Niacin vs. ketosis
Part I. Rodents
It is thought: niacin causes red itchy face (> 100 mg/d) and acutely lowers FFAs; chronically, it raises some questionable fraction of HDL (> 1000 mg/d) and probably causes diabetes.
It is speculated: niacin
It is known: niacin is ketogenic in rats. Repeat: niacin is ketogenic in rats.
Niacin aka nicotinic acid and nicotamide aka niacinamide both fulfill the requirement for Vitamin B3 (ie, prevent pellagra). But only the former causes flushing… and only the former is ketogenic (two apparently unrelated phenomena).