L-Carnitine

L-carnitine is one of the better-evidenced products on the sports shelf, but the effect is still small. These are the questions our naturopaths ask in store, and half of them are about patience.

A good fit if

• You're carrying extra weight and you're already changing what you eat and how much you move
• You'll give it three months or more rather than judging it in a fortnight
• You train at high intensity and want the daily approach, not a pre-workout scoop
• You eat little or no red meat, which is where nearly all the carnitine in food comes from

Check with us first if

• You have kidney problems, especially if you're on dialysis, where muscle weakness has been reported.
• You have a seizure disorder, as seizures have been reported.
• You take valproic acid, phenobarbital, phenytoin or carbamazepine. These medicines lower blood carnitine themselves, so this is one for your prescriber.
• You take an antibiotic such as pivampicillin (a pivalate type), which can run down carnitine over time.
• You're pregnant or breastfeeding. We don't have data either way, and we won't guess.
• You plan to take it long term, because fasting TMAO rises on 1 to 4 g a day, and we'd rather you heard that from us.

• L-Carnitine, free base (levocarnitine, item 3008). Best known for: The plain form, and the one that does the fat-transport job. Absorption: About 14 to 18 per cent of a supplement dose is absorbed, against 63 to 75 per cent of the carnitine you eat in food. Typical use: Body weight and fat mass in adults carrying extra weight, and high-intensity training over a longer program.
• L-Carnitine L-tartrate (levocarnitine tartrate, item 3012). Best known for: The sports powder version of the same molecule. Absorption: There's no separate absorption data, so treat it as equivalent to the plain form. It's roughly 68% carnitine by weight, so the label number and the carnitine number differ. Typical use: Powders and pre-workouts, because it's stable and takes up less moisture. The tartrate is a formulation choice; it doesn't act differently.
• Acetyl-L-carnitine (item 350). Best known for: The brain and nerve form, with a completely different evidence base. Absorption: We found no head-to-head comparison with L-carnitine, so we won't claim one is absorbed better. Typical use: Studied for nerve and thinking outcomes, mostly in people with diagnosed conditions we can't advertise to. Don't buy it for body composition.
• Propionyl-L-carnitine (item 4159). Best known for: The circulation form, for the arms and legs. Absorption: We found no data. Typical use: Its trials were all in people with a diagnosed disease, so none of it applies to general use.
• D-carnitine, or a label that just says "carnitine". Best known for: The mirror-image molecule your body doesn't use. Absorption: Not applicable. Typical use: Neither is in Schedule 1, so neither is allowed in a listed medicine. None of the evidence on this page applies.

Reference values. There's no NRV or RDI for L-carnitine, because healthy adults make their own. Your body needs about 15 mg a day from diet and its own production combined, and people who eat meat get about 24 to 145 mg a day from food.

Typical supplemental range. These are trial doses, not label doses. The weight research covers 150 mg to 4,000 mg a day, and modelling puts the biggest effect at 2,000 mg a day. Exercise trials used 3 to 4 g taken 60 to 90 minutes before hard training, or 2 to 2.7 g a day for 9 to 24 weeks. If you're buying the tartrate form, it's about 68% carnitine by weight.

Upper level. None has been set. There's no Upper Intake Level for carnitine, and no levocarnitine entry on Australia's permitted ingredients list (Schedule 1) has a dose cap. Side effects start to appear at around 3 g a day.

Worth knowing. Two practical points. Give it months rather than weeks, because muscle carnitine barely shifts within a month, and the regimens that worked took 12 to 24 weeks with carbohydrate alongside. And take it earlier in the day: one in ten people in a 2025 trial had trouble sleeping after a 3 g dose taken 90 minutes before exercise. What you need depends on your age, diet and health, so talk to one of our naturopaths.

Food first, where the diet allows it.

• Beef steak, cooked, 85 g: 42 to 122 mg
• Ground beef, cooked, 85 g: 65 to 74 mg
• Whole milk, 1 cup: 8 mg
• Cod, cooked, 85 g: 3 to 5 mg
• Chicken breast, cooked, 85 g: 2 to 4 mg
• Asparagus, cooked, half a cup: 0.1 mg, and a whole vegan day comes to about 1.2 mg

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• You have metabolic syndrome with existing plaque in your neck (carotid) arteries. A randomised trial found 2 g a day for six months was linked to a 9.3% greater increase in carotid narrowing than placebo, and bigger rises in total and LDL cholesterol. See your doctor; this isn't one for us to sell you.
• You plan to take it long term. Fasting blood TMAO rises on 1 to 4 g a day over 12 to 24 weeks, and TMAO is thought to contribute to artery plaque. It's a flag, not an alarm.
• You have kidney failure. Muscle weakness has been reported in people with uraemia.
• You have a seizure disorder. Seizures have been reported in people who have one.
• You'd take around 3 g a day or more. Nausea, vomiting, stomach cramps, diarrhoea and a fishy body odour can occur. The odour is the usual reason people stop.
• You take anticonvulsants. Valproic acid, phenobarbital, phenytoin and carbamazepine all lower blood carnitine. The medicine affects the nutrient here, and it needs medical supervision.
• You take a pivalate-containing antibiotic such as pivampicillin. Long-term use can deplete carnitine.
• You're having cancer treatment. Professional guidelines advise against L-carnitine for cancer-related fatigue, and against acetyl-L-carnitine for preventing nerve damage from chemotherapy.
• Sleep. One in ten people reported trouble sleeping after a single 3 g dose taken 90 minutes before exercise, so take it during the day.
• You're pregnant or breastfeeding. We found no data either way, and Schedule 1 records no warning for any levocarnitine item. We can't give guidance we don't have.