How to Read a Supplement Label: What the Law Requires

What does the FDA actually approve before a supplement is sold?

The FDA approves nothing about a dietary supplement before it reaches a shelf. The Dietary Supplement Health and Education Act of 1994 (DSHEA, Public Law 103-417) placed supplements in a category separate from drugs, one in which the manufacturer rather than the government is responsible for establishing that a product is safe and its label truthful. There is no premarket review of effectiveness, and none of safety for ingredients already in commerce.

The single premarket step in the statute is narrow. Under 21 U.S.C. 350b, a manufacturer must notify the FDA at least 75 days before introducing a new dietary ingredient, defined as one not marketed in the United States before October 15, 1994. Ingredients sold before that date are grandfathered and require no notification. Notification is not approval, and the agency has no authority to grant or withhold one.

Removing a product afterward is slow, because DSHEA puts the burden of proof on the government. The FDA rule declaring supplements containing ephedrine alkaloids adulterated for presenting an unreasonable risk of illness or injury was published on February 11, 2004, a decade after the statute took effect. That timeline is the practical meaning of post-market regulation. Consumer health products regulated as medical devices follow a different route, and the first over-the-counter glucose sensors needed FDA clearance before sale.

What does the "not intended to diagnose, treat, cure, or prevent any disease" disclaimer mean?

The FDA disclaimer is a legal marker that the claim printed beside it has never been reviewed by a regulator. Under 21 CFR 101.93, any label carrying a structure/function claim, meaning a statement that an ingredient affects a structure or function of the body such as "supports immune health," must carry this exact wording: "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."

The regulation governs the format of the disclaimer rather than the substance of the claim. It must appear in boldface type no smaller than one-sixteenth of an inch, adjacent to the claim or linked to it by a symbol. The manufacturer must notify the FDA of the claim no later than 30 days after first marketing, which is after the product is already on sale. Nobody at the agency assesses whether the underlying claim is supported.

Advertising is policed on a separate track. The Federal Trade Commission's Health Products Compliance Guidance, issued in December 2022 to replace its 1998 supplement advertising guide, states that competent and reliable substantiation for a health-related claim generally means randomized, controlled human clinical testing. That standard governs the advertisement rather than the label.

How should a Supplement Facts panel be read?

The Supplement Facts panel is the only part of a supplement package whose contents are dictated by regulation, and it should be read before the front label. Four elements carry most of the information: serving size, servings per container, the amount per serving of each dietary ingredient, and the % Daily Value (%DV).

Serving size is set by the manufacturer rather than by a standard. A bottle listing a serving of two capsules and containing 60 capsules holds 30 servings, and every figure in the panel refers to two capsules. Products become comparable only on amount per day.

%DV states what proportion of an established daily reference amount one serving supplies, and many ingredients have no such amount. Under 21 CFR 101.36, a dietary ingredient for which the FDA has set no Daily Value carries a symbol in the %DV column pointing to a footnote reading "Daily Value not established." That footnote is standard on botanicals and amino acids, and it implies nothing about whether the dose is useful.

Below the panel sits the "Other ingredients" statement, required by 21 CFR 101.4. It lists everything not declared inside the panel: binders, fillers, flow agents, colors, sweeteners, and capsule material. Gelatin sources and allergens appear here rather than in Supplement Facts, which makes this the line to check when avoiding a specific excipient.

Why do the milligrams on the front not match the amount of mineral?

Mineral supplements are declared by elemental weight in the Supplement Facts panel, while the compound weight advertised elsewhere on the package can be several times larger. Calcium carbonate is roughly 40 percent elemental calcium and calcium citrate roughly 21 percent, so 1,250 mg of calcium carbonate supplies about 500 mg of calcium. The same arithmetic applies to magnesium and iron salts, where the anion contributes most of the compound's mass. Read the elemental figure inside the panel and disregard any larger number printed outside it.

What does a "proprietary blend" hide?

A proprietary blend is a labeling structure that discloses which ingredients are present without disclosing how much of each. Under 21 CFR 101.36, the blend must be identified by name, the total weight of the blend must be declared, and its ingredients must be listed in descending order of predominance by weight. Individual ingredient amounts inside the blend are not required.

A blend declared at 1,500 mg containing eight ingredients could consist almost entirely of the first one listed, with milligram traces of the rest, and the label would be fully compliant. Descending order reveals the ranking only. The ratio remains undisclosed, which means no published dose-response trial can be matched to the product with confidence.

Two features of the panel partly defeat the structure. Ingredients declared with their own amounts outside the blend remain fully specified. And a blend whose total weight falls below the studied dose of its first-listed ingredient cannot deliver that dose at any internal ratio.

What do USP, NSF, and Informed Sport certifications actually verify?

Third-party certification marks verify manufacturing quality and label accuracy. None of them evaluate whether an ingredient produces a health benefit, and the marks differ enough that they are not interchangeable:

• USP Verified (United States Pharmacopeia): confirms the product contains the ingredients declared on the label in the declared amounts, does not contain harmful levels of specified contaminants, and is made in a facility audited on site against FDA current Good Manufacturing Practice regulations at 21 CFR Part 111. USP also conducts off-the-shelf testing of verified products.
• NSF Contents Certified (NSF/ANSI 173): tests label claims and nutritional markers, heavy metals including arsenic, lead and mercury, pesticides, aflatoxins, and microbiological contaminants, plus compliance with federal Good Manufacturing Practice regulations. Screening for substances banned in sport is not part of this standard.
• NSF Certified for Sport: verifies that the product contains none of 290 substances banned by major athletic organizations, that contents match the label, that contaminants are not present at unsafe levels, and that manufacturing occurs in a GMP-certified facility audited annually or twice yearly.
• Informed Sport (LGC): screens for more than 285 substances banned in sport or considered contamination risks, in a laboratory accredited to ISO/IEC 17025, and states that every batch is tested before release to market.
• Informed Choice (LGC): applies the same substance screen but samples at least twelve lots per year at random from retail rather than testing every batch before release.

Testing frequency is the distinction that matters most for anyone subject to doping control, since a certificate covers the lots actually tested. A mark also applies to a specific product, not to a company, so certification of one item in a range says nothing about the others.

How often are supplements mislabeled or adulterated?

Adulteration is concentrated in a few product categories. A 2018 analysis in JAMA Network Open by Tucker and colleagues identified 776 dietary supplements containing unapproved pharmaceutical ingredients in FDA warnings issued from 2007 through 2016, traced to 146 companies. Sexual enhancement products accounted for 45.5 percent, weight loss for 40.9 percent, and muscle building for 11.9 percent, and 20.2 percent contained more than one unapproved ingredient. Only 360 of the 776 products, 46.4 percent, were associated with a voluntary recall.

Label accuracy also fails outside deliberate adulteration. A 2023 research letter in JAMA by Cohen and colleagues chemically analyzed 25 melatonin gummy products, a category sold to people trying to change how they sleep, and found 22 of 25, or 88 percent, inaccurately labeled, with measured melatonin ranging from 74 percent to 347 percent of the declared quantity. Three products fell within 10 percent of the label. One contained no detectable melatonin and 31.3 mg of cannabidiol.

Enforcement does not reliably clear affected products from the market. A 2014 JAMA research letter analyzed 27 supplements recalled between 2009 and 2012 that were still purchasable an average of 34 months after recall, and found 18 of 27, or 66.7 percent, still contained a banned drug. A 2022 JAMA research letter followed 31 supplements that received FDA warning letters over prohibited stimulants: one was recalled, nine remained for sale roughly six years later, and five of those nine still contained at least one prohibited ingredient on analysis.

These figures describe products that already drew regulatory attention or were selected for testing, not a random sample of the shelf. They establish that adulteration is common within specific categories. They do not support an estimate of how often any given multivitamin is contaminated.

What a supplement label cannot tell you

A supplement label carries no information about interactions with prescription medication, and no part of the required panel format asks for it. Geller and colleagues, in the New England Journal of Medicine in 2015, estimated 23,005 emergency department visits per year in the United States attributable to supplement-related adverse events (95% CI 18,611 to 27,398), based on 3,667 cases captured at 63 emergency departments from 2004 through 2013, with an estimated 2,154 hospitalizations annually. Those figures are surveillance associations rather than proof of causation.

Every label must provide a route to report harm. The Dietary Supplement and Nonprescription Drug Consumer Protection Act (Public Law 109-462), enacted December 22, 2006, requires a domestic address or telephone number on the label for reporting serious adverse events and requires the responsible firm to forward such reports to the FDA. The reporting requirement took effect December 22, 2007. A label lacking that contact information is out of compliance.

Supplement use is close to universal. National Center for Health Statistics data from the 2017 to 2018 NHANES cycle found 57.6 percent of US adults aged 20 and over had used a dietary supplement in the previous 30 days, rising to 80.2 percent among women aged 60 and over. Anyone taking prescription medication, pregnant or nursing, or scheduled for surgery should review supplement use with a clinician, because the label will not flag an interaction.