Acetyl-L-Carnitine
Evidence Fact Sheet
ALC · ALCAR
Acetyl-L-carnitine (ALC/ALCAR) is the acetyl ester of L-carnitine, a mitochondrial fatty-acid-oxidation substrate and acetyl-group donor studied in randomized trials for peripheral neuropathic pain, depressive symptoms, cognition and male fertility, typically at 1.5-3 g/day. Sold as a DSHEA supplement (US); no EFSA authorized claim.
Also known as: ALC · ALCAR · Acetylcarnitine · Levocarnitine acetyl
Overview
Acetyl-L-carnitine (ALC, ALCAR) is the acetylated ester of L-carnitine that crosses the blood-brain barrier more readily than L-carnitine and acts as a mitochondrial long-chain fatty-acid β-oxidation substrate (acetyl-CoA donor) and as an acetyl-group donor for acetylcholine synthesis, with proposed neurotrophic effects. Human research clusters around peripheral neuropathic pain, depressive symptoms, cognitive support and male fertility, with typical research doses of 1.5-3 g/day oral. In the US it is regulated as a GRAS/DSHEA dietary supplement permitting structure/function claims and is not an FDA-approved drug for any condition; the EU has no EFSA Reg 432/2012 authorized health claim, and Brazil regulates it as an ANVISA dietary supplement without a functional claim. Reported adverse events in trials are generally mild and similar to control.
Mechanism of Action
Carnitine ester form crossing the blood-brain barrier more efficiently than L-carnitine · Mitochondrial long-chain fatty acid β-oxidation substrate (acetyl-CoA donor) · Acetyl group donor for acetylcholine synthesis · Neurotrophic effect via nerve growth factor receptor modulation
Body systems: Neurological & Cognitive · METABOLISM · Cellular Renewal
Evidence-Based Benefits
Each benefit below is anchored to a specific PubMed-indexed study. Effect sizes, sample sizes, and p-values are reported as published; no values are inferred. Honest negatives and null results are kept alongside the positive findings, and disease-research populations are described as such — Acetyl-L-Carnitine is not characterized as a treatment for any disease.
Peripheral Neuropathic Pain
Meta-analysis supported- 4 RCTs (n = 523)pooled trials
- MD 1.20VAS · 95% CI 0.68-1.72
- P <0.00001ALC vs placebo
A systematic review and meta-analysis of randomized trials found acetyl-L-carnitine reduced visual analogue scale pain scores versus placebo in people with peripheral neuropathic pain, an effect the authors describe as moderate. The reduction appeared larger in the diabetic subgroup than the non-diabetic subgroup, and no severe adverse events were attributed to ALC.
Reported effect: MD of VAS 1.20 (95% CI 0.68-1.72, P<0.00001); diabetic subgroup MD 1.47 (95% CI 1.06-1.87); n=523 across 4 RCTs
“Four RCTs comparing ALC with placebo and reporting in three articles (n = 523) were included. Compared with placebo, ALC significantly reduced VAS scores of PNP patients (MD of VAS, 1.20; 95% CI, 0.68-1.72, P <0.00001). ... ALC appeared more effective in diabetic PNP patients than non-diabetic PNP patients (diabetic subgroup: MD, 1.47; 95%CI, 1.06-1.87, P <0.00001; non-diabetic subgroup: MD, 0.71; 95% CI, -0.01-1.43, P = 0.05). No severe adverse events were reported related to ALC.”
Source: PMID 25751285 · Li 2015 · PLoS One
Depressive Symptoms
Meta-analysis supported- 12 RCTs · 791participants pooled
- SMD -1.10vs placebo · CI -1.65 to -0.56
- SMD 0.06vs antidepressants · CI -0.22 to 0.34
A systematic review and meta-analysis of randomized trials reported that acetyl-L-carnitine significantly reduced depressive symptoms versus placebo or no intervention. Across three trials comparing it directly with antidepressants, ALC showed similar effectiveness with a significantly lower incidence of adverse effects, and subgroup analyses suggested it was most efficacious in older adults.
Reported effect: ALC vs placebo SMD -1.10 (95% CI -1.65 to -0.56); ALC vs antidepressants SMD 0.06 (95% CI -0.22 to 0.34); 12 RCTs, 791 participants
“Twelve RCTs (11 of which were ALC monotherapy) with a total of 791 participants ... showed that ALC significantly reduced depressive symptoms (SMD = -1.10, 95% CI = -1.65 to -0.56, I = 86%). In three RCTs comparing ALC versus antidepressants (162 for each group), ALC demonstrated similar effectiveness compared with established antidepressants in reducing depressive symptoms (SMD = 0.06, 95% CI = -0.22 to 0.34, I = 31%). In these latter RCTs, the incidence of adverse effects was significantly lower in the ALC group than in the antidepressant group.”
Source: PMID 29076953 · Veronese 2018 · Psychosom Med
Cognition (Mild Cognitive Impairment / Mild Alzheimer's)
Meta-analysis supported- ES 0.201summary effect · CI 0.107-0.295
- ES 0.32CGI-CH · CI 0.18-0.47
A meta-analysis of double-blind, placebo-controlled trials of acetyl-L-carnitine in mild cognitive impairment and mild Alzheimer's disease reported a small but significant advantage over placebo on both an integrated summary measure and clinician global impression of change. The studies pooled were of at least three months' duration at doses of 1.5-3.0 g/day, with the advantage seen by the first assessment at three months and increasing over time.
Reported effect: Integrated summary effect ES 0.201 (95% CI 0.107-0.295); CGI-CH ES 0.32 (95% CI 0.18-0.47)
“Meta-analysis showed a significant advantage for Alcar compared to placebo for the integrated summary effect [ES =0.201, 95% confidence interval (CI)=0.107-0.295] and CGI-CH (ES =0.32, 95% CI=0.18-0.47).”
Source: PMID 12598816 · Montgomery 2003 · Int Clin Psychopharmacol
Male Fertility (Idiopathic Oligoasthenoteratozoospermia)
Meta-analysis supported- 7 RCTs · 693patients pooled
- MD 6.98forward motility % · CI 1.06-12.90
- OR 3.76pregnancies · CI 1.66-8.50
A meta-analysis of randomized trials of combined L-carnitine and L-acetyl carnitine in men with idiopathic oligoasthenoteratozoospermia found significant improvements in forward sperm motility and in the number of pregnancies versus control. The authors noted, however, that no significant differences were found in other semen indicators, an honest mixed result.
Reported effect: Forward sperm motility MD 6.98 (95% CI 1.06-12.90, p=.02); pregnancies OR 3.76 (95% CI 1.66-8.50, p=.002); 7 RCTs, 693 patients
“Seven randomised controlled trials (RCTs) involving 693 patients were included in our analysis. ... percentage of forward sperm motility (MD 6.98; 95% CI 1.06-12.90; p = .02) ... the number of pregnancies (OR 3.76; 95% CI 1.66-8.50; p = .002) ... However, no significant differences were found in other semen indicators between the two groups.”
Source: PMID 31701550 · Zhang 2020 · Andrologia
Dosage (research context · not a recommendation)
1.5-3 g/day oral or IM-oral sequential dosing for peripheral neuropathic pain (Li 2015 PMID 25751285 PLoS One systematic review and meta-analysis of 4 RCT · n=523 · ALC vs control MD VAS 1.20 95% CI 0.68-1.72 P<0.00001 · stronger effect in diabetic subgroup); no severe adverse events reported across the trial pool
Regulatory Status · 4 Markets
- US · FDA
- GRAS · DSHEA dietary supplement · structure/function claims permitted; not an FDA-approved drug for any condition in the US
- EU · EFSA
- No standalone EFSA Reg 432/2012 authorized health claim adopted for acetyl-L-carnitine
- CN · China
- China: acetyl-L-carnitine is mainly a pharmaceutical-grade ingredient, not a separately authorized health-food/GB 14880 fortifier; no confirmed supplement pathway for the ALCAR ester (parent L-carnitine is listed).
- BR · ANVISA
- RDC 243/2018 dietary supplement · no IN 28/2018 Anexo V alegação funcional for acetil-L-carnitina
Safety
Common adverse events (pain, headache, paraesthesia, hyperaesthesia, GI symptoms) are mild and similar to control rates; thyroid disorder caution at very high doses; check for separately-marketed L-carnitine vs ALC formulation when comparing doses
Related
Goals: cognitive-support · longevity-stack
Lifestyles: senior-60-plus
References
PubMed-indexed citations anchoring the benefit findings above. Effect sizes are reported as published.
- PMID 25751285 · Li 2015 · PLoS One — Peripheral Neuropathic Pain
- PMID 29076953 · Veronese 2018 · Psychosom Med — Depressive Symptoms
- PMID 12598816 · Montgomery 2003 · Int Clin Psychopharmacol — Cognition (Mild Cognitive Impairment / Mild Alzheimer's)
- PMID 31701550 · Zhang 2020 · Andrologia — Male Fertility (Idiopathic Oligoasthenoteratozoospermia)
Frequently Asked Questions
1. What is acetyl-L-carnitine and how is it thought to work?
Acetyl-L-carnitine (ALC, also called ALCAR) is the acetyl ester of L-carnitine. It crosses the blood-brain barrier more readily than L-carnitine and acts as a mitochondrial fatty-acid-oxidation substrate (an acetyl-CoA donor) and as an acetyl-group donor for acetylcholine synthesis, with proposed neurotrophic effects. These mechanisms are why it has been studied in nerve, mood, cognitive and metabolic research contexts.
2. What dose is used in the research?
Human trials reviewed here typically use oral doses in the range of 1.5-3 g/day, including the cognition meta-analysis, which pooled studies at 1.5-3.0 g/day of at least three months' duration. This is an evidence-reporting summary rather than dosing guidance; appropriate use should be discussed with a qualified professional.
3. Where is the evidence strongest, and are there honest negatives?
Meta-analyses of randomized trials report significant effects for peripheral neuropathic pain (VAS MD 1.20) and for reducing depressive symptoms versus placebo (SMD -1.10), with a smaller signal in mild cognitive impairment / mild Alzheimer's (ES 0.201). For male fertility, a meta-analysis found improved forward sperm motility (MD 6.98) and more pregnancies (OR 3.76), but also stated no significant differences were found in other semen indicators, an honest mixed result.
4. Is acetyl-L-carnitine an approved treatment?
No. In the US it is regulated as a GRAS/DSHEA dietary supplement that permits structure/function claims and is not an FDA-approved drug for any condition. The EU has no EFSA-authorized health claim for it, and Brazil regulates it as an ANVISA dietary supplement without a functional claim. The findings above describe research outcomes in studied populations, not disease treatment.
Last evidence review: 2026-06-04