How to read a Supplement Facts label
Every dietary supplement sold in the United States carries a Supplement Facts panel. Read it in the order below and you will know what one serving contains, how much of it, and where the label leaves gaps.
Start with the serving size
Every number on the panel is for one serving, and a serving is whatever the manufacturer says it is: one scoop, two capsules, or one stick pack. A product that looks generous may only be generous at three capsules a day.
Check servings per container next. You need it to work out the real cost per serving, which is the only fair way to compare products of different sizes.
Read "amount per serving" and "% Daily Value" together
The amount column tells you how much of each ingredient is in a serving. The % Daily Value (% DV) column compares that amount with the reference daily amount the U.S. Food and Drug Administration (FDA) sets for that nutrient.
- Around 100% DV means one serving supplies roughly a full day's reference amount of that nutrient.
- Well above 100% DV is common for some vitamins. It isn't automatically a problem, but it is a reason to check what else you take (see upper limits below).
- A symbol instead of a percentage, usually a dagger or asterisk, means no Daily Value has been set for that ingredient. Herbal extracts, probiotics and many "greens" ingredients fall into this group.
Look at the form of each ingredient
Labels often name the form a vitamin or mineral comes in, for example magnesium (as magnesium citrate) or vitamin D3 (as cholecalciferol). Different forms can differ in how well the body absorbs them and how they are tolerated. The form won't tell you whether a product is right for you, but its absence is worth noticing: a brand that names its forms is giving you more to check.
Be careful with proprietary blends
A proprietary blend is a group of ingredients listed under one name, such as "Superfood Blend 4.2 g". U.S. rules require the blend's total weight and require its ingredients to be listed in descending order by weight, but not the amount of each ingredient.
That means you can't tell whether an ingredient near the end of the list is present in a meaningful amount. If a specific ingredient matters to you, prefer products that list its amount on its own line.
Read "other ingredients"
Below the panel you'll find everything else in the product: flavours, sweeteners, thickeners, capsule materials and anti-caking agents. This is where to look for added sugar, sugar alcohols, artificial sweeteners and allergens.
Add it up across everything you take
For many vitamins and minerals, the U.S. National Academies have set a Tolerable Upper Intake Level (UL): the highest daily amount from all sources, food included, that is unlikely to cause harm for most adults. Vitamin A, vitamin D, iron, zinc and niacin are examples with established limits.
Upper limits matter most when you combine products. An all-in-one powder plus a separate multivitamin plus a fortified breakfast cereal can add up faster than any single label suggests. The NIH Office of Dietary Supplements publishes the UL for each nutrient in its health professional fact sheets.
Know what the label does not prove
The FDA does not approve dietary supplements for safety or effectiveness before they are sold. Manufacturers are responsible for what is in the product and for the accuracy of the label. If you want independent evidence that the contents match the label, look for third-party certification, which we explain in a separate guide.
If you are pregnant or nursing, take prescription medication, or have a medical condition, show the label to your doctor or pharmacist before you start a new supplement. Some ingredients interact with medicines.
Sources
- U.S. Food and Drug Administration, Dietary Supplements.
- NIH Office of Dietary Supplements, Dietary Supplements: What You Need to Know.