L-Carnitine

What it is

L-carnitine is not a research peptide; it is an amino-acid-like nutrient your body makes and you eat in red meat, sold here as a shot because pills barely absorb. It helps your muscles use fat for fuel, which in practice means a bit more endurance, less soreness and, during a real calorie deficit, a modest nudge toward fat loss.

The people who get something from it are the ones already in a deficit doing fasted or steady cardio, who want their muscles pulling more from fat and want to recover a little faster between sessions. Vegans and vegetarians, who get almost none from food, often notice more than meat eaters. It also has a real medical job, treating carnitine deficiency and dialysis patients, which is why there is an FDA-approved prescription version called Carnitor. It is the wrong tool if you are hoping a shot will burn fat without a diet; alone, it does nothing visible.

Do not expect to feel much. Some people get a mild energy lift and a cleaner feel during cardio within the first week; the better-documented effect is less muscle soreness after hard sessions. Fat loss, if it shows, shows as a slightly better rate of loss over a month of dieting, not as pounds you can attribute to the shot. If you are not training, there is nothing for it to do.

It comes as a ready liquid, usually 100 mg/ml, so there is no mixing. Start at 50 mg, which is half a millilitre, and work up toward 200 mg; 500 mg is the top of the range. Take it 30 to 60 minutes before training, daily or just on training days. The practical catch is volume: at 100 mg/ml, 200 mg is 2 ml, which is a large subQ shot and stings, and 500 mg is 5 ml, which most people put in the glute IM or skip. The common mistake is misreading the concentration and taking a fifth of what they meant to, or the reverse. A 1200 mg vial is six 200 mg shots, so it is cheap to run.

The human evidence is better than almost anything else in this category, which is a low bar it clears easily. Carnitine's role in fat transport is textbook, it reliably reduces post-exercise soreness and muscle damage markers in trials, and it treats deficiency. The honest limit is that trials of supplementation for fat loss in healthy people show small effects, and that loading muscle with carnitine takes months of consistent intake alongside carbohydrates. It supports a cut; it does not run one.

If you want a compound that actually changes your appetite or metabolism, this is not it; the GLP-1s are a different league, and AOD-9604 or 5-Amino-1MQ are the research-peptide options in this group. Skip it if you have hypothyroidism treated with medicine, since carnitine blunts thyroid hormone action, and skip high doses if you have a seizure history. Everyone else can run it for as long as they like; it is a nutrient your body uses every day, so there is nothing to reset and no reason to cycle off.

What people use it for

How it works

Safety, in brief

The full picture — stop signs and who should talk to a doctor first — is on the dosing guide.

Sources

The labels and studies behind this page. Each link opens the original on PubMed, DailyMed or ClinicalTrials.gov.

1. Carnitor (levocarnitine) prescribing informationDailyMed: Carnitor (levocarnitine) · Label
2. The effect of (L-)carnitine on weight loss in adults: a systematic review and meta-analysis of randomized controlled trialsPooyandjoo et al., Obes Rev 2016 · Review
3. The Effect of L-Carnitine Supplementation on Exercise-Induced Muscle Damage: A Systematic Review and Meta-Analysis of Randomized Clinical TrialsYarizadh et al., J Am Coll Nutr 2020 · Review
4. l-carnitine and l-acetylcarnitine supplementation for idiopathic male infertilityKhaw et al., Reprod Fertil 2020 · Review