Niacin Side Effects

It is possible that some side effects of niacin may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

For the Consumer

Applies to niacin: oral capsule, oral capsule extended release, oral elixir, oral tablet, oral tablet extended release

As well as its needed effects, niacin may cause unwanted side effects that require medical attention.

If any of the following side effects occur while taking niacin, check with your doctor immediately:

Less commonWith prolonged use of extended-release niacin
  • Darkening of urine
  • light gray-colored stools
  • loss of appetite
  • severe stomach pain
  • yellow eyes or skin

Some niacin side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

Less common
  • Abdominal pain
  • feeling of warmth
  • flushing or redness of skin, especially on face and neck
  • headache
  • rash
  • runny nose
  • sneezing
  • stuffy nose
With high doses
  • Diarrhea
  • dizziness or faintness
  • dryness of skin
  • fever
  • frequent urination
  • itching of skin
  • joint pain
  • muscle aching or cramping
  • nausea or vomiting
  • side, lower back, or stomach pain
  • swelling of feet or lower legs
  • unusual thirst
  • unusual tiredness or weakness
  • unusually fast, slow, or irregular heartbeat

For Healthcare Professionals

Applies to niacin: compounding powder, oral capsule, oral capsule extended release, oral liquid, oral tablet, oral tablet extended release


Generally, the incidences of hepatic and gastrointestinal side effects have been significantly greater with use of timed release niacin when compared to an immediate release form, however, the incidence of cutaneous flushing has been significantly less.


Dermatologic flushing (facial and whole body) and pruritus as a result of stimulation and release of prostaglandins by niacin have been major drawbacks of this drug. These symptoms have occurred in up to 78% of patients and usually resolved after 2 weeks of continued therapy. Flushing can be minimized with use of an extended release form of the drug, gradual dosage titration (over 2 to 3 months), and by administering the dosage during or within 30 minutes after meals. Aspirin (325 mg), if not otherwise contraindicated, taken within 30 minutes of niacin ingestion and avoidance of hot beverages and alcohol which can aggravate flushing by causing peripheral vasodilation may be recommended to reduce flushing.

In addition, maculopapular rash, urticaria, dry skin, skin burning sensation, and sweating have been associated with niacin use. Rare cases of hyperpigmentation and acanthosis nigricans have also been reported.


Dose-related increases in aspartate aminotransferase and alkaline phosphatase have been associated with dosage increases greater than 2.5 grams over 1 month. Computerized tomography has revealed changes consistent with focal fatty liver in some cases. Although these changes usually resolve with dose reduction, continued routine monitoring of liver function tests is recommended. Rare cases of fulminant, even fatal, hepatic failure have been reported.

In one retrospective analysis of 969 predominantly elderly male veterans treated for dyslipoproteinemia with controlled release niacin (average dose 3.1 grams/day), the incidences of possible and probable hepatotoxicity (biochemical criteria) were 2.2% and 4.7%, respectively. Predisposing risk factors included high dose, alcohol use, preexisting liver disease, and concurrent oral sulfonylurea use. The incidence of hepatotoxicity was significantly less among patients who were taking an average daily dose of 2.1 grams.

Hepatic side effects including hepatotoxicity and hepatitis have been reported in 2% to 3% patients who have taken larger doses (3 grams or more daily) or who have used timed release preparations. Hepatotoxicity usually reverses within one week after drug discontinuation, but sometimes can be avoided with dosage reductions or switching to crystalline niacin (if hepatotoxicity developed while using a timed release preparation). Clinical monitoring of patient response and tolerance, including laboratory evaluation of liver function tests is generally recommended.


Gastrointestinal disturbances have included exacerbation of peptic ulcer disease, eructation, nausea, vomiting, diarrhea, flatulence, and dyspepsia. Persistent fatigue, nausea or anorexia may be a sign of hepatotoxicity.


Nicotinic acid competes with uric acid for excretion by the kidneys. Hyperuricemia associated with niacin appears to be more common in men.

Metabolic changes associated with niacin have included hyperuricemia and hyperglycemia. Clinical monitoring of patient response and tolerance, including laboratory evaluations of serum uric acid and blood glucose levels, is recommended in patients with a history of gout or diabetes mellitus.


Cardiovascular side effects generally have been rare. Transient tachycardia, palpitations, atrial fibrillation, orthostasis, syncope, hypotension, and dizziness have been reported. The Coronary Drug Project (1975) reported a significant increase in cardiac arrhythmias associated with the use of niacin; some experts consider preexisting arrhythmias or angina pectoris contraindications to its use.

Niacin has been shown to increase plasma homocysteine levels. Homocysteine is an independent risk factor for arterial occlusive disease. Clinical implications of these increases and the influence of folic acid supplementation as a means to decrease homocysteine levels remain to be determined.

Nervous system

Nervous system side effects have included rare reports of paresthesias, nervousness, dizziness, headache, fatigue, and insomnia.


Hematologic side effects including rare hematologic coagulopathies associated with niacin-induced elevations of liver function tests have occurred.


Genitourinary complaints of decreased sexual function have been reported in up to 3% and 22% of male patients who have taken unmodified and timed release niacin, respectively.


Endocrine side effects including rare incidences of altered thyroid function tests have been reported. Changes appeared to be due to decreased thyroid binding capacity and concentration of thyroid binding globulin.


Niacin appears to cause a reversible toxic cystoid maculopathy in approximately 0.7% of patients taking at least 1.5 grams daily. The maculopathy typically has been reversible upon discontinuation of therapy.

Ocular side effects have included amblyopia, sicca syndromes, blurred vision, eyelid edema, and macular edema.


Musculoskeletal side effects associated with niacin have included myalgia, myasthenia, myopathy, and leg cramps. Creatine kinase increase was reported post-marketing in the sustained release product.


Hypersensitivity effects associated with niacin have included rash, generalized edema, facial edema, and peripheral edema.


Respiratory side effects have included dyspnea.

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