Independent supplement ratingsUS and Canada · Updated weekly
A ratings desk for a category that has spent thirty years grading its own homework.
A ratings desk for a category that has spent thirty years grading its own homework.
The five lines that tell you whether a product is worth buying — and the one that hides the truth.
A supplement label is a legal document dressed up as packaging. Almost everything on the front is marketing; almost everything that matters is on the back, in six-point type. Here is how to read the back in under a minute.
In the United States, dietary supplements are not approved by the FDA before they are sold. Under the 1994 DSHEA law, the manufacturer is responsible for making sure its product is safe and its label is truthful — the FDA mostly acts after something goes wrong. That is why the label is your only real inspection point, and why the small print is where the honesty lives. (FDA, Questions and Answers on Dietary Supplements)
Every number in the Supplement Facts panel is per serving, and the manufacturer decides what a serving is. "Serving size: 4 capsules" is the oldest trick in the category: the impressive milligram figures on the panel are what you get from four capsules, while the bottle of 60 is quietly a fifteen-day supply. Divide the price by servings, not by capsules, and divide the doses by capsules before you compare anything.
A mineral on a label is a compound, and only part of that compound is the mineral you actually want. "Magnesium oxide 500 mg" is 500 mg of the compound; the elemental magnesium inside it is roughly 300 mg, and very little of that is absorbed. A well-made label gives you the elemental figure, usually in brackets. A label that only shows compound weight is either careless or counting on you not knowing the difference. Our dose bars track elemental figures for exactly this reason — see the magnesium ranking for what the gap looks like in practice.
A "proprietary blend" lets a brand declare the total weight of a group of ingredients and list what is in it in descending order by weight, without ever disclosing how much of each. That is not a loophole someone found; it is written into the regulation, at 21 CFR 101.36. (eCFR, 21 CFR 101.36)
The practical consequence: a 1,200 mg "Testosterone Support Matrix" can be 1,150 mg of a cheap filler and a decorative pinch of everything the front of the box is shouting about. Descending order is the only clue you get — whatever is listed first is the biggest part of the blend. If the ingredient you are buying the product for is listed fourth, you are buying a rumour of it.
One useful limit: vitamins and minerals with an established Daily Value cannot be buried inside a blend. They have to be declared individually with real amounts. So a blend that hides its herbs but names its zinc is behaving normally, not generously.
Ingredients with an established Daily Value show a percentage. Everything else — most herbs, most amino acids, most of what makes a product interesting — carries a dagger (†) and the footnote "Daily Value not established". That symbol is neutral: it means science has not set a reference intake, not that the ingredient is junk. But it also means the % DV column cannot tell you whether the dose is useful. Only the research can, which is what our ingredient index and the Label Dose Checker are for.
Below the panel sits the "Other ingredients" line: capsule shell, rice flour, magnesium stearate, silicon dioxide, colours, sweeteners. Mostly boring and mostly harmless — but it is where you find the gelatin if you avoid it, the added sugar in a drink mix, and the allergens.
Under that, in the smallest type on the package: "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." That disclaimer is legally required whenever a product makes a structure/function claim — "supports healthy testosterone levels", "promotes restful sleep". Its presence is normal. Its usefulness is as a translation key: it tells you the claim above it was written to stay on the legal side of a line, not to describe a proven effect.
Written and fact-checked by the NFS editorial team · Educational only — not medical advice.