L-carnitine: Proven Benefits, Risks, and More

Medically Reviewed By Katherine Marengo LDN, R.D.
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L-carnitine is derived from amino acids and can be found in animal products. Some people take L-carnitine supplements to help with their overall health. L-carnitine is a naturally occurring substance in the body and can be found in animal products. Most people produce enough L-carnitine in their bodies, even if they are vegan and do not eat animal products.

This article covers what L-carnitine is and some of its benefits.

What is L-carnitine?

A person cutting into a steak on their plate
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L-carnitine is derived from an amino acid and is found in almost all the cells in the body. The word comes from the Latin, carnus, or flesh, being that the L-carnitine compound is isolated from meat. L-carnitine plays a role in energy production and is concentrated in skeletal and cardiac muscles.

For most people, the body naturally produces enough L-carnitine to meet their needs. But for some individuals, such as preterm infants or those with genetic or medical conditions, the body can’t make enough L-carnitine. For these individuals, L-carnitine is considered an essential nutrient.

Sources

L-carnitine is mostly found in animal products, such as meat, fish, poultry, and dairy. The redder the meat is, the higher it is in L-carnitine. For instance, 4 ounces of cooked beef steak contains 56–162 milligrams of L-carnitine. In dairy products, L-carnitine is primarily found in the whey portion.

Why might people use it?

People may supplement with L-carnitine for many reasons, such as athletic performance, fat burning, aging, cardiovascular protection, cancer, and infertility. However, the Food and Drugs Administration (FDA) has approved the supplementation of L-carnitine only for people with a true deficiency.

Some people receiving certain treatment, such as hemodialysis, may also be deficient in L-carnitine.

Sports

Some people take L-carnitine to improve athletic performance. However, there is very limited research to show that supplementation with L-carnitine improves athletic performance in healthy individuals.

In people without a fatty acid oxidation defect, the benefits of L-carnitine are likely to be minimal.

Fat burning

L-carnitine is frequently marketed as a weight loss supplement, but the research is inconclusive. Some research suggests that oral L-carnitine might reduce fat mass, especially in people with overweight or obesity.

Learn how to talk with your doctor about your weight.

Aging

L-carnitine is thought to play a role in the aging process because its concentration in bodily tissues decreases with age, causing a decline in mitochondrial function.

The National Institutes of Health (NIH) reported older research done in rats has found that high doses of L-carnitine may reduce mitochondrial decay and improve mental function.

Type 2 diabetes

Some research, such as this 2020 study, has investigated the effects of L-carnitine supplementation on people with type 2 diabetes.

Researchers noted some positive effects of the supplement on blood sugar, but it was not always statistically significant. There were other effects on reducing some symptoms of type 2 diabetes, including fatigue and insomnia, after 6 months of treatment.

The researchers concluded that much more research is needed. Still, L-carnitine could one day be a beneficial supplement in people with type 2 diabetes alongside their recommended treatment and the Mediterranean diet.

Learn about commonly prescribed drugs for type 2 diabetes.

Cardiovascular and peripheral arterial disease

Some research has found that L-carnitine supplementation and standard pharmacological treatment after a heart attack reduce mortality and subsequent occurrences of chest pain. However, not all studies have found this.

Some other research has found that taking L-carnitine can help reduce muscle cramping in individuals with peripheral arterial disease. This cramping is called claudication and results from an inadequate supply of oxygen-rich blood to the legs.

Cancer

Some research has found that L-carnitine can help with the fatigue associated with cancer treatments, such as chemotherapy and radiation. It may also help improve mood and quality of sleep.

Learn more about what to expect with radiation therapy.

Male infertility

L-carnitine may be of value for treating male infertility because carnitine content in seminal fluid is directly related to sperm count and motility. Several studies suggest that L-carnitine may improve sperm quality and reduce cell death in the testes.

However, more research is needed to determine the overall effects of L-carnitine on male fertility.

What are the side effects of L-carnitine?

High doses of L-carnitine can cause diarrhea and gastrointestinal distress.

Other side effects include:

Generally, the side effects of taking L-carnitine are mild.

What precautions should people be aware of before taking L-carnitine?

People who decide to take L-carnitine should do so under the supervision of their doctor in case there are interactions with other medications or supplements.

Because more research is needed on the benefits of L-carnitine, people should be aware that they may not always see desired effects from L-carnitine supplementation.

Always talk with your doctor before starting any new supplement, especially if you have an underlying condition. Your doctor will be able to tell you more about its safety in your circumstances and will also be able to recommend other measures to help you achieve your aims.

Can L-carnitine interact with other medications?

L-carnitine can interact with other medications. People taking the following medications should be aware of the following possible interactions with L-carnitine:

  • pivalate-conjugated antibiotics, such as pivampicillin, used to prevent urinary tract infections
  • some anticonvulsants, including:
    • valproic acid
    • phenobarbital
    • phenytoin
    • carbamazepine

How much L-carnitine does a person need in a day?

According to the 2020–2025 Dietary Guidelines for Americans, most people can and should meet their required daily amount of L-carnitine through their food intake rather than supplements.

Exceptions to this are people who have a medical reason to take a supplement, such as people who are pregnant or have a specific medical condition.

For individuals who need to take L-carnitine supplements, their doctor will recommend the appropriate dosage for them. However, they should never exceed 3 g per day, as this can cause side effects.

Summary

L-carnitine is derived from amino acids and plays a role in energy production. Most people naturally produce enough L-carnitine to meet their body’s needs.

L-carnitine is found in animal products, with the highest concentrations found in red meat. Although many people take L-carnitine supplements, more research is needed on its benefits.

You should talk with your doctor before taking L-carnitine supplements, especially if you have certain medical conditions or take prescription medications.

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Medical Reviewer: Katherine Marengo LDN, R.D.
Last Review Date: 2022 Nov 30
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. 2020–2025 Dietary Guidelines for Americans. (2020). https://www.dietaryguidelines.gov/sites/default/files/2021-03/Dietary_Guidelines_for_Americans-2020-2025.pdf
  2. AIS sports supplement framework: Carnitine (L-carnitine). (2021). https://www.ais.gov.au/__data/assets/pdf_file/0010/1000072/36194_Sport-supplement-fact-sheets-Carnitine-v2.pdf
  3. Ames, B. N., et al. (2004). Delaying the mitochondrial decay of aging with acetylcarnitine [Abstract]. https://nyaspubs.onlinelibrary.wiley.com/doi/abs/10.1196/annals.1320.010?sid=nlm%3Apubmed
  4. Askarpour, M., et al. (2020). Beneficial effects of l-carnitine supplementation for weight management in overweight and obese adults: An updated systematic review and dose-response meta-analysis of randomized controlled trials. https://www.sciencedirect.com/science/article/abs/pii/S1043661819315117?via%3Dihub
  5. Carnitine. (2021). https://ods.od.nih.gov/factsheets/Carnitine-HealthProfessional/
  6. Carnitine: The science behind a conditionally essential nutrient. (n.d.). https://ods.od.nih.gov/News/Carnitine_Conference_Summary.aspx
  7. Ferreira, G. C., et al. (2018). L-Carnitine and acetyl-L-carnitine roles and neuroprotection in developing brain. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5621476/
  8. Fielding, R., et al. (2018). L-carnitine supplementation in recovery after exercise. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5872767/
  9. Karalis, D. T., et al. (2020). L-Carnitine as a diet supplement in patients with type II diabetes. https://www.cureus.com/articles/29978-l-carnitine-as-a-diet-supplement-in-patients-with-type-ii-diabetes
  10. Maruyama, T., et al. (2019). Efficacy of L-carnitine supplementation for improving lean body mass and physical function in patients on hemodialysis: A randomized controlled trial [Abstract]. https://pubmed.ncbi.nlm.nih.gov/30353121/
  11. Sawicka, A. K., et al. (2020). The bright and the dark sides of L-carnitine supplementation: A systematic review. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7507632/
  12. Talenezhad, N., et al. (2020). Effects of l-carnitine supplementation on weight loss and body composition: A systematic review and meta-analysis of 37 randomized controlled clinical trials with dose-response analysis. https://clinicalnutritionespen.com/article/S2405-4577(20)30053-X/fulltext