I have fatigue that comes with Fibromyalgia and poor sleep. I’m trying SAMe Rt now but it will take 6-8 wks to take noticeable effect. I just got info today from Dr Hyman that NAD supplement helps the body produce more energy. But with Fibro, powerful supplements are not tolerated well. I can’t speak for Chronic fatigue Syndrome. But for ppl who don’t have these problems, NAD should be tolerated well. Start low and wk up to recommended dose.