L-Carnitine — Research, Dosing & Price Guide

L-Carnitine is a naturally occurring amino acid derivative essential for mitochondrial fatty acid transport. It shuttles long-chain fatty acids across the inner mitochondrial membrane for beta-oxidation — making it critical for fat metabolism and cellular energy production. Injectable L-Carnitine is used for enhanced fat burning, exercise performance, and metabolic support.

L-Carnitine's primary function is operating the carnitine shuttle system in mitochondria. Long-chain fatty acids cannot cross the inner mitochondrial membrane on their own — they must first be conjugated to carnitine by carnitine palmitoyltransferase I (CPT-I) on the outer membrane, transported across as acylcarnitine by carnitine-acylcarnitine translocase, then reconverted to acyl-CoA by CPT-II on the inner membrane for beta-oxidation. Without adequate carnitine, fatty acid oxidation is rate-limited regardless of fat availability. L-Carnitine also buffers excess acetyl-CoA (as acetylcarnitine), maintaining CoA availability for the citric acid cycle. It has demonstrated antioxidant properties, reduces markers of exercise-induced muscle damage, and improves endothelial function through increased nitric oxide production.

• A meta-analysis in Obesity Reviews (2016) showed L-carnitine supplementation produced significant weight loss averaging 1.3 kg compared to placebo across 9 RCTs
• Research in the American Journal of Clinical Nutrition (2007) showed L-carnitine improved insulin sensitivity and glucose disposal in type 2 diabetics
• Studies demonstrated 2g/day L-carnitine reduced muscle damage markers (CK, LDH) after eccentric exercise by 30–40% (Journal of Strength and Conditioning Research)
• A clinical trial showed IV L-carnitine improved cardiac function and reduced mortality in heart failure patients (Mayo Clinic Proceedings, 2013)
• Acetyl-L-carnitine studies in elderly subjects showed improved cognitive function and reduced fatigue (Clinical Interventions in Aging, 2012)
• Research showed L-carnitine improved sperm motility and morphology in infertile men (Fertility and Sterility, 2005)

• Injectable: 500–2,000 mg intramuscular or subcutaneous injection daily
• IV infusion: 1,000–3,000 mg in clinical settings for metabolic support
• Oral (acetyl-L-carnitine or L-carnitine L-tartrate): 1,000–3,000 mg daily in divided doses
• Fat burning protocol: 1,000–2,000 mg IM injection 30–60 minutes before exercise
• Cognitive support (acetyl-L-carnitine form): 500–1,500 mg oral daily
• Cycle: continuous use is common — no cycling typically required
• Can be combined with fat burners, GH secretagogues, or metabolic peptides

Known Side Effects

• Injection site pain and soreness (IM injections can be uncomfortable)
• Nausea and GI discomfort with oral supplementation
• Fishy body odor at high oral doses (due to trimethylamine production by gut bacteria)
• Diarrhea at high oral doses (>3 g/day)
• Rare: headache, insomnia if taken late in the day
• Theoretical concern: TMAO production from oral carnitine may affect cardiovascular risk (controversial)

Safety Profile

L-Carnitine is FDA-approved as a prescription medication (Carnitor) for carnitine deficiency and is GRAS as a supplement. It has a robust safety profile from decades of clinical use. Oral doses up to 3 g/day are well-tolerated in most studies. The injectable route bypasses gut metabolism, eliminating the TMAO concern associated with oral supplementation. Contraindications are minimal: hypothyroidism (carnitine may reduce thyroid hormone action), seizure disorders (high doses may lower seizure threshold in susceptible individuals). Drug interactions: may enhance warfarin effects. Safe for long-term continuous use. Widely used in clinical medicine for metabolic support.

Week 1: Subtle increase in exercise energy and endurance. Injectable form may provide more immediate energy effects than oral. Weeks 2–4: Improved exercise recovery, reduced post-workout soreness. Fat oxidation during exercise is enhanced. Weeks 5–8: Modest but measurable improvements in body composition when combined with exercise and caloric management. Exercise capacity continues to improve. Ongoing use: Benefits are maintenance-level — L-carnitine ensures optimal fatty acid metabolism rather than producing dramatic standalone effects. It is most effective as part of a comprehensive metabolic optimization protocol.

Prices sourced from peptides.gg marketplace. Prices may vary.