I took K2 and my blood pressure almost doubled. Seems like dangerous stuff to me.
The only thing I've ever seen is a link between specifically MK7 (currently only sourced from Natto; MK4 is what you normally see in all other fermented foods and the majority of K2 supplements; MK7 supplements are very expensive comparatively) combined with large doses of flavonoids (often found in Vitamin C complexes).
I have not seen this mentioned in a study, but I suspect the combination of both may be an issue for a minority of people. Lowering the dose or switching to a more conventional MK4 lowered their BP back to normal.
As with any supplementation, no matter how innocent, always keep a Doctor handy to run labs: the difference between screwing around and science is keeping notes.
That said, studies like https://journals.lww.com/md-journal/Fulltext/2021/06110/Vita... and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7230802/ seem to indicate that even MK7, as opposed to just MK4, should be strongly considered for inclusion in the common multivitamin.
Also doesn't help education of the public due to all the weird forms. It isn't as bad as how the B complex works; a bunch of different vitamins who keep appearing next to each other in numerous reactions.
The damage is still true though. Natural != good, especially when you screw with doses.
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Oh, B. When all the other subscripts are for Vitamers, there's this one guy that just wants to be different. It's not like we don't have enough letters! Having some similarities does not justify this terrible nomenclature!