Indications
L-carnitine is a natural nutrient made in the body from the amino acids lysine and methionine, and found in meat, fish and dairy foods. As a medicine it is used under medical supervision to treat carnitine deficiency, for example in some inherited metabolic disorders or in people on kidney dialysis. As a supplement it is used to support sperm movement (motility) in men with fertility problems, and is also promoted for energy, exercise performance and weight loss, where evidence is weak.
How It Works
L-carnitine carries long-chain fatty acids into the mitochondria, the energy-producing parts of cells, where they are burned for fuel. Sperm rely heavily on this energy for movement, and the fluid in which sperm mature is naturally rich in carnitine. It also has antioxidant effects that may help protect sperm from damage. Some studies show improved sperm motility, but effects on pregnancy rates are less certain.
Dosage and Administration
As a supplement, take by mouth as directed on the label, usually 1 to 3 g a day divided into two or three doses with meals. For male fertility, it is usually taken for at least 3 months, as sperm take about that long to develop. Doses for treating carnitine deficiency, and injections, are only given as prescribed by a doctor.
Interactions
L-carnitine may increase the effect of the blood thinners Warfarin and Acenocoumarol, so INR (blood clotting test) should be checked more often. It may reduce the effect of thyroid hormone, so people taking Levothyroxine should tell their doctor. Tell your doctor about all medicines and supplements you take.
Contraindications
- Allergy to L-carnitine or any ingredient of the product.
- Underactive thyroid (hypothyroidism) or a history of seizures, unless a doctor agrees.
Side Effects
Usually well tolerated at normal doses. Possible effects include nausea, vomiting, stomach cramps, diarrhoea and a fishy body odour, especially at doses above 3 g a day. Seizures have been reported rarely, mainly in people who already had seizure disorders.
Get urgent medical help if you have a fit, signs of a severe allergic reaction such as swelling of the face or difficulty breathing, or unusual bleeding or bruising if you take a blood thinner.
Pregnancy and Lactation
There is not enough safety information for L-carnitine supplements during pregnancy or breastfeeding beyond what is in a normal diet. Use only if a doctor advises it.
Precautions and Warnings
Male fertility problems need proper assessment of both partners, including a semen analysis. People with kidney disease, thyroid disease or epilepsy should ask a doctor before use. Avoid D-carnitine or DL-carnitine products, which can interfere with the body’s own L-carnitine.
Overdose
Very large doses may cause severe diarrhoea, vomiting and stomach cramps. Seek medical advice and take the pack with you.
Therapeutic Class
Nutritional supplement (amino acid derivative)
Storage
Store below 30°C in a dry place, away from light and out of the reach of children. Keep the container tightly closed, as it absorbs moisture.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.