L-carnitine
L-carnitine

Background

L-carnitine is a chemical that is made in the human brain, liver, and kidneys. It helps the body turn fat into energy.

L-carnitine is important for heart and brain function, muscle movement, and many other body processes. The body can convert L-carnitine to other chemicals called acetyl-L-carnitine and propionyl-L-carnitine. But it's not clear whether the benefits of these other carnitines are the same.

L-carnitine is used 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, serious kidney disease, and many other conditions, but there is no good scientific evidence to support these uses.
When taken by mouth: L-carnitine is likely safe when taken for up to 12 months. It can cause side effects such as stomach upset, heartburn, diarrhea, and seizures. It can also cause the urine, breath, and sweat to have a "fishy" odor. Avoid using D-carnitine and DL-carnitine. These forms of carnitine might block the effects of L-carnitine and cause symptoms that resemble L-carnitine deficiency.

Special Precautions & Warnings:

Pregnancy: There isn't enough reliable information to know if L-carnitine is safe to use when pregnant. Stay on the safe side and avoid use.

Breast-feeding: Taking L-carnitine is possibly safe when taken by mouth while breast-feeding in the amounts recommended by a healthcare provider. 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 are unknown.

Children: L-carnitine is possibly safe when used appropriately by mouth, short-term. It has been used safely by mouth for up to 6 months.

Underactive 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 take L-carnitine.

Effectiveness

Natural Medicines rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
  • L-carnitine deficiency. Taking L-carnitine by mouth or by IV is effective for treating L-carnitine deficiency caused by certain genetic diseases or other disorders. It's approved by the FDA for this use. IV products can only be given by a healthcare provider.
Likely effective Effectiveness definitions
Possibly effective Effectiveness definitions
  • Chest pain (angina). Taking L-carnitine by mouth or 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. IV products can only be given by a healthcare provider.
  • Heart failure and fluid build up in the body (congestive heart failure or CHF). Taking L-carnitine by mouth or by IV seems to improve symptoms and increase exercise ability in people with heart failure. IV products can only be given by a healthcare provider.
  • High levels of cholesterol or other fats (lipids) in the blood (hyperlipidemia). Taking L-carnitine by mouth or by IV can improve cholesterol and triglyceride levels by a small amount. IV products can only be given by a healthcare provider.
  • Kidney failure. The FDA has approved giving L-carnitine by IV, but not by mouth, for kidney failure. This can only be given by a healthcare provider.
  • Conditions in a male that prevent a female partner from getting pregnant (male infertility). Taking L-carnitine by mouth, alone or together with acetyl-L-carnitine, increases sperm count and sperm movement in males with fertility problems. Some research shows that this increases the chance of pregnancy.
  • Swelling (inflammation) of the heart (myocarditis). Some children who have had diphtheria can develop myocarditis. Taking DL-carnitine by mouth seems to reduce the risk of myocarditis and death in these children.
  • A hormonal disorder that causes enlarged ovaries with cysts (polycystic ovary syndrome or PCOS). Taking L-carnitine by mouth can increase ovulation and the chance of getting pregnant in some people who don't respond to the medication clomiphene. Also, taking L-carnitine might help with weight loss and improving blood sugar levels.
  • Toxic side effects caused by the drug valproic acid. Toxicity caused by valproic acid seems to be linked with L-carnitine deficiency. Taking L-carnitine by mouth or by IV can prevent liver toxicity from valproic acid. IV products can only be given by a healthcare provider.
There is interest in using L-carnitine for a number of other purposes, but there isn't enough reliable information to say whether it might be helpful.
Likely ineffective Effectiveness definitions
Possibly ineffective Effectiveness definitions
Insufficient evidence Effectiveness definitions

Dosing & administration

L-carnitine has most often been used by adults in doses of 2 grams by mouth daily. In children, L-carnitine has most often been used in doses of 50-100 mg/kg by mouth daily, for up to one year. Speak with a healthcare provider to find out what dose might be best for a specific condition.

Interactions with pharmaceuticals

Acenocoumarol (Sintrom)

Interaction Rating=Moderate Be cautious with this combination.

Acenocoumarol is used to slow blood clotting. L-carnitine might increase the effects of acenocoumarol and increase the chance of bruising and bleeding. Be sure to have your blood checked regularly. The dose of your acenocoumarol might need to be changed.

Thyroid hormone

Interaction Rating=Moderate Be cautious with this combination.

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)

Interaction Rating=Moderate Be cautious with this combination.

Warfarin is used to slow blood clotting. L-carnitine might increase the effects of warfarin and increase the chances of bruising and bleeding. Be sure to have your blood checked regularly. The dose of your warfarin might need to be changed.

Interactions with herbs & supplements

D-carnitine: D-carnitine might interfere with the way the body uses L-carnitine. Taking D-carnitine might cause L-carnitine levels to drop too low. Don't take D-carnitine with L-carnitine.

Interactions with foods

There are no known interactions with foods.
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This monograph was last reviewed on 16/12/2021 00:45:42 and last updated on 24/03/2022 02:53:42. Monographs are reviewed and/or updated multiple times per month and at least once per year.
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