How to Read a Protein Powder Label

Two tubs can both say "24 g protein" and be different products. This guide walks through a U.S. protein powder label in the order to read it: the kind of panel, the serving, the protein figure, the other nutrients, the ingredients and the marks. It is general information for healthy adults, and it applies the rules of the Food and Drug Administration (FDA). For the wider set of buying checks, see our protein powder buying guide.

Supplement Facts or Nutrition Facts

A powder is sold either as a dietary supplement or as a conventional food, and the panel tells you which. FDA says a product is a dietary supplement only if its label identifies it as one and it is not represented as a conventional food or as the sole item of a meal or the diet. A supplement carries a Supplement Facts panel with the serving size, servings per container and each dietary ingredient, plus an "Other Ingredients" list. A food carries a Nutrition Facts panel, which our guide to the Nutrition Facts label covers. FDA does not approve dietary supplements before they are sold. A supplement label must also show the maker's name and place of business, the net quantity, and a domestic address or phone number for reporting serious adverse events.

Serving size first

Everything on the panel is per serving, and the maker chooses the serving size: FDA says no regulation limits the size of a supplement serving or the amount of an ingredient in it. Scoops vary from tub to tub, so read the weight in grams. A scale confirms what a level scoop holds: a digital kitchen scale on Amazon (opens in a new tab) is a search for them. Then check servings per container, since a larger tub is not always more servings.

Protein per serving and per 100 g

Divide the grams of protein by the serving size in grams and multiply by 100 to get protein per 100 g, the unit our protein ranking uses. For example, 24 g of protein in a 31 g serving is 24 ÷ 31 × 100, about 77 g per 100 g. A powder with 20 g in a 30 g serving is about 67 g per 100 g. The U.S. Dairy Export Council defines whey protein isolate as at least 90% protein, so a flavored powder with sweeteners and thickeners lands lower, and a figure well above the isolate range (the USDEC gives 90% to 92% as typical) would deserve a question. The same arithmetic gives a cost check: divide the price you see by the number of servings times the protein per serving to get a cost per gram of protein.

How the protein number is measured

FDA's labeling regulation says protein content may be calculated as 6.25 times the nitrogen content of the food, measured by an AOAC method. That is a nitrogen count. LGC, which sells the Informed Protein certification, states that the common nitrogen tests (Dumas and Kjeldahl) determine total nitrogen, not true protein, so any nitrogen-containing compound could raise the figure without adding protein. It calls adding free-form amino acids to boost the apparent protein amino spiking, and screens for it. LGC is describing its own service, so treat that as the program's view. The practical step is to read the ingredient list: if free-form amino acids appear in the ingredients beside the protein, the panel does not tell you whether the protein figure includes them.

%DV, claims and blends

When a Supplement Facts panel shows a percent Daily Value for protein, it is calculated on a quality-corrected amount, using an amino acid score corrected for digestibility. A %DV well below what the grams suggest points to a lower-quality protein; our guide to percent Daily Value explains the column. A "proprietary blend" is listed as one total weight, with its parts in descending order of predominance by weight, so the amount of each part is not given. If protein sits in a blend, the serving may hold less of it than the headline suggests. FDA defines claims such as "high protein" in its nutrient content claim rules; see protein claims decoded.

Calories, sugar and sweeteners

Check calories, carbohydrate, fat and added sugars per serving, because serving sizes and calories vary widely between a plain isolate and a "mass gainer" style product. For sweeteners, FDA says high-intensity sweeteners can be identified by name in the ingredient list, and lists six approved as food additives: saccharin, aspartame, acesulfame potassium, sucralose, neotame and advantame, with "generally recognized as safe" (GRAS) notices received for certain stevia-leaf and monk-fruit extracts. The Dietary Guidelines for Americans 2025–2030 say to limit foods with low-calorie non-nutritive sweeteners. Sugar alcohols are covered in our sweeteners guide. Anything containing aspartame must state "PHENYLKETONURICS: CONTAINS PHENYLALANINE". An unflavored powder avoids the question: unflavored whey protein on Amazon (opens in a new tab).

Allergens

Milk and soy are two of the nine major allergens, and FDA enforces declaration of them on dietary supplements. Look for a "Contains" line or an allergen named in parentheses in the ingredient list. Statements such as "may contain" or "made in a facility that also uses" are not required by law, so their absence does not prove a product is free of cross-contact. Formulas change by flavor and size, so read the pack you hold.

Testing marks

A mark covers what its certifier says it covers, so read the certifier's own page. NSF says its Certified for Sport program verifies no banned substances, a label that matches the contents, no unsafe levels of contaminants and a good-manufacturing-practice facility. LGC says Informed Sport tests every batch for banned substances before release, and that Informed Protein verifies the protein amount. The U.S. Anti-Doping Agency advises matching the lot number on your tub to the certifier's database, and says certification significantly reduces, but does not necessarily eliminate, risk. A mark is not a promise about every concern, and Consumer Reports notes there is no federal limit for heavy metals in protein powders, so ask a maker whether it publishes its own results. Try NSF Certified for Sport protein powder on Amazon (opens in a new tab) to see what carries the mark, and confirm it on the pack and in the database.

Claims on the front

A supplement may carry a structure/function claim without FDA pre-approval, with a disclaimer that FDA has not evaluated it and that the product is not intended to diagnose, treat, cure or prevent any disease. The Federal Trade Commission's guidance says health claims need competent and reliable scientific evidence. Treat the front as marketing and the panel as the label.

The label on the pack in front of you is the authority on serving size, ingredients and warnings, ahead of any article, this one included. If you have a health condition or take medicines, ask your doctor, pharmacist or a registered dietitian before you start. FDA asks people to report a product problem through its Safety Reporting Portal.