@singingbones You are correct that the Japanese MK-4 Rx for a total of 45 mg taken in (3) 15 mg, as described in the second reference that @daisy17 provides above. But later research has suggested that lower doses and other forms in lower doses may be just as good, as described in the first reference from Daisy.

I also wanted to know what doses, frequencies, and type of Vitamin K take. I have read some or all of about 28 papers and doctor's discussions etc. I save the links in my browser bookmarks, so I really do have a count. But I do not have clear conclusions which frustrates the heck out of me! The data and conclusions are varied, and often tough technical reading. My memory is that every study supported Vitamin K2 in the form of MK-4 and/or MK-7 for bone health.

With no drug company to benefit from patents there are not newer big RCT research into Vitamin K2 that measure fractures or BMD as response. Instead the researchers have to do the cheaper blood tests especially Osteocalcin γ-Carboxylation.

Normally when I post I also try to put in good references, for what I have found, but this topic is to hard to that. Below is one reference, to add to the 2 references that @daisy17 has above.

"Efficacy and safety of vitamin K2 for postmenopausal women with osteoporosis at a long-term follow-up: meta-analysis and systematic review"
https://pubmed.ncbi.nlm.nih.gov/35711002/
This meta-analysis and systematic review seemed to support the hypothesis that vitamin K2 plays an important role in the maintenance and improvement of BMD, and it decreases uc-OC and increases OC significantly at a long-term follow-up. Vitamin K2 supplementation is beneficial and safe in the treatment of osteoporosis for postmenopausal women.

@singingbones I haven't found any MK-4 supplements in a 15 mg dose. I did find one that has two tablets equalling 45mg but it also has 1000IU vitamin D and my daily vitamin already contains that amount of D.

I did find this article that says: "MK4's serum half-life is roughly two hours — and that rapid disappearance from blood isn't a weakness. It's the opposite. Your body pulls MK4 straight into the brain, bone, kidney, pancreas, and reproductive organs...What leaves the bloodstream fastest may be doing the most work. If a nutrient's invisible in a blood draw, it's often because it already reached where it needs to be. https://threearrowsnutra.com/blogs/ironwarrior/mk4-vs-mk7