L-Carnitine - A Review Of Benefits, Side Effects And Dosage

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Evidence BasedWhat to Know About the Amino Acid L-Carnitine

Medically reviewed by Jared Meacham, PhD., RD, CSCS — Written by Rudy Mawer, MSc, CISSN and Rachael Ajmera, MS, RD — Updated on November 29, 2024

What is it?
Weight loss
Brain health
Heart health
Exercise performance
Diabetes
Depression
Side effects
Food sources
Worth taking?
Dosage
FAQ
Takeaway

L-carnitine is an amino acid produced by the body and found in some foods and supplements. It may offer some health benefits, including increased weight loss, improved brain function, and more.

L-carnitine is a naturally occurring amino acid derivative that’s often taken as a supplement. It’s used for weight loss and may have an impact on brain function.

However, popular claims about supplements don’t always match up with the science.

Keep reading to learn more about the possible functions, risks, and benefits of L-carnitine.

What is L-carnitine?

L-carnitine is a nutrient and dietary supplement. It plays a crucial role in the production of energy by transporting fatty acids into your cells’ mitochondria.

The mitochondria act as engines within your cells, burning these fats to create usable energy. Your body can produce L-carnitine out of the amino acids lysine and methionine.

For your body to produce it in sufficient amounts, you also need plenty of vitamin C.

More than 95% of your L-carnitine stores are contained in your muscles, along with trace amounts in your blood, liver, heart, and kidneys.

You can also obtain small amounts by eating animal products like meat and dairy products.

People who eat plant-based diets or those with certain genetic issues may be unable to produce or obtain enough L-carnitine, which makes it a conditionally essential nutrient.

Does it aid weight loss?

L-carnitine helps move more fatty acids into your cells to be burned for energy, so it’s sometimes used as a weight loss supplement.

A 2020 review of 37 studies found that L-carnitine supplementation significantly reduced body weight, body mass index (BMI), and fat mass. However, it had no effect on belly fat or body fat percentage.

Another 2021 review in 1,239 people with type 2 diabetes also found that taking 2 grams (g) of L-carnitine daily for at least 2 weeks helped promote weight loss.

Still, more research is needed to understand how it may impact long-term weight loss.

Furthermore, while it may aid in weight loss for some people, consider speaking with a dietician to develop a thorough diet and exercise regimen first.

Effects on brain function

L-carnitine may benefit brain function.

Some research suggests that the acetyl form, acetyl-L-carnitine (ALCAR), may help prevent age-related mental decline and improve markers of learning.

In fact, a 2018 study found that taking 1,500 milligrams (mg) of ALCAR daily for 28 weeks significantly improved brain function in people with dementia.

However, other studies have turned up mixed results.

For instance, a 2017 review of two studies showed that taking L-carnitine for 3 days had no effect on markers of brain function — including reaction time, vigilance, immediate memory, and delayed recall — in young adults without cognitive impairment.

Therefore, more research is needed on the potential benefits of supplementation.

Heart health

Some studies demonstrate that L-carnitine could benefit several aspects of heart health.

For example:

A 2019 review found that L-carnitine significantly reduced diastolic blood pressure, especially in people with overweight and obesity.
A 2017 analysis showed that L-carnitine may improve heart function and decrease symptoms in people with congestive heart failure.
A 2019 review showed that L-carnitine may reduce total and LDL (bad) cholesterol while increasing HDL (good) cholesterol in people at risk for heart disease.

Exercise performance

The evidence is mixed regarding the effects of L-carnitine on sports performance, but it may offer some benefits.

According to a 2021 review, some studies suggest that L-carnitine may help improve:

exercise and muscle recovery
muscle oxygen supply
exercise performance, endurance, and power

However, the researchers note that some studies found no significant benefits from L-carnitine supplementation on these parameters.

L-carnitine’s benefits may also be indirect and take weeks or months to appear. This differs from supplements like caffeine or creatine, which can directly enhance sports performance.

Consider speaking with a healthcare professional before taking L-carnitine to boost exercise performance. They may suggest a better alternative for you.

Type 2 diabetes

L-carnitine may be beneficial for people with type 2 diabetes.

A 2023 review concluded that L-carnitine supplementation may reduce fasting blood sugar and hemoglobin A1c, while also improving insulin sensitivity in people with diabetes, overweight, or obesity.

L-carnitine is believed to work by altering insulin receptors and changing the expression of specific genes that regulate sugar metabolism.

It may also help improve the function of beta cells, which are responsible for producing insulin in the pancreas.

Depression

Some research suggests that L-carnitine could be beneficial for the treatment of depression.

In a 2018 review, acetyl-L-carnitine significantly reduced symptoms of depression compared with placebo.

Several studies included in this review also found that acetyl-L-carnitine was as effective as antidepressant medications but caused fewer adverse effects.

Still, more research is needed to understand how L-carnitine may affect depression.

Safety and side effects

For most people, taking 2 g or less per day is relatively safe and free from any serious side effects. However, some mild side effects like heartburn and indigestion are possible.

Some research has also used doses of up to 4,500 mg per day.

It’s important to note, however, that L-carnitine supplements may raise your blood levels of trimethylamine-N-oxide (TMAO) over time. High levels of TMAO are linked to an increased risk of atherosclerosis — a disease that clogs your arteries.

More studies on the safety of L-carnitine supplements are needed.

Food sources

You can get small amounts of L-carnitine from your diet by eating meat and dairy products.

The best sources of L-carnitine are:

Beef: 139 to 143 mg per 3.5 ounces (oz), or 100 g
Pork: 25 to 61 mg per 3.5 oz (100 g)
Chicken: 13 to 34 mg per 3.5 oz (100 g)
Cow’s milk: 40 mg per 3.5 oz (100 g)
Hard cheese: 3 mg per 3.5 oz (100 g)

Interestingly, food sources of L-carnitine have a greater absorption rate than supplements.

According to a 2004 study, 57% to 84% of L-carnitine is absorbed when it’s consumed from food, compared to only 14% to 18% when taken as a supplement.

Your body also produces L-carnitine naturally from the amino acids methionine and lysine if your stores are low.

As such, L-carnitine supplements are only necessary in special cases, such as disease treatment.

Should you take it?

Your L-carnitine levels are influenced by how much you’re eating and how much your body is producing.

Vegans and vegeterians

L-carnitine levels are often lower in vegetarians and vegans since they restrict or avoid animal products.

Therefore, vegetarians and vegans may want to consider L-carnitine supplements, which can help normalize carnitine levels in the blood and muscles.

Older adults

Older adults may also benefit from L-carnitine supplements.

A 2016 study found that taking 1.5 g of L-carnitine per day for 10 weeks improved functional status and frailty in older adults.

On the other hand, a 2018 study showed that L-carnitine supplementation had no effect on muscle strength or markers of inflammation in older women.

Chronic conditions

The risk of deficiency is higher for those with diseases like cirrhosis and kidney disease. If you have one of these conditions, a supplement may be beneficial.

However, as with any supplement, you should speak with a doctor before taking L-carnitine.

Dosage recommendations

Studies on the potential benefits of L-carnitine have used a wide range of doses.

Dosage varies from study to study and may vary depending on the form of carnitine you take:

Acetyl-L-carnitine: This form is best for brain health and function. Doses vary from 500 to 3,000 mg per day.
L-carnitine L-tartrate: This form is most effective for exercise performance. Doses vary from 1,000 to 4,500 mg per day.
Propionyl-L-carnitine: This form may help improve blood flow in those with high blood pressure or related health conditions. A 2005 study used a dose of 2 g per day.

Frequently asked questions

Does L-carnitine affect sleep?

Some research suggests that taking 500 to 510 mg of L-carnitine daily may help treat narcolepsy, a sleeping condition characterized by abnormal sleeping patterns.

Is L-carnitine good for females?

Some research suggests that L-carnitine may reduce body weight, BMI, and belly fat in people with polycystic ovary syndrome (PCOS).

If you’re pregnant or have recently delivered, consider speaking with a doctor about your carnitine levels. People who are pregnant have a higher risk of carnitine deficiency.

Who should not take carnitine?

People who are taking certain types of antibiotics and anticonvulsants should speak with a doctor before taking L-carnitine, as this supplement may interact with the medications.

The bottom line

L-carnitine is an amino acid that may help support weight loss, brain function, and disease prevention.

It’s produced naturally in your body, but it’s also found in foods like meat and dairy products. Supplements may benefit those with lower levels, such as older adults, vegans, and vegetarians.

Consider speaking with a healthcare professional before taking L-carnitine. They could help you decide whether it’s appropriate and recommend the best dosage.

How we reviewed this article:

SourcesHistoryHealthline 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.

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Evidence Based

This article is based on scientific evidence, written by experts and fact checked by experts.

Our team of licensed nutritionists and dietitians strive to be objective, unbiased, honest and to present both sides of the argument.

This article contains scientific references. The numbers in the parentheses (1, 2, 3) are clickable links to peer-reviewed scientific papers.

Medically reviewed by Jared Meacham, PhD., RD, CSCS — Written by Rudy Mawer, MSc, CISSN and Rachael Ajmera, MS, RD — Updated on November 29, 2024

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