L-Carnitine is an amino acid that plays a role in energy production. It helps the body turn fat into energy. L-Carnitine is found in red meat and other animal-based foods.
L-Carnitine supplements are often marketed as weight loss aids. However, there is no scientific evidence to support these claims. In fact, most studies have found that L-carnitine has no effect on weight loss (1, 2).
The body produces L-carnitine from the amino acids lysine and methionine. It can also be obtained from food or supplements. L-Carnitine supplements are available in capsules, tablets, powders, and injectable forms.
L-Carnitine has a variety of other purported benefits, including improved exercise performance, heart health, brain function, and male fertility. However, most of these claims are based on anecdotal evidence and need to be investigated further.
L-Carnitine is generally considered safe when taken in recommended doses. However, side effects are possible, such as nausea, vomiting, diarrhea, heartburn, and fishy body odor. L-Carnitine should be used with caution in people with kidney or liver disease.
Pregnant and breastfeeding women should avoid L-carnitine supplements. People with diabetes should also use L-carnitine supplements with caution because they can lower blood sugar levels.
L-Carnitine supplements are available without a prescription. However, as with all supplements, it is important to choose a reputable brand and to talk to your healthcare provider before starting any supplement regimen.
L-carnitine is LIKELY SAFE for most people when taken by mouth appropriately. Most people do not experience side effects from L-carnitine supplements. L-carnitine can cause side effects including nausea, vomiting, diarrhea, heartburn, and a fishy body odor.
L-carnitine should be used with caution in people with kidney or liver disease. Pregnant and breastfeeding women should avoid L-carnitine supplements. People with diabetes should also use L-carnitine supplements with caution because they can lower blood sugar levels.
L-Carnitine might interact with certain medications. Below is a list of medications that L-carnitine might interact with. This list does not contain all drugs that may interact with L-carnitine.
Angiotensin converting enzyme (ACE) inhibitors, such as lisinopril (Zestril), enalapril (Vasotec), and captopril (Capoten)
Beta blockers, such as metoprolol (Lopressor) and propranolol (Inderal)
Calcium channel blockers, such as diltiazem (Cardizem) and verapamil (Calan)
Corticosteroids, such as prednisone (Deltasone), methylprednisolone (Medrol), and dexamethasone (Decadron)
Diabetes medications, such as insulin, metformin (Glucophage), glipizide (Glucotrol), and glyburide (Micronase, Glynase)
HMG-CoA reductase inhibitors (“statins”), such as lovastatin (Mevacor), atorvastatin (Lipitor), simvastatin (Zocor), and pravastatin(Pravachol)
NSAIDs, such as ibuprofen (Advil, Motrin IB) and naproxen (Aleve, Naprosyn)
Phenothiazines, such as chlorpromazine (Thorazine), prochlorperazine (Compazine), and trifluoperazine (Stelazine)
Thyroid medications, such as levothyroxine (Synthroid), liothyronine (Cytomel), and L-thyroxine (Levoxyl)
Do not take L-carnitine supplements if you are taking clozapine (Clozaril). L-carnitine might increase the risk of seizures in people taking clozapine.
Do not take L-carnitine supplements if you are taking warfarin (Coumadin). L-carnitine might increase the effects of warfarin.
Do not take L-carnitine supplements if you are taking zidovudine (Retrovir). L-carnitine might decrease the effectiveness of zidovudine.
The appropriate dose of L-carnitine depends on several factors such as the user’s age, health, and several other conditions. At this time there is not enough scientific information to determine an appropriate range of doses for L-carnitine. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using.
The following dosage has been studied in scientific research:
For heart disease: 500-2500 mg of L-carnitine has been used daily for up to one year. For brain function improvement in people with Alzheimer’s disease: 1 gram of L-carnitine has been used daily for up to 3 months. For improving sperm quality: 1-3 grams of L-carnitine has been used daily for up to 6 months, in some cases with L-acetylcarnitine as well. For exercise performance enhancement: 500 mg of L-carnitine has been used daily for 2 weeks. For improving walking distance in people with intermittent claudication: 500 mg of L-carnitine has been used three times daily with meals for 8 weeks.
How does it work?
L-carnitine is involved in energy production. It transports fatty acids into the mitochondria, which are the powerhouses of the cells. Once inside the mitochondria, the fatty acids are used for energy. L-carnitine also helps to remove waste products from the mitochondria.
Are there safety concerns?
L-carnitine is LIKELY SAFE for most people when taken by mouth appropriately. L-carnitine can cause side effects including nausea, vomiting, stomach upset, heartburn, diarrhea, and a “fishy” body odor. It can also cause low blood pressure, muscle weakness, and seizures. Special Precautions & Warnings:
Pregnancy and breast-feeding: L-carnitine is LIKELY SAFE when used appropriately by mouth in pregnant women. Pregnant women should avoid taking L-car
Childbirth: L-carnitine is LIKELY SAFE when used appropriately by mouth during childbirth.
Kidney disease: L-carnitine can increase how much ammonia the body produces. People with kidney disease should avoid L-carnitine supplements.
Liver disease: L-carnitine can increase how much ammonia the body produces. People with liver disease should avoid L-carnitine supplements.
Seizures: L-carnitine might increase the risk of seizures. If you have a seizure disorder, talk to your healthcare provider before taking L-carnitine supplements.
Surgery: L-carnitine might affect blood sugar levels. If you have surgery, you might need to stop using L-carnitine for a short time.
There is no known antidote for L-carnitine overdose. Treatment is supportive and symptomatic. Intravenous fluids might be necessary to maintain hydration. Dialysis does not seem to enhance L-carnitine clearance from the blood.