Third-Party Tested Supplements: What USP, NSF and Informed Sport Seals Actually Verify

The protein tub sits on the gym counter, and a phone is being passed around. On the screen is a viral post claiming that a popular powder is “full of lead.” Someone asks the obvious question: how would anyone actually know? As of early 2026, that question is being typed into search engines at a pace not seen in years, driven by a run of independent heavy-metal reports on protein and creatine products, a widely shared study showing melatonin gummies that contained far more or far less than their labels promised, and a steady stream of athletes who tested positive after taking a product they trusted.

Third party tested supplements are the industry’s answer to that unease, and the answer is partly good. A seal from USP, NSF or Informed Sport means an outside laboratory checked the product. The trouble is that each seal checks something different, and none of them checks the thing people most want to know: whether the supplement will do them any good.

This piece walks through what each program verifies, what it leaves out, and how to read a bottle like a chemist would.

What are third-party tested supplements, and what does the seal promise?

A third-party tested supplement is one that has been analyzed by a laboratory with no financial stake in the sale of the product. The manufacturer did not run the test, and neither did the retailer. That independence is the whole point. A company that tests its own powder has every incentive to report good news; an outside certifier that stakes its reputation on a seal has an incentive to find problems.

The three seals most shoppers in the United States encounter are USP Verified, from the United States Pharmacopeia, a nonprofit that writes quality standards used by medicine manufacturers worldwide; NSF Certified, from NSF, a nonprofit public-health certifier; and Informed Sport, run by a sports-nutrition testing lab. Each seal is a short promise about four things:

• Identity: the ingredient in the bottle is the one on the label, not a cheaper substitute.
• Potency: the amount present matches the amount declared, within an allowed range.
• Purity: contaminants such as heavy metals, pesticides, solvents and microbes sit below accepted limits.
• Process: the factory follows good manufacturing practice, a set of rules governing cleanliness, record-keeping and ingredient checks.

Sport-focused seals add a fifth promise: screening for substances prohibited in competitive athletics.

Notice what is missing. No seal promises that the supplement improves health, prevents disease or does anything at all. A perfectly certified vitamin can still be one you do not need, or one that interacts with a medicine you take. The seal is a quality-control statement, closer to a food-safety inspection grade than to a clinical endorsement. Keeping that distinction in mind is the single most useful habit a supplement buyer can build.

Why supplements need outside checking in the first place

In the United States, dietary supplements are regulated as a category of food, not as medicines. Under the Dietary Supplement Health and Education Act of 1994, a company does not need approval from the Food and Drug Administration before selling a vitamin, mineral, herb or protein powder. The FDA can act after a product reaches shelves, when it finds a problem, but it does not review safety or label accuracy in advance. The National Institutes of Health Office of Dietary Supplements states this plainly in its consumer guide: the manufacturer, not the government, is responsible for making sure a product is safe and accurately labeled.

Manufacturers are required to follow current good manufacturing practice, abbreviated cGMP, which is a federal rulebook covering everything from how raw ingredients are confirmed to how batches are recorded. Those rules do oblige companies to test the identity of incoming ingredients. They do not oblige anyone outside the company to look at the results. The FDA inspects a portion of facilities each year, and inspection reports regularly cite firms that failed to verify ingredient identity or to test finished products.

The United Kingdom takes a similar approach, regulating most supplements as foods, which is why the NHS advises that supplements sold there should be treated as food products rather than as medicines with proven effects.

The practical result is a market where the honest and the careless sit on the same shelf, wearing similar labels. A certifier’s seal is one of the few signals available to a shopper that someone outside the company opened the bottle and checked. It is not a perfect signal, but it exists because the regulatory system leaves a gap that most people assume is already filled.

What changed recently

Several developments explain why third-party testing has moved from an industry conversation to a dinner-table one.

In April 2023, a study published in a major medical journal analyzed melatonin gummies sold in the United States and reported that most were inaccurately labeled, with measured melatonin content ranging from roughly 74 percent to 347 percent of the declared amount, and one product containing a cannabis-derived compound instead. The figures circulated widely because gummies are marketed to parents, and because the gap between label and contents was so large.

In March 2023, the FDA launched its Dietary Supplement Ingredient Directory, a public list that tells consumers whether the agency has taken action or raised concerns about specific ingredients. It does not certify products, but it gives shoppers a government source to check against marketing claims.

The NIH Office of Dietary Supplements continues to expand its Dietary Supplement Label Database, which now holds label information for well over a hundred thousand products, searchable by ingredient and brand. The ODS consumer fact sheet, updated in recent years, explicitly recommends looking for independent quality seals and names USP, NSF and ConsumerLab-style programs as examples of what to look for.

On the sport side, the World Anti-Doping Agency publishes a revised Prohibited List that takes effect on January 1 each year, which means sport-certification programs must update their screening panels annually. A product certified under last year’s panel has, in principle, been checked against a slightly different list than one certified this year.

Mayo Clinic’s supplement guidance, likewise refreshed in recent years, now tells readers to look for seals from USP, NSF or similar independent organizations as a way to judge manufacturing quality. When conservative, mainstream medical sources converge on the same advice, it usually reflects a settled consensus rather than a trend.

USP Verified vs NSF Certified: what each program actually checks

The two most common general-purpose seals look similar on a bottle and are often treated as interchangeable. They overlap heavily, but the details differ.

USP Verified is awarded after a product passes four categories of testing. The ingredients on the label must be present in the declared amounts. The product must be free of harmful levels of specified contaminants, including heavy metals, pesticides and microbes. A tablet or capsule must break apart within a set time in a laboratory test called disintegration, which matters because a pill that passes through the body intact delivers nothing. The manufacturing facility must comply with FDA good manufacturing practice, confirmed by a USP audit. After certification, USP buys products from retail shelves and retests them, which catches drift between the sample a company submits and the product people actually buy.

NSF Certified, built on a public standard called NSF/ANSI 173, covers similar ground. Label contents are verified, contaminants are screened, and the manufacturing facility is audited, with annual follow-up inspections and periodic retesting of products. NSF also reviews formulation to confirm it does not contain ingredients that exceed accepted safety thresholds.

Where they diverge is emphasis. USP leans on its pharmacopeial heritage, applying monographs, which are published specifications for how a given ingredient should be identified and measured, and it places weight on disintegration. NSF’s standard was written for the supplement industry specifically and includes more formulation review. In practice, a product carrying either seal has cleared a meaningful bar. Neither program certifies every product category: proprietary herbal blends with no validated test method, for instance, may be ineligible for USP verification, which is one reason you see USP seals mainly on vitamins, minerals and single-ingredient products.

NSF Certified for Sport meaning: the banned-substance layer

NSF Certified for Sport is a separate, stricter program layered on top of standard NSF certification. It exists because an athlete who tests positive is held responsible regardless of intent, and because supplements have been a documented source of inadvertent positives for decades.

Every product in the program is first certified to the general NSF standard for label accuracy and contaminants. Then each lot, meaning each production batch, is screened for roughly 280 substances banned by major sporting bodies, including anabolic agents, stimulants, diuretics, masking agents and certain hormones. The screening uses analytical chemistry methods sensitive enough to detect trace contamination, which matters because cross-contamination in a factory that also handles prohibited ingredients can leave residues far below any level a label would ever declare.

Two features distinguish the sport program from the general seal. The first is lot-by-lot testing rather than periodic sampling; a batch cannot carry the mark until its own test comes back clean. The second is a public, searchable database where anyone can type a product name and confirm whether that specific product, in that specific flavor and size, holds current certification. Several professional leagues and anti-doping bodies in North America recognize the program, and some recommend that their athletes use only products that appear in it.

The meaning for a non-athlete is narrower than the marketing sometimes implies. A banned-substance screen tells you a product does not contain stimulants or steroid-like compounds at detectable levels. That is reassuring for anyone, since hidden stimulants are a real cause of adverse events reported to the FDA. It does not, however, tell you anything about whether the protein, creatine or electrolyte formula inside performs as advertised. The seal answers a contamination question, not a performance question.

Informed Sport certified supplements: every batch, before release

Informed Sport is a certification run by a laboratory accredited for anti-doping analysis, and it is the program most often seen on products sold in the United Kingdom, Europe and Australia, though it appears increasingly on American shelves. Its defining feature is that every batch of a certified product is tested for banned substances before it is released for sale. If a batch fails, it never carries the logo.

The screening panel covers substances on the World Anti-Doping Agency Prohibited List, with the testing lab updating its methods as the list changes each January. The program also audits the manufacturing site and reviews raw-material sourcing, since many contamination incidents trace back to a single compromised ingredient supplier rather than to the finished-product factory.

The same organization runs a sister program, Informed Choice, which is less intensive. Under Informed Choice, products are tested through blind retail purchases on a regular schedule rather than batch by batch. Both logos look alike at a glance, so it is worth reading the small print: a product bearing Informed Choice has been sampled; a product bearing Informed Sport has had its specific batch cleared.

For shoppers, the useful habit is to find the batch or lot number printed on the package and check it in the Informed Sport online database, which lists certified batches by product. If the number is not there, the batch in your hand was not tested under the program, even if an earlier batch was.

As with NSF Certified for Sport, the Informed Sport logo speaks only to contamination and banned substances. It does not evaluate whether the amounts of protein, caffeine or vitamins listed are appropriate for a given person, and it makes no claim about results. Those judgments still belong to the individual and, where health conditions or medicines are involved, to a clinician.

Comparison table: what USP, NSF and Informed Sport seals verify

The differences among the major seals are easier to see side by side. The table summarizes what each program checks, how often, and what it leaves out. Where programs describe their own procedures in slightly different language, the table uses plain terms.

Feature	USP Verified	NSF Certified	NSF Certified for Sport	Informed Sport
Label ingredients present in declared amounts	Yes	Yes	Yes	Yes, for banned-substance screen; label content checked at audit
Heavy metals, pesticides, microbes screened	Yes	Yes	Yes	Site audit; focus is banned substances
Banned-substance screen for athletes	No	No	Yes, roughly 280 substances	Yes, WADA-based panel
Tablet disintegration tested	Yes	Not a core requirement	Not a core requirement	No
Testing frequency	Initial plus random retail retesting	Initial plus annual audit and periodic retesting	Every lot before use of mark	Every batch before release
Manufacturing facility audited	Yes	Yes	Yes	Yes
Public searchable product database	Yes	Yes	Yes, by product and lot	Yes, by product and batch
Verifies health benefit or efficacy	No	No	No	No

Two patterns stand out. First, the bottom row is identical across every column: no program verifies that a supplement works. Second, the sport programs trade breadth for depth. They test more often, on more batches, but their added layer is narrow. A general-purpose seal tells you more about potency and dissolution; a sport seal tells you more about what should not be there.

For most people choosing a basic vitamin or mineral, a USP or NSF mark covers the questions that matter. For a competitive athlete subject to drug testing, a sport-specific seal with lot-level verification is the relevant standard, and the general seals alone are not sufficient.

What the tests actually measure inside the laboratory

Behind every seal is a set of analytical procedures that would look familiar in any pharmaceutical quality lab. Understanding them in plain terms helps explain both what a seal can catch and what slips past.

Identity testing confirms that the material is what it claims to be. For a vitamin or mineral, that is usually straightforward chemistry. For a botanical, labs use chromatography, a technique that separates a mixture into its components so each can be measured, and compare the resulting fingerprint to a reference standard. DNA-based methods are sometimes used for raw plant material, though they work poorly on extracts where DNA has been destroyed by processing.

Potency, or assay, testing measures how much of the active ingredient is present. Liquid chromatography paired with mass spectrometry, often written LC-MS, separates compounds and then weighs their molecules, allowing precise quantification even at very low concentrations. This is the method that revealed the melatonin gummy discrepancies and the one used to detect trace banned substances.

Contaminant testing screens for several categories at once:

• Heavy metals such as lead, arsenic, cadmium and mercury, measured with instruments that detect metal atoms at parts-per-billion levels.
• Microbial contamination, including total bacterial counts, yeasts, molds and specific pathogens such as salmonella and E. coli.
• Pesticide residues and residual solvents left over from extraction.
• Undeclared drug ingredients, the hidden pharmaceuticals that the FDA repeatedly finds in products marketed for weight loss, sexual function and muscle building.

Disintegration testing, used by USP, drops a tablet into a warm, agitated liquid and times how long it takes to fall apart. A tablet that fails cannot release its contents in the gut.

What none of these tests measure is biological effect. A lab can confirm that a capsule contains exactly the declared amount of a herb and is free of lead. It cannot tell you whether that herb lowers anything, improves anything or interacts with your prescription. That requires clinical trials in people, which is a different enterprise entirely.

How to know if a supplement is third party tested: a five-minute check

The phrase “third-party tested” is not a protected term. Any company can print it. A real certification, by contrast, leaves a trail you can follow, and following it takes about as long as reading the back of the bottle.

Start with the seal itself. A genuine mark is a specific logo: the USP Verified mark, the blue NSF circle, the NSF Certified for Sport shield, or the Informed Sport logo. Words alone, such as “lab tested,” “GMP certified” or “pharmaceutical grade,” are not certifications. GMP certification in particular refers to the factory’s processes, not to any test of the product you are holding.

Next, verify the seal online. Every major certifier maintains a free public database. Type the brand and product name and confirm that the exact product, including flavor and size, is listed as currently certified. Counterfeit seals and expired certifications both exist, and the database is the only way to tell. For sport seals, go one step further and match the lot or batch number printed on the package against the database.

Then look for a certificate of analysis, often shortened to COA, which is a laboratory report listing what was measured in a specific batch and the result for each test. Reputable brands either print a code or link on the label or will supply the document on request. A useful COA names the testing laboratory, lists the lot number, states the method used for each test, and shows the acceptable limit alongside the measured result. A document with no lab name or no lot number is a marketing sheet, not a certificate.

Finally, cross-check the product in the NIH Dietary Supplement Label Database and glance at the FDA’s ingredient directory for any flagged ingredients. If a product passes all four steps, you have done more diligence than the regulatory system requires of anyone.

What the evidence actually says about third-party tested supplements

Grading the evidence here means separating three distinct questions, because the strength of what we know differs sharply among them.

Question one: is label inaccuracy and contamination a real problem? The evidence is strong and consistent, though it comes from laboratory surveys rather than randomized trials. Repeated analyses of products bought off the shelf, including the 2023 melatonin study, earlier work on herbal products using DNA methods, and the FDA’s own running list of products found to contain hidden drug ingredients, all point the same direction. A meaningful share of supplements on the market do not match their labels, and a smaller but non-trivial share contain something they should not. This is observational data, but it is direct measurement, and it has been replicated across product categories and years.

Question two: do certified products perform better on these measures? The evidence is moderate and largely inferential. The certification programs publish their own pass rates and retest results, and independent surveys that have included certified products have generally found them more accurate than uncertified ones. There is no large, independent, head-to-head study randomly sampling certified and uncertified products across the market. The mechanism is plausible and the available data support it, but the strength of evidence is lower than for question one.

Question three: does taking a certified supplement improve health? Here the seal is irrelevant. The health evidence belongs to the ingredient, not the certification. Randomized trials of multivitamins in generally healthy adults have mostly shown little benefit for major outcomes; trials of specific nutrients in specific deficiencies show clear benefit. Harvard Health’s summary of the field puts it well: supplements can help when they correct a documented gap and can harm when taken in excess or combined with certain medicines.

The honest conclusion is that certification reliably answers a quality question and says nothing about a benefit question.

What a quality seal cannot tell you

The limits of certification deserve as much attention as its strengths, because the gaps are where people get into trouble.

A seal does not evaluate whether the amount in the product is appropriate for you. A certified vitamin D product contains exactly what it says, but whether that amount is too much, too little or unnecessary depends on your blood level, your diet, your kidney function and your other medicines. The certifier has no way to know any of that.

A seal does not assess interactions. St. John’s wort, a herb sometimes taken for mood, can reduce the effectiveness of many prescription medicines by speeding up how the liver clears them. A certified St. John’s wort product is a pure, accurately labeled version of something that may still be a poor choice for a person on certain prescriptions. The NIH Office of Dietary Supplements and the NHS both warn specifically about this interaction, and no quality mark addresses it.

A seal does not cover every ingredient equally. Complex herbal blends, novel compounds and ingredients without an established reference standard are hard to test, and some certifiers simply decline to certify them. The absence of a seal on such a product may mean the company chose not to apply, or it may mean no program could verify it. Both are worth knowing.

A seal is a snapshot. Even lot-by-lot programs test the batch at a point in time. Storage in a hot car, a humid bathroom cabinet or beyond the expiration date can degrade contents after testing.

And a seal does not confer safety in every circumstance. Pregnancy, kidney disease, liver disease, upcoming surgery and treatment for cancer are all situations in which a well-made supplement can still be the wrong supplement. In each of those cases, the decision belongs with the treating clinician, not with a logo on a label.

Common myths about supplement testing, corrected

The viral conversation has produced a set of claims that sound right and are not.

“If it’s on a store shelf, the FDA approved it.” The FDA does not approve dietary supplements before sale. It can remove unsafe products after they are marketed, and it inspects some facilities, but there is no pre-market approval for a vitamin the way there is for a medicine.

“GMP certified means the product was tested.” Good manufacturing practice certification evaluates how a factory operates. It does not involve testing the finished product you are holding. A clean, well-run factory can still ship a mislabeled batch if its own in-house testing is weak.

“Pharmaceutical grade is a higher standard.” In the United States the phrase has no regulatory definition when applied to supplements. It is a marketing term. A product can be described as pharmaceutical grade without any independent verification at all.

“Natural ingredients don’t need testing.” Botanical products are among the most frequently mislabeled, because plants vary by species, growing region and harvest time, and because substitution of a cheaper plant is hard for a buyer to detect. Several documented cases of liver injury have involved natural herbal products, including some green tea extract concentrates.

“A third-party seal proves it works.” No seal evaluates efficacy. Certification is about what is in the bottle, not what it does in the body.

“Any mention of a lab on the label is good enough.” Phrases such as “tested in our state-of-the-art lab” describe in-house testing, which is exactly what third-party programs exist to supplement. Look for a named external certifier and check its database.

“If it has heavy metals, it should have zero.” Trace metals occur naturally in soil and therefore in plant-derived foods and supplements. Testing programs set limits based on safety assessments, and a product that meets those limits is not the same as one that fails them. The meaningful question is whether the level sits below the accepted threshold, not whether a sensitive instrument can detect anything at all.

Who should pay closest attention to third-party tested supplements

Not everyone faces the same stakes when a label turns out to be wrong. A few groups have more to gain from choosing certified products, and more to lose from skipping the check.

Competitive athletes are the clearest case. Under the strict-liability rules used by most sporting bodies, an athlete is responsible for anything found in a drug test regardless of how it got there. Documented cases of suspensions traced to contaminated supplements are the reason sport-specific certifications exist. For this group, a general USP or NSF seal is not enough; the relevant protection is a lot-verified sport seal.

People taking prescription medicines occupy a different kind of risk. For them, the hazard is less about contamination and more about interaction and dose, which no seal addresses. Certification still matters, because an accurately labeled product at least lets a clinician reason about what the patient is actually taking. A pharmacist or prescriber cannot judge an interaction if the bottle’s contents are a guess.

Pregnant and breastfeeding people, older adults, and anyone with kidney or liver disease fall into a category where excess matters. Fat-soluble vitamins, iron and certain minerals accumulate, and the melatonin findings show that “excess” can arrive unannounced when a product delivers several times its stated content. A verified potency claim reduces that particular uncertainty.

Parents buying products for children face the same arithmetic in a smaller body. Gummies, which are especially prone to potency variation because their manufacturing process is hard to control, are mostly marketed to children.

For a healthy adult taking a basic multivitamin, the stakes are lower but not zero. Mayo Clinic and the NIH Office of Dietary Supplements both suggest the same practical rule: prefer products carrying an independent seal, and discuss any supplement with a clinician if you take medicines or have a health condition. That advice is grounded in observational data on label accuracy, not in trials proving that certified products improve outcomes, and it is still the most sensible default available.

When to see a doctor

Most supplement use never produces a problem that needs medical attention. Some situations do, and a quality seal does not change the advice.

Seek care promptly, the same day, if you develop any of the following after starting or increasing a supplement:

• Yellowing of the skin or the whites of the eyes, dark urine, pale stools, or pain in the upper right abdomen. These can signal liver injury, which has been linked to some herbal and bodybuilding products.
• Racing or irregular heartbeat, chest pain, severe headache, or a sudden rise in blood pressure, which can indicate a hidden stimulant.
• Unusual bruising or bleeding, especially if you also take a blood thinner or aspirin.
• Hives, swelling of the lips or throat, or difficulty breathing, which are signs of an allergic reaction and warrant emergency care.
• Confusion, severe vomiting, or muscle weakness in someone with kidney disease or in a child who may have taken too much.

Make an appointment, rather than waiting for symptoms, before starting any supplement if you are pregnant or breastfeeding, have kidney or liver disease, are being treated for cancer, have surgery scheduled, or take prescription medicines, particularly blood thinners, thyroid medicines, antidepressants, immune-suppressing drugs or medicines for heart rhythm. The NHS and the NIH Office of Dietary Supplements both single out these groups because the margin for error is narrower.

Bring the bottle, or a photo of the full label, to the visit. A clinician or pharmacist can reason about interactions only if they know what is actually in the product, which is one practical reason to favor certified supplements in the first place.

Never stop or change a prescribed medicine because a supplement seems to be helping, and never substitute a supplement for a prescribed treatment. Those decisions belong to the prescribing clinician. If you suspect a product caused a reaction, the FDA’s MedWatch program accepts reports from the public, and those reports are how contaminated products get identified and removed.

Frequently asked questions

What is the best supplement brand that is third-party tested?

There is no single best brand, because certification is granted product by product, not company by company. A brand may certify its multivitamin but not its herbal blend. The reliable approach is to search the USP, NSF or Informed Sport public databases for the exact product you plan to buy, confirm it is currently listed, and treat any brand’s general claims about testing as secondary to that listing.

What is the best website for third-party supplement testing?

The most authoritative sources are the certifiers’ own free databases: USP’s verified products list, NSF’s certified products search and the Informed Sport batch lookup. For label information on nearly any product, the NIH Dietary Supplement Label Database is free and searchable. Independent subscription services that test products and publish results also exist, and they can be useful, but they are not certifications that appear on the package.

How do you know a supplement is third-party tested?

Look for a specific certifier’s logo on the package, then confirm it in that certifier’s online database by product name, size and flavor. For sport seals, match the lot or batch number too. Ask the company for a certificate of analysis that names the testing laboratory, the lot number and the measured results. If any of those steps fails, the product has not been independently verified, whatever the label says.

Are third party tested vitamins different from ones labeled 'quality tested' or 'lab tested'?

Yes. “Quality tested” and “lab tested” usually describe a company’s own in-house testing, which no outside party has checked. Third-party tested vitamins have been analyzed by an independent certifier whose logo and database listing you can verify. Many large national vitamin brands do carry USP or NSF marks on some products, so the quickest way to settle the question for your bottle is to search the certifier’s database.

Is NSF Certified for Sport the same as NSF Certified?

No. NSF Certified confirms label accuracy, contaminant limits and factory practice through initial testing and periodic retesting. NSF Certified for Sport includes all of that and adds lot-by-lot screening for roughly 280 substances banned in athletic competition. The sport version is the one recognized by several professional leagues and anti-doping organizations. A product can hold the general mark without holding the sport mark.

Does USP Verified mean the FDA approved the supplement?

No. The FDA does not approve dietary supplements before sale, and USP is an independent nonprofit, not a government agency. The USP Verified mark means USP tested the product for label accuracy, contaminants and disintegration and audited the factory for good manufacturing practice. It is a quality statement about what is in the bottle, not a regulatory approval and not a judgment about health benefit.

What does Informed Sport test for?

Informed Sport screens every batch of a certified product for substances on the World Anti-Doping Agency Prohibited List, including stimulants, anabolic agents, diuretics and masking agents, using an accredited anti-doping laboratory. It also audits the manufacturing site and raw-material sourcing. The program does not evaluate whether the product improves performance or health; it confirms that a tested batch contained no detectable banned substances at the time of testing.

Do third-party tested supplements work better?

Certification does not make a supplement more effective; it makes the label more trustworthy. Whether a supplement works depends on the ingredient and on whether you have a need for it, questions answered by clinical trials and by your own health picture rather than by a seal. Randomized trials of multivitamins in healthy adults show little benefit for major outcomes, certified or not, while correcting a documented deficiency does help.

Can a certified supplement still cause side effects?

Yes. A certified product accurately contains what its label states, but that ingredient can still interact with medicines, accumulate in people with kidney or liver conditions, or cause allergic or digestive reactions. Seek care promptly for yellowing skin, dark urine, racing heartbeat, unusual bleeding or breathing difficulty. Anyone taking prescription medicines or managing a health condition should review supplements with the prescribing clinician.

How often are certified supplements retested?

It depends on the program. USP retests by purchasing products from retail shelves at random after certification. NSF audits facilities annually and retests products periodically. NSF Certified for Sport tests every lot before it can carry the mark, and Informed Sport tests every batch before release. For sport seals, checking the lot number in the database confirms your specific batch was tested; for general seals, confirm the product is currently listed.

References

• MedlinePlus: Dietary Supplements
• NHS: Vitamins and minerals

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.