Supplement brands on iHerb: how to judge a manufacturer and what USP and NSF seals mean

How to judge a supplement brand: five signs

A brand is a promise; the product is what gets tested. The same maker can have a certified bottle and an uncertified one side by side on the shelf. So rely on things you can check yourself:

• an independent testing seal on the specific product;
• GMP manufacturing and a third-party audit of the factory;
• an honest label: the form in brackets, the dose per serving, no “proprietary blends” without amounts;
• the recall history and any FDA warning letters;
• who owns the brand and where the product is made.

Independent testing seals: USP, NSF, IFOS, Informed Sport

A seal means an organisation independent of the maker tested the product. NIH ODS says it shows the product was made properly, contains what the label says and isn’t contaminated. But a seal doesn’t guarantee that a supplement is safe or useful for you.

Seal	What’s tested	Who it matters to
USP Verified	label accuracy, contaminants, how tablets dissolve	everyone
NSF	label accuracy and contaminants	everyone
NSF Certified for Sport	plus 280 substances banned in sport, every lot	athletes
Informed Sport	substances banned in sport, searchable product database	athletes
IFOS	fish oil: results published by lot number	anyone buying fish oil
iTested (iHerb’s programme)	label, microbes, heavy metals at ISO/IEC 17025 labs	iHerb customers

Seals are awarded to products, not brands. A seal on a brand’s fish oil says nothing about its zinc, so look up each bottle in the organisation’s database by its exact name.

How to check the seal on a specific bottle

Six checks that work for any brand – about five minutes on the product page

0 / 6 checked

• The seal is printed on this bottle. Certification is awarded to a product, not a brand. A seal on another product from the same maker tells you nothing about yours.
• The product is in the organisation's database. Search the USP, NSF or Informed Sport website by the exact product name. If there's no entry, pick another bottle.
• For drug testing, a sport mark. You need NSF Certified for Sport or Informed Sport: they screen for substances banned in sport. A standard NSF seal doesn't.
• For fish oil, an IFOS report for the lot. IFOS publishes results by lot number. It should match the number on your bottle. Read more
• Don't count "GMP" as testing. In the US every supplement maker must follow GMP rules. A third-party factory audit is a plus, but it doesn't test each bottle.
• Look the brand up in the FDA recall list. Note the reason, how long ago it was and what the company did afterwards.

NSF Certified for Sport on iHerb

GMP: the legal minimum, not a quality seal

In the US, the FDA doesn’t approve supplements before they go on sale. The maker is responsible for safety and an accurate label. It must follow GMP (good manufacturing practice) rules covering identity, purity and strength.

So “made in a GMP facility” on a bottle adds nothing: every maker has to work that way. A third-party audit of the factory, for example by NSF or NPA, is a plus. Even that checks the plant rather than each bottle.

Recalls and FDA letters: how to read them

Almost every large brand has had a recall at some point, so the bare fact tells you little. Look at the details:

• the reason: contamination is serious; a labelling error is less so;
• how long ago and how often: one case 20 years ago and a run of problems are different stories;
• the response: whether the company recalled the product itself and what it changed afterwards.

What matters most to you in a brand

Pick your priority to see which signs to look for and which brands in our review fit best

My priority

I'm drug-tested I want test results Cost per dose Gentle forms Vegan, kosher, halal

What to look for

NSF Certified for Sport or Informed Sport on the bottle

These programmes test for substances banned in sport. Certification covers a specific product, not the whole brand. Thorne has more than 20 NSF Certified for Sport products; NOW Foods has its Informed Sport NOW Sports range.

How to check: Look the product up by name in the programme's database

NSF Certified for Sport on iHerb Thorne and NSF Certified for Sport

Five iHerb brands compared

Brand	Founded	Owner	Manufacturing	Independent testing	Recalls and warnings
Solgar	1947, New York	Nestlé Health Science (since 2021)	own US plants	check the specific bottle	2001, 2014: two product recalls
NOW Foods	1968, Illinois	founding family and employees	own plants in Illinois and Nevada	Informed Sport on NOW Sports, GMP audit	2004: FDA letter; 2024: lot recall
California Gold Nutrition	2013	iHerb	outside cGMP manufacturers	iTested reports on some products	2025: iron packaging recall
Thorne	1984	Procter & Gamble (since October 2026)	own plant in South Carolina	20+ NSF Certified for Sport products	2014: Captomer recall
Doctor’s Best	1990	Kingdomway (China, since 2016)	cGMP sites in the US	check the bottle; branded raw materials	2014: Red Yeast Rice lot recall

What doesn’t depend on the brand

Even a perfectly made supplement may not suit you: the seal on the bottle knows nothing about your blood tests or medicines. Speak to your GP or pharmacist if you’re pregnant or breastfeeding, take regular medicines, have kidney or liver disease, or are buying for a child. Check doses and upper limits in our guides, for example on zinc or vitamin D.

How to choose a brand on iHerb

Work in this order: form and dose first, brand second. Start with the logo and it’s easy to buy a well-made bottle of the wrong form.

1. Decide on the form and dose using the nutrient guide, for example types of magnesium compared.
2. Shortlist 2–3 bottles of that form from different brands.
3. Check any USP, NSF or IFOS seal in the organisation’s database.
4. Compare the cost of a daily dose, not the bottle price – our label guide shows how.
5. Check that the product ships to the UK or your EU country.

FAQ

What is the best supplement brand on iHerb?

There isn’t one. The same maker can sell products with and without independent certification. Compare specific bottles: the form, the dose per serving, any testing seal and the cost of a daily dose.

What does a USP or NSF seal on a supplement mean?

That an independent organisation tested the product: it contains the listed ingredients, has no harmful levels of contaminants and was made properly. NIH ODS points out that a seal doesn’t guarantee a supplement is safe or effective for you.

How is NSF Certified for Sport different from standard NSF?

The sport programme also tests every lot for 280 substances banned in sport and makes unannounced plant inspections. If you’re drug-tested, look for this mark or Informed Sport.

Is "GMP" on the label enough?

No. In the US every supplement maker must follow GMP rules; it’s the legal minimum. A third-party GMP audit is a plus, but it checks the factory, not each batch.

Where can I check whether a brand has had recalls?

The FDA website lists recalls, market withdrawals and safety alerts, and has a warning letter database. The reason for a recall and how the company responded tell you more than the fact that it happened.

Sources

1. NIH ODS. Dietary Supplements: What You Need to Know
2. FDA. Questions and Answers on Dietary Supplements
3. NSF. Certified for Sport Program
4. SGS Nutrasource. International Fish Oil Standards (IFOS) Product Certification
5. iHerb. iTested: third-party tested products