Generally, it's not a good idea to self-prescribe high dosage nicotinic acid (niacin), especially if you have diabetes, hypertension, peptic ulcer disease, or any liver function problems. Some common side-effects include: Itching, gi discomfort, headache, tachycardia, and dizziness. Generally, you should start with a low-dose (500mg/day) and increase slowly over a period of several weeks. Your final dosage also must take into account, whether it's immediate-release (Do not exceed 6g daily) or extended-release (max dose is 2000mg/day; also, never crush and ingest). The intended responses: Decrease total cholesterol, total triglyceride, and LDL and increase HDL. Again, it's best that you be monitored by a physician, since it can be very dangerous. (Understanding Pharmacology-Workman, LaCharity, Kruchko).