Gen-Tec 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 the fat-transport role belongs to. Absorption: About 14 to 18 per cent of a supplemental dose, against 63 to 75 per cent for carnitine eaten in food. Typical use: Body weight and fat mass in adults carrying extra weight, and high-intensity training run as a long protocol.
• L-Carnitine L-tartrate (levocarnitine tartrate, item 3012). Best known for: The sports powder version of the same molecule. Absorption: No separate absorption data exists, so treat it as equivalent to the free base. 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 less hygroscopic. The tartrate is a formulation choice, not a different action.
• Acetyl-L-carnitine (item 350). Best known for: The brain and nerve form, and a different evidence base entirely. Absorption: No head-to-head comparison against L-carnitine exists in our sources, so we won't claim one absorbs better. Typical use: Studied in nerve and cognitive outcomes, largely in diagnosed populations we can't advertise to. Don't buy it for body composition.
• Propionyl-L-carnitine (item 4159). Best known for: The peripheral circulation form. Absorption: Not found in our sources. Typical use: Its trials sit entirely in a diagnosed disease population, so nothing about it transfers 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 a permitted listed ingredient. None of the evidence on this page carries over.

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

This list is the part of the page we will not shorten. If any of it applies to you, talk to one of our naturopaths or your doctor before starting.

• Metabolic syndrome with existing carotid plaque. A randomised trial found 2 g a day for six months was associated with a 9.3% greater increase in carotid stenosis than placebo, and greater rises in total and LDL cholesterol. Refer, don't sell.
• Long-term use generally. Fasting plasma TMAO rises on 1 to 4 g a day over 12 to 24 weeks, and TMAO is thought to be pro-atherogenic. A flag, not an alarm.
• Kidney failure. Muscle weakness has been reported in people with uraemia.
• Seizure disorders. Seizures have been reported in people who have them.
• Around 3 g a day and above. Nausea, vomiting, abdominal cramps, diarrhoea and a fishy body odour. The odour is the usual reason people stop.
• Anticonvulsants. Valproic acid, phenobarbital, phenytoin and carbamazepine all reduce blood carnitine. The interaction runs drug to nutrient, and it needs medical supervision.
• Pivalate-conjugated antibiotics such as pivampicillin. Chronic use can deplete carnitine.
• Cancer treatment. Professional guidelines advise against L-carnitine for cancer-related fatigue, and against acetyl-L-carnitine for preventing chemotherapy nerve damage.
• Sleep. One in ten participants reported difficulty sleeping after a single 3 g dose taken 90 minutes before exercise. Take it during the day.
• Pregnancy and breastfeeding. No data was found in either direction, and Schedule 1 records no warning for any levocarnitine item. We won't write guidance we don't have.