MK-4 vs. MK-7 — Which Form of Vitamin K2 Should You Choose?

"Vitamin K2" on a supplement label is a collective name for a whole group of compounds called menaquinones, but in market and research practice it comes down almost entirely to two specific forms: MK-4 (menaquinone-4) and MK-7 (menaquinone-7). They differ in the length of the isoprenoid side chain attached to the same chemical core — MK-4 has a shorter chain, MK-7 a much longer one. This seemingly minor structural difference translates into drastically different pharmacokinetic behavior of the two forms in the body, which has practical implications when choosing a supplement.

This article doesn't repeat the general overview of evidence for vitamin K2's effects on bone and heart health, which we cover in more depth in our article on vitamin K2, bones, and the heart, nor the interaction with warfarin, which we cover separately. It focuses on one practical question only: how do MK-4 and MK-7 differ pharmacokinetically, which form was used in the key clinical trials, and what that means for choosing a specific supplement.

The most compelling source on pharmacokinetic differences is a study specifically designed to directly compare both forms in the same people, under the same conditions.

The result of the Sato et al. study might suggest MK-4 is a "useless" form — but that's a hasty conclusion that ignores a crucial piece of context: in Japan, MK-4 has been used clinically for decades to treat osteoporosis, but at a pharmacological dose of 45 milligrams daily — roughly 1,000 times higher than the 45-microgram dose typical of popular MK-7 supplements on the Western market. That's not a cosmetic difference in unit notation — it's a three-order-of-magnitude difference that fundamentally changes what a given form can and can't do in the body.

In other words: MK-4 "works" on bone in clinical trials, but at a pharmacological dose registered in Japan as a drug, not at the microgram doses typical of dietary supplements sold in the West. Carrying over conclusions from these pharmacological MK-4 trials to a supplement containing low-dose MK-4 is an extrapolation error — it's an entirely different dosing range, with a different pharmacological logic.

While the key MK-4 trials in osteoporosis relied on pharmacological doses, studies of MK-7 tested the form at much lower, typically supplemental doses — consistent with its different pharmacokinetics described above.

This study is especially valuable because the dose used (180 mcg daily) is close to the doses found in popular MK-7 supplements on the market, which makes it easier to translate the results directly into a real supplementation decision — unlike MK-4 studies at pharmacological doses, which are harder to compare to a typical dietary supplement.

In the context of cardiovascular health, which we cover in more depth (along with the caveat that evidence for this specific effect is much weaker than for bone) in our article on vitamin K2, bones, and the heart, the key, best-designed clinical trial — evaluating progression of aortic valve calcification — also used MK-7, combined with vitamin D3, not MK-4. This is an important piece of context when comparing evidence between the two forms: most newer, large clinical trials in the West, regardless of the endpoint evaluated (bone or heart), focus on MK-7, likely because of its more favorable pharmacokinetic profile at low, supplemental doses.

The question "MK-4 or MK-7" doesn't have one universal answer, because it depends on a dosing context that supplement marketing materials often skip over. For someone choosing a dietary supplement at typical, microgram doses, the evidence for actually raising blood vitamin K levels and translating that into bone health is stronger for MK-7. For MK-4, solid clinical evidence exists mainly in an entirely different, pharmacological dosing range, registered as a drug in Japan rather than sold as a dietary supplement in the West.