- 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?
What is it used for?
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?
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
Carnitine is a nutrient that plays an important role in fatty acid absorption and mitochondrial function. It can be found in diets that include meat, or synthesized endogenously from lysine and methionine. Deficiencies can be caused by genetic disorders, malnutrition, malabsorption, and kidney dialysis. These can affect the heart, skeletal muscles, liver, nerve, and endocrine functions. Carnitine is marketed as a dietary supplement to enhance physical performance and to treat fatigue, cardiovascular disease, diabetes, obesity, chronic fatigue syndrome, liver disorders, and cancer.
Animal models suggest that L-carnitine has cardioprotective (8) (14) and antioxidant effects (31). A large systematic review and meta-analysis found that L-carnitine supplementation may help improve body weight and BMI in overweight and obese individuals (55). Supplementation also alleviates muscle damage in resistance trained and untrained groups (56), and helps prevent cardiovascular disease in hemodialysis patients (24). Long-term carnitine supplementation in humans is correlated with improved myocardial mechanical performance, reduction in ventricular arrhythmias, and increased exercise tolerance (7). However, L-carnitine administration did not improve risk of death or heart failure in patients with anterior acute myocardial infarction (36).
Preliminary results suggest L-carnitine may improve symptoms of chronic fatigue syndrome (22) and physical performance in patients undergoing dialysis for end-stage renal disease (9), but data of its benefits in alleviating fatigue associated with multiple sclerosis are inconclusive (21). Several trials have shown enhanced physical performance (17) (20), and improved aerobic capacity and exercise tolerance (32). Other studies show mixed results (37) (38) (39) and its clinical value and safety need additional study.
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, carnitine supplementation may improve mental health parameters and biomarkers of oxidative stress (2).
Carnitine has also been evaluated for its potential anticancer effects. Supplementation improved nutritional status and quality of life in pancreatic cancer patients (27). Other preliminary data show that L-carnitine by itself (15) (23) or in combination with Coenzyme Q10 (33) may relieve chemotherapy-related fatigue. L-carnitine also demonstrated benefits against fatigue both in younger hypothyroid patients receiving levothyroxine and thyroid cancer patients who have hypothyroidism post-surgery (41). However, carnitine did not improve fatigue in patients with invasive malignancies (28). In patients with hepatocellular carcinoma, lenvatinib therapy affected the carnitine system, which may result in carnitine insufficiency to increase fatigue (58). Other preliminary data suggest l-carnitine may reduce vismodegib-associated muscle spasms (52). Additional studies are needed to determine the cancer populations in which carnitine supplementation may be most beneficial.
An ester derivative, acetyl-L-carnitine, is also available as a dietary supplement and is often used as a neuroprotective agent. It may help to reduce diabetic neuropathy (42) (43) or improve cognition in patients with severe hepatic encephalopathy (44). In elderly patients with dysthymic disorder, it was found to be comparable with fluoxetine (45); however, other studies did not find it effective for Alzheimer’s disease (46) (47). In another study, acetyl-L-carnitine increased chemotherapy-induced peripheral neuropathy (CIPN) (35), and this negative effect persisted at long-term follow-up over 2 years (53). Guidelines also do not recommend acetyl-l-carnitine to prevent CIPN because of a possibility of harm (54). Therefore, patients receiving chemotherapy should avoid this product.
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).
Rare: Dyspepsia, heartburn (5).
Hypoglycemia: In a patient with a rare genetic metabolic disorder who took carnitine supplements (11).