L-carnitine (levocarnitine)
Carnitor, L-carnitine base, Liquid carnitine
Forms: Plain L-carnitine in liquids, tablets and capsules; prescription levocarnitine for oral use and injection. The tartrate (LCLT) and acetyl forms are on the L-carnitine L-tartrate card.
Other esters and forms: L-carnitine L-tartrate
The plain form of carnitine, which carries fatty acids into mitochondria; the body makes it and meat supplies it. As a medicine it treats carnitine deficiency; as a supplement it is sold mainly for fat loss.
Legal status: Sold freely as a supplement and as a prescription drug for carnitine deficiency; not prohibited by WADA, but large-volume IV infusions or injections of any substance are banned (M2.2).
What it gives
What people use it for and what the sources report. Strength is a general category from the literature: mild, clear or strong.
Purpose
Used in sport for fat loss and endurance. A doctor may prescribe it for inborn carnitine deficiency or for people on dialysis. In healthy athletes on a normal diet, its effects on body fat and performance are small.
What people seek and what studies show
In a 37-trial meta-analysis, carnitine cut body weight by about 1.2 kg and fat mass by about 2 kg more than placebo, mostly in overweight adults; body-fat percentage and waist size did not change. Oral carnitine alone barely raises muscle carnitine; in a six-month study, taking it with plenty of carbohydrate raised it by about a fifth. Human data on sport performance are thin.
Effects
Evidence: Approved medicine — studied in people for its medical use
Sought effects by goal (as reported)
Possible side effects
Possible does not mean certain: whether they appear depends on dose, duration, individual response and monitoring. Below — what to watch for and how to notice it early.
4 possible side effects
level · how often it is reportedWhat the levels mean
Level: general category from the literature, not your personal risk
How often
- common
- reported often
- possible
- reported in some people
- rare
- reported occasionally
How to lower the risks
For 1 of 4 possible side effects there are specific ways to lower the chance: everyday measures, supplements and options a doctor may consider. For the rest — general advice. No measure removes a risk completely.
Do not combine blood-thinning products (aspirin, painkillers such as ibuprofen, high intakes of fish oil, nattokinase, vitamin E) without a doctor; warn doctors and dentists before procedures; alcohol adds to stomach-bleeding risk. On anticoagulants, contact sports are usually put on hold.
Low-level side effects
How each option helps (2)
- Working with a doctor — Assesses persistent vomiting or severe belly pain (possible pancreatitis or gallstones) and adjusts prescribed GLP-1 treatment when nausea persists.
- Pancreatin + dimeticone (Pankreoflat) — May ease heaviness and gas after meals; can cause nausea or diarrhea. Not for pork or cow's milk protein allergy (anaphylaxis reported) or early acute pancreatitis.
Check-ups and blood tests
Which tests and check-ups to do and when. This is a guide — agree the exact schedule with a sports physician.
Which doctors can help
Get medical help at once if
- Black or bloody stools, vomiting blood or “coffee grounds”, bleeding that won’t stop, a sudden severe headache, any head blow on blood thinners (not aspirin alone) — urgent care or your local emergency number.
In an emergency, call your local emergency number.
Myth & fact
“Carnitine burns fat on its own.”
Not meaningfully. In meta-analyses the extra weight loss is about 1 kg, mostly in overweight adults, and body-fat percentage does not change.
Combinations
No specific combination notes for this substance yet. The stack check still adds up side effects that several substances share.
Sources
Possible side effects by body system, combinations, how to lower the risks and which tests to do — free.
Open the stack check