What do L-Carnitine supplements really do?

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d3sign/Getty Images

Medical examination by Roxana Ehsani, MS

L-carnitine—also known as levocarnitine— is an amino acid that occurs naturally in the body and is available in supplement form. It is a subtype of the substance carnitine, which aids metabolism and can be used to prevent a lack of carnitine.

L-carnitine produces energy in the body and removes toxins from cells. Because of this action, L-carnitine is sometimes taken as a supplement to lose weight and improve physical performance.

This article will discuss the uses of L-carnitine and its role in the body.

d3sign/Getty Images

d3sign/Getty Images

L-Carnitine: what it does and what it doesn’t

L-carnitine is a crucial component of energy production in the body. It moves fatty acids into cells to be converted into energy. L-carnitine also helps remove toxins from cells.

It can help with various symptoms of different illnesses and conditions as listed below.

Alzheimer’s disease

Alzheimer’s disease is a progressive neurodegenerative disease (breakdown of nerve cells in the brain) and the most common type of dementia. It can be treated by preventing breakdown or by increasing levels of the neurotransmitter called acetylcholine.

Researchers have studied L-carnitine to determine if it can help produce acetylcholine.

A 2020 review of several papers regarding the use of L-carnitine for dementia and Alzheimer’s disease found mixed results. Many studies reviewed have shown favorable results with the use of L-carnitine, while other studies have shown minimal or no results.

More research is needed on the effects of L-carnitine on people with Alzheimer’s disease.

Heart disease

L-carnitine supplements may aid cardiovascular health by decreasing markers of inflammation and reducing the likelihood of fatal irregular heart rhythms in people with heart disease.

A 2017 study revealed the benefits of L-carnitine supplementation in people with chronic heart failure. Improvements in several areas of cardiac function, including cardiac output and left ventricular ejection fraction.

Other studies have shown that L-carnitine supplementation has negative effects on the cardiovascular system. Research still needs to be done to determine if L-carnitine supplementation is an effective treatment for cardiovascular disease.


L-carnitine moves fatty acids into cells to produce energy, so it has been speculated that L-carnitine may help with weight loss. Some studies support this theory, but more research is needed to draw conclusions.

A literature review of 37 randomized controlled trials found that L-carnitine decreased body weight by 1.21 kilograms (kg) (2.66 pounds). The weight reduction was mostly seen in people who also ate a low-calorie diet and exercised.

athletic performance

Carnitine preserves muscle fuel and promotes the breakdown of fat into energy. As a result, some people take L-carnitine supplements to improve athletic performance.

However, research has shown no evidence that L-carnitine supplements improve exercise performance.


L-carnitine has been used successfully to improve fertility. Research has shown that supplementation improves sperm motility.

Other research has shown that L-carnitine supplementation improves ovulation and pregnancy rates in people with polycystic ovary syndrome (PCOS). People with PCOS who took the supplement had 64.4% higher ovulation rates. It has also improved pregnancy rates and reduced miscarriages in people with PCOS.

Daily dosage of L-carnitine

Carnitine is made in the liver, kidneys and brain. The body stores 95% of carnitine in the heart and skeletal muscles. The body needs 15 milligrams (mg) per day of carnitine from outside sources, such as food, or from the body making its own carnitine.

Most people who follow a diet based on meat and non-meat sources consume between 24 and 145 mg of carnitine per day. However, people following a vegan diet will likely only consume 1.2 mg per day.

Interestingly, the diet does not seem to influence the amount of carnitine produced by the body. According to the National Institutes of Health, a person following a vegan diet still produces 14.4 mg of carnitine per day.

Because carnitine is a supplement, the Food and Drug Administration (FDA) does not regulate it, and there is no suggested daily amount of supplementation.

Types of L-carnitine supplements

L-carnitine is a type of carnitine. There are several forms of carnitine available for supplementation. They understand:

  • L-carnitine: The most popular and cheapest form of carnitine. Its absorption rate is 14% to 18%.

  • Acetyl-L-carnitine: This is absorbed more easily in the intestine and crosses the blood-brain barrier. As a result, it is more likely to be used in patients with Alzheimer’s disease.

  • Propionyl-L-carnitine: This form of carnitine is used in people with heart and peripheral vascular diseases.

Carnitine is usually taken as an oral supplement, but can be given intravenously (IV).

L-Carnitine Side Effects

There are potential side effects when too much L-carnitine is taken. They understand:

Certain medications, such as those to treat seizures or antibiotics, lower carnitine levels in the body. Taking a carnitine supplement can help prevent this. Always consult a healthcare professional before starting a carnitine supplement.

L-carnitine in food

The best source of L-carnitine is in food. The body’s ability to absorb L-carnitine from food is much higher than from a supplement. The best sources (listed from highest source to lowest) of L-carnitine are:


L-carnitine is an amino acid produced by the body and found in many food products of animal origin. It produces energy and removes toxins from cells. L-carnitine is often promoted as a supplement for weight loss, to improve physical performance, etc.

Research still needs to be done to confirm the effectiveness of L-carnitine supplementation. Always speak to a health care provider before starting any supplement as it may negatively interact with other medications or affect certain conditions.

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