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.
- Treating and preventing L-carnitine deficiency. The US Food and Drug Administration (FDA) has approved L-carnitine for treating L-carnitine deficiency caused by certain genetic diseases.
- Increasing red blood cell count in people with serious kidney disease. The FDA has approved L-carnitine for this use.
Possibly Effective for:
- Improving low birth weight. Premature infants seem to get more benefit from the nutrition they get in the hospital when they are also given L-carnitine by mouth or intravenously (by IV).
- Preventing side effects caused by valproic acid (Depacon, Depakene, Depakote, VPA), a seizure medication.
- Improving symptoms and complications of heart disease and heart failure (chest pain, heart attack, and others).
- Symptoms of high thyroid hormone levels (hyperthyroidism). Taking L-carnitine seems to significantly improve symptoms such as rapid or pounding heartbeat, nervousness, and weakness.
- Treating male infertility caused by inflammation of some reproductive organs and tissues (prostate, seminal vesicles, and epididymis).
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.
- Tiredness (fatigue) due to age, cancer, hepatitis, or a digestive disorder called celiac disease.
- Taking L-carnitine might improve physical and mental fatigue, increase muscle mass, and decrease fat mass in elderly people.
- Taking L-carnitine might improve fatigue in advanced cancer patients who have an L-carnitine deficiency.
- Taking L-carnitine seems to reduce fatigue in hepatitis C patients who are treated with a medication called interferon-alpha. L-carnitine appears to reduce fatigue within the first 3 months of treatment, but not after 6 months.
- Taking-L-carnitine seems to help fatigue associated with celiac disease. But, L-carnitine doesn’t seem to improve depression or quality of life.
- Leg pain due to poor circulation (intermittent claudication). L-carnitine seems to help people with this condition walk farther without pain.
- Attention deficit-hyperactivity disorder (ADHD). There is some evidence that taking L-carnitine might reduce ADHD symptoms.
- 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.
- Eating disorders.
- High cholesterol.
- Blood disorders.
- Leg ulcers.
- Lyme disease.
- Other conditions.
Side Effects & Safety
L-carnitine is LIKELY SAFE for most people when taken by mouth. It is also safe 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.
L-carnitine is POSSIBLY SAFE when used appropriately, short-term in children.
Special Precautions & Warnings:Pregnancy and breast-feeding: Not enough is known about safety of using L-carnitine during pregnancy. Stay on the safe side and avoid use.
Taking L-carnitine is POSSIBLY SAFE in breast-feeding women when taken 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.
Under-active thyroid (hypothyroidism): Taking L-carnitine might make symptoms of hypothyroidism worse.
Seizures: L-carnitine seems to make seizures more likely in people who have had seizures before. If you have had a seizure, don’t 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.