L-carnitine is an amino acid-like compound that the body makes and that appears in certain foods and dietary supplements. It’s been linked to potential benefits such as enhanced fat loss, better cognitive performance, and other health effects.
As a naturally occurring derivative of amino acids, L-carnitine is commonly used as a supplement. People often take it to support weight management and possibly to influence brain health.
That said, popular claims about supplements don’t always align with the scientific evidence.
Read on to explore how L-carnitine might work, its possible advantages, and any safety concerns.
What is L-carnitine?
L-carnitine is both a nutrient and a supplement. It plays a vital role in cellular energy production by shuttling fatty acids into mitochondria.
Mitochondria are the powerhouses of cells, where these fats are oxidized to produce usable energy. Your body can synthesize L-carnitine from the amino acids lysine and methionine.
To make enough of it, adequate amounts of vitamin C are also required.
The majority of your L-carnitine—over 95%—is stored in skeletal muscle, with smaller quantities in the blood, liver, heart, and kidneys.
You can also obtain modest amounts from animal-derived foods such as meats and dairy.
People following plant-based diets or those with particular genetic disorders may not produce or consume sufficient L-carnitine, making it a conditionally essential nutrient for some.
Does it aid weight loss?
Because L-carnitine facilitates the transport of fatty acids into cells for burning, it’s sometimes marketed as a weight-loss aid.
A meta-analysis of 37 trials reported that L-carnitine supplementation led to significant reductions in body weight, body mass index (BMI), and fat mass, though it did not affect abdominal fat or overall body fat percentage.
Another 2021 review involving 1,239 participants with type 2 diabetes found that taking 2 grams (g) of L-carnitine daily for a minimum of two weeks supported weight reduction.
Nonetheless, additional research is required to determine its effects on long-term weight management.
Also, while it may help some individuals lose weight, consult a registered dietitian to create a comprehensive nutrition and exercise plan first.
Effects on brain function
L-carnitine might have positive effects on cognitive health.
Research indicates that the acetylated form, acetyl-L-carnitine (ALCAR), could slow age-associated cognitive decline and improve certain learning measures.
For instance, a 2018 trial found that 1,500 milligrams (mg) of ALCAR daily for 28 weeks significantly enhanced cognitive function in people with dementia.
However, findings have been inconsistent across studies.
A 2017 review of two trials showed that three days of L-carnitine supplementation did not affect cognitive markers—such as reaction time, vigilance, immediate memory, or delayed recall—in healthy young adults.
Therefore, further study is necessary to clarify the cognitive benefits of supplementation.
Heart health
Some evidence suggests L-carnitine could support various elements of cardiovascular health.
Examples include:
- A study that found L-carnitine significantly lowered diastolic blood pressure, particularly in people with overweight or obesity.
- A 2017 analysis indicating potential improvements in cardiac function and reduced symptoms in individuals with congestive heart failure.
- Research showing L-carnitine may decrease total and LDL (“bad”) cholesterol while raising HDL (“good”) cholesterol in people at increased risk for cardiovascular disease.
Exercise performance
The data are mixed about L-carnitine’s effects on athletic performance, though some benefits have been reported.
A 2021 review noted that some trials suggest L-carnitine can improve:
That said, other studies found no meaningful improvements. Moreover, L-carnitine’s gains may be indirect and require weeks or months to show, unlike supplements such as caffeine or creatine, which can produce more immediate performance effects.
Talk with a healthcare professional before using L-carnitine for exercise enhancement; they might recommend a different supplement better suited to your goals.
Type 2 diabetes
L-carnitine may offer advantages for people living with type 2 diabetes.
A 2023 review concluded that supplementation could lower fasting glucose and hemoglobin A1c and improve insulin sensitivity in individuals with diabetes, overweight, or obesity.
L-carnitine is thought to act by modifying insulin receptor activity and altering the expression of genes involved in glucose metabolism.
It may also support beta-cell function in the pancreas, which are the cells that produce insulin.
Depression
Some studies indicate that L-carnitine could be helpful in treating depressive symptoms.
In a meta-analysis, acetyl-L-carnitine produced a significant reduction in depressive symptoms compared with placebo.
Several trials included in the review suggested acetyl-L-carnitine was as effective as standard antidepressants but was associated with fewer side effects.
Yet further research is needed to fully understand L-carnitine’s role in mood disorders.
Safety and side effects
For most individuals, taking up to 2 g per day is generally considered safe and unlikely to cause serious adverse effects, though mild issues like heartburn or indigestion can occur.
Some studies have used doses as high as 4,500 mg per day.
It’s important to be aware that L-carnitine supplements may gradually raise blood levels of trimethylamine-N-oxide (TMAO). Elevated TMAO has been associated with increased risk of atherosclerosis, a condition that narrows arteries.
More research is required to confirm the long-term safety of L-carnitine supplementation.
Food sources
You can obtain modest amounts of L-carnitine through dietary choices, primarily from meat and dairy products.
The richest sources include:
- 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, L-carnitine from whole foods is absorbed more efficiently than supplemental forms.
A 2004 study reported that approximately 54% to 87% of food-derived L-carnitine is absorbed, compared with only 14% to 18% from supplements.
Your body also synthesizes L-carnitine from methionine and lysine when stores are depleted.
Consequently, supplements are generally only necessary in particular situations, such as certain medical conditions.
Should you take it?
Your circulating L-carnitine depends on dietary intake and how much your body manufactures.
Vegans and vegetarians
L-carnitine concentrations are often lower in vegetarians and vegans because they exclude or limit animal foods.
Therefore, people following these diets might consider supplementation to restore normal carnitine levels in blood and muscle.
Older adults
Older adults could also benefit from L-carnitine supplementation.
A 2016 trial found that 1.5 g per day for 10 weeks improved functional capacity and frailty measures in elderly participants.
Conversely, a 2018 study reported no changes in muscle strength or inflammatory markers in older women taking L-carnitine.
Chronic conditions
The likelihood of deficiency is greater in people with conditions such as cirrhosis and chronic kidney disease. In such cases, supplementation might be warranted.
As with any supplement, consult your physician before starting L-carnitine.
Dosage recommendations
Research into L-carnitine has used a broad range of doses, and the ideal amount depends on the specific form you take:
- Acetyl-L-carnitine: Preferred for cognitive support. Doses in studies range from 500 to 3,000 mg daily.
- L-carnitine L-tartrate: Often used for exercise-related goals. Doses vary from 1,000 to 4,500 mg per day.
- Propionyl-L-carnitine: May improve circulation in people with hypertension or related issues. A 2005 trial used a specific dose in this context.
Frequently asked questions
Does L-carnitine affect sleep?
Some evidence indicates that taking 500 to 510 mg of L-carnitine daily may help treat narcolepsy, a disorder characterized by abnormal sleep-wake patterns.
Is L-carnitine good for females?
Some research suggests L-carnitine may reduce weight, BMI, and abdominal fat in people with polycystic ovary syndrome (PCOS).
If you are pregnant or recently postpartum, consult a healthcare provider about your carnitine status. Pregnant people have a higher risk of carnitine insufficiency.
Who should not take carnitine?
Individuals taking certain antibiotics or anticonvulsant medications should consult their doctor before using L-carnitine, as interactions are possible.
The bottom line
L-carnitine is a compound that may support fat loss, cognitive health, and help manage certain conditions. It’s produced by the body and is present in foods like meat and dairy. Supplements can be useful for those with low levels, including older adults and people following vegan or vegetarian diets.
Talk with a healthcare professional before beginning L-carnitine supplements so they can advise whether it’s suitable for you and recommend an appropriate dose.
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