How to Read a Supplement Label (Before You Buy)

1. Start with the serving size

Every supplement must carry a “Supplement Facts” panel.^[2] Start at the top, with the serving size. The FDA defines one serving as the maximum amount the label recommends taking at one time, or one unit (such as one tablet or capsule) if the label doesn’t say.^[2]

Every amount on the panel is per serving, not per day. If the directions say to take two tablets a day and the serving size is one tablet, you’ll get twice the amounts shown.

This also tells you how long a bottle lasts. Our sample has 60 servings of one tablet. At one tablet a day, it lasts 60 days; at two a day, only 30. Divide the price by the number of days it lasts to get the real cost per day.

2. Read the % Daily Value

The “% Daily Value” (%DV) column shows how much one serving contributes to your daily diet.^[4] In our sample, 20 mcg of vitamin D is 100%, because the Daily Value for vitamin D is 20 mcg. The 130 mg of calcium is 10%, because the Daily Value for calcium is 1,300 mg.^[4]

A high %DV doesn’t mean a better product. If you take more than one supplement, or eat fortified foods, the amounts add up. If you’re unsure, ask your doctor or pharmacist to look at everything you take together.

3. Notice the “Daily Value not established” mark

Many supplement ingredients, such as herbs and probiotics, have no official Daily Value. The label must mark them with a symbol, often a dagger (†), that points to the footnote “Daily Value not established.”^[2]

That symbol isn’t a warning. It just means there’s no official daily amount to compare with, so the %DV column can’t help you judge these ingredients.

4. Look closely at “proprietary blends”

A proprietary blend is a group of ingredients listed together under one name, such as the “Proprietary Fresh Blend” in our sample. The label must show the total weight of the blend and list its ingredients in order of weight, from most to least. It does not have to show how much of each ingredient is in the blend.^[2]

In our sample, you know the blend weighs 100 mg and that xylitol makes up the largest share. You don’t know whether that’s 90 mg or 34 mg. That matters, because research on an ingredient usually uses a specific amount. When the amount is hidden, you can’t tell whether the product contains as much as the studies used.

5. For probiotics, check the strain and the CFU count

Probiotics are named by genus, species and strain. In Lacticaseibacillus rhamnosus GG, for example, Lacticaseibacillus is the genus, rhamnosus is the species and GG is the strain.^[5] Look for the full name, including the strain. Different types of probiotics may have different effects, so research on one strain doesn’t necessarily apply to another.^[6]

The Supplement Facts panel lists the total weight of the microorganisms, and many labels also list the number of colony-forming units (CFUs) per serving.^[5] The FDA said in a 2018 draft guidance that it would allow companies to list CFUs in addition to the weight.^[7] CFU is the more useful number when you compare products, because it counts the microorganisms rather than weighing them.

Our sample lists 5 billion CFU for the whole blend, but not for each strain. Also check the expiration or use-by date and the storage instructions on the label.^[5]

6. Read the “other ingredients”

Below the panel you’ll find “Other Ingredients.” These are things like binders, colors, fillers, flavors and sweeteners, listed from the largest amount to the smallest.^[3]

This list matters if you have allergies, avoid certain sweeteners, or follow a special diet. In our sample, sorbitol (a sweetener) is listed first, so there’s more of it than of the other extras.

7. Understand the FDA disclaimer

When a supplement says something like “supports healthy teeth,” that’s called a structure/function claim. These claims are not approved by the FDA ahead of time. The company must have evidence that the claim is truthful and must tell the FDA about it, and the label must carry a disclaimer saying the FDA hasn’t evaluated the claim.^[8]

So when you see the disclaimer at the bottom of our sample, read it literally: nobody at the FDA has checked whether the claims on the bottle are true.

Look the product up in the NIH label database

The National Institutes of Health runs a free Dietary Supplement Label Database with more than 200,000 labels from products sold in the United States. For each product it shows the ingredients and amounts, the % Daily Value, the company, any claims and warnings, and a picture of the label.^[9]

Here’s how to use it:

Step 1. Go to dsld.od.nih.gov.
Step 2. Type the product or brand name in the search box.
Step 3. Open the matching label. If there are several versions, check the dates, because labels can change over time.
Step 4. Compare it with the bottle or the sales page, line by line.

If the ingredients or amounts don’t match, ask the company why. Keep in mind that the labels come from the companies themselves, so they may be incomplete.^[9] If you can’t find a product at all, that isn’t proof of a problem; the database doesn’t cover every product. It just means you’ll need to rely on the label itself.

What a label can’t tell you

A careful read of the label tells you a lot, but not everything. It can’t tell you whether the product will do what the sales page says. Claims like “supports healthy gums” aren’t approved by the FDA before the product is sold.^[8] To judge a claim, you need to look at the research on each ingredient, at the amounts used in that research, and ideally at a study of the product itself.

A label also can’t tell you whether a product is right for you. Some ingredients can interact with medicines, and your health history matters. The FTC puts it simply: your doctor or health provider is your best source on whether a product is safe for you.^[10]

Then compare the label with the sales page

The Federal Trade Commission warns about sales pitches that say one product works for many different conditions, promise quick or “miraculous” results, push you to act now, or use scientific-sounding terms to impress you. It adds: “Your doctor or health provider is your best and most important source of information on whether a product is safe for you.”^[10]

If the sales page promises more than the label supports, trust the label.

Sources

1. Questions and answers on dietary supplements. U.S. Food and Drug Administration. Content current as of August 27, 2026. www.fda.gov
2. Dietary Supplement Labeling Guide: Chapter IV. Nutrition labeling. U.S. Food and Drug Administration. www.fda.gov
3. Dietary Supplement Labeling Guide: Chapter V. Ingredient labeling. U.S. Food and Drug Administration. www.fda.gov
4. Daily Value on the Nutrition and Supplement Facts labels. U.S. Food and Drug Administration. Content current as of March 5, 2024. www.fda.gov
5. Probiotics: fact sheet for consumers. NIH Office of Dietary Supplements. Updated November 17, 2025. ods.od.nih.gov
6. Probiotics: usefulness and safety. National Center for Complementary and Integrative Health (NIH). www.nccih.nih.gov
7. Draft guidance for industry: policy regarding quantitative labeling of dietary supplements containing live microbials. U.S. Food and Drug Administration. September 2018 (draft). www.fda.gov
8. Structure/function claims. U.S. Food and Drug Administration. Content current as of March 28, 2024. www.fda.gov
9. Dietary Supplement Label Database (DSLD): about the database. NIH Office of Dietary Supplements. dsld.od.nih.gov
10. Federal Trade Commission consumer advice on false health claims. November 2024. consumer.ftc.gov