For high blood pressure (AKA hypertension) B12 (injection or subnasal/sublingual pills) will lower high blood pressure in most women to "normal" levels within 20-30 minutes.
I was the first to report this in the Orthomolecular Journal in 1982. For almost all women I have advised since that time who have actually tried this, their blood pressure came down to "normal" range within a half hour or so after an injection. I usually advise to try 0.50 ml (50 cc) on an insulin needle) to begin with.
The usual B12 for injection is "cyanocobalamin". A better one is "hydroxycobalamin", but I've found that few drugstores or hospitals carry this newer form. (Perhaps because MD's and hospital staff don't know enough about vitamins.)
The subnasal and sublingual B12 does not work nearly as fast or as well, but it can probably be used for maintenance. And, you can get these forms in most good health food stores without prescription. There are no known bad side effects as with prescription drugs!
For men, niacin probably works better than most anti-hypertensive drugs. The only side-effect is a harmless one of what is often described as a "flush". NUTZ! For me, and lots of other people it's like a moderate to severe sunburn, and it can last up to a half hour on some. The only way is to start with small doses, and gradually work up to large doses. (By the way - this niacin also works for women).
Niacin also has another good effect - it lowers cholesterol.
Hope this helps you and yours!