L-Carnitine
L-Carnitine L-Tartrate
TL;DR
L-carnitine shuttles fatty acids into mitochondria for energy. Supplementing helps most in deficiency, fatigue and recovery; effects in healthy, well-fed people are small.
Ideal For
- People with fatigue linked to low carnitine status
- Athletes focused on recovery between hard sessions
- Adults with diabetic or chemotherapy-related neuropathy (acetyl form)
- Older adults with low dietary meat intake
Avoid If
- You have a seizure disorder
- You are on warfarin without INR monitoring
- You have advanced kidney disease not on dialysis, without specialist input
Frequently Asked Questions
Overview
L-carnitine is an amino acid derivative that transports long-chain fatty acids across the inner mitochondrial membrane so they can be burned for energy. Most people obtain 20–200 mg a day from red meat and dairy and synthesise the rest from lysine and methionine, so frank deficiency is uncommon outside dialysis, some genetic disorders and certain drug therapies.
The clearest signals come from populations where carnitine status is compromised or turnover is high. In haemodialysis and in chronic fatigue, trials report meaningful reductions in fatigue scores. In cardiovascular research, meta-analyses of post-myocardial-infarction trials found lower all-cause mortality and fewer ventricular arrhythmias, though the underlying studies are older and heterogeneous. Acetyl-L-carnitine has separate evidence in diabetic and chemotherapy-related neuropathy.
For sport, the interesting finding is not fat burning but recovery: 2 g/day for several weeks reduces markers of muscle damage and soreness after intense exercise. Claims that carnitine is a fat-loss agent are not supported — pooled weight change is around 1 kg and inconsistent.
How It Works
- Carries long-chain fatty acids across the inner mitochondrial membrane via the carnitine shuttle
- Buffers the mitochondrial acyl-CoA to CoA ratio, keeping oxidative metabolism running
- Reduces exercise-induced markers of muscle damage and oxidative stress
- Acetyl-L-carnitine crosses the blood-brain barrier and supports acetylcholine synthesis
- Improves endothelial function and oxygen utilisation in ischaemic tissue
Quick Facts
- Transports fatty acids for energy production
- Supports fat metabolism and weight management
- Enhances exercise performance and recovery
- Supports cardiovascular health
- May improve insulin sensitivity
Benefits & Outcomes
Fatty Acid Oxidation
Only useful when carnitine status is genuinely low. Not a fat burner.
Ketone Production Support
L-carnitine supports fatty acid transport but rarely raises ketones in people who are not deficient.
Thermogenic Effect
Carnitine helps only where levels are low; muscle stores are hard to raise by supplementing.
Sperm Quality
L-carnitine has consistent trial evidence for motility improvement.
Weight Loss Support
Carnitine produces small weight reductions, mainly in obese and older populations.
Increased Energy Production
Carnitine reduces fatigue in elderly, dialysis and deficiency populations, with little effect in healthy adults.
Metabolic Flexibility
Carnitine supports fat oxidation biochemically, but human trials show only modest metabolic effects and unreliable weight change.
Enhanced Athletic Performance
Carnitine does not act as a fat burner, but long-term supplementation with carbohydrate improves recovery and reduces muscle damage markers.
Heart Health Support
L-carnitine improved outcomes after myocardial infarction in older pooled analyses, but concerns about TMAO production complicate the picture.
Health Concerns Addressed
Poor Circulation
Propionyl-L-carnitine is one of the few supplements with genuine vascular trial evidence — improved walking distance in peripheral artery disease — but for the common cold-hands-and-feet pattern, warmth, movement, and trigger avoidance remain the proven approach.
Chronic Fatigue Syndrome (ME/CFS)
L-carnitine improved fatigue scores in early chronic fatigue trials, but the evidence is old, small and largely unreplicated.
Supporting Research39 studies
Effect of acetyl-l-carnitine in the treatment of diabetic peripheral neuropathy: a systematic review and meta-analysis
Veronese N, Sergi G, Stubbs B +5 more
Acetyl-L-carnitine significantly improved pain scores and nerve conduction velocity compared with placebo in people with diabetic peripheral neuropathy, with a good tolerability profile.
Acetyl-L-carnitine supplementation and the treatment of depressive symptoms: a systematic review and meta-analysis
Veronese N, Stubbs B, Solmi M +3 more
Acetyl-L-carnitine significantly reduced depressive symptoms versus placebo (standardized mean difference around -1.10), and produced comparable symptom reduction to established antidepressants with significantly fewer adverse events.
Acetyl-L-carnitine improves pain, nerve regeneration, and vibratory perception in patients with chronic diabetic neuropathy: an analysis of two randomized placebo-controlled trials
Sima AA, Calvani M, Mehra M +1 more
The 1000 mg dose significantly reduced pain scores and improved vibratory perception and sural nerve fibre regeneration versus placebo; the 500 mg dose was largely ineffective. Benefits were greatest in patients with shorter neuropathy duration.
Acetyl-L-carnitine in the treatment of peripheral neuropathic pain: a systematic review and meta-analysis of randomized controlled trials
Li S, Li Q, Li Y +3 more
Pooled analysis found acetyl-L-carnitine significantly reduced pain versus placebo, with the largest effects at 2 g/day or higher and in diabetic neuropathy. Electrophysiological nerve conduction measures also improved. Adverse events were mostly mild gastrointestinal effects.
Meta-analysis of double blind randomized controlled clinical trials of acetyl-L-carnitine versus placebo in the treatment of mild cognitive impairment and mild Alzheimer's disease
Montgomery SA, Thal LJ, Amrein R
Acetyl-L-carnitine showed a significant advantage over placebo on both clinical global impression of change and psychometric test performance, with benefit apparent by 3 months and increasing over time. Effect sizes were small to moderate.
Thioctic acid and acetyl-L-carnitine in the treatment of sciatic pain caused by a herniated disc: a randomized, double-blind, comparative study
Memeo A, Loiero M
In 64 patients with sciatic pain from a herniated disc, combined thioctic (alpha-lipoic) acid and acetyl-L-carnitine over 60 days reduced pain intensity and improved neurological and functional scores more than the comparator regimen, with reduced need for analgesics and good tolerability.
Comparison of vitamin E and propionyl-L-carnitine, separately or in combination, in patients with early chronic Peyronie's disease: a double-blind, placebo controlled, randomized study
Safarinejad MR, et al.
This study did not show significant improvement in pain, curvature or plaque size in patients with PD treated with vitamin E, propionyl-L-carnitine, or vitamin E plus propionyl-L-carnitine compared with those treated with placebo. Note: an Expression of Concern (PMID 36626346) was issued for this paper in 2023.
Combined Rehabilitation with Alpha Lipoic Acid, Acetyl-L-Carnitine, Resveratrol, and Cholecalciferol in Discogenic Sciatica in Young People: A Randomized Clinical Trial
Scaturro D, Vitagliani F, Tomasello S +3 more
Rehabilitation plus ALA 600 mg, acetyl-L-carnitine 1000 mg, resveratrol 50 mg and vitamin D 800 IU for 30 days improved pain, disability and quality of life more than either intervention alone.
Acetyl-L-carnitine vs tamoxifen in the oral therapy of Peyronie's disease: a preliminary report
Biagiotti G, Cavallini G
These results suggest that acetyl-L-carnitine is significantly more effective and safe than tamoxifen in the therapy of acute and early chronic Peyronie's disease.
Acetyl-L-carnitine for the treatment of diabetic peripheral neuropathy
Sparse, low-certainty evidence on pain reduction with acetyl-L-carnitine; data on function and sensory symptoms lacking.
Randomized Double-Blind Placebo-Controlled Trial of Acetyl-L-Carnitine for the Prevention of Taxane-Induced Neuropathy in Women Undergoing Adjuvant Breast Cancer Therapy
Hershman DL, Unger JM, Crew KD +7 more
Acetyl-L-carnitine did not prevent taxane-induced peripheral neuropathy and was associated with worse neuropathy scores than placebo at 24 weeks.
Effects of acetyl-L-carnitine and methylcobalamin for diabetic peripheral neuropathy: A multicenter, randomized, double-blind, controlled trial
Li S, Chen X, Li Q +7 more
Acetyl-L-carnitine was non-inferior to methylcobalamin for symptom and nerve conduction improvement over 24 weeks, with good tolerability.
The Effect of Nutrients and Dietary Supplements on Sperm Quality Parameters: A Systematic Review and Meta-Analysis of Randomized Clinical Trials
Salas-Huetos A, Rosique-Esteban N, Becerra-Tomás N +1 more
Sperm progressive motility was increased only after supplementation with carnitines (7.45%; 6.24%, 8.67%)
Increasing skeletal muscle carnitine content in older individuals increases whole-body fat oxidation during moderate-intensity exercise
Chee C, Shannon CE, Burns A
Increasing skeletal muscle carnitine content in older individuals increases whole-body fat oxidation during moderate-intensity exercise
The effect of (L-)carnitine on weight loss in adults: a systematic review and meta-analysis of randomized controlled trials
Pooyandjoo M, Nouhi M, Shab-Bidar S
Subjects who received carnitine lost significantly more weight, approximately 1.33 kg, than control subjects.
The efficacy of combined l-carnitine and l-acetyl carnitine in men with idiopathic oligoasthenoteratozoospermia: A systematic review and meta-analysis
Zhang X, et al
LC and LAC can significantly increase part of the semen parameters. The combination therapy of LC and LAC is effective in the men with iOAT.
Topically applied L-carnitine effectively reduces sebum secretion in human skin
Peirano RI, et al.
Our results show that the treatment of human sebocytes with L-carnitine significantly augments beta-oxidation and significantly decreases intracellular lipid content in human sebocytes. Topically applied L-carnitine is bioavailable and leads to a significant sebum reduction in vivo. In conclusion, L-carnitine represents a valuable compound, produced naturally within the body, for the topical treatment of oily skin in humans.
Amantadine and L-carnitine treatment of Chronic Fatigue Syndrome
Plioplys AV, Plioplys S
With L-carnitine we found statistically significant clinical improvement in 12 of the 18 studied parameters after 8 weeks of treatment.
L-carnitine as primary or adjuvant treatment in infertile patients with varicocele. A systematic review
L-carnitine improved sperm motility in varicocele patients, particularly as adjuvant therapy after varicocelectomy.
Clinical evidence of the effects of carnitine supplementation on body weight, glycemic control and serum lipids in women with polycystic ovary syndrome: a systematic review and meta-analysis
Liao D, Liu X, Yuan X +4 more
carnitine supplements significantly decreased ... body weight, body mass index, hip circumference, and waist circumference
The Effect of L-Carnitine Supplementation on Exercise-Induced Muscle Damage: A Systematic Review and Meta-Analysis of Randomized Clinical Trials
Fielding R, Riede L
L-carnitine reduced post-exercise creatine kinase and myoglobin, consistent with improved mitochondrial fatty acid handling
The bright and the dark sides of L-carnitine supplementation: a systematic review
L-carnitine supported fatty acid transport and recovery, but performance effects were inconsistent.
Nutritional interventions for exercise-induced muscle damage: an umbrella review of systematic reviews and meta-analyses of randomized trials
Talebi S, Mohammadi H, Zeraattalab-Motlagh S +1 more
Fifty-three randomized controlled trial meta-analyses were included, evaluating 24 nutritional interventions on 10 different outcomes.
Propionyl-L-carnitine for intermittent claudication
Delaney CL, Spark JI, Thomas J
Low-certainty evidence suggests propionyl-L-carnitine may improve maximum walking distance compared with placebo.
Patients with medium-chain acyl-coenzyme A dehydrogenase deficiency have impaired oxidation of fat during exercise but no effect of L-carnitine supplementation
Madsen KL, Preisler N, Orngreen MC
Palmitate oxidation and FAO rates were unchanged by the l-carnitine supplementation.
Influence of oral vitamin and mineral supplementation on male infertility: a meta-analysis and systematic review
Buhling K, Schumacher A, Eulenburg CZ +1 more
L-carnitine (2 g/day) and acetyl-L-carnitine (LAC; 1 g/day) combined (SMD 0.57 for asthenozoospermia)
Propionyl-L-carnitine for intermittent claudication
Kamoen V, Vander Stichele R, Campens L +1 more
The objective of this review is to determine whether propionyl-L-carnitine is efficacious compared with placebo, other drugs, or other interventions used for treatment of intermittent claudication
Efficacy of antioxidant therapy on sperm quality measurements after varicocelectomy: A systematic review and meta-analysis
Antioxidant therapy after varicocelectomy, including carnitines, improved sperm concentration and motility.
Alternative medical interventions used in the treatment and management of myalgic encephalomyelitis/chronic fatigue syndrome and fibromyalgia
Porter NS, Jason LA
Magnesium, l-carnitine, and S-adenosylmethionine are nonpharmacological supplements with the most potential for further research.
A randomised controlled trial comparing duloxetine and acetyl L-carnitine in fibromyalgic patients: preliminary data
Leombruni P
These preliminary findings suggest that acetyl L-carnitine is efficacious in improving depressive symptoms, pain, and the quality of life of FMS patients.
L-carnitine in the secondary prevention of cardiovascular disease: systematic review and meta-analysis
DiNicolantonio JJ, Lavie CJ, Fares H
L-carnitine was associated with reduced all-cause mortality after acute myocardial infarction, but no reduction in reinfarction or heart failure.
Liver-Oriented Acute Metabolic Effects of A Low Dose of L-Carnitine under Fat-Mobilizing Conditions: Pilot Human Clinical Trial
Odo S, Tanabe K, Yohda M
The acute metabolic effect of low dosages of L-carnitine under fat-mobilizing conditions was investigated.
The effect of L-carnitine supplementation on lipid profile and glycaemic control in adults with cardiovascular risk factors: a systematic review and meta-analysis of randomized controlled clinical trials
Askarpour M, Hadi A, Symonds ME
L-carnitine supplementation modestly reduced total cholesterol, LDL-C, fasting glucose and HbA1c in adults with cardiovascular risk factors.
Usefulness of L-Carnitine, a Naturally Occurring Peripheral Antagonist of Thyroid Hormone Action, in Iatrogenic Hyperthyroidism: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial
Benvenga S, Ruggeri RM, Russo A +3 more
L-carnitine is effective in both reversing and preventing symptoms of hyperthyroidism and has a beneficial effect on bone mineralization.
Adding L-Carnitine and Selenium to Methimazole in Graves' Disease: A Prospective Randomized Trial on Thyroid Markers and Quality of Life
Rossi M, Meomartino L, Zavattaro M +1 more
Adding L-Carnitine and Selenium to Methimazole in Graves' Disease: A Prospective Randomized Trial on Thyroid Markers and Quality of Life.
Effects of L-carnitine supplementation on blood lactate and exercise performance: a systematic review and meta-analysis
Sawicka AK, Renzi G, Olek RA
Pooled effects on post-exercise blood lactate were small and inconsistent
L-carnitine supplementation, muscle carnitine content and fuel metabolism during exercise
Wall BT, Stephens FB, Constantin-Teodosiu D +3 more
Carnitine feeding raised muscle carnitine content and altered fuel selection
Effect of L-carnitine and/or L-acetyl-carnitine in nutrition treatment for male infertility: a systematic review
Zhou X, Liu F, Zhai S
Carnitine supplementation improved sperm motility in men with idiopathic infertility in the pooled trials reviewed.
Intestinal microbiota metabolism of L-carnitine, a nutrient in red meat, promotes atherosclerosis
Koeth RA, Wang Z, Levison BS
Microbial metabolism of dietary L-carnitine produces TMAO, which was associated with increased cardiovascular event risk in humans.
Safety Information
Potential Side Effects
Nausea, cramping and diarrhoea at higher doses. A fishy body odour from trimethylamine production is dose-dependent and reversible. Gut bacteria convert carnitine to TMAO, a marker associated with cardiovascular risk, though the clinical meaning of supplement-derived TMAO remains debated.
Contraindications
May lower seizure threshold in people with epilepsy. Avoid unsupervised use in hypothyroidism, where carnitine can antagonise thyroid hormone action at the nucleus.
Drug Interactions
- Warfarin — case reports of increased INR
- Thyroid hormone — may blunt peripheral thyroid hormone action
- Valproate and pivalate-containing antibiotics — these deplete carnitine, which is why supplementation is sometimes prescribed
Pregnancy & Breastfeeding
Pregnancy: insufficient_data
Breastfeeding: insufficient_data
Dosage Guidelines
Dosage Used in Studies
500-2000 mg
Best Time to Take
Split morning and afternoon with meals
Best Form
L-carnitine tartrate for exercise and general use; acetyl-L-carnitine when the target is nerve or cognitive support
Bioavailability
Oral bioavailability 5-18% from supplements vs 75% from food. L-carnitine L-tartrate well-absorbed. Acetyl-L-carnitine crosses blood-brain barrier more readily.
Forms Compared
L-carnitine tartrate
Acetyl-L-carnitine
Propionyl-L-carnitine
L-carnitine fumarate
Food & Timing
With a carbohydrate-containing meal — insulin markedly improves muscle carnitine uptake
Medical Disclaimer
The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.
Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.