I will add the link to the niacin flush below, but keep a couple of things in mind.
If you get a flush like that and you get it everyday with the same amount then you will need to look into another way to improve circulation.
One of the flavors of mycoplasma steals sterol from your red blood cells and they in turn steal from your arteries.
BTW: Large Niacin doses may require more Methylation; see my rant on that for more info.
Also my Dad's friend, retired MD was over the other day and did a bit of pulse checking. He remarked on how well my Dads circulation had become. It took Niacin as inositol hexanicotinate and Bearlic to achieve that…