There are multiple types of B3, all of which really are B3, but you want Niacin. You want flushing niacin. If you take slow release niacin that can damage your liver and also it avoids the flush. So for all that info, it's as simple as that. It's nice for some AF stuff to be simple, for once :)
The flush is really good for you (well most people), and it helps lower bad cholesterol a lot. It helps me sleep really well. I have no sex drive issues happily. It also helps blood sugar, and really does calm down my sympathetic system. A little too much in fact. So I use it every other night (maybe) now. Happily I don't have sleep issues anymore due to it! Huge win!
It is often used in combo with chromium picolinate. If you do that take the niacin at night an the CP in the am. That seems to work best.
For goodness sake start out really low with niacin. Like 50 mg. Generally you'll find it for sale in 50mg or 500mg. You'll slowly up the dose to keep flushing at nights. I stabilised at 350mg or so. (I bite off chunks)
CP was pretty powerful for me too. I'm just working back into it.
BTW, B3 is not really a B vitamin, but was called that to get it more accepted by AA, or so the story goes. See it turns out that a lot of alcholics are really hypoglycemic and that's both a reason they became alcoholics and a reason that they find it hard to stop. Wine is a lovely burst of sugar. At night when my blood sugars are off I really crave either chocolate chips or wine. It's the bump of sugar.
In fact, after really solid studies studies, the founder of AA tried to get AA to agree to put niacin in as a recommended action for AA plans, but the board rejected it. Even there they were not open to ideas.