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Printed from https://bottledhope.co/supplements/l-carnitine/. Last reviewed 2026-10-11. Check the site for the latest version.

L-carnitine

A compound the body makes from amino acids and gets from foods such as red meat. People take it as a supplement for weight loss, exercise, fertility and memory.

Explained simply · Last reviewed

What it is

L-carnitine is a compound the body makes from amino acids and uses to carry fats into mitochondria, the parts of cells that burn them for energy. ODS, the US office that reviews dietary supplements, says carnitine is the general name for several related compounds, including L-carnitine, acetyl-L-carnitine and propionyl-L-carnitine. It says the liver, kidneys and brain make carnitine from the amino acids lysine and methionine, and that it is present in animal products, especially red meat.

More about L-carnitine

ODS, the US office that reviews dietary supplements, says carnitine is the general name for several related compounds, including L-carnitine, acetyl-L-carnitine and propionyl-L-carnitine. It says the liver, kidneys and brain make carnitine from the amino acids lysine and methionine, and that it is present in animal products, especially red meat.

ODS says healthy children and adults do not need carnitine from food or supplements, because the body makes enough. EFSA, the EU food safety agency, notes a consensus that L-carnitine is not an essential nutrient, but that infants cannot yet make enough of it, which is why infant formula must contain a minimum amount. ODS says babies born prematurely and people with kidney failure, especially on dialysis, can run short.

According to ODS, the two main forms in supplements are L-carnitine and acetyl-L-carnitine. A 2021 review says L-carnitine became popular as a supplement after rumors that it helped the Italian national football team win the world championship in 1982, and that it is often portrayed as a fat burner. ODS describes research on carnitine for dementia, heart and artery disease, diabetes, infertility, osteoarthritis, athletic performance and weight loss. Each claim below says which form its reviews studied.

Also known as: carnitine, acetyl-L-carnitine, ALCAR

At a glance

Safety: known risks, 2 groups who should avoid it or take extra care and 2 documented interactions. See Safety ↓

Claims made about L-carnitine, and how strong the evidence is for each:

Each rating follows our published rules and the sources cited for it. We don’t add our own medical judgment. How we rate

Safety

Read this before the ratings below.

Risks

  • ODS states that carnitine "does not have an established tolerable upper intake level". It adds: "However, doses of approximately 3 g/day of carnitine supplements can cause nausea, vomiting, abdominal cramps, diarrhea, and a fishy body odor."
  • ODS states that carnitine can also cause muscle weakness in people with uremia and seizures in people with seizure disorders.
  • ODS says some research indicates that gut bacteria turn unabsorbed carnitine into TMAO (trimethylamine-N-oxide) and gamma-butyrobetaine, which might increase the risk of heart and blood vessel disease. It says the effect appears stronger in people who eat meat than in vegans or vegetarians, and that the implications are not well understood and need more research.
  • A 2022 Cochrane review of trials in people on dialysis found that L-carnitine makes little or no difference to adverse events, at low certainty, from 12 trials. Its authors say carnitine "does not appear to have any adverse effects", but that the limited evidence could not definitively establish its safety.
  • A 2019 Cochrane review of acetyl-L-carnitine for diabetic nerve pain reports that in one trial, 6 of 147 people on acetyl-L-carnitine and 2 of 147 on placebo stopped because of adverse events such as headache, tingling in the face and stomach upset. The reviewers say the evidence on adverse events is too uncertain to judge safety.
  • EFSA, the EU food safety agency, states that its opinions on L-carnitine health claims are not a positive assessment of its safety.
  • A 2017 review of carnitine for cancer-related fatigue reports that in one trial of acetyl-L-carnitine in women having breast cancer treatment, symptoms of nerve damage increased with the supplement. The reviewers say this should be considered before clinical use.

Who should avoid it or take extra care

  • People with seizure disorders: ODS states that carnitine can cause seizures in people with seizure disorders.
  • People with uremia: ODS states that carnitine can cause muscle weakness in them.

Documented interactions

  • Pivalate-conjugated antibiotics, such as pivampicillin: ODS states that long-term use of these antibiotics can deplete carnitine. It adds that no cases of illness from carnitine deficiency have been described in people taking them. Source [1]
  • Valproic acid and other anticonvulsants (phenobarbital, phenytoin, carbamazepine): ODS states that treatment with these seizure medicines reduces blood levels of carnitine. It advises people who take these or other medicines regularly to discuss their carnitine intake with their healthcare providers. Source [1]

Safety sources: Source [1]Source [2]Source [3]Source [4]Source [5]Source [6]

What the evidence says

Each claim is rated on its own evidence. Ratings follow the scale on our methodology page.

  • Helps with weight loss Evidence rating: Limited

    People take it hoping it will help their body burn fat and lose weight.

    A 2025 review reports about 1.1 kg more weight lost with L-carnitine, with results that varied widely; ODS calls the trial results equivocal and says larger studies are needed.

    A 2025 review pooled earlier meta-analyses of L-carnitine and body weight, an approach called an umbrella meta-analysis. Combining six of them, it found about 1.1 kg more weight lost with L-carnitine than in control groups. Body mass index fell slightly. For both weight and body mass index, results varied widely between the meta-analyses. Pooling the four meta-analyses that measured waist size, it found a smaller waist. The reviewers note that some trials were counted in several of them, and they did not grade how sure they could be (certainty).

    ODS, the US office that reviews dietary supplements, describes a 2016 review of nine trials in 911 adults in which people taking carnitine lost more weight than with placebo. ODS notes that weight loss was a secondary outcome in most studies, often alongside a low-calorie diet, exercise or weight-loss drugs, and that results have been equivocal. It says larger studies are needed.

    A 2020 review limited to L-carnitine taken without other medicines found a smaller waist with L-carnitine than with placebo, but from only two trials. None of these sources graded certainty, so this page rates the claim limited: a small average difference, from trials that varied widely.

    Sources: Source [1]Source [2]Source [3]

  • Improves exercise performance Evidence rating: Limited

    People take it around training hoping it will boost their stamina and power.

    A 2021 review found better results in some high-intensity tests and none in moderate-intensity exercise; ODS calls the evidence mixed, and EFSA found an endurance benefit not established.

    A 2021 systematic review gathered 11 controlled trials in physically active and untrained adults. Nine gave L-carnitine or L-carnitine L-tartrate, and two gave propionyl-L-carnitine forms. In high-intensity exercise, some trials found less perceived effort, more work done in an all-out test, or more power in short cycling sprint tests. Other trials of high-intensity exercise found no improvement. In moderate-intensity exercise, no trial found better performance.

    The reviewers list small samples, varied populations and a lack of muscle biopsy data among the limits of the trials. They did not grade certainty. ODS describes this review and others, and calls the evidence on athletic performance mixed. It says additional investigations are needed.

    EFSA, the EU food safety agency, assessed a claim in 2011 that L-carnitine increases endurance capacity. The only study it was given that measured endurance capacity had no control group, in seven marathon runners, so it drew no conclusions from it. It concluded that a cause and effect relationship had not been established. This page rates the claim limited: small trials, with improvements in some high-intensity tests and none in moderate-intensity exercise.

    Sources: Source [1]Source [2]Source [3]

  • Speeds recovery after exercise Evidence rating: Limited

    People take it hoping it will ease sore muscles and help them bounce back after hard workouts.

    ODS describes trials in which some found less soreness or faster recovery and others found no effect; EFSA found faster recovery and muscle repair not established.

    ODS, the US office that reviews dietary supplements, describes a 2018 review of L-carnitine for exercise and recovery. In well-trained athletes, it says L-carnitine hastened recovery and lowered lactate and heart rate in some studies, and did not affect performance in others. In recreationally active adults, it says some studies found less muscle soreness and better recovery, while others found no effect on lactate, heart rate, endurance or perceived effort.

    ODS calls the evidence on performance enhancement mixed and says additional investigations are needed. The 2021 exercise review cited on this page did not include recovery outcomes.

    EFSA, the EU food safety agency, assessed claims in 2011 that L-carnitine speeds recovery from muscle fatigue after exercise and helps repair muscle tissue. It was given no references from which it could draw conclusions; the one pilot study on recovery, in 12 people, lacked the detail needed for a full evaluation. It concluded that a cause and effect relationship had not been established for either. This page rates the claim limited: a mix of small studies, some finding faster recovery and some not.

    Sources: Source [1]Source [2]Source [3]

  • Lowers blood sugar or improves insulin resistance Evidence rating: Limited

    People with type 2 diabetes or prediabetes take it hoping it will bring their blood sugar down.

    Reviews report improved insulin resistance and, in some analyses, lower fasting glucose, but not overall in a 2020 review of L-carnitine alone; ODS says larger trials are needed.

    ODS, the US office that reviews dietary supplements, describes meta-analyses of L-carnitine and blood sugar. A 2017 one of five trials in adults with insulin resistance found improved measures of insulin resistance. Another, of four trials in type 2 diabetes, found lower fasting glucose but no change in HbA1c.

    A 2020 review pooled only trials of L-carnitine taken without other medicines. Across five trials, it found no significant change in fasting blood sugar overall. In the four trials in people whose fasting blood sugar was already raised, it was lower with L-carnitine. Its authors note that the four-trial diabetes review ODS describes included two trials that combined L-carnitine with drugs and one of acetyl-L-carnitine, which they left out.

    ODS says additional trials with larger samples are needed to determine whether L-carnitine can reduce the risk of diabetes or the severity of its effects.

    This page rates the claim limited: reviews of few trials, with lower fasting blood sugar in some groups but not overall.

    Sources: Source [1]Source [2]

  • Improves cholesterol and other blood fats Evidence rating: Limited

    People take it hoping it will lower their cholesterol and triglycerides.

    A 2023 review found small falls in LDL cholesterol and other blood fats, at moderate to very low certainty; EFSA cited no sustained cholesterol effect, and one trial found it higher.

    A 2023 review pooled 13 earlier meta-analyses of L-carnitine and blood fats. It found lower total cholesterol, triglycerides and LDL cholesterol, and slightly higher HDL cholesterol. The reviewers rated how sure they could be (certainty) moderate for LDL, low for total cholesterol and triglycerides, and very low for HDL. They write that only the change in LDL reached the smallest difference they treat as meaningful, and that results varied widely between studies.

    EFSA, the EU food safety agency, assessed a claim in 2011 that L-carnitine maintains normal LDL cholesterol. One 30-day trial it was given found lower total and LDL cholesterol, but two longer trials, of 12 weeks and six months, found no effect. EFSA judged that the trials did not show a sustained effect, and concluded that a cause and effect relationship had not been established. In 2018, it reached the same conclusion for a claim that L-carnitine contributes to normal lipid metabolism.

    ODS, the US office that reviews dietary supplements, describes a 2022 trial in 157 people aged 58 to 75 with metabolic syndrome. After six months, total and LDL cholesterol were higher with L-carnitine than with placebo, and total plaque volume in the arteries did not differ. This page rates the claim on the lowest certainty the 2023 review gives these outcomes, very low.

    Sources: Source [1]Source [2]Source [3]Source [4]

  • Improves sperm quality or the chance of pregnancy in men with infertility Evidence rating: Limited

    Men trying for a baby take it hoping it will improve their sperm and their chances of becoming a father.

    A 2020 review found better sperm movement and shape at low certainty; neither it nor a Cochrane review found more pregnancies, and evidence on sperm concentration is very low certainty.

    This claim covers sperm measures and pregnancy in men with unexplained infertility. A 2020 review pooled randomized trials of L-carnitine, acetyl-L-carnitine or both, against placebo or no treatment. It found better total and forward sperm movement (motility) and more normally shaped sperm, rating each low certainty. Sperm concentration did not change significantly, at very low certainty. Results varied widely between trials.

    The 2020 review found no significant improvement in pregnancy rates, at low certainty. None of the trials that reported pregnancy gave live-birth data. Its authors conclude that it remains unclear whether carnitines are a suitable intervention for unexplained male infertility.

    A 2022 Cochrane review of antioxidants for male subfertility analyzed carnitines as one group. It found no evidence of more live births, from one trial of 60 men, or of more clinical pregnancies, from two trials of 125 men. Some sperm motility analyses favored carnitines, with very high variation between trials. Its certainty ratings cover antioxidants as a whole: very low for live birth and low for clinical pregnancy.

    ODS, the US office that reviews dietary supplements, describes the Cochrane review as finding higher sperm motility and concentration at some time points, with no effect on live births or pregnancy. It says more research is needed. EFSA, the EU food safety agency, assessed a claim in 2011 that L-carnitine contributes to normal sperm production in men generally. It was given no human studies it could draw conclusions from, and concluded that a cause and effect relationship had not been established. This page rates the claim on the lowest certainty for these outcomes, very low.

    Sources: Source [1]Source [2]Source [3]Source [4]

  • Improves memory or thinking in healthy people Evidence rating: Insufficient

    People take it hoping it will sharpen their memory and focus.

    A 2017 Cochrane review found only two small, short trials in healthy young adults, could draw no conclusions, and rated the evidence very low certainty.

    A 2017 Cochrane review searched for trials of L-carnitine, acetyl-L-carnitine or propionyl-L-carnitine in people without memory or thinking problems. It found two trials, both of L-carnitine in healthy young adults with an average age of about 21. In one, about 200 women took L-carnitine or placebo for three days. The reviewers found no evidence of an effect on reaction time, vigilance, or immediate or delayed recall. The other, a single-dose trial in 18 people, reported no effect but gave no data.

    The reviewers rated the evidence very low certainty for every outcome. They say they were unable to draw any conclusions about whether L-carnitine helps thinking in healthy adults, or about its safety. Two short trials are too little research to show an effect either way, so this page rates the claim insufficient.

    Sources: Source [1]

  • Acetyl-L-carnitine improves symptoms of dementia or mild cognitive decline Evidence rating: Limited

    People worried about memory loss, and families of people with dementia, take it hoping it will slow the decline.

    A 2003 Cochrane review found benefit on a few measures at some time points, possibly by chance, and none on most; it found no evidence to recommend routine use.

    This claim is about acetyl-L-carnitine, not L-carnitine. A 2003 Cochrane review gathered 16 placebo-controlled trials in people with mild to moderate dementia or cognitive decline, mostly with Alzheimer's disease. More people were rated improved by their clinicians at 12 and 24 weeks, but not at 52 weeks. Scores on the Mini-Mental State Examination, a memory and thinking test, were better at 24 weeks only.

    The review's plain-language summary states: "There is no evidence of benefit of ALC in the areas of cognition, severity of dementia, functional ability or Clinical Global Impression as a continuous measure." It says the 24-week result on that test "must be interpreted with caution in the context of significant heterogeneity in these trials".

    The reviewers write that, given the large number of comparisons, the significant results "may be due to chance". They conclude that there is no evidence to recommend its routine clinical use. They note that many trials were supported by Sigma-Tau, a maker of acetyl-L-carnitine, which also supplied data. The review's last search was in 2007, and it did not grade certainty.

    ODS, the US office that reviews dietary supplements, describes a 2003 meta-analysis of 21 trials in mild cognitive impairment or mild Alzheimer's disease that found better scores with acetyl-L-carnitine. ODS says the effects remain unclear. The sources disagree, so this page takes the lower reading and rates the claim limited.

    Sources: Source [1]Source [2]

  • Acetyl-L-carnitine eases nerve pain from diabetic neuropathy Evidence rating: Limited

    People with diabetes and nerve pain in their feet or hands take it hoping it will ease the pain.

    A 2019 Cochrane review found lower pain scores than with placebo in three trials, but rated the evidence very low certainty and is very uncertain whether it helps.

    This claim is about acetyl-L-carnitine, not L-carnitine. A 2019 Cochrane review found three placebo-controlled trials in people with diabetic nerve damage (neuropathy). Pain scores were about 9 points lower on a 100-point scale with acetyl-L-carnitine, at very low certainty. Two trials reported better vibration sense after 12 months, but gave no figures, also at very low certainty. No trial measured how many people had meaningful pain relief.

    The reviewers write: "We are very uncertain whether ALC causes a reduction in pain after 6 to 12 months' treatment in people with DPN, when compared with placebo, as the evidence is sparse and of low certainty." They say evidence on daily function and other symptoms is lacking or very low certainty. The review's authors report that two of its four trials were funded by a maker of acetyl-L-carnitine, and the other two had a co-author who consulted for one.

    This page rates the claim on the review's certainty for these outcomes, very low.

    Sources: Source [1]

  • Acetyl-L-carnitine eases symptoms of depression Evidence rating: Limited

    People with low mood or depression take it hoping it will lift their mood.

    A 2026 review of mostly small, older trials found lower depression scores with acetyl-L-carnitine, but results varied widely and the review did not grade certainty.

    This claim is about acetyl-L-carnitine, not L-carnitine. A 2026 review gathered 15 trials in adults with depression or related mood disorders, most of them in Italy, published between 1983 and 2024. Pooling ten randomized trials, it found lower depression scores with acetyl-L-carnitine than in control groups. The effect was largest in trials of acetyl-L-carnitine alone against placebo, and in trials of older adults. When it was added to other treatment, the range of likely effects included no difference.

    The reviewers note very high variation between trials, and signs of small-study effects that they say raise concerns about publication bias. Many trials were small, and older ones were at high risk of bias. The reviewers did not formally grade certainty, but write that it "would probably be low". Several authors disclose ties to companies.

    This page rates the claim limited: mostly small, older trials, with results that varied widely.

    Sources: Source [1]

  • Eases fatigue in people with cancer Evidence rating: Evidence against

    People with cancer take it hoping it will ease the exhaustion that comes with the illness and its treatment.

    A 2017 review found that the better-designed trials showed no benefit for cancer-related fatigue, and pooling three of them found no reduction.

    A 2017 systematic review found 12 studies of carnitine for fatigue in people with cancer. Eight reported less fatigue, but many were not randomized or were open-label, where everyone knew what they were taking. Every study the reviewers judged at low risk of bias found no difference in fatigue. Pooling the three trials with enough data, 659 participants in all, carnitine did not significantly reduce fatigue. Those three gave L-carnitine or acetyl-L-carnitine. In one of them, of acetyl-L-carnitine, fatigue was a secondary outcome.

    The reviewers conclude that results from studies with lower risk of bias "do not support the use of carnitine supplementation for cancer-related fatigue". They say carnitine is unlikely to give a clinically meaningful benefit for fatigue in people having chemotherapy. They also write that "Only 3 of the 12 studies were suitable for meta-analysis which reduces the conclusions which can be drawn from the analysis", and that "there is currently insufficient evidence to recommend its use in the cancer setting". They suggest future trials focus on people with confirmed carnitine deficiency. The review did not grade certainty.

    This page rates the claim evidence against: the better-designed trials, pooled, found no benefit.

    Sources: Source [1]

Which form the evidence used

Supplements are sold in several forms. This is what the sources on this page say about them — which form the research used, and any comparison those sources themselves made. Where they made none, this page does not rank the forms.

  • L-carnitine, including L-carnitine L-tartrate, What the sources supportDetails

    ODS, the US office that reviews dietary supplements, says the two main forms in supplements are L-carnitine and acetyl-L-carnitine. It says the body absorbs about 14% to 18% of supplemental L-carnitine, much less than of the carnitine in food. Most claims on this page rest on trials of L-carnitine. The 2021 exercise review also included trials of L-carnitine L-tartrate. Source [1]Source [2]

  • Acetyl-L-carnitine (ALCAR), What the sources supportDetails

    The claims on dementia, diabetic nerve pain and depression rest on trials of acetyl-L-carnitine, and are kept apart from L-carnitine on this page. ODS says the bioavailability of acetyl-L-carnitine has not been well studied. The two male fertility reviews pooled L-carnitine, acetyl-L-carnitine and the two together. In the one trial the 2022 Cochrane review describes that compared them directly, it found no evidence of a difference in sperm motility, from 30 men. Source [1]Source [2]Source [3]

  • Propionyl-L-carnitine, Details

    ODS describes propionyl-L-carnitine as a form of carnitine. The 2021 exercise review included two trials of propionyl-L-carnitine forms, and no claim on this page rests on it alone. Source [1]Source [2]

Sources

  1. The Effect of the L-Carnitine Supplementation on Obesity Indices: An Umbrella Meta-Analysis
    International Journal for Vitamin and Nutrition Research, 2025 · Meta-analysis · Primary source
  2. Carnitine - Health Professional Fact Sheet
    NIH Office of Dietary Supplements, 2023 · Health authority summary · Primary source
  3. L-Carnitine's Effect on the Biomarkers of Metabolic Syndrome: A Systematic Review and Meta-Analysis of Randomized Controlled Trials
    Nutrients, 2020 · Meta-analysis · Primary source
  4. Effect of Acute and Chronic Oral l-Carnitine Supplementation on Exercise Performance Based on the Exercise Intensity: A Systematic Review
    Nutrients, 2021 · Systematic review · Primary source
  5. Scientific Opinion on the substantiation of health claims related to L-carnitine and faster recovery from muscle fatigue after exercise (ID 738, 1492, 1493), skeletal muscle tissue repair (ID 738, 1492, 1493), increase in endurance capacity (ID 4305, 4684), maintenance of normal blood LDL-cholesterol concentrations (ID 1494, 4684), contribution to normal spermatogenesis (ID 1822), "energy metabolism" (ID 1821), and increasing L-carnitine concentrations and/or decreasing free fatty acids in blood during pregnancy (ID 1495) pursuant to Article 13(1) of Regulation (EC) No 1924/2006
    EFSA Panel on Dietetic Products, Nutrition and Allergies (EFSA Journal), 2011 · Health authority summary · Primary source
  6. The effect of L-carnitine supplementation on lipid profile in adults: an umbrella meta-analysis on interventional meta-analyses
    Frontiers in Nutrition, 2023 · Meta-analysis · Primary source · Certainty: very low
  7. L-carnitine and contribution to normal lipid metabolism: evaluation of a health claim pursuant to Article 13(5) of Regulation (EC) No 1924/2006
    EFSA Panel on Dietetic Products, Nutrition and Allergies (EFSA Journal), 2018 · Health authority summary · Primary source
  8. l-carnitine and l-acetylcarnitine supplementation for idiopathic male infertility
    Reproduction and Fertility, 2020 · Meta-analysis · Primary source · Certainty: very low
    Some of its authors disclose ties to industry.
  9. Antioxidants for male subfertility
    Cochrane Database of Systematic Reviews, 2022 · Systematic review · Primary source · Certainty: very low
    Some of its authors disclose ties to industry.
  10. L-carnitine for cognitive enhancement in people without cognitive impairment
    Cochrane Database of Systematic Reviews, 2017 · Systematic review · Primary source · Certainty: very low
  11. Acetyl-L-carnitine for dementia
    Cochrane Database of Systematic Reviews, 2003 · Systematic review · Primary source
  12. Acetyl-L-carnitine for the treatment of diabetic peripheral neuropathy
    Cochrane Database of Systematic Reviews, 2019 · Systematic review · Primary source · Certainty: very low
    Some of its authors disclose ties to industry.
  13. Current Evidence of Acetyl-L-Carnitine Use in Mood Disorders-: A Systematic Review and Meta-Analysis
    Neuropsychiatric Disease and Treatment, 2026 · Meta-analysis · Primary source
    Some of its authors disclose ties to industry.
  14. Efficacy and Effectiveness of Carnitine Supplementation for Cancer-Related Fatigue: A Systematic Literature Review and Meta-Analysis
    Nutrients, 2017 · Meta-analysis · Primary source
  15. Carnitine supplements for people with chronic kidney disease requiring dialysis
    Cochrane Database of Systematic Reviews, 2022 · Systematic review · Primary source · Certainty: low
    Some of its authors disclose ties to industry.

Page history

Show all 2 changes to this page
  • — Published.
  • — First drafted. Weight loss, exercise performance, recovery after exercise, blood sugar, cholesterol, male fertility, and acetyl-L-carnitine for dementia, diabetic nerve pain and depression rated limited; memory in healthy people rated insufficient; cancer-related fatigue rated evidence against.