Skip to Content

Niacor Side Effects

Generic Name: niacin

Note: This page contains side effects data for the generic drug niacin. It is possible that some of the dosage forms included below may not apply to the brand name Niacor.

It is possible that some side effects of Niacor 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 (the active ingredient contained in Niacor) 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 common
  • 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 or stomach pain
  • cough
  • diarrhea
  • feeling of warmth
  • flushing or redness of the skin, especially on the face and neck
  • headache
  • nausea or vomiting
  • rash or itching
  • runny nose
  • sneezing
  • stuffy nose
Incidence not known
  • Dizziness or faintness
  • dryness of the skin
  • fever
  • frequent urination
  • joint pain
  • muscle aching or cramping
  • side, lower back, or stomach pain
  • swelling of the 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 (the active ingredient contained in Niacor) when compared to an immediate release form, however, the incidence of cutaneous flushing has been significantly less.[Ref]


Dermatologic flushing (facial and whole body) and pruritus as a result of stimulation and release of prostaglandins by niacin (the active ingredient contained in Niacor) 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.[Ref]


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 (the active ingredient contained in Niacor) (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.[Ref]

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.[Ref]


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.[Ref]


Nicotinic acid competes with uric acid for excretion by the kidneys. Hyperuricemia associated with niacin (the active ingredient contained in Niacor) appears to be more common in men.[Ref]

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.[Ref]


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 (the active ingredient contained in Niacor) 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.[Ref]

Nervous system

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


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


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 (the active ingredient contained in Niacor) respectively.[Ref]


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.[Ref]


Niacin (the active ingredient contained in Niacor) 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.[Ref]

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


Musculoskeletal side effects associated with niacin (the active ingredient contained in Niacor) have included myalgia, myasthenia, myopathy, and leg cramps. Creatine kinase increase was reported post-marketing in the sustained release product.[Ref]


Hypersensitivity effects associated with niacin (the active ingredient contained in Niacor) have included rash, generalized edema, facial edema, and peripheral edema.[Ref]


Respiratory side effects have included dyspnea.[Ref]


1. Weiner M "Safety and side effects of sustained-release niacin." JAMA 272 (1994): d514;isc. 514-5

2. ChojnowskaJezierska J, AdamskaDyniewska H "Efficacy and safety of one-year treatment with slow-release nicotinic acid. Monitoring of drug concentration in serum." Int J Clin Pharmacol Ther 36 (1998): 326-32

3. Morgan JM, Capuzzi DM, Guyton JR "A new extended-release niacin (Niaspan): Efficacy, tolerability, and safety in hypercholesterolemic patients." Am J Cardiol 82 (1998): u29-34

4. Rindone JP, Arriola OG "Experience with crystalline niacin as the preferred drug for dyslipidemia in a specialty clinic." Pharmacotherapy 17 (1997): 1296-9

5. Knopp RH, Alagona P, Davidson M, Goldberg AC, Kafonek SD, Kashyap M, Sprecher D, Superko HR, Jenkins S, Marcovina S "Equivalent efficacy of a time-release form of niacin (Niaspan) given once-a-night versus plain niacin in the management of hyperlipidemia." Metabolism 47 (1998): 1097-104

6. "Product Information. Niaspan ER (niacin)." Abbott Pharmaceutical, Abbott Park, IL.

7. Capuzzi DM, Guyton JR, Morgan JM, Goldberg AC, Kreisberg RA, Brusco OA, Brody J "Efficacy and safety of an extended-release niacin (Niaspan): A long-term study." Am J Cardiol 82 (1998): u74-81

8. Rader JI, Calvert RJ, Hathcock JN "Hepatic toxicity of unmodified and time-release preparations of niacin." Am J Med 92 (1992): 77-81

9. Goldberg AC "Clinical trial experience with extended-release niacin (Niaspan): Dose-escalation study." Am J Cardiol 82 (1998): u35-8

10. Fischer DJ, Knight LL, Vestal RE "Fulminant hepatic failure following low-dose sustained-release niacin therapy in hospital." West J Med 155 (1991): 410-2

11. Shields M, Beckmann SL "Safety and side effects of sustained-release niacin." JAMA 272 (1994): d514;isc. 514-5

12. Keenan JM, Fontaine PL, Wenz JB, Myers S, Huang ZQ, Ripsin CM "Niacin revisited. A randomized, controlled trial of wax-matrix sustained-release niacin in hypercholesterolemia." Arch Intern Med 151 (1991): 1424-32

13. Ranchoff RE, Tomecki KJ "Niacin or niacinamide? Nicotinic acid or nicotinamide? What is the difference?." J Am Acad Dermatol 15 (1986): 116-7

14. Malloy MJ, Frost PH, Kane JP "Niacin--the long and the short of it." West J Med 155 (1991): 424-6

15. Naito HK "Reducing cardiac deaths with hypolipidemic drugs." Postgrad Med 82 (1987): 102-12

16. Tornvall P, Walldius G "A comparison between nicotinic acid and acipimox in hypertriglyceridaemia--effects on serum lipids, lipoproteins, glucose tolerance and tolerability." J Intern Med 230 (1991): 415-21

17. Hoeg JM, Maher MB, Bailey KR, Brewer HB Jr "Comparison of six pharmacologic regimens for hypercholesterolemia." Am J Cardiol 59 (1987): 812-5

18. Truswell AS "ABC of nutrition. Vitamins I." Br Med J (Clin Res Ed) 291 (1985): 1033-5

19. "Lipid-lowering drugs." Med Lett Drugs Ther 27 (1985): 74-6

20. Alhadeff L, Gualtieri CT, Lipton M "Toxic effects of water-soluble vitamins." Nutr Rev 42 (1984): 33-40

21. Malinow MR "Adverse effects of the treatment for hyperlipidemia." Cardiol Clin 4 (1986): 95-103

22. Illingworth DR, Stein EA, Mitchel YB, Dujovne CA, Frost PH, Knopp RH, Tun P, Zupkis RV, Greguski RA "Comparative effects of lovastatin and niacin in primary hypercholesterolemia. A prospective trial." Arch Intern Med 154 (1994): 1586-95

23. Palumbo PJ "Rediscovery of crystalline niacin." Mayo Clin Proc 66 (1991): 112-3

24. Dalton TA, Berry RS "Hepatotoxicity associated with sustained-release niacin." Am J Med 93 (1992): 102-4

25. Perry RS "Contemporary recommendations for evaluating and treating hyperlipidemia." Clin Pharm 5 (1986): 113-27

26. Hoffer A "Niacin reaction." J Fam Pract 34 (1992): 677,680-1

27. Simpson T "Extended-release niacin not problem free." Am J Hosp Pharm 48 (1991): 237-8

28. Gotto AM, Bierman EL, Connor WE, et al. "Recommendations for treatment of hyperlipidemia in adults: a joint statement of the nutrition committee and the council on arteriosclerosis." Circulation 69 (1984): a1067-90

29. "Choice of cholesterol-lowing drugs." Med Lett Drugs Ther 35 (1993): 19-22

30. Grundy SM "Management of hyperlipidemia of kidney disease." Kidney Int 37 (1990): 847-53

31. Florkowski CM, Cramb R "Approaches to the management of hypercholesterolaemia." J Clin Pharm Ther 17 (1992): 81-9

32. Davignon J, Roederer G, Montigny M, Hayden MR, Tan MH, Connelly PW, Hegele R, McPherson R, Lupien PJ, Gagne C, et al "Comparative efficacy and safety of pravastatin, nicotinic acid and the two combined in patients with hypercholesterolemia." Am J Cardiol 73 (1994): 339-45

33. Hunninghake DB "The pharmacology and therapeutics of lipid-lowering drugs." Am Pharm ns27 (1987): s18-25

34. Blum CB, Levy RI "Rational drug therapy of the hyperlipoproteinemias, Part II." Ration Drug Ther 20 (1986): 1-4

35. Knapp TR, Middleton RK "Adverse effects of sustained-release niacin." DICP 25 (1991): 253-4

36. Gibbons LW, Gonzalez V, Gordon N, Grundy S "The prevalence of side effects with regular and sustained-release nicotinic acid." Am J Med 99 (1995): 378-85

37. McKenney JM, Proctor JD, Harris S, Chinchili VM "A comparison of the efficacy and toxic effects of sustained- vs immediate-release niacin in hypercholesterolemic patients." JAMA 271 (1994): 672-7

38. Capurso A "Drugs affecting triglycerides." Cardiology 78 (1991): 218-25

39. Knopp RH "New approaches to cholesterol lowering: efficacy and safety." Hosp Pract (Off Ed) 23 Suppl 1 (1988): 22-30

40. Witztum JL "Current approaches to drug therapy for the hypercholesterolemic patient." Circulation 80 (1989): 1101-14

41. DiPalma JR, Thayer WS "Use of niacin as a drug." Annu Rev Nutr 11 (1991): 169-87

42. "Choice of cholesterol-lowering drugs." Med Lett Drugs Ther 33 (1991): 1-4

43. Whelan AM, Price SO, Fowler SF, Hainer BL "The effect of aspirin on niacin-induced cutaneous reactions." J Fam Pract 34 (1992): 165-8

44. Tikkanen MJ, Nikkila EA "Current pharmacologic treatment of elevated serum cholesterol." Circulation 76 (1987): 529-33

45. Figge HL, Figge J, Souney PF, Mutnick AH, Sacks F "Nicotinic acid: a review of its clinical use in the treatment of lipid disorders." Pharmacotherapy 8 (1988): 287-94

46. Earthman TP, Odom L, Mullins CA "Lactic acidosis associated with high-dose niacin therapy." South Med J 84 (1991): 496-7

47. Drinka PJ "Alterations in thyroid and hepatic function tests associated with preparations of sustained-release niacin." Mayo Clin Proc 67 (1992): 1206

48. Henkin Y, Oberman A, Hurst DC, Segrest JP "Niacin revisited: clinical observations on an important but underutilized drug." Am J Med 91 (1991): 239-46

49. Etchason JA, Miller TD, Squires RW, Allison TG, Gau GT, Marttila JK, Kottke BA "Niacin-induced hepatitis: a potential side effect with low-dose time- release niacin." Mayo Clin Proc 66 (1991): 23-8

50. Hodis HN "Acute hepatic failure associated with the use of low-dose sustained- release niacin." JAMA 264 (1990): 181

51. Lavie CJ, Milani RV "Safety and side effects of sustained-release niacin." JAMA 272 (1994): 513-4;disc. 514-5

52. Patterson DJ, Dew EW, Gyorkey F, Graham DY "Niacin hepatitis." South Med J 76 (1983): 239-41

53. Reimund E, Ramos A "Niacin-induced hepatitis and thrombocytopenia after 10 years of niacin use." J Clin Gastroenterol 18 (1994): 270-1

54. Etchason JA, Miller TD, Squires RW, et al "Niacin-induced hepatitis: a potential side effect with low-dose time-release niacin." Mayo Clin Proc 66 (1991): 23-8

55. Knopp RH "Niacin and hepatic failure." Ann Intern Med 111 (1989): 769

56. Keenan JM, Ripsin CM, Huang Z, McCaffrey DJ "Safety and side effects of sustained-release niacin." JAMA 272 (1994): d513;isc. 514-5

57. Henkin Y, Johnson KC, Segrest JP "Rechallenge with crystalline niacin after drug-induced hepatitis from sustained-release niacin." JAMA 264 (1990): 241-3

58. Mullin GE, Greenson JK, Mitchell MC "Fulminant hepatic failure after ingestion of sustained-release nicotinic acid." Ann Intern Med 111 (1989): 253-5

59. Jungnickel PW, Maloley PA "Comment: adverse-effect profile of sustained-release niacin." DICP 25 (1991): 1014-5

60. Frost PH "All niacin is not the same." Ann Intern Med 114 (1991): 1065

61. Gray DR, Morgan T, Chretien SD, Kashyap ML "Efficacy and safety of controlled-release niacin in dyslipoproteinemic veterans." Ann Intern Med 121 (1994): 252-8

62. Goldstein MR "Potential problems with the widespread use of niacin." Am J Med 85 (1988): 881

63. Lawrence SP "Transient focal hepatic defects related to sustained-release niacin." J Clin Gastroenterol 16 (1993): 234-6

64. Coppola A, Brady PG, Nord HJ "Niacin-induced hepatotoxicity: unusual presentations." South Med J 87 (1994): 30-2

65. Darby WJ, McNutt KW, Todhunter EN "Niacin." Nutr Rev 33 (1975): 289-97

66. Schwartz ML "Severe reversible hyperglycemia as a consequence of niacin therapy." Arch Intern Med 153 (1993): 2050-2

67. Garg R, Malinow MR, Pettinger M, Upson B, Hunninghake D "Niacin treatment increases plasma homocyst(E)ine levels." Am Heart J 138 (1999): 1082-7

68. Gershon SL, Fox IH "Pharmacologic effects of nicotinic acid on human purine metabolism." J Lab Clin Med 84 (1974): 179-86

69. Gorrell RL "Niacin caution." Postgrad Med 89 (1991): 262

70. "Niacin and myocardial metabolism." Nutr Rev 31 (1973): 80-1

71. Coronary Drug Project "Clofibrate and niacin in coronary heart disease." JAMA 231 (1975): 360-81

72. Pasternak RC, Kolman BS "Unstable myocardial ischemia after the initiation of niacin therapy." Am J Cardiol 67 (1991): 904-6

73. Dyson A, Henderson AM "Continuous axillary brachial plexus blockade following intra-arterial injection of nicotinic acid." Anaesth Intensive Care 15 (1987): 462-5

74. Millay RH, Klein ML, Illingworth DR "Niacin maculopathy." Ophthalmology 95 (1988): 930-6

75. Jampol LM "Niacin maculopathy." Ophthalmology 95 (1988): 1704-5

76. Dearing BD, Lavie CJ, Lohmann TP, Genton E "Niacin-induced clotting factor synthesis deficiency with coagulopathy." Arch Intern Med 152 (1992): 861-3

77. Cashin-Hemphill L, Spencer CA, Nicoloff JT, Blankenhorn DH, Nessim SA, Chin HP, Lee NA "Alterations in serum thyroid hormonal indices with colestipol-niacin therapy." Ann Intern Med 107 (1987): 324-9

78. Ciardella AP "Ocular side effects from herbal medicines and nutritional supplements." Am J Ophthalmol 139 (2005): 950; author reply 950

79. Fraunfelder FW, Fraunfelder FT, Illingworth DR "Adverse ocular effects associated with niacin therapy." Br J Ophthalmol 79 (1995): 54-6

80. Callanan D, Blodi BA, Martin DF "Macular edema associated with nicotinic acid (niacin)." JAMA 279 (1998): 1702

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.