1,6

Read the serving size before anything else, because every other number is per serving. FDA defines a serving as the largest amount the label recommends for one eating occasion, or one unit when no amount is recommended. If the directions say to take 1 to 3 tablets with breakfast, the serving size is 3 tablets. NIH adds that the manufacturer suggests the serving size, and your health care provider might decide a different amount is more appropriate for you.^1,7

How do you read the amount per serving?

The panel gives the weight of the nutrient itself. For calcium from calcium carbonate, FDA says to list the weight of calcium, not of the whole salt. NIH says the same about magnesium: the panel declares elemental magnesium, not the weight of the entire compound that carries it. The table shows common cases.^1,4

Label wording and what it means^1,2,4,8
On the label	What it means	Source
Magnesium (as magnesium glycinate) 120 mg	120 mg is the magnesium; the glycinate weighs more on top of that	NIH ODS magnesium sheet
Calcium (as calcium carbonate) 500 mg	500 mg is the calcium, not the weight of calcium carbonate	FDA labeling guide
Vitamin D3 25 mcg (1,000 IU)	Two units for one amount, since 1 mcg of vitamin D equals 40 IU	NIH ODS vitamin D sheet
Folate 400 mcg DFE	Dietary folate equivalents, the unit of the Daily Value for folate	FDA Daily Value page
Vitamin A 900 mcg RAE	Retinol activity equivalents, the unit of the Daily Value for vitamin A	FDA Daily Value page
A dagger or asterisk where the percent should be	No Daily Value has been set for the ingredient	FDA labeling guide

Our glossary explains the unit terms: mcg, IU, DFE, RAE and elemental amounts. Unit abbreviations on the label follow FDA's key, with g for grams, mg for milligrams and mcg for micrograms.²

What does % Daily Value mean on a supplement?

FDA describes Daily Values as recommended amounts of nutrients to consume, or in a few cases not to exceed, each day, and the percent Daily Value as how much a serving contributes. If the Daily Value is 300 mcg and a serving has 30 mcg, the percent Daily Value is 10%. As a general guide, 5% or less per serving is low and 20% or more is high.²

Daily Values on supplement labels (adults and children 4 and older)²
Nutrient	Daily Value
Calcium	1,300 mg
Iron	18 mg
Magnesium	420 mg
Zinc	11 mg
Vitamin C	90 mg
Vitamin D	20 mcg
Vitamin B12	2.4 mcg
Folate	400 mcg DFE
Potassium	4,700 mg

The Daily Value is a labeling yardstick, not a safety limit. A separate number, the tolerable upper intake level, is set for safety, and for vitamin D, iron, zinc and several others NIH says it counts intake from all sources: food, drinks and supplements. The two numbers can sit far apart: the adult vitamin D upper limit of 100 mcg is five times its Daily Value of 20 mcg, while the magnesium upper limit for supplements, 350 mg, is below its Daily Value of 420 mg. Compare the actual amount with the upper limit for your age, not only the percent.^2,9,10,11

What is a proprietary blend on a supplement label?

FDA requires a blend to be named with the term Proprietary Blend or a descriptive name. On the same line the label gives the total weight of the blend, and indented below it the ingredients in descending order of predominance by weight, each followed by a symbol meaning no Daily Value is set. Ingredients that do have a Daily Value must be listed separately with their own weights.¹

The order tells you which ingredient there is most of, not by how much. A 500 mg blend of five ingredients could be mostly the first one. Our glossary page on proprietary blends covers what to ask a maker.¹

What is listed under Other Ingredients?

Anything not in the panel goes under Other Ingredients: fillers, binders, excipients, preservatives, sweeteners and flavorings, with gelatin, starch and stabilizers as common examples. FDA's guide says ingredients are listed in descending order of weight, and that a separate list is not needed when every ingredient already appears in the panel.^6,12

Allergens belong here too. FDA names nine major food allergens (milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat, soybeans and sesame), and a label must name the food source of any ingredient made from them, for example whey (milk).¹³

Where do you find the maker, the quantity and the dates?

FDA's labeling guide lists five required statements: the product name, the net quantity of contents, the nutrition labeling, the ingredient list, and the name and place of business of the maker, packer or distributor. FDA also requires a domestic address or phone number for reporting serious adverse events. An expiration date is not required, although a firm may print one if data back it up, so dates vary by brand.^3,6

How to read a magnesium supplement label

Three details matter on a magnesium label. The form named in parentheses (glycinate, citrate, oxide) describes what carries the magnesium. The number beside it is elemental magnesium, per serving. And the percent Daily Value is measured against 420 mg. The adult upper limit of 350 mg a day applies to magnesium from supplements and medicines only, a different number from the Daily Value, so a product at 100% of the Daily Value can exceed it.^2,4,11

How to read a fish oil supplement label

NIH says omega-3 products vary widely, so the label is where to check the types and amounts. A typical fish oil capsule provides about 1,000 mg of fish oil containing about 180 mg of EPA and 120 mg of DHA, which means the larger number on the front is the oil and the omega-3 fats are a smaller number on the panel. Omega-3s come in several chemical forms: the natural triglyceride form, free fatty acids, ethyl esters, the re-esterified triglyceride form and phospholipids. NIH says the re-esterified triglyceride, natural triglyceride and free fatty acid forms have somewhat higher bioavailability than ethyl esters, though all forms raise blood EPA and DHA.¹⁴

NIH's Dietary Supplement Label Database lists the label information of many products, which is a way to compare amounts across brands.^14,15

What can a supplement label not tell you?

A label is the maker's statement. NCCIH says what is on the label may not be what is in the product. In an FDA survey of 110 melatonin products marketed for children, the measured melatonin ranged from 0% to 667% of the declared amount, and in a USDA analysis of adult multivitamins the measured amounts exceeded the label for every nutrient except thiamin, partly because makers add extra to cover losses over shelf life.^5,15,16

A lab report for the lot is how that gap is checked, and our guide to third-party testing explains what such a report does and does not show. Our glossary pages on overage and on certificates of analysis cover the two terms.¹⁷

What do the claims, the disclaimer and the warnings mean?

A supplement label may describe how a nutrient affects the structure or function of the body. These claims are not approved by FDA before use, so the label must carry a disclaimer that FDA has not evaluated the claim and that the product is not intended to diagnose, treat, cure or prevent any disease, because only a drug can legally make such a claim.^6,18

Solid iron supplements must carry a boxed warning that accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under 6. FDA also says supplements can interact with medicines, so ask a doctor or pharmacist about any product you take with a prescription.^19,20

Questions people ask

How to read a magnesium supplement label?

Check the form in parentheses, the elemental magnesium per serving, and the percent Daily Value against 420 mg. The adult upper limit of 350 mg a day counts supplements and medicines only.^2,4,11

How to read a fish oil supplement label?

Look for EPA and DHA amounts, not only the fish oil weight. A typical capsule has about 1,000 mg of fish oil with about 180 mg of EPA and 120 mg of DHA, and the form of omega-3 is named on the label.¹⁴

How to read supplement facts?

Read the serving size, then the amount of each ingredient per serving, then percent Daily Value. FDA calls 5% or less low and 20% or more high, and marks ingredients with no Daily Value with a symbol.^1,2

How to read a vitamin label?

Match the unit to the nutrient: mcg for vitamin D, B12 and K, mcg DFE for folate and mcg RAE for vitamin A. Then compare the amount with the upper limit as well as the Daily Value.^2,9

What does the FDA disclaimer on a supplement label mean?

It says FDA has not evaluated a claim, because supplements are not approved before sale, and that the product is not intended to diagnose, treat, cure or prevent any disease. Ask a doctor or pharmacist about any claim that matters for your health.^6,18

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.