L-carnitine is an amino acid (a building block for proteins) that is naturally produced in the body.
L-carnitine supplements are used to increase L-carnitine levels in people whose natural level of L-carnitine is too low because they have a genetic disorder, are taking certain drugs (valproic acid for seizures), or because they are undergoing a medical procedure (hemodialysis for kidney disease) that uses up the body’s L-carnitine. It is also used as a replacement supplement in strict vegetarians, dieters, and low-weight or premature infants.
L-carnitine is used for conditions of the heart and blood vessels including heart-related chest pain, congestive heart failure (CHF), heart complications of a disease called diphtheria, heart attack, leg pain caused by circulation problems (intermittent claudication), and high cholesterol.
Some people use L-carnitine for muscle disorders associated with certain AIDS medications, difficulty fathering a child (male infertility), a brain development disorder called Rett syndrome, anorexia, chronic fatigue syndrome, diabetes, overactive thyroid, attention deficit-hyperactivity disorder (ADHD), leg ulcers, Lyme disease, and to improve athletic performance and endurance.
The body can convert L-carnitine to other amino acids called acetyl-L-carnitine and propionyl-L-carnitine. But, no one knows whether the benefits of carnitines are interchangeable. Until more is known, don’t substitute one form of carnitine for another.
How does it work?
L-carnitine helps the body produce energy. It is important for heart and brain function, muscle movement, and many other body processes.
- Serious kidney disease. Most research suggests that taking L-carnitine by mouth or intravenously (by IV) can improve red blood cell counts during hemodialysis. The US Food and Drug Administration (FDA) has approved L-carnitine for the treatment and prevention of L-carnitine deficiency in people with serious kidney disease who are undergoing hemodialysis.
- L-carnitine deficiency. The FDA has approved L-carnitine for treating L-carnitine deficiency caused by certain genetic diseases.
Possibly Effective for:
- Chest pain (angina). Taking L-carnitine by mouth seems to improve exercise tolerance in people with chest pain. Taking L-carnitine along with standard treatment also seems to reduce chest pain and improve exercise ability in people who have chest pain but not blocked arteries.
- Heart failure. Taking L-carnitine by mouth seems to improve symptoms and increase exercise ability in people with heart failure. Taking a specific product containing L-carnitine and coenzyme Q-10 (Carni Q-Gel) also appears to improve symptoms of heart failure.
- High thyroid hormone levels (hyperthyroidism). Taking L-carnitine seems to improve symptoms such as rapid or pounding heartbeat, nervousness, and weakness in people with high thyroid hormone levels.
- Male infertility. Most research shows that taking L-carnitine, alone or in combination with acetyl-L-carnitine, increases sperm count and sperm movement in men with fertility problems.
- Inflammation of the heart (myocarditis). Taking L-carnitine by mouth seems to reduce the risk of death from myocarditis.
- Preventing side effects caused by valproic acid (Depacon, Depakene, Depakote, VPA), a seizure medication. Using L-carnitine intravenously (by IV) can prevent the side effects of valproic acid.
Likely Ineffective for:
- Improving athletic ability. There is no evidence that taking L-carnitine supplements will improve exercise performance or endurance, even in trained athletes.
- Age-related fatigue. Taking L-carnitine might improve physical and mental fatigue, increase muscle mass, and decrease fat mass in elderly people.
- Hair loss (androgenetic alopecia). Early research suggests that applying an L-carnitine solution twice daily for 6 months increases hair on the scalp.
- Athletic performance. Intense exercise has been linked to a decrease in L-carnitine blood levels. However, research on the use of L-carnitine for improving athletic performance is inconsistent. Some studies suggest that L-carnitine improves athletic performance and endurance. However, other research suggests L-carnitine provides no benefits.
- Attention deficit-hyperactivity disorder (ADHD). Taking L-carnitine does not appear to reduce ADHD symptoms in most children.
- Autism. Early research suggests that taking L-carnitine by mouth daily for 3 months reduces the severity of autism in children according to some but not all scales.
- Irregular heartbeat (arrhythmia). Early research suggests that L-carnitine might reduce irregular heartbeat.
- Blood disorder called beta-thalassemia. Early research suggests that L-carnitine might reduce symptoms of a blood disorder called beta-thalassemia.
- Wasting syndrome (cachexia). Early research suggests that taking L-carnitine can increase body mass index (BMI) and improve lean body mass in people with cancer and wasting syndrome.
- Weakening heart muscle (cardiomyopathy). Early research suggests that L-carnitine improves heart function in adults or children with a weak heart muscle.
- Cancer-related fatigue. Some cancer patients have low blood levels of L-carnitine. Some early research suggests that taking L-carnitine might improve fatigue in advanced cancer patients. However, other research suggests that it has no benefit.
- Celiac disease-related fatigue. Some research shows that taking-L-carnitine seems to help fatigue associated with celiac disease. However, L-carnitine does not seem to improve depression or quality of life.
- Chronic fatigue syndrome. Early research suggests that taking L-carnitine for 2 months can improve symptoms of fatigue.
- Lung disease (chronic obstructive pulmonary disease). Early research suggests that L-carnitine can improve exercise performance in people with chronic obstructive pulmonary disease (COPD).
- Clogged arteries (coronary artery disease). Early research suggests that taking L-carnitine before exercise does not improve endurance in people with clogged arteries.
- Diabetes. Some research suggests that L-carnitine might improve blood sugar control, but most research shows that L-carnitine does not improve blood sugar in people with diabetes. However, L-carnitine might improve glycemic control when taken along with certain diabetes medications.
- Fatigue. Early research shows that taking L-carnitine daily for 8 days does not reduce fatigue in healthy people.
- Fragile-X syndrome. Some research suggests that L-carnitine reduces hyperactive behavior in children with fragile-X syndrome.
- Declining brain function related to liver disease. Early research shows that taking L-carnitine daily for 60-90 days reduces ammonia levels and improves brain function in people with declining brain function related to severe liver disease.
- Fatigue due to hepatitis. Early research shows that taking L-carnitine daily reduces fatigue in people with hepatitis C who are also being treated with medication.
- Hepatitis C. Taking L-carnitine with the medications interferon-alpha and ribavirin seems to improve the response to treatment in people with hepatitis C.
- High lipid (fat) levels in the blood. Early research shows that taking L-carnitine daily can reduce total cholesterol, low-density lipoprotein (LDL or “bad”) cholesterol, and triglycerides in children with high lipid levels. Also, taking L-carnitine can reduce levels of lipoprotein(a), a possible risk factor for cardiovascular disease, in people with high levels of lipoprotein(a).
- High triglycerides. Early research suggests that L-carnitine does not reduce triglyceride levels in people with high triglyceride levels.
- Low birth weight. Some research suggests that giving premature infants L-carnitine by mouth or intravenously (by IV) can increase weight. However, other research suggests that it does not increase body weight in premature infants.
- Memory. Early research shows that taking L-carnitine daily for 3 days does not improve memory in young adult females.
- Migraine headache. Early research suggests that taking L-carnitine daily, with or without magnesium oxide for 12 weeks, does not reduce migraines.
- Multiple sclerosis-related fatigue. Some people with multiple sclerosis have low blood levels of L-carnitine. Early research shows that taking L-carnitine daily decreases some aspects of fatigue in people with multiple sclerosis who also have low L-carnitine levels.
- Heart attack. There is inconsistent evidence about the effects of using of L-carnitine after a heart attack. Some research suggests that taking L-carnitine by mouth after a heart attack improves heart function and reduces the risk of death. However, other studies suggest that it provides no benefit.
- Breathing problems while sleeping in infants. Early research suggests that adding L-carnitine to intravenous (IV) nutrition does not reduce breathing problems while sleeping in infants.
- Nonalcoholic liver disease (nonalcoholic steatohepatitis, NASH). Early research suggests that L-carnitine improves some aspects of liver function in people with liver disease not related to drinking alcohol.
- Blocked blood vessels not in the heart or brain. Some early research suggests that L-carnitine might improve walking in people with blocked blood vessels not in the heart or brain. However, other research suggests that it does not provide any benefits.
- A rare inherited disorder that affects the nervous system (Rett syndrome). Taking L-carnitine might improve well-being and movement in girls with Rett syndrome.
- Weight loss. Taking L-carnitine by itself does not appear to reduce body weight in overweight or obese people. However, other research suggests that taking L-carnitine with certain other medications or supplements appears to reduce body weight and body mass index.
- Eating disorders.
- Leg ulcers.
- Lyme disease.
- Other conditions.
Side Effects & Safety
L-carnitine is LIKELY SAFE for most people when taken by mouth and when used as an injection, with the approval of a healthcare provider. It can cause side effects such as nausea, vomiting, stomach upset, heartburn, diarrhea, and seizures. It can also cause the urine, breath, and sweat to have a “fishy” odor.
Special Precautions & Warnings:Pregnancy and breast-feeding: There is not enough reliable information about the safety of using L-carnitine if you are pregnant. Stay on the safe side and avoid use.
Taking L-carnitine is POSSIBLY SAFEin breast-feeding women when taken by mouth in the amounts recommended. Small amounts of L-carnitine have been given to infants in breast milk and formula with no reported side effects. The effects of large amounts taken by a breast-feeding mother are unknown.
Children: L-carnitine is POSSIBLY SAFE when used appropriately by mouth or intravenously (by IV), short-term.
Under-active thyroid (hypothyroidism): Taking L-carnitine might make symptoms of hypothyroidism worse.
Kidney failure: Using DL-carnitine has been reported to cause symptoms such as muscle weakness and eye drooping when administered intravenously (by IV) after dialysis. L-carnitine does not seem have this effect.
Seizures: L-carnitine seems to make seizures more likely in people who have had seizures before. If you have had a seizure, do not use L-carnitine.
Moderate Interaction Be cautious with this combination
- Acenocoumarol (Sintrom) interacts with L-CARNITINE
Acenocoumarol (Sintrom) is used to slow blood clotting. L-carnitine might increase the effectiveness of acenocoumarol (Sintrom). Increasing the effectiveness of acenocoumarol (Sintrom) might slow blood clotting too much. The dose of your acenocoumarol (Sintrom) might need to be changed.
- Thyroid hormone interacts with L-CARNITINE
L-carnitine seems to decrease how well thyroid hormone works in the body. Taking L-carnitine with thyroid hormone might decrease the effectiveness of the thyroid hormone.
- Warfarin (Coumadin) interacts with L-CARNITINE
Warfarin (Coumadin) is used to slow blood clotting. L-carnitine might increase the effects of warfarin (Coumadin) and increase the chances of bruising and bleeding. Be sure to have your blood checked regularly. The dose of your warfarin (Coumadin) might need to be changed.
The following doses have been studied in scientific research:
- For L-carnitine deficiencies in adults: 990 mg two to three times per day in tablets or as an oral solution.
- For preventing side effects caused by valproic acid (Depacon, Depakene, Depakote, VPA): 50 to 100 mg/kg/day in three or four divided doses, to a maximum of 3 grams/day.
- For chest pain and congestive heart failure (CHF): 1 gram twice daily.
- Following heart attack: 2 to 6 grams daily.
- For symptoms of overactive thyroid: 1-2 grams twice daily.
- For male infertility: 2 grams of L-carnitine plus 1 gram of L-acetyl-carnitine daily.