How to Read a Supplement Label Without Getting Fooled

Walk into almost any pharmacy from Kittery to Presque Isle and you hit a wall of bottles before you reach the prescription counter. Vitamins by the registers at the outdoor outfitter. Fish oil next to the antacids. Greens powders that promise the energy of a salad you do not have to chew. Plenty of Mainers buy them: nationally, the CDC reported that 57.6% of US adults used a dietary supplement during 2017 to 2018, and among women aged 60 and over that figure climbed to 80.2%. The bottle in your hand follows the same federal rules whether you grab it in Portland or in Conway. Knowing how to read it is the difference between an informed purchase and an expensive guess.

Nobody approved this before it hit the shelf

Start with the assumption most shoppers get backwards. Prescription drugs and over-the-counter medicines are reviewed by the Food and Drug Administration before they can be sold. Dietary supplements are not. Under the law that governs them (the 1994 Dietary Supplement Health and Education Act), the manufacturer, not the FDA, is responsible for making sure a product is safe and honestly labeled before it goes to market. The FDA itself says that in many cases a company can put a supplement on sale without even notifying the agency first. The FDA mostly steps in after the fact, once a problem surfaces.

That does not make supplements dangerous. It does mean the burden of judgment lands on you, at the shelf, with a bottle and your phone. The label is your main tool.

The Supplement Facts panel and the %DV

Flip the bottle over. Every supplement carries a Supplement Facts panel, which the FDA requires to list the serving size, the ingredients, the amount per serving, and the percent Daily Value, or %DV, for any nutrient that has an established Daily Value. It is the same idea as the Nutrition Facts panel on a box of cereal.

The %DV tells you how much one serving contributes to a day’s worth of that nutrient. If the Daily Value is 300 micrograms and a serving gives you 30, the panel reads 10%. Quick math, useful at a glance. Watch the serving size while you do it, because “two gummies” doubles everything you just read.

Botanicals and many other ingredients have no established Daily Value. Those still have to be listed by name with their amount, but in the %DV column you will see a small symbol pointing to a footnote that reads “Daily Value Not Established.” That is not a red flag. It just means science has not set a daily target for that ingredient, so the number is on you to research.

What the front of the bottle is allowed to say

The front is marketing. The claims there fall into a category the FDA calls structure/function claims, lines like “supports immune health” or “promotes healthy joints.” These are not pre-approved. A company can print them as long as it holds evidence the claim is truthful and not misleading, and it has to notify the FDA within 30 days of first selling the product.

The tell is the fine print. Any product making one of those claims has to carry this exact disclaimer near the panel: “This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.” If you see that sentence, you are looking at a claim the government never vetted. Read it as a hypothesis, not a guarantee.

Proprietary blends, where the label hides the math

This is the one that trips up careful shoppers. When ingredients are grouped into a “proprietary blend,” the label only has to state the total weight of the whole blend. It lists the individual ingredients in order from most to least by weight, but it does not have to tell you how much of each one is in there.

So a blend might total 500 milligrams and name eight impressive-sounding botanicals. The first one could be 480 milligrams and the other seven a sprinkle each, just enough to put the name on the label. You cannot tell. The industry nickname for that sprinkle is fairy dusting. When you see “proprietary blend” with no per-ingredient amounts, treat it as a question the company chose not to answer. Greens powders lean on this especially hard, which is why our greens powders review digs in further.

The same nutrient is not always the same nutrient

Two bottles can both shout “Calcium” on the front and deliver very different things. FDA rules require the label to name the specific source compound, so you will see something like “Calcium (as calcium carbonate).” That parenthetical matters. Different source forms absorb differently and suit different people, and the listed amount reflects the nutrient itself, not the heavier source compound it rides in on.

Vitamin D is the classic Maine example, where the choice between D3 and D2 is not just branding. We get into that head-to-head in our piece on vitamin D3 versus D2. Fish oil is another, where “1,000 mg of fish oil” and the actual EPA and DHA content can be wildly different numbers, something our fish oil label guide walks through. The headline ingredient is the start of the question, not the answer.

The seals worth trusting

Because nobody checks the bottle before it sells, a few independent groups check it for you and stamp the ones that pass. The two names worth knowing on a Maine shelf are USP and NSF.

A USP Verified Mark means the product actually contains the listed ingredients, at the stated potency and amount, without harmful levels of contaminants like heavy metals, and that it will dissolve and release in your body within a set time, made under the FDA’s manufacturing standards. NSF runs a similar certification. For athletes, or anyone subject to drug testing, NSF Certified for Sport goes further and screens against roughly 290 banned substances. The US Anti-Doping Agency recognizes it as the program best suited to lower supplement risk, and the NFL and PGA recommend it. USADA notes the seal significantly reduces, but does not entirely eliminate, the chance of a positive test.

None of these seals judge whether the supplement works for you. They verify that what is in the bottle matches what is on the label. Given how often that is not true, that alone is worth a lot.

Why the seal matters: the label can lie

Consider melatonin, a staple of the long Maine winter when daylight quits around four in the afternoon. A 2023 analysis published in JAMA tested 25 melatonin gummy products and found 22 of them, 88%, were inaccurately labeled. The actual melatonin ranged from 74% to 347% of what the label claimed. One product had no detectable melatonin at all. Another, labeled for a modest dose, contained more than three times that amount.

That is the predictable result of a market where nobody verifies the bottle before it sells. It is also the argument for the boring stuff: read the panel, decode the claims, distrust blends that hide their math, and lean toward products carrying a third-party seal. If you are weighing whether a daily multivitamin earns its place in the cabinet at all, our multivitamin review looks at what the big trials found.

One last thing for the register. Under Maine law, vitamins and supplements are left out of the grocery-staples sales-tax exemption unless a physician prescribes them, so they get taxed at the state’s general 5.5% rate, the same as a toaster. New Hampshire, with no general sales tax, charges nothing extra. The pricing math differs on either side of the river. The label rules, and the homework they ask of you, do not.

Sources

• U.S. Food and Drug Administration. Questions and Answers on Dietary Supplements. 2022. https://www.fda.gov/food/information-consumers-using-dietary-supplements/questions-and-answers-dietary-supplements
• U.S. Food and Drug Administration. Dietary Supplement Labeling Guide: Chapter IV. Nutrition Labeling. 2024. https://www.fda.gov/food/dietary-supplements-guidance-documents-regulatory-information/dietary-supplement-labeling-guide-chapter-iv-nutrition-labeling
• U.S. Food and Drug Administration. Daily Value on the Nutrition and Supplement Facts Labels. 2024. https://www.fda.gov/food/nutrition-facts-label/daily-value-nutrition-and-supplement-facts-labels
• U.S. Food and Drug Administration. Structure/Function Claims. 2022. https://www.fda.gov/food/nutrition-food-labeling-and-critical-foods/structurefunction-claims
• Electronic Code of Federal Regulations (eCFR). 21 CFR 101.93 – Certain types of statements for dietary supplements. 2024. https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-101/subpart-F/section-101.93
• Electronic Code of Federal Regulations (eCFR). 21 CFR 101.36 – Nutrition labeling of dietary supplements. 2024. https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-101/subpart-C/section-101.36
• U.S. Food and Drug Administration. Dietary Supplement Labeling Guide: Chapter V. Ingredient Labeling. 2024. https://www.fda.gov/food/dietary-supplements-guidance-documents-regulatory-information/dietary-supplement-labeling-guide-chapter-v-ingredient-labeling
• U.S. Pharmacopeia (USP). Dietary Supplement Manufacturing – USP Verified Mark. 2024. https://www.usp.org/verification-services/verified-mark
• NSF. Dietary Supplement and Vitamin Certification. 2024. https://www.nsf.org/consumer-resources/articles/supplement-vitamin-certification
• NSF. Certified for Sport Program. 2024. https://www.nsf.org/consumer-resources/articles/certified-for-sport-program
• U.S. Anti-Doping Agency (USADA). Reduce Your Supplement Risk with NSF Certified for Sport. 2023. https://www.usada.org/substances/supplement-connect/reduce-risk-testing-positive-experiencing-adverse-health-effects/
• JAMA (research letter) / National Library of Medicine (PMC). Quantity of Melatonin and CBD in Melatonin Gummies Sold in the US. 2023. https://pmc.ncbi.nlm.nih.gov/articles/PMC10130950/
• CDC National Center for Health Statistics. Dietary Supplement Use Among Adults: United States, 2017-2018 (NCHS Data Brief No. 399). 2021. https://www.cdc.gov/nchs/products/databriefs/db399.htm
• Maine Revenue Services. Retailers of Food Products (Instructional Bulletin No. 12). 2020. https://www.maine.gov/future/sites/maine.gov.revenue/files/inline-files/IB12RetailersofFoodProducts022020.pdf

This article is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare provider before making any health decisions.