Peptide Schedule
L-CarnitineSmall moleculeNo amino acid sequence. Icon reflects category theme only.L-Carnitine
Benefits
About L-Carnitine
L-Carnitine is a naturally occurring amino acid derivative that plays a central role in shuttling long-chain fatty acids into the mitochondria for beta-oxidation — the process your cells use to turn stored fat into usable energy. Your body makes it from lysine and methionine in the liver and kidneys, and you get some from red meat and dairy. But endogenous production and dietary intake don't always keep up with demand, especially during intense exercise or caloric restriction. The FDA approved injectable levocarnitine (brand name Carnitor) back in 1999 for treating primary and secondary carnitine deficiency. That's the clinical use case. But L-Carnitine injections have gained traction in wellness and body composition circles because of a straightforward pharmacokinetic reality: oral supplements have a bioavailability of only 15-18%, while injectable delivery bypasses the gut entirely and achieves 100% bioavailability. At oral doses above 2 grams, absorption actually gets worse because intestinal transporters saturate. A 2020 meta-analysis of 37 randomized controlled trials found that L-Carnitine supplementation reduced body weight by an average of 1.21 kg compared to placebo, with more pronounced effects in overweight and obese individuals. The weight loss isn't dramatic on its own — nobody's losing 20 pounds from carnitine alone — but the effect is real and additive when stacked with caloric deficit and exercise. A separate dose-response analysis suggested 2,000 mg per day as the sweet spot for measurable fat loss effects. One thing worth knowing: about 76% of an injected dose gets excreted through the kidneys within 24 hours. The body tightly regulates circulating carnitine levels through renal reabsorption, which becomes less efficient as plasma concentrations rise. This means you're not building up indefinitely — the system has a built-in ceiling. That same renal clearance is why L-Carnitine is generally well tolerated, but also why consistent daily dosing matters more than occasional large boluses.
Who Should Consider L-Carnitine
- Individuals with primary or secondary carnitine deficiency
- People seeking enhanced fat oxidation during caloric deficit
- Athletes looking to improve exercise recovery and endurance
- Patients on hemodialysis with carnitine depletion
- Those with poor oral carnitine absorption seeking injectable alternative
- Individuals combining with GLP-1 agonists for body recomposition support
How L-Carnitine Works
L-Carnitine's primary job is operating the carnitine shuttle system — the only way long-chain fatty acids (14+ carbons) can cross the inner mitochondrial membrane to reach the beta-oxidation machinery. The process works in three steps. First, carnitine palmitoyltransferase I (CPT-I) on the outer mitochondrial membrane transfers the fatty acyl group from coenzyme A to L-Carnitine, forming acylcarnitine. Then carnitine-acylcarnitine translocase (CACT) moves the acylcarnitine across the inner membrane while simultaneously exporting free carnitine back out. Finally, CPT-II on the inner membrane matrix side cleaves the acylcarnitine, regenerating free carnitine and releasing fatty acyl-CoA for beta-oxidation. Beyond fatty acid transport, L-Carnitine serves as a buffer for the intracellular CoA pool. When acyl-CoA esters accumulate — as happens during metabolic stress or high-fat feeding — carnitine accepts the acyl groups, freeing CoA for other metabolic pathways including the citric acid cycle and pyruvate oxidation. This CoA-buffering function helps prevent metabolic bottlenecks and maintains cellular energy flexibility.
What to Expect
Plasma carnitine levels rise immediately with injectable dosing. Some users report increased energy and warmth within hours of first injection.
Tissue carnitine stores begin to replenish. Mild improvements in exercise tolerance and recovery may be noticed.
Fat oxidation during exercise measurably increases. Body composition changes begin to appear when combined with caloric deficit and training.
Full metabolic adaptation. Meta-analysis data suggests average 1.2 kg weight reduction with continued use. Most pronounced in overweight individuals with consistent exercise.
Dosing Protocol
| Level | Dose / Injection | Frequency |
|---|---|---|
| Beginner | 250mg | Daily |
| Moderate | 500mg | Daily |
| Aggressive | 1000mg | Daily |
Note: Pre-filled injectable solution (200 mg/mL) — no reconstitution needed. FDA-approved as Carnitor for primary and secondary carnitine deficiency. Compounded injectable versions commonly available at 500 mg/mL in 30 mL vials. Oral bioavailability is only 15-18%, which is why injectable administration is strongly preferred for clinical effect.
How to Inject L-Carnitine
Carnitor injection (200 mg/mL) is FDA-approved for IV use, but compounded L-Carnitine injectables are commonly administered IM or subcutaneously. For intramuscular injection, the gluteal or deltoid muscle works well — the solution can have a mild burning sensation, so slower injection helps. Subcutaneous injection into abdominal fat is also used at lower volumes. IV push should be given slowly over 2-3 minutes. Typical protocol: 250-500 mg daily for general metabolic support, up to 1,000 mg daily for active fat loss phases. Some practitioners dose 500 mg pre-workout for performance enhancement.
Cycling Protocol
No strict cycling requirement for carnitine deficiency patients (continuous use approved). For body composition goals, 8-12 weeks on followed by 4 weeks off is common practice to assess baseline and avoid TMAO accumulation from any concurrent oral intake.
Pharmacokinetics
Source: FDA Prescribing Information (Carnitor Injection), Clinical Pharmacology section — mean apparent terminal elimination half-life
Loading the interactive decay curve.
Side Effects
L-Carnitine is one of the better-tolerated injectables out there, but it's not side-effect free. The most common complaints at injectable doses are injection site discomfort, warmth or flushing shortly after administration, and a transient fishy body odor that comes from trimethylamine metabolism — this affects a meaningful percentage of users and can be socially noticeable. GI symptoms like nausea, vomiting, diarrhea, and abdominal cramps are more common with oral dosing but can still occur with injections. At doses above 3 grams per day, GI side effects become significantly more likely. There's a longer-term concern about TMAO (trimethylamine N-oxide) production: gut bacteria convert carnitine to TMA, which the liver oxidizes to TMAO, and elevated TMAO levels have been associated with increased cardiovascular risk in observational studies. This is primarily an oral supplementation concern, since injectable carnitine bypasses the gut microbiome. Rarely, seizures have been reported in patients with or without pre-existing seizure disorders. In hemodialysis patients receiving 3 g/day IV, clinically significant increases in platelet aggregation have been documented.
Contraindications
- Known hypersensitivity to levocarnitine or any component of the formulation
- Pregnancy — insufficient safety data; avoid use unless treating diagnosed deficiency under physician supervision
- Breastfeeding — carnitine is excreted in breast milk; risk-benefit assessment required
- Severe seizure disorder (rare reports of seizure exacerbation)
- Active peripheral vascular disease with TMAO concerns (discuss with physician)
Drug Interactions
- Thyroid hormones — L-Carnitine may inhibit thyroid hormone entry into cell nuclei, reducing effectiveness; monitor thyroid levels
- Warfarin and other anticoagulants — may potentiate anticoagulant effect; monitor INR closely
- Valproic acid and other anticonvulsants — can deplete carnitine levels; supplementation may actually be indicated
- Acenocoumarol — increased bleeding risk reported in case studies
- Zidovudine (AZT) — may reduce carnitine levels; concurrent supplementation may be beneficial
Storage & Stability
Related Peptides
References
- Effects of L-carnitine supplementation on weight loss and body composition: A systematic review and meta-analysis of 37 randomized controlled clinical trialsPubMed 32359762
- Pharmacokinetics of L-carnitinePubMed 12908852
- Kinetics, pharmacokinetics, and regulation of L-carnitine and acetyl-L-carnitine metabolismReview
- The bright and the dark sides of L-carnitine supplementation: a systematic reviewPubMed 32958033
- CARNITOR (levocarnitine) Injection FDA Prescribing InformationFDA Label