Amino Acids

L-Carnitine (ALCAR / Acetyl-L-Carnitine)

Evidence: strong_human

Mechanism of Action

L-Carnitine's primary function is transporting long-chain fatty acids across the inner mitochondrial membrane via the carnitine shuttle (CPT-I/CPT-II system) for beta-oxidation. Acetyl-L-Carnitine (ALCAR) additionally donates its acetyl group to form acetyl-CoA (bypassing pyruvate dehydrogenase) and serves as a precursor for acetylcholine synthesis. ALCAR crosses the blood-brain barrier, providing neuroprotective effects through mitochondrial energetics, reduction of lipofuscin accumulation, enhancement of NGF receptor sensitivity, and modulation of synaptic plasticity. It also reduces oxidative stress via upregulation of heme oxygenase-1.

Dosing Protocol

Standard: 500-2000mg ALCAR daily or 1000-3000mg L-Carnitine L-Tartrate (for exercise performance)

Maintenance: 500-1000mg ALCAR/day

Administration: oral

Timing: Morning on empty stomach for cognitive effects. Pre-workout for fat oxidation/performance. ALCAR for brain; L-Carnitine L-Tartrate for muscle/exercise.

Duration: ongoing

Notes

The TMAO (trimethylamine N-oxide) concern: gut bacteria convert L-carnitine to TMA, which liver FMO3 oxidizes to TMAO, a cardiovascular risk marker. This is primarily a concern with L-carnitine (not ALCAR) and is more pronounced in chronic, high-dose supplementation. Vegetarians/vegans produce less TMAO from carnitine due to different gut flora. The thyroid-blocking effect is clinically useful in hyperthyroidism (published Italian trial) but contraindicated in hypothyroidism. ALCAR is the preferred form for most health optimization applications. The Mitochondrial Cocktail: ALCAR + CoQ10 + ALA is a classic combination.

Stacking

  • CoQ10
  • Alpha Lipoic Acid
  • Omega-3 (DHA)
  • B-Complex

Interactions

  • Thyroid hormones [MEDIUM] — L-Carnitine inhibits T3 and T4 entry into cell nuclei — may reduce thyroid hormone action. Therapeutic in hyperthyroidism; avoid in hypothyroidism.
  • Warfarin [MEDIUM] — Case reports of enhanced anticoagulant effect
  • Valproic acid [MEDIUM] — Valproic acid depletes carnitine — supplementation recommended during VPA therapy

Contraindications

  • Hypothyroidism (may worsen)
  • Seizure disorders (conflicting data)
  • TMAO concerns (see notes)

Side Effects

  • Fishy body odor (TMA production by gut bacteria)
  • GI upset/nausea
  • Restlessness/insomnia (ALCAR)
  • Increased appetite
  • TMAO elevation (cardiovascular concern with L-Carnitine, less with ALCAR)

Key Papers

  • 10.1016/j.mayocp.2013.06.007
  • 10.1016/j.jalz.2013.04.447
  • 10.1113/jphysiol.2006.113522

Source Quality

ALCAR (acetyl-L-carnitine) for cognitive/neurological applications. L-Carnitine L-Tartrate (Carnipure brand, Lonza) for exercise performance and androgen receptor density. Propionyl-L-Carnitine (PLCAR) specifically for cardiovascular/peripheral vascular disease. Brands: NOW ALCAR, Jarrow ALCAR, Thorne Carnityl.

Disclaimer: This information is for educational purposes only and is not medical advice. BioAccelera Labs does not diagnose, treat, or prescribe. Consult a licensed healthcare provider before using any compound.

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