Niacin
High-dose niacin, at a gram a day or more, improves cholesterol numbers: it lowers low-density lipoprotein (LDL, "bad") cholesterol and raises high-density lipoprotein (HDL, "good") cholesterol. But two large trials found it did not prevent heart attacks or strokes when added to a statin, and the larger one counted a long list of serious side effects, from infections and bleeding to new diabetes.
Don't take gram-dose niacin for heart protection. It remains a prescription drug for specific uses and the treatment for pellagra; routine use to protect the heart is what's out.
What it is
Niacin (nicotinic acid) is one form of vitamin B3, and the treatment for pellagra, the niacin-deficiency disease. At around 1 g a day or more it acts as a lipid drug, and it is still prescribed as one for specific uses. It is a different molecule from nicotinamide, nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), which are covered on Nicotinamide and Geroprotectors.
Better cholesterol numbers, no fewer heart attacks
Older lipid trials showed that flushing-dose niacin lowered LDL and raised HDL cholesterol. The question was whether that translated into fewer heart attacks and strokes in people already on a statin. Two large randomised trials of niacin added to a statin, AIM-HIGH and HPS2-THRIVE (the second Heart Protection Study), found no benefit on cardiovascular events.[1][2]
It is one of the clearer examples of a drug that moves a blood marker in the right direction without moving the outcome the marker was supposed to predict.
The harms, counted
HPS2-THRIVE put numbers on the harm. Across its 25,673 participants, followed for a median of 3.9 years, these serious problems were more common on niacin than on placebo, in percentage points:[3]
- serious infections: 1.4 points
- new diabetes diagnoses: 1.3 points
- serious gut (gastrointestinal) problems: 1.0 point
- serious muscle and bone (musculoskeletal) problems: 0.7 points
- serious bleeding: 0.7 points
- serious skin problems: 0.3 points
The largest excess belongs to the 8,299 participants who already had diabetes when they enrolled: in them, serious loss of blood-sugar control was 3.7 percentage points more common.[4] Measured another way, serious disturbance of diabetes control ran 56% higher than on placebo in that group, an excess of 12 per 1,000 person-years.[5]
One caveat: the trial gave niacin combined with laropiprant, an anti-flushing drug not sold as a supplement, so not every excess is provably niacin's alone.
What the guidelines say now
The 2025 American Association of Clinical Endocrinology guideline on managing abnormal blood lipids strongly recommends against niacin for adults with high triglycerides who have, or are at increased risk of, heart disease from clogged arteries. That is its strongest form of words; the guideline's other drug recommendations only "suggest".[6]
What to do
- Don't take gram-dose niacin to protect your heart. The trials tested it on top of a statin; the guideline advice against it is broader.
- If you have diabetes, be especially wary: that is where the biggest harm showed up.
- For high LDL, see Lipid management. Niacin for a specific medical reason belongs under a prescriber's care. Other vitamins taken at drug doses are on Supplements to avoid.
Further reading
- Boden WE et al. (AIM-HIGH Investigators). Niacin in patients with low HDL cholesterol levels receiving intensive statin therapy. NEJM 2011.[7]
- HPS2-THRIVE Collaborative Group. Effects of extended-release niacin with laropiprant in high-risk patients. NEJM 2014.[8]
- Haynes R et al. Serious Adverse Effects of Extended-release Niacin/Laropiprant: Results From the Heart Protection Study 2-Treatment of HDL to Reduce the Incidence of Vascular Events (HPS2-THRIVE) Trial. Clin Ther 2019.[9]
- Patel SB et al. American Association of Clinical Endocrinology Clinical Practice Guideline on Pharmacologic Management of Adults With Dyslipidemia. Endocr Pract 2025.[10]