I weigh over three hundred pounds, and my doctor prescribe me over 1500 mg of niacin for cholesterol and anxiety, gerd, does this sound right.

Good for cholesterol. Niacin is often used to raise HDL cholesterol and has been proven to lower risk/frequency of cardiovascular events as well as the progression of atherosclerotic disease. Whether or not it can do the other things is not as clear, but it is a vitamin and its deficiency can result in syndromes like pellagra which includes diarrhea, dermatitis, and dementia, even death so it's good for you.