L-Carnitine: Types, Benefits, And Side Effects - Medical News Today

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Medical News TodaySubscribePotential benefits of L-carnitine, and who needs it

Medically reviewed by Angelica Balingit, MD — Written by Jon Johnson — Updated on November 5, 2025

What is it?
Benefits
Side effects
Dosage
How and when to take
Types
Summary

L-carnitine, also known as levocarnitine, is a naturally occurring amino acid structure that the body produces. It plays a critical role in energy production, converting fat into energy.

Most people will get enough L-carnitine from their diet or their body’s production of this compound. Those with low L-carnitine levels may benefit from taking an oral supplement.

As well as supporting energy production, L-carnitine may help some other functions in the body, such as maintaining general brain function and reducing the risk of certain disorders.

Some people may experience mild side effects when increasing their L-carnitine intake, especially with long-term use.

This article explains current research about L-carnitine, including its benefits, effectiveness, and side effects.

What is L-carnitine?

A hand holding two blue pills.-1 — Catherine Falls Commercial/Getty Images

L-carnitine is a type of carnitine, which is a derivative of amino acids. Amino acids combine to make proteins, which carry out many essential tasks in the body. Carnitine helps the body break down fatty acids and turn them into energy to power the cells.

L-carnitine is a conditionally essential nutrient, meaning that the body can generally make enough of it, but, in some cases, a person may have to get the compound from food or oral supplements if they cannot make enough.

In the body, the liver and kidneys create L-carnitine from the amino acids lysine and methionine. The kidneys can also store L-carnitine for later use and eliminate the excess through the urine stream.

Possible benefits of L-carnitine

L-carnitine, and carnitine in general, is a key component in creating energy for the cells. Its main function, helping break down fatty acids for use as energy, keeps the body’s cells powered and working efficiently.

L-carnitine also has a secondary function of helping remove some waste products from the cells to prevent them from accumulating and causing problems.

In addition to its core functions, L-carnitine may offer the following benefits to the body.

Heart health

According to a 2024 review, L-carnitine may significantly impact heart health. It may help to reduce oxidative stress and maintain efficient energy production, which can benefit the heart muscle.

It may also have some beneficial effects for:

heart failure
coronary artery disease
heart attack recovery
peripheral vascular disease, which causes narrow arteries

However, it is important to note that L-carnitine’s heart benefits remain controversial, and further research is necessary.

Key terms explained: Oxidative stress

Oxidative stress is an imbalance of free radicals and antioxidants in the body. Free radicals are a type of reactive molecule that can accumulate and damage cells.

Cancer treatment

A small 2018 study suggests certain cancer treatments, such as chemotherapy, may cause L-carnitine deficiencies. In these cases, L-carnitine supplements may help reduce symptoms such as fatigue and weakness.

However, it is important to note that this study was very small and only looked at a sample of 11 people. No larger study has currently validated the same conclusion.

Researchers are currently studying the compound as a possible way to prevent tissue damage due to chemotherapy, but this research is in the early stages.

Diabetes

Some research suggests L-carnitine has benefits for blood sugar management in people with diabetes.

A 2023 review concludes that L-carnitine supplementation may help to reduce the following:

fasting blood sugar levels
HbA1c levels, which are the average blood sugar level over 90 days
insulin resistance

L-carnitine supplements cannot substitute diabetes treatments. People should speak with a healthcare professional before using this supplement if they have diabetes.

Kidney or liver disease

As the kidneys and liver help create and use L-carnitine, disease in these organs or organ failure may lead to L-carnitine deficiency.

Doctors may recommend L-carnitine supplementation in these cases to support the function of the kidneys and liver and prevent deficiency.

What are the side effects of L-carnitine?

Most people tolerate L-carnitine well. However, some may experience digestive side effects when taking high dosages of L-carnitine, such as:

stomach cramps
nausea
vomiting
diarrhea
“fishy” body odor

People with high levels of urea may also experience muscle weakness, and those with a seizure disorder may experience seizures due to high L-carnitine dosages.

Some studies suggest that high levels of L-carnitine may raise the long-term risks of cardiovascular diseases, though more research is necessary.

L-carnitine supplements may interact with certain antibiotics or anticonvulsants. Anyone considering taking L-carnitine should talk with their doctor to discuss any medications they are taking and the possible drug interactions.

L-carnitine dosage recommendations

It is a good idea to talk with a healthcare professional before taking L-carnitine. They may have additional recommendations to support any treatment that the person needs and can help them avoid possible reactions and interactions.

The recommended dosage is roughly 1 to 3 grams (g) per day. However, people with genetic irregularities or other health conditions causing a lack of L-carnitine should talk with their doctor for a more specific dosage.

The National Institutes of Health (NIH) states that most people do not need extra L-carnitine from food or supplements. The liver and kidneys will create enough to meet their daily needs.

Even though the body produces it naturally, carnitine is widely available in a number of simple foods. Animal proteins, such as fish, red meat, and poultry, are some of the best sources.

The NIH suggests adults with an omnivorous diet get about 24 to 145 milligrams (mg) of carnitine per day. People who avoid animal products, such as those following a vegan diet, may get around 1 to 14.5 mg from their diet.

However, the kidneys can store carnitine for later use, so people’s overall levels will be about the same, regardless of their diet. The kidneys also eliminate excess carnitine through urine to maintain healthful concentrations.

Key terms explained: Omnivorous

An omnivorous diet is a mixed diet that includes fruits, vegetables, grains, and animal products, including meat.

How and when to take L-carnitine

The best amount and form of L-carnitine may vary depending on the person’s reason for wanting more of this compound. Generally speaking, healthy adults do not need to take L-carnitine to support their health.

Athletes

Some athletes take extra L-carnitine, believing that it will boost their athletic performance.

Some research suggests this supplement may aid recovery following exercise, including muscle soreness.

However, a 2020 review notes that more research is necessary to support the use of L-carnitine for better exercise performance.

For weight loss

As L-carnitine helps burn fatty acids for energy, people may assume that taking more may help them lose weight. More research is necessary, but some studies support this idea.

For example, a 2025 review suggests L-carnitine supplements may help people with obesity manage their body weight, body mass index (BMI), and reduce their waist circumference.

However, L-carnitine cannot replace habits such as a balanced diet and regular exercise. It is a good idea to speak with a healthcare professional before taking L-carnitine for weight loss.

»Learn more:Tips for successful weight loss

Other types of carnitine

Carnitine is a broad term that describes a few different compounds. L-carnitine is a form of carnitine present in the body and many supplements. Other forms include:

Acetyl L-carnitine: This form, sometimes known as ALCAR, also plays a role in metabolism. It possesses neuroprotective properties that may help protect the nervous system.
D-carnitine: This type is the optical isomer (mirror image) of L-carnitine. It is toxic to the body, as it may inhibit the absorption of other forms of carnitine.
L-carnitine L-tartrate: Athletes may take this type as a sports supplement. Research suggests that it may be useful in lowering fatigue and aiding recovery after exercise.
Propionyl-L-carnitine: This form displays pain relieving and antirheumatic properties and may benefit heart health.

Summary

L-carnitine is an amino acid that the body naturally produces. In people with good health, the liver and kidneys produce and store enough of the compound to prevent deficiency.

People with L-carnitine deficiencies may need to get the compound through their diet or as a supplement. It is advisable to talk with a doctor before taking an L-carnitine supplement.

Some people may wish to take L-carnitine supplements for their potential benefits, such as aiding athletic performance or weight loss. However, more research is necessary to confirm these benefits.

Nutrition / Diet
Obesity / Weight Loss / Fitness
Pharmacy / Pharmacist
Sports Medicine / Fitness
Complementary Medicine / Alternative Medicine

How we reviewed this article:

SourcesMedical News Today has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

(-)-Carnitine. (n.d.).https://pubchem.ncbi.nlm.nih.gov/compound/L-Carnitine
Acetyl-L-carnitine. (n.d.).https://pubchem.ncbi.nlm.nih.gov/compound/7045767
Carnitine. (2023).https://ods.od.nih.gov/factsheets/Carnitine-HealthProfessional/
CARNITOR® (levocarnitine) tablets (330 mg). (2018).https://www.accessdata.fda.gov/drugsatfda_docs/label/2018/018948s028,019257s014lbl.pdf
Durazzo A, et al. (2020). The nutraceutical value of carnitine and its use in dietary supplements.https://www.mdpi.com/1420-3049/25/9/2127
Elantary R, et al. (2024). Role of L-carnitine in cardiovascular health: Literature review.https://pmc.ncbi.nlm.nih.gov/articles/PMC11427024/
Eyth E, et al. (2025). Hemoglobin A1C.https://www.ncbi.nlm.nih.gov/books/NBK549816/
Gnoni A, et al. (2020). Carnitine in human muscle bioenergetics: Can carnitine supplementation improve physical exercise?https://www.mdpi.com/1420-3049/25/1/182
Hamedi-Kalajahi F, et al. (2025). The effect of the L-carnitine supplementation on obesity indices: An umbrella meta-analysis.https://pubmed.ncbi.nlm.nih.gov/40298161/
Kazeminasab F, et al. (2025). Effects of L-carnitine supplementation on markers of exercise-induced muscle damage in healthy adults: A systematic review and meta-analysis of randomized controlled trials.https://www.sciencedirect.com/science/article/pii/S2950273X25000256
Matsui H, et al. (2018). L-Carnitine supplementation reduces the general fatigue of cancer patients during chemotherapy.https://pmc.ncbi.nlm.nih.gov/articles/PMC5795559/
Propionylcarnitine. (n.d.).https://pubchem.ncbi.nlm.nih.gov/compound/107738#section=Information-Sources
Stefan M, et al. (2021). L-carnitine tartrate supplementation for 5 weeks improves exercise recovery in men and women: A randomized, double-blind, placebo-controlled trial.https://pmc.ncbi.nlm.nih.gov/articles/PMC8541253/
Zamani M, et al. (2023). The effects of L-carnitine supplementation on glycemic markers in adults: A systematic review and dose-response meta-analysis.https://pmc.ncbi.nlm.nih.gov/articles/PMC9871499/

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Medically reviewed by Angelica Balingit, MD — Written by Jon Johnson — Updated on November 5, 2025

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