Purported Benefits, Side Effects & More


Purported Benefits, Side Effects & More

Common Names

  • Vitamin BT
  • Vitamin B7

For Patients & Caregivers

Tell your healthcare providers about any dietary supplements you’re taking, such as herbs, vitamins, minerals, and natural or home remedies. This will help them manage your care and keep you safe.

What is it?

Carnitine is a chemical that your body makes to produce energy. It’s also found in foods such as meat, dairy products, beans, and avocados.

You can also take carnitine supplements as pills or capsules.

What are the potential uses and benefits?

Carnitine is used to treat:

  • Heart disease
  • Nerve pain from diabetes
  • Insulin resistance, which can increase your blood sugar
  • Fatigue (feeling more weak or tired than usual)
  • Fatigue due to cancer treatments
  • Male infertility

Carnitine also has other uses that haven’t been studied by doctors to see if they work.

Carnitine that you get from food is safe. Talk with your healthcare provider before taking carnitine supplements. Supplements are stronger than the carnitine you get from food. They can also interact with some medications and affect how they work.

For more information, read the “What else do I need to know?” section below.

What are the side effects?

Side effects of using carnitine supplements may include:

  • Nausea (feeling like you’re going to throw up)
  • Heartburn
  • Flu-like symptoms (such as a cough, fever, or chills)
  • Headache
  • Diarrhea (loose or watery bowel movements)
  • High blood pressure
  • Body odor
What else do I need to know?
  • Talk with your healthcare provider if you’re taking blood thinners such as warfarin (Coumadin®), clopidogrel (Plavix®), apixaban (Eliquis®), or rivaroxaban (Xarelto®). Carnitine can increase your risk of bleeding.
  • L-carnitine and acetyl-L-carnitine are not the same. Acetyl-L-carnitine can increase nerve pain caused by chemotherapy.

For Healthcare Professionals

Scientific Name
Beta-hydroxy-gamma-trimethyl-amino-butyric acid
Clinical Summary

Carnitine is a nutrient that plays an important role in fatty acid absorption and mitochondrial function. It is synthesized endogenously from lysine and methionine and is also found in meat and dairy products. Deficiencies can be caused by genetic disorders, malnutrition, malabsorption and kidney dialysis, and affect the heart, skeletal muscles, liver, nerve, and endocrine functions. Carnitine supplements are used to enhance physical performance and to treat fatigue, cardiovascular disease, diabetes, obesity, chronic fatigue syndrome, liver disorders, and cancer.

A meta-analysis determined that supplementation improves body weight and BMI in overweight and obese individuals (55). It also alleviated muscle damage in resistance trained and untrained groups (56), muscle wasting in patients with pemphigus vulgaris (61), and prevented cardiovascular disease in hemodialysis patients (24). Long-term supplementation has been correlated with improved myocardial mechanical performance, reduction in ventricular arrhythmias and increased exercise tolerance (7), and higher levels of carnitine were associated with lower risks of cardiovascular events and recurrent stroke after ischemic stroke (63). Carnitine also improved oxidative and inflammatory markers in patients with cardiovascular disease (62), but did not reduce risk of death or heart failure in patients with anterior acute myocardial infarction (36).

In critically-ill patients, supplements improved nutritional status indicators, which have a key role in prognosis of diseases (64) and adjunctive use improved symptoms of autism spectrum disorder in children and adolescents (65).

Preliminary findings also suggest improvement in symptoms of chronic fatigue syndrome  (22) and physical performance in patients undergoing dialysis for end-stage renal disease (9), but data on benefits against fatigue associated with multiple sclerosis are inconclusive (21). Some trials reported enhanced physical performance (17) (20), and improved aerobic capacity and exercise tolerance (32) whereas others yielded mixed results (37) (38) (39).

L-carnitine used by itself or in combination with clomiphene citrate may help treat idiopathic male infertility (25), although it did not improve sperm count or motility (40). An antioxidant formulation containing L-carnitine was also ineffective in improving semen parameters or DNA integrity (57). In women with polycystic ovary syndrome, supplementation may improve mental health parameters and biomarkers of oxidative stress (2).

Small studies in oncology settings found supplementation to improve nutritional status and quality of life in pancreatic cancer patients (27), and to reduce vismodegib-associated muscle spasms (52). L-carnitine by itself (15) (23) or in combination with Coenzyme Q10 (33) may also relieve chemotherapy-related fatigue, reduce fatigue in both younger hypothyroid patients receiving levothyroxine, and in thyroid cancer patients who have hypothyroidism, post-surgery (41). But it did not improve fatigue in patients with invasive malignancies (28). Confirmatory data are also needed to determine if chemo-induced carnitine insufficiency increases malaise or fatigue (58) (59).
In prostate cancer patients initiating androgen deprivation therapy (ADT), a low-carb diet reversed ADT-induced metabolic abnormalities which included reductions in acylcarnitine  (60).

Acetyl-L-carnitine, an ester derivative available as a supplement, is often used as a neuroprotective agent. It may help reduce diabetic neuropathy (42) (43) and improve cognition in patients with severe hepatic encephalopathy (44). In elderly patients with dysthymic disorder, it was found comparable to fluoxetine (45), but ineffective against Alzheimer’s disease (46) (47).
In cancer settings, acetyl-L-carnitine increased chemotherapy-induced peripheral neuropathy (CIPN) (35), which persisted at the 2-year follow-up (53). Current guidelines do not recommend this supplement for preventing CIPN (54).

Food Sources

Meat, dairy products, beans, avocado

Purported Uses and Benefits
  • Cardiovascular disease
  • Diabetic neuropathy
  • Insulin resistance
  • Chronic fatigue syndrome
  • Chemo-induced fatigue
  • Male infertility
Mechanism of Action

Carnitine is a non-essential amino acid, with only the L-isomer utilized in human bodies. It is available in many foods, and bioavailability from dietary sources is much higher (54%–87%) than from oral supplements (14%–18%) (48). L-carnitine plays a role in the transport of long chain fatty acids across the inner mitochondrial membrane, facilitating beta-oxidation of fatty acids and acting as an intracellular energy reservoir of acetyl groups. In deficiencies, these acyl esters accumulate and cause deleterious effects including inhibition of adenine nucleotide translocase, which impedes ATP production (5). Carnitine supplementation prevents oxidative stress and ameliorates mitochondrial function (29). L-carnitine may protect against statin-induced cellular damage via antioxidative properties in rat hepatocytes (31).

Animal studies show L-carnitine has cardioprotective effects by preventing skeletal muscle myopathy (14) and may improve myocardial metabolic patterns, reduce necrosis, diminish enzymatic infarct size, and preserve left ventricular function (8). Effects on congestive heart failure-associated myopathy may be due to caspase inhibition and decreased TNF-alpha levels (14). Metabolism of dietary L-carnitine by intestinal microbiota produced trimethylamine-N-oxide, a proatherogenic species, which accelerated atherosclerosis (30). Anticatabolic effects may occur by improving nitrogen balance either via increased protein synthesis or reduced protein degradation. Other studies show it prevents oxidative stress and ameliorates mitochondrial function (29). Carnitine is often proposed for the treatment of obesity and metabolic syndrome. Possible mechanisms include inhibition of stearoyl-CoA desaturase-1 activity, β-oxidation of fatty acids, and increased storage in the body tissues (49). It may help cancer-related cachexia by reducing proteasome activity (50), but studies in humans are needed.

In one clinical trial, carnitine reversed hyperthyroidism by acting as a peripheral antagonist of thyroid hormone action (3). In hemodialysis patients, carnitine has anti-inflammatory and anticoagulation effects which may contribute to its cardioprotective activity (24).

Adverse Reactions

Rare: Dyspepsia, heartburn (5).

Reported: Flu syndrome, injection-site reaction, pain, pharyngitis, headache, diarrhea, and hypertension (6) (9). High oral doses may cause unpleasant body odor (5).

Case Report
In a patient with a rare genetic metabolic disorder after taking carnitine supplements (11).

Herb-Drug Interactions

Warfarin: L-carnitine may have additive anticoagulant effects when used with warfarin (24) (51).

Dosage (OneMSK Only)
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  2. Jamilian H, Jamilian M, Samimi M, et al. Oral carnitine supplementation influences mental health parameters and biomarkers of oxidative stress in women with polycystic ovary syndrome: a randomized, double-blind, placebo-controlled trial. Gynecol Endocrinol. Jun 2017;33(6):442-447.
  3. Benvenga S, et al. Usefulness of L-carnitine, a naturally occurring peripheral antagonist of thyroid hormone action, in iatrogenic hyperthyroidism: a randomized, double-blind, placebo-controlled clinical trial. J Clin Endocrinol Metab 2001:86:3579-94.
  4. Breitkreutz R, et al. Effect of carnitine on muscular glutamate uptake and intramuscular glutathione in malignant diseases. Br J Cancer 2000:82;399-403.
  5. Lango R, et al. Influence of L-carnitine and its derivatives on myocardial metabolism and function in ischemic heart disease and during cardiopulmonary bypass. Cardiovasc Res 2001;51:21-9.
  6. Plioplys AV, Plioplys S. Amantadine and L-carnitine treatment of chronic fatigue syndrome. Neuropsychobiology 1997;35:16-23.
  7. Rizos I. Three-year survival of patients with heart failure caused by dilated cardiomyopathy and L-carnitine administration. Am Heart J 2000;139:S120-3.
  8. Atar D, et al. Carnitine - from cellular mechanisms to potential clinical applications in heart disease. Eur J Clin Invest 1997;27:973-6.
  9. Brass EP, et al. Intravenous L-carnitine increases plasma carnitine, reduces fatigue, and may preserve exercise capacity in hemodialysis patients. Am J Kidney Dis 2001:37;1018-28.
  10. Food and Drug Administration. Carnitor® (levocarnitine).
  11. Green A, et al. Possible deleterious effect of L-carnitine supplementation in a patient with mild multiple acyl-CoA dehydrogenation deficiency (ethylmalonic-adipic aciduria). J Inher Metab Dis 1991;14:691-7.
  12. Vicari E, Calogero AE. Effects of treatment with carnitines in infertile patients with prostato-vesiculo-epididymitis. Human Reprod 2001;16:2338-42.
  13. Chang B, et al. L-Carnitine inhibits cisplatin-induces injury of the kidney and small intestine. Arch Biochem Biophys. 2002;405:55.
  14. Vescovo G, et al. L-Carnitine: a potential treatment for blocking apoptosis and preventing skeletal muscle myopathy in heart failure. Am J Physiol Cell Physiol. 2002;283:C802-10.
  15. Graziano F, et al. Potential role of levocarnitine supplementation for the treatment of chemotherapy-induced fatigue in non-anaemic cancer patients. Br J Cancer 2002;86:1854-7.
  16. Hurot JM, et al. Effects of L-carnitine supplementation in maintenance hemodialysis patients: a systematic review. J Am Soc Nephrol 2002;13:708-14.
  17. Ellaway CJ, et al. Medium-term open label trial of L-carnitine in Rett syndrome. Brain Dev 2001:23;S85-9.
  18. Loignon M, Toma E. L-Carnitine for the treatment of highly active antiretroviral therapy-related hypertriglyceridemia in HIV-infected adults. AIDS 2001;15:1194-5.
  19. Benvenga S, et al. Usefulness of L-carnitine, a naturally occurring peripheral antagonist of thyroid hormone action, in iatrogenic hyperthyroidism: a randomized, double-blind, placebo-controlled clinical trial. J Clin Endocrinol Metab 2001:86:3579-94.
  20. Cacciatore L, et al. The therapeutic effect of L-carnitine in patients with exercise-induced stable angina: a controlled study. Drugs Exp Clin Res 1991;17:225-35.
  21. Tejani AM, Wasdell M, Spiwak R, Rowell G, Nathwani S. Carnitine for fatigue in multiple sclerosis. Cochrane Database Syst Rev. 2012 May 16;5:CD007280.
  22. Vermeulen RC, Scholte HR. Exploratory open label, randomized study of acetyl- and propionylcarnitine in chronic fatigue syndrome. Psychosom Med. 2004 Mar-Apr;66(2):276-82.
  23. Gramignano G, Lusso MR, Madeddu C, et al. Efficacy of l-carnitine administration on fatigue, nutritional status, oxidative stress, and related quality of life in 12 advanced cancer patients undergoing anticancer therapy. Nutrition 2006 22(2):136-45.
  24. Hakeshzadeh F, Tabibi H, Ahmadinejad M, Malakoutian T, Hedayati M. Effects of L-Carnitine supplement on plasma coagulation and anticoagulation factors in hemodialysis patients. Ren Fail.2010;32(9):1109-14.
  25. Moradi M, Moradi A, Alemi M, et al. Safety and efficacy of clomiphene citrate and L-carnitine in idiopathic male infertility: a comparative study. Urol J. 2010 Summer;7(3):188-93.
  26. Benvenga S, Amato A, Calvani M, Trimarchi F. Effects of carnitine on thyroid hormone action. Ann N Y Acad Sci. 2004 Nov;1033:158-67.
  27. Kraft M, Kraft K, Gärtner S, et al. L-Carnitine-supplementation in advanced pancreatic cancer (CARPAN)—a randomized multicentre trial. Nutr J. 2012 Jul 23;11:52.
  28. Cruciani RA, Zhang JJ, Manola J, et al. L-carnitine supplementation for the management of fatigue in patients with cancer: an eastern cooperative oncology group phase III, randomized, double-blind, placebo-controlled trial. J Clin Oncol. 2012 Nov 1;30(31):3864-9.
  29. Ringseis R, Keller J, Eder K. Mechanisms underlying the anti-wasting effect of L-carnitine supplementation under pathologic conditions: evidence from experimental and clinical studies.Eur J Nutr. 2013;52(5):1421-42.
  30. Koeth RA, Wang Z, Levison BS, et al. Intestinal microbiota metabolism of l-carnitine, a nutrient in red meat, promotes atherosclerosis. Nat Med. 2013;19(5):576-85.
  31. Abdoli N, Azarmi Y, Eghbal MA. Mitigation of statins-induced cytotoxicity and mitochondrial dysfunction by L-carnitine in freshly-isolated rat hepatocytes. Res Pharm Sci. 2015 Mar-Apr;10(2):143-51.
  32. Gimenes AC, Bravo DM, Nápolis LM, et al. Effect of L-carnitine on exercise performance in patients with mitochondrial myopathy. Braz J Med Biol Res. 2015 Apr;48(4):354-62.
  33. Iwase S, Kawaguchi T, Yotsumoto D, et al. Efficacy and safety of an amino acid jelly containing coenzyme Q10 and L-carnitine in controlling fatigue in breast cancer patients receiving chemotherapy: a multi-institutional, randomized, exploratory trial (JORTC-CAM01). Support Care Cancer. 2016;24(2):637-46.
  34. Greenlee H, Balneaves LG, Carlson LE, et al. Clinical practice guidelines on the use of integrative therapies as supportive care in patients treated for breast cancer. J Natl Cancer Inst Monogr. Nov 2014;2014(50):346-358.
  35. Hershman DL, Unger JM, Crew KD, et al. Randomized double-blind placebo-controlled trial of acetyl-L-carnitine for the prevention of taxane-induced neuropathy in women undergoing adjuvant breast cancer therapy. J Clin Oncol. Jul 10 2013;31(20):2627-2633.
  36. Tarantini G, Scrutinio D, Bruzzi P, et al. Metabolic treatment with L-carnitine in acute anterior ST segment elevation myocardial infarction. A randomized controlled trial. Cardiology. 2006;106(4):215-223.
  37. Rafraf M, Karimi M, Jafari A. Effect of L-carnitine supplementation in comparison with moderate aerobic training on serum inflammatory parameters in healthy obese women. J Sports Med Phys Fitness. Nov 2015;55(11):1363-1370.
  38. Ahmadi S, Dehghan Banadaki S, Mozaffari-Khosravi H. Effects of Oral L-Carnitine Supplementation on Leptin and Adiponectin Levels and Body Weight of Hemodialysis Patients: a Randomized Clinical Trial. Iran J Kidney Dis. May 2016;10(3):144-150.
  39. Serban MC, Sahebkar A, Mikhailidis DP, et al. Impact of L-carnitine on plasma lipoprotein(a) concentrations: A systematic review and meta-analysis of randomized controlled trials. Sci Rep. Jan 12 2016;6:19188.
  40. Sigman M, Glass S, Campagnone J, et al. Carnitine for the treatment of idiopathic asthenospermia: a randomized, double-blind, placebo-controlled trial. Fertil Steril. May 2006;85(5):1409-1414.
  41. An JH, Kim YJ, Kim KJ, et al. L-carnitine supplementation for the management of fatigue in patients with hypothyroidism on levothyroxine treatment: a randomized, double-blind, placebo-controlled trial. Endocr J. Oct 29 2016;63(10):885-895.
  42. Sima AA, Calvani M, Mehra M, et al. Acetyl-L-carnitine improves pain, nerve regeneration, and vibratory perception in patients with chronic diabetic neuropathy: an analysis of two randomized placebo-controlled trials. Diabetes Care. Jan 2005;28(1):89-94.
  43. Li S, Chen X, Li Q, et al. Effects of acetyl-L-carnitine and methylcobalamin for diabetic peripheral neuropathy: A multicenter, randomized, double-blind, controlled trial. J Diabetes Investig. Sep 2016;7(5):777-785.
  44. Malaguarnera M, Vacante M, Motta M, et al. Acetyl-L-carnitine improves cognitive functions in severe hepatic encephalopathy: a randomized and controlled clinical trial. Metab Brain Dis. Dec 2011;26(4):281-289.
  45. Bersani G, Meco G, Denaro A, et al. L-Acetylcarnitine in dysthymic disorder in elderly patients: a double-blind, multicenter, controlled randomized study vs. fluoxetine. Eur Neuropsychopharmacol. Oct 2013;23(10):1219-1225.
  46. Thal LJ, Calvani M, Amato A, et al. A 1-year controlled trial of acetyl-l-carnitine in early-onset AD. Neurology. Sep 26 2000;55(6):805-810.
  47. Thal LJ, Carta A, Clarke WR, et al. A 1-year multicenter placebo-controlled study of acetyl-L-carnitine in patients with Alzheimer’s disease. Neurology. Sep 1996;47(3):705-711.
  48. Rebouche CJ. Kinetics, pharmacokinetics, and regulation of L-carnitine and acetyl-L-carnitine metabolism. Ann N Y Acad Sci. Nov 2004;1033:30-41.
  49. Panchal SK, Poudyal H, Ward LC, et al. Modulation of tissue fatty acids by L-carnitine attenuates metabolic syndrome in diet-induced obese rats. Food Funct. Aug 2015;6(8):2496-2506.
  50. Busquets S, Serpe R, Toledo M, et al. L-Carnitine: an adequate supplement for a multi-targeted anti-wasting therapy in cancer. Clin Nutr. Dec 2012;31(6):889-895.
  51. Martinez E, Domingo P, Roca-Cusachs A. Potentiation of acenocoumarol action by L-carnitine. J Intern Med. Jan 1993;233(1):94.
  52. Cannon JGD, Tran DC, Li S, et al. Levocarnitine for vismodegib-associated muscle spasms: a pilot randomized, double-blind, placebo-controlled, investigator-initiated trial. J Eur Acad Dermatol Venereol. Jul 2018;32(7):e298-e299.
  53. Hershman DL, Unger JM, Crew KD, et al. Two-Year Trends of Taxane-Induced Neuropathy in Women Enrolled in a Randomized Trial of Acetyl-L-Carnitine (SWOG S0715). J Natl Cancer Inst. Jun 1 2018;110(6):669-676.
  54. Lyman GH, Greenlee H, Bohlke K, et al. Integrative Therapies During and After Breast Cancer Treatment: ASCO Endorsement of the SIO Clinical Practice Guideline. J Clin Oncol. Sep 1 2018;36(25):2647-2655.
  55. Askarpour M, Hadi A, Miraghajani M, et al. Beneficial effects of l-carnitine supplementation for weight management in overweight and obese adults: An updated systematic review and dose-response meta-analysis of randomized controlled trials. Pharmacol Res. 2020 Jan;151:104554.
  56. Yarizadh H, Shab-Bidar S, Zamani B, et al. The Effect of L-Carnitine Supplementation on Exercise-Induced Muscle Damage: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. J Am Coll Nutr. 2020 Jul;39(5):457-468.
  57. Steiner AZ, Hansen KR, Barnhart KT, et al. The effect of antioxidants on male factor infertility: the Males, Antioxidants, and Infertility (MOXI) randomized clinical trial. Fertil Steril. 2020 Mar;113(3):552-560.e3.
  58. Okubo H, Ando H, Ishizuka K, et al. Carnitine insufficiency is associated with fatigue during lenvatinib treatment in patients with hepatocellular carcinoma. PLoS One. 2020 Mar 3;15(3):e0229772.
  59. Ito T, Tsukahara K, Sato H, Shimizu A, Okamoto I. Changes in carnitine levels through induction chemotherapy in head and neck cancer patients as a potential cause of therapy-related malaise. BMC Cancer. 2021 Jun 28;21(1):742.
  60. Chi JT, Lin PH, Tolstikov V, et al. The influence of low-carbohydrate diets on the metabolic response to androgen-deprivation therapy in prostate cancer. Prostate. 2021 Jul;81(10):618-628.
  61. Noormohammadi Z, Arghavani H, Javanbakht M, Daneshpazhooh M, Jalili M. l-carnitine downregulate the muscle wasting effect of glucocorticoids in pemphigus patient: A randomized double-blind placebo-controlled study. Physiol Rep. 2023 Apr;11(8):e15657.
  62. Nachvak SM, Shabanpur M, Mostafai R, Heidari Moghaddam R, Moludi J. L-Carnitine supplementation reduces biomarkers of inflammatory and oxidative stress in patients with coronary artery disease: a randomised controlled trial. Arch Physiol Biochem. 2023 Feb;129(1):61-68.
  63. Du J, Miao M, Lu Z, et al. Plasma l-carnitine and risks of cardiovascular events and recurrent stroke after ischemic stroke: A nested case-control study. Nutr Metab Cardiovasc Dis. 2022 Nov;32(11):2579-2587.
  64. Yahyapoor F, Keshani M, Sedaghat A, et al. The effects of adjunctive treatment with L-carnitine on monitoring laboratory variables in ICU patients: a double-blinded randomized controlled clinical trial. Trials. 2023 Jan 3;24(1):3.
  65. Shakibaei F, Jelvani D. Effect of Adding l -Carnitine to Risperidone on Behavioral, Cognitive, Social, and Physical Symptoms in Children and Adolescents With Autism: A Randomized Double-Blinded Placebo-Controlled Clinical Trial. Clin Neuropharmacol. 2023 Mar-Apr 01;46(2):55-59.
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