Acetyl-L-Carnitine
Acetyl-L-Carnitine
TL;DR
Acetyl-L-carnitine crosses the blood-brain barrier where plain carnitine largely does not. The strongest human evidence is in painful diabetic and chemotherapy-adjacent neuropathy at 1,500-3,000 mg/day; cognitive effects in healthy adults are small, and one large trial found it worsened chemotherapy-induced neuropathy, which is worth knowing before starting.
Ideal For
- Adults with painful diabetic peripheral neuropathy, alongside glycaemic control
- Older adults with mild age-related cognitive complaints, with realistic expectations
- Vegetarians and vegans, who have lower dietary carnitine intake
- People with fatigue related to documented carnitine deficiency
Avoid If
- You are receiving taxane chemotherapy — a large trial showed worse neuropathy
- You have seizure disorder, where carnitine derivatives have been reported to lower threshold
- You have hypothyroidism — carnitine can antagonise thyroid hormone action peripherally
- You are on warfarin without INR monitoring
- You are sensitive to stimulation and cannot dose it early in the day
Frequently Asked Questions
Overview
ALCAR is L-carnitine with an acetyl group attached, and that group changes two things: it makes the molecule brain-penetrant, and it donates acetyl units to acetyl-CoA and acetylcholine synthesis. The clearest clinical signal is peripheral neuropathy. Randomised trials in diabetic neuropathy report reduced pain scores and improved nerve fibre regeneration at 1,500-3,000 mg/day over six to twelve months, with the larger effect in earlier-stage disease. A meta-analysis in age-related cognitive decline and early Alzheimer's shows small but consistent benefits on clinician-rated impression, though the trials are old and predate current diagnostic standards. Against that sits an important negative: a large trial of ALCAR for preventing taxane-induced neuropathy found the supplement group had significantly worse neuropathy at 24 weeks, so it should not be used prophylactically during chemotherapy. In healthy young adults with no deficiency and no neurological complaint, the honest expectation is minimal. ALCAR is well tolerated but genuinely stimulating for some people, which is a dosing-time problem rather than a safety one.
How It Works
- Crosses the blood-brain barrier via organic cation transporter OCTN2, unlike free L-carnitine
- Shuttles long-chain fatty acids into mitochondria for beta-oxidation
- Donates acetyl groups for acetylcholine synthesis in cholinergic neurons
- Upregulates nerve growth factor receptor expression in peripheral neurons
- Improves mitochondrial membrane potential and reduces neuronal oxidative stress
- Modulates glutamatergic and dopaminergic signalling in animal models
Supporting Research17 studies
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.
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 morphology was enhanced by ... carnitine (4.91%; 3.68%, 6.15%) supplementation
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
Across 21 double-blind trials, acetyl-L-carnitine beat placebo on both clinical global impression and psychometric tests in mild cognitive impairment and early Alzheimer's disease.
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
This prospective study aims to evaluate the effectiveness of a rehabilitation program combined with the administration of Alpha Lipoic Acid, Acetyl-L-Carnitine, Resveratrol, and Cholecalciferol in the treatment of sciatica due to herniated discs in young patients.
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.
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.
Acetyl-L-carnitine for the treatment of diabetic peripheral neuropathy
We are very uncertain whether ALC causes a reduction in pain after 6 to 12 months' treatment in people with DPN.
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 randomized data show acetyl-L-carnitine significantly reduces peripheral neuropathic pain, with the largest effects at doses of 2 g/day or above.
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 reduced depressive symptoms versus placebo and matched antidepressant efficacy with significantly fewer adverse events.
Two-Year Trends of Taxane-Induced Neuropathy in Women Enrolled in a Randomized Trial of Acetyl-L-Carnitine (SWOG S0715)
Hershman DL, Unger JM, Crew KD +1 more
Patients receiving ALC had a statistically significantly (P = .01) greater reduction in NTX scores (worse CIPN) of -1.39 points (95% confidence interval [CI] = -2.48 to -0.30) than the placebo group.
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
In two 52-week trials, 1000 mg three times daily improved pain, vibratory perception and sural nerve fibre regeneration, while 500 mg was largely ineffective.
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
ALC is as effective as MC in improving clinical symptoms and neurophysiological parameters for patients with diabetic peripheral neuropathy over a 24-week period with good tolerance.
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
Meta-analysis in diabetic peripheral neuropathy found significant improvement in pain scores and nerve conduction velocity versus placebo.
A Comprehensive Review of Safety, Efficacy, and Indications for the Use of Alpha-Lipoic Acid and Acetyl-L-Carnitine in Neuropathic Pain
Aldendail CF, Chen P, Dibble HS +1 more
Meta-analysis of randomized controlled trials demonstrates that ALA can significantly improve neuropathic pain and nerve conduction velocity.
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 total and forward sperm motility in idiopathic male infertility, though pregnancy-rate evidence was limited.
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.
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 was inferior to placebo in the prevention of chemotherapy-induced peripheral neuropathy.
Safety Information
Potential Side Effects
Nausea, abdominal discomfort, restlessness and insomnia at higher doses. A fishy body odour occurs occasionally due to trimethylamine production. Headache and increased irritability are reported.
Contraindications
Concurrent taxane chemotherapy, seizure disorders, untreated hypothyroidism.
Drug Interactions
- Warfarin — case reports of increased INR
- Thyroid hormone — carnitine can inhibit peripheral thyroid hormone action
- Taxane chemotherapy — associated with worsened neuropathy in a randomised trial
- Valproate — depletes carnitine, so supplementation is sometimes clinically indicated
Pregnancy & Breastfeeding
Pregnancy: insufficient_data
Breastfeeding: insufficient_data
Dosage Guidelines
Dosage Used in Studies
1500-3000 mg
Best Time to Take
Morning and early afternoon, avoiding evening doses
Best Form
Acetyl-L-carnitine HCl, 1,500-3,000 mg/day in divided doses
Bioavailability
Oral bioavailability is roughly 10-20% and saturable, which is why divided dosing outperforms a single large dose. Plasma acetylcarnitine rises within 3-4 hours of dosing.
Forms Compared
Acetyl-L-carnitine HCl
Acetyl-L-carnitine arginate
L-carnitine L-tartrate
Propionyl-L-carnitine
Free L-carnitine
Food & Timing
Can be taken with or without food; absorption is adequate either way, though food reduces the occasional nausea
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.