How to Choose a Protein Powder

Protein powder looks like one product on the shelf, but tubs differ in the protein source, how much protein a serving supplies, what else goes in, and whether anyone outside the company has checked a batch. This guide sets out what to check before you buy, for healthy adults. If you are under 18, pregnant or breastfeeding, have kidney disease or take regular medicines, read the cautions near the end first.

The criteria come from named public sources: the Food and Drug Administration (FDA), the Dietary Guidelines for Americans 2025–2030, the National Institutes of Health (NIH), the U.S. Anti-Doping Agency (USADA), the International Society of Sports Nutrition (ISSN) and the nonprofit Consumer Reports. We do not rank products or rate brands. Amazon links open searches built from the criteria, and you check each listing against its label.

Decide whether you need a powder at all

A powder is a convenience, not a requirement. The Dietary Guidelines set a protein goal of 1.2 to 1.6 grams per kilogram of body weight a day and tell people to prioritize protein foods at every meal, naming eggs, poultry, seafood, red meat, beans, lentils, nuts, seeds and soy. Consumer Reports, citing researchers it interviewed, says most people can get enough protein from food alone. Our guide to how much protein you need turns the numbers into grams. A powder can still fill a gap: the ISSN calls supplemental protein a safe and convenient option for exercising people, although several of its authors disclose ties to protein-supplement companies.

Choose a protein source

Whey and casein are the two proteins in milk; soy, pea and rice are the common plant sources. The ISSN describes whey as quickly digested and casein as slowly digested. A 2021 systematic review found that protein source did not change gains in absolute lean mass or strength, although animal protein did better on percent lean mass. Our guide to whey, casein and plant proteins compares them. Three searches to start from: whey protein isolate on Amazon (opens in a new tab), micellar casein on Amazon (opens in a new tab) and pea protein on Amazon (opens in a new tab).

Count the protein in one serving

Read the serving size in grams and the grams of protein, then divide. A powder that lists 24 g of protein in a 31 g serving is about 77% protein by weight, and 20 g in a 30 g serving is about 67%. U.S. labels give amounts per serving, so you do the sum yourself. Two cautions from the rules: FDA's regulation lets a maker calculate protein as 6.25 times the nitrogen content, so the figure alone does not show where the nitrogen came from, and a Supplement Facts panel may declare a "proprietary blend" as one total weight. Our guide to reading a protein powder label works through both.

Check the sweeteners and the allergens

Flavored powders add sweeteners, flavorings and thickeners. FDA has approved six high-intensity sweeteners as food additives, including aspartame (foods with it must state "PHENYLKETONURICS: CONTAINS PHENYLALANINE") and sucralose, and has received "generally recognized as safe" notices for certain stevia and monk-fruit extracts. The Dietary Guidelines say to limit foods with low-calorie non-nutritive sweeteners. Using one is your decision, and an unflavored powder avoids the question: unflavored whey protein on Amazon (opens in a new tab) is a search for them.

Milk and soy are two of the nine major food allergens that U.S. law requires to be declared, and FDA enforces the rule on dietary supplements too. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) lists protein powders among products that can contain lactose, and says the words milk, lactose and whey in an ingredient list mean the product does. See our guide to the nine major allergens.

Look for independent testing

FDA cannot approve dietary supplements for safety and effectiveness before they are sold, and says it does not routinely analyze their contents. USADA says no supplement can be guaranteed risk-free. For drug-tested athletes it recommends third-party certified products and names NSF Certified for Sport as the program best suited, adding that this significantly reduces, but does not necessarily eliminate, the chance of a positive test. It advises matching the lot number on your tub to NSF's database.

NSF says its program verifies that a product has no banned substances, that the label matches the contents, that contaminants are not at unsafe levels and that the plant follows good manufacturing practice. LGC's Informed Sport says every batch is tested for banned substances before release, and its Informed Protein says it verifies the protein amount and screens for amino spiking, the addition of free amino acids or other non-protein nitrogen to inflate the figure. These are the programs' own descriptions: find the logo, then check the lot on the certifier's website. NSF Certified for Sport protein powder on Amazon (opens in a new tab) matches words only, so confirm the mark on the pack.

Heavy metals: what 2025 testing found

In October 2025 Consumer Reports (CR) published lead results for 23 protein powders and shakes, testing two to four lots of each. For more than two-thirds, one serving held more lead than CR's level of concern, set at 0.5 micrograms a day from California's Proposition 65 limit. The plant-based products, all built on pea protein, averaged about nine times the lead of the dairy-based ones, and CR did not establish why. Dairy-based products generally had the lowest levels, but several were also above that level. An industry group, the Council for Responsible Nutrition, replied that exceeding CR's own threshold is not exceeding a government limit. There is no federal limit for lead in protein powders; FDA's interim reference levels, which are benchmarks rather than rules, are 2.2 micrograms a day for children and 8.8 for women of childbearing age. CR advises against daily use of most powders and against labels with Proposition 65 warnings, and suggests checking whether a maker publishes heavy-metal results. Its results are listed by product and flavor, so read its page for a specific tub instead of judging by brand.

Be wary of big claims

A supplement label may carry a structure/function claim, about a nutrient's role in the body, without FDA pre-approval. It needs a disclaimer that FDA has not evaluated the claim 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. USADA, citing FDA, says muscle-building products are among those most often found spiked with drugs, so treat dramatic promises with suspicion.

Two examples of how the criteria read on a maker's page

These are examples, not recommendations or a ranking. The descriptions are in our words from each manufacturer's page, which changes, so check the pack you receive.

• Optimum Nutrition Gold Standard 100% Whey. The page states 24 g of protein and 5.5 g of naturally occurring BCAAs per serving and names whey protein isolate as the primary source. The page lists "Banned Substance Tested" but names no certifier, so look at the pack. CR's chart puts this powder in chocolate below its lead level of concern, and the same brand's Gold Standard Protein Shake above it. Search Amazon for this product (opens in a new tab).
• Transparent Labs Grass-Fed Whey Protein Isolate. The page states 28 g of protein per serving and an 87.5% protein-by-weight figure that may vary slightly by flavor, lists an unflavored option and links to third-party certificates of analysis. CR says Transparent Labs told it that it publishes heavy-metal results. Search Amazon for this product (opens in a new tab).

Who should speak to a doctor, pharmacist or dietitian first

• Kidney disease. The ISSN calls concern about higher protein intakes harming healthy, exercising people unfounded, but NIDDK says some people with chronic kidney disease may need moderate protein and should work with a dietitian or health care professional.
• Pregnant or breastfeeding, or buying for a child. NIH's National Center for Complementary and Integrative Health notes that many supplements have not been tested in pregnant women, nursing mothers or children. The American Academy of Pediatrics says most young athletes with a well-balanced diet do not need and would not benefit from protein supplements.
• Medicines or a diagnosed condition. FDA advises asking your doctor, pharmacist or other health care professional before using a supplement.
• Milk or soy allergy, or phenylketonuria. Read the allergen statement and sweetener names every time.

Where the links go

Links marked "on Amazon" or "Search Amazon" open an Amazon search for the words in the link. Amazon decides what appears, and results can include products that do not meet the criteria above. Check who sells and ships a listing, that the tub arrives sealed, and that it shows a lot number, which you need to look a product up with a certifier.

Read next

• Whey, casein and plant proteins: how the sources differ.
• How much protein you need: the RDA and the guidelines.
• How to read a protein powder label: serving math and marks.

For protein in everyday foods, see our list of high-protein products and our guide to protein claims.

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.