Hi Catheine. I took the vitamin after reading about it in a newer article of an interview with a professor at the University of Iowa. He made a good car for it scientifically, so I started at 300 or 250 mg per day. I didn't notice anything for weeks - maybe 7 weeks. I took it for general purposes, and had no expectations of it clearing up my skin. What I noticed first was that I no longer had muslce stiffness in the mornings. My skin gradually got better and better. At some stage I read that it was dose dependent, and that people really noticed benefits at 600 mg, so I increased my dosage, which is now 900 mg per day. Since then I have tried to follow the science since I got really interested in it. I started telling friends and family about it, and various ones experienced benefits - restless leg syndrome, carpal tunnel, neuropathy relief, relief from inflammatory knee pain that was associated with an old sports injury and that they either didn't get colds or COVID or recovered very fast after having mild symptoms. I read that the other two B-3 variants have draw backs in higher doses. Niacin has poor access to neuron cells and causes annoying "flushing", and does something negative additionally (cannot recall) in high doses. Nicotinamide (niacinamide) is damaging to certain cellular things (parps and sirtuins - I know little about them) that are important. In an Q&A with Dr. Charles Brenner (City of Hope research hospital) I asked a follow-up question about the accessibility of the variants to distressed cells. He responded briefly about what I already mentioned, and added that in some cell types (specifically mentioned those of a failing heart) that not only did Niagen have better access but that the access pathways for the other two actually stopped functioning. One more little comment. After telling five people about it with restless leg syndrome, all of whom brought it under control, I posted about it at a forum. A woman from England started taking the vitamin and had success within two weeks. Then she switched to nicotinamide and ribose supplements separately, because that combination was less expensive. Her symptoms soon returned, and she switched back to Niagen (nicotinamide riboside) and again brought it under control. Apparently the molecule has to be complete before it is taken as a supplement. I am writing too much, but I will add a few more comments. A University of Missouri study with mice that indicated by a small percentage that the vitamin increased cancer, was debunked, and the university walked t back. The NIH FDA has given it GRAS (safety) recognition, and a trial in Norway regarding Parkinson's disease found it safe to at least 3,000 mg per day. BTW; he early stage Parkinson's trial there showed positive results. All the best. Jeff