Which Vitamin K2 Supplements Are Third-Party Tested?

Our recommendation

Buy Nature Made Vitamin K2 100 mcg

The only plain MK-7 we found on a testing list. USP checks that it holds what the label says and screens it for harmful contaminants. One softgel gives 100 mcg of MK-7, the form used in most K2 trials outside Japan.

Buy on Amazon · $15.52

Nature Made’s own store marks this softgel discontinued but still sells it. Amazon had it in stock on October 10, 2026. If it runs out, we will change this pick.

• Want K1 and MK-4 too? Thorne Vitamin K is on NSF/ANSI 173. One capsule has 90 mcg MK-7, 5,000 mcg MK-4 and 1,000 mcg K1 ($0.52 a day).
• Want the dose from the 3-year bone trial? Sports Research Vitamin K2 MK-7 180 mcg gives 180 mcg a softgel for $0.30 a day, but it is not on a testing list.
• Want vitamin D3 in the same product? The D3 + K2 pick in our vitamin D guide is Thorne Vitamin D + K2 drops, on NSF/ANSI 173. Their K2 is MK-4. See the vitamin D guide.

On warfarin or another blood thinner? Do not start K2 without your doctor. Even small doses can change the clotting test your dose is based on.

✓ On a testing list (2)

An outside program checked each of these and lists it by name. USP Verified and NSF/ANSI 173 check that the bottle holds what the label says. More on each list

1. 

   Our pick · the only plain MK-7 on a list

   Nature Made Vitamin K2 100 mcg

   ✓ USP Verified

   100 mcg MK-7 a softgel · 30 in the bottle

   $0.70 a day

   Buy on Amazon · $15.52
2. 

   K1, MK-4 and MK-7 in one

   Thorne Vitamin K

   ✓ NSF/ANSI 173

   90 mcg MK-7, 5,000 mcg MK-4 and 1,000 mcg K1 a capsule · 60 in the bottle

   $0.52 a day

   Buy on Amazon · $31.00

Not on any testing list (4 of 15)

The best-known K2 brands on Amazon. Each listing talks about testing, but none of these products is on a public list. Here is what each one says, and what that means.

1. 

   Horbaach Vitamin K2 MK-7 100 mcg

   Not on a public list

   100 mcg MK-7 a softgel · 250 in the bottle

   Its listing says “Laboratory Tested”. It names no lab.

   $0.062 a day

   Check price
2. 

   Nutricost Vitamin K2 MK-7 100 mcg

   Not on a public list

   100 mcg MK-7 a softgel · 240 in the bottle

   Its listing says “Made in a NSF Certified, GMP Compliant, FDA Registered Facility”. That is the factory, not this product. The product is not on NSF’s list.

   $0.083 a day

   Check price
3. 

   Sports Research Vitamin K2 MK-7 180 mcg

   Not on a public list

   180 mcg MK-7 a softgel · 60 in the bottle

   Its listing says “Each batch is third-party tested”. It names no lab.

   $0.30 a day

   Check price
4. 

   NOW Foods MK-7 Vitamin K2 100 mcg

   Not on a public list

   100 mcg MK-7 a capsule · 60 in the bottle

   Its listing says its factory has an “A-rated, third-party certification” and its own labs test products. That covers how NOW makes products. This product is not on a public list.

   $0.37 a day

   Check price

A day is a full dose (90 mcg of MK-7 or more) at each brand’s own list price, checked October 5, 2026. These are the same prices as our best vitamin K2 guide, which ranks all 17. Buttons show the Amazon price on October 10, 2026.

Why a public list matters for K2

In 2024, Alkemist Labs tested 38 vitamin K2 products bought from a large U.S. online store. Only 29% met the standard for how much MK-7 they held and how pure it was (NutraIngredients, August 2024). The test was done with Balchem, a company that sells a K2 ingredient, and the products were not named. A product on a public list has been checked by someone who does not sell it.

What “third-party tested” means

A company outside the brand checks the product and lists it by name, so you can look it up yourself. There are two kinds. A contents program checks that the bottle holds what the label says, without harmful contaminants. A banned-substance program screens for drugs banned in sport, which matters only if you are drug-tested. “Third-party tested” printed on a label, with no program named, is the brand’s word.

How to check your bottle

1. Find the mark. Look for an NSF or USP mark on the product. “Third-party tested” with no program named is a claim.
2. A certified factory is not a certified product. “Made in an NSF certified facility” means NSF checked the plant. It does not mean NSF tested what is in your bottle.
3. Open the program’s own list. USP Verified, NSF/ANSI 173, NSF Certified for Sport, Informed Choice, Informed Sport. Or search all five on our testing-list index.
4. Check the form. The label should say MK-7 or MK-4. Most K2 trials outside Japan used MK-7.

MK-7 or MK-4: which do you need?

For most people, MK-7. It is the form used in most K2 trials outside Japan, and it stays in the blood for about 3 days (Schurgers 2007), so a daily dose builds up.

MK-4 at small doses may not reach your blood. In one study of healthy women, a single 420 mcg dose of MK-4 could not be found in the blood, and 60 mcg a day for a week did not raise it (Sato 2012). The bone trials in Japan used 45 mg of MK-4 a day as a prescription drug (NIH).

Not medical advice. Vitamin K works against warfarin and similar blood thinners. Ask your doctor or pharmacist. More: MK-7 vs MK-4 · how much K2 to take · vitamin D with or without K2.

Questions

The best vitamin K2 supplement, all 17 ranked · vitamin K2 guide.

Where each answer comes from

For the 2 listed products, the entry as the program’s own list shows it. For the others, the lists we searched.

NSF’s listing for Thorne Vitamin K gives a serving of 2 capsules; the label says 1. The brand claims quoted above are from each product’s Amazon listing, read October 11, 2026.

Sources

1. NSF/ANSI 173 (info.nsf.org), searched by company October 11, 2026. NSF Certified for Sport, Informed Choice and Informed Sport searched October 5, 2026. USP Verified from our copy of September 22, 2026 (USP’s site blocks automated reads).
2. Labels: each brand’s page or the NIH Dietary Supplement Label Database. List prices: each brand’s own store, checked October 5, 2026. Amazon prices: October 10, 2026. Amazon listing text: October 11, 2026.
3. NIH Office of Dietary Supplements. Vitamin K fact sheet for health professionals.
4. NutraIngredients. Balchem-Alkemist analysis reveals vitamin K2 supplement quality concerns. August 14, 2024.
5. Sato T, Schurgers LJ, Uenishi K. Comparison of menaquinone-4 and menaquinone-7 bioavailability in healthy women. Nutr J. 2012. PubMed 23140417
6. Schurgers LJ, et al. Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7. Blood. 2007. PubMed 17158229
7. Theuwissen E, et al. Effect of low-dose supplements of menaquinone-7 (vitamin K2) on the stability of oral anticoagulant treatment. J Thromb Haemost. 2013. PubMed 23530987