L-carnitine is an amino acid that is produced in the body. L-carnitine helps the body turn fat into energy. The body can convert L-carnitine to other amino acids called acetyl-L-carnitine and propionyl-L-carnitine.
L-carnitine is taken by mouth to increase L-carnitine levels in people whose natural level of L-carnitine is too low. Some people also use L-carnitine for conditions of the heart and blood vessels, overactive thyroid, inability to become pregnant within a year of trying to conceive (infertility), serious kidney disease, and many other conditions.
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.
Uses & Effectiveness
- 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.
- Chest pain (angina). Taking L-carnitine by mouth or intravenously (by IV) 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 with cardiac syndrome X. People with this condition have chest pain but not blocked arteries.
- Heart failure and fluid build up in the body (congestive heart failure or CHF). Taking L-carnitine by mouth or intravenously (by IV) seems to improve symptoms and increase exercise ability in people with heart failure. Taking a specific product containing L-carnitine and coenzyme Q10 also appears to improve symptoms of heart failure.
- Serious kidney disease (end-stage renal disease or ESRD). People in the last stage of long-term, serious kidney disease need to undergo hemodialysis, which can lower L-carnitine levels. The US Food and Drug Administration (FDA) has approved giving L-carnitine intravenously (by IV) but not by mouth to treat and prevent L-carnitine deficiency in these patients. There is mixed evidence about the effects of L-carnitine in treating disorders caused by low carnitine levels in people with serious kidney disease undergoing hemodialysis. Taking L-carnitine by mouth or giving L-carnitine intravenously might improve markers of anemia and inflammation in people with this condition. But L-carnitine does not seem to improve quality of life, muscle cramping, low blood pressure, breathing function, or exercise performance.
- Overactive thyroid (hyperthyroidism). Taking L-carnitine seems to improve symptoms such as rapid or pounding heartbeat, nervousness, and weakness in people with high thyroid hormone levels.
- Conditions in a man that prevent him from getting a woman pregnant within a year of trying to conceive (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.
- Swelling (inflammation) of the heart (myocarditis). Taking D,L-carnitine by mouth seems to reduce the risk of death from myocarditis.
- A hormonal disorder that causes enlarged ovaries with cysts (polycystic ovary syndrome or PCOS). Clomiphene is a medication used to help with ovulation. However, it doesn’t work well in some women with PCOS. In these women, taking L-carnitine increases ovulation and the chance of getting pregnant. Also, taking L-carnitine might help with weight loss and improve blood sugar levels in these women.
- Toxic side effects caused by the drug valproic acid. Toxicity caused by valproic acid seems to be linked with L-carnitine deficiency. Giving L-carnitine intravenously (by IV) can prevent severe liver toxicity in people who accidentally ingested or took too much valproic acid.
Some Evidence for
- Acne. Early research shows that applying a product containing L-carnitine to the face twice daily for 8 weeks reduces acne and improves quality of life in people with acne.
- Tiredness in older adults. Early research shows that taking L-carnitine daily for 30 days improves physical and mental fatigue, increase muscle mass, and decrease fat mass in elderly people.
- Male-pattern baldness (androgenic alopecia). Early research shows that applying an L-carnitine solution twice daily for 6 months increases hair on the scalp in people with male or female pattern hair loss.
- 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 show that L-carnitine improves athletic performance and endurance. However, other research shows L-carnitine provides no benefits.
- Attention deficit-hyperactivity disorder (ADHD). Research shows that taking L-carnitine does not appear to reduce ADHD symptoms in most children.
- Autism. Early research shows 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 shows that L-carnitine might reduce irregular heartbeat.
- A blood disorder that reduces levels of protein in the blood called hemoglobin (beta-thalassemia). Early research shows that L-carnitine might reduce symptoms of a blood disorder called beta-thalassemia.
- Involuntary weight loss in people who are very ill (cachexia or wasting syndrome). Early research shows that taking L-carnitine can increase body mass index (BMI) and improve lean body mass in people with cancer and wasting syndrome. Also, taking L-carnitine in combination with antioxidants and certain prescription drugs used to increase appetite seems to improve lean body mass better than taking the prescription drugs alone.
- Tiredness in people with cancer. Some cancer patients have low blood levels of L-carnitine, which might reduce energy and lead to fatigue. Some early research suggests that taking L-carnitine might improve fatigue in advanced cancer patients. However, other research suggests that it has no benefit.
- Weakened and enlarged heart (dilated cardiomyopathy). An inherited disorder that causes low L-carnitine levels can lead to dilated cardiomyopathy in kids. Adults with dilated cardiomyopathy may also have low levels of L-carnitine in their heart. For these reasons, L-carnitine has been studied for treating dilated cardiomyopathy. Some benefit to heart function has been shown. But the studies have been small and low quality. Higher quality research is needed to confirm.
- Celiac disease. Some celiac disease patients have low blood levels of carnitine, which might reduce energy and lead to fatigue. Some research shows that taking L-carnitine reduces fatigue associated with celiac disease. However, L-carnitine does not seem to improve depression or quality of life.
- Tiredness in people treated with cancer drugs. Early research shows that taking L-carnitine daily for 2 weeks might help people with renal cell carcinoma who are feeling tired from treatment with a drug called sunitinib.
- Chronic fatigue syndrome (CFS). Early research shows that taking L-carnitine for 2 months can improve symptoms of fatigue.
- A lung disease that makes it harder to breathe (chronic obstructive pulmonary disease or COPD). Early research shows that L-carnitine can improve exercise performance in people with chronic obstructive pulmonary disease (COPD).
- Memory and thinking skills (cognitive function): Early research shows that taking L-carnitine does not improve mental function or memory in healthy young adults.
- Heart disease. Early research shows that taking L-carnitine before exercise does not improve endurance in people with clogged arteries.
- Diabetes. Although some research shows that L-carnitine might improve blood sugar control in people with diabetes, most research shows that L-carnitine does not have this effect. However, L-carnitine might improve blood sugar control and decrease body weight in people with diabetes when taken along with certain weight loss medications. There is mixed evidence regarding the effects of L-carnitine on cholesterol levels in people with diabetes. Some research shows that L-carnitine can decrease cholesterol levels, but other research shows no benefit. Some research also shows that taking L-carnitine might help to reduce muscle cramps in people with diabetes.
- Dry eye: Early research shows that using eye drops that contain L-carnitine decreases dry eye symptoms in about half of patients who use eye drops for glaucoma that contain benzalkonium chloride.
- Fatigue. Early research shows that taking L-carnitine daily for 8 days does not reduce fatigue in healthy people.
- Reduced brain function in people with advanced liver disease (hepatic encephalopathy). 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 in people with swelling (inflammation) of the liver. Early research shows that taking L-carnitine daily reduces fatigue in people with hepatitis C who are also being treated with medication.
- Swelling (inflammation) of the liver caused by the hepatitis B virus (hepatitis B). Research shows that taking a specific vitamin complex containing L-carnitine together with the drug entecavir daily for 12 months improve liver function in people with hepatitis B. But it does not seem to affect the amount of hepatitis B virus in the blood.
- Swelling (inflammation) of the liver caused by the hepatitis C virus (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 levels of cholesterol or other fats (lipids) in the blood (hyperlipidemia). Lipoprotein(a) is a blood protein that is linked with increased risk of heart disease. Early research shows that taking L-carnitine by mouth can reduce levels of lipoprotein(a) in people with high levels. But L-carnitine doesn’t seem to reduce levels of low-density lipoprotein (LDL or “bad”) cholesterol or triglycerides or increase levels of high-density lipoprotein (HDL or “good”) cholesterol.
- High levels of fats called triglycerides in the blood (hypertriglyceridemia). Early research shows that L-carnitine does not reduce triglyceride levels in people with high triglyceride levels.
- Underactive thyroid (hypothyroidism). Early research shows that taking L-carnitine while being treated for underactive thyroid doesn’t seem to help most people. However, it might help with fatigue in people under the age of 50 years.
- Inability to become pregnant within a year of trying to conceive (infertility). Early research shows that taking L-carnitine might help women going through IVF achieve pregnancy.
- Infants born weighing less than 2500 grams (5 pounds, 8 ounces). Some research shows that giving premature infants L-carnitine by mouth or intravenously (by IV) can increase weight. However, other research shows that it does not increase body weight in premature infants.
- A grouping of symptoms that increase the risk of diabetes, heart disease, and stroke (metabolic syndrome). Early research shows that L-carnitine given intravenously (by IV) daily for 7 days increases weight loss and reduces waist circumference in people with metabolic syndrome. But it does not seem to affect blood pressure in people with this condition.
- Migraine. Early research shows that taking L-carnitine daily, with or without magnesium oxide for 12 weeks, does not reduce migraines.
- Fatigue in people with multiple sclerosis (MS). Some people with multiple sclerosis have low blood levels of L-carnitine, which might cause low energy and fatigue. 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 shows 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.
- Excessive daytime sleepiness (narcolepsy). Early research shows that taking L-carnitine in the morning and evening for 8 weeks reduces dozing off during the day in people with narcolepsy. But it does not seem to affect the number of naps needed, quality of life, or sleepiness.
- Pauses in breathing that may be followed by low heart rate and low oxygen levels in newborns. Early research shows that adding L-carnitine to intravenous (IV) nutrition does not reduce breathing problems while sleeping in infants.
- Swelling (inflammation) and build up of fat in the liver in people who drink little or no alcohol (nonalcoholic steatohepatitis or NASH). Early research shows that L-carnitine improves some aspects of liver function in people with liver disease not related to drinking alcohol.
- Obesity. Some research shows that taking L-carnitine can improve weight loss in adults. L-carnitine seems to work best when taken along with weight-loss drugs such as orlistat or sibutramine and when used by people with diabetes. L-carnitine doesn’t seem to greatly improve weight loss in people without diabetes. L-carnitine also doesn’t seem to improve weight loss when used along with exercise.
- Narrowing of blood vessels that causes poor blood flow to the limbs (peripheral arterial disease). Some early research shows 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.
- An inherited disorder the affects brain development in girls (Rett syndrome). Taking L-carnitine might improve well-being and movement in girls with Rett syndrome.
- Age-related muscle loss (sarcopenia). Early research shows that taking L-carnitine might increase muscle in people who are very old and weak. But it doesn’t seem to help healthy, active older women.
- Liver damage caused by chemicals. Some drugs used to treat tuberculosis have been linked to liver damage. Early research shows that taking L-carnitine by mouth along with these drugs for 4 weeks reduces the risk for liver damage. Some drugs used to treat blood cancer in children have also been linked to liver damage. Early research shows that giving L-carnitine by IV can help children to recover from liver damage caused by these drugs.
More evidence is needed to rate L-carnitine for these uses.
- Liver scarring (cirrhosis).
- Eating disorders.
- Leg ulcers.
- Lyme disease.
- Spinal muscle loss.
- Other conditions.