In 30 seconds
- Studies use between 1 and 3 g of L-carnitine a day; in trials on body weight, 1.8 to 4 g.
- For recovery, in a meta-analysis of 14 trials using 1-3 g a day, there was less muscle soreness at 24 and 48 hours; in the tartrate trials, the most common amount is around 2 g a day.
- More is not better: with 2 g taken at once, 16% was absorbed, and with 6 g, only 5%. At around 3 g a day, digestive discomfort has been reported.
Between 1 and 3 g of L-carnitine a day: that is the amount that comes up most often in the studies, and trials on body weight went as high as 4 g 1. For recovery, the usual amount is around 2 g a day for 3 to 5 weeks 4 5.
Here is how much is used for each goal, how to read the label and when it becomes too much.
L-carnitine a day
The dose in the studies and your 20 ml serving
The dose in the studies, by goal
The amount depends on why you are taking it. This is a summary of what has been used in the studies 1 7:
| Goal | Amount a day | For how long |
|---|---|---|
| Fat loss (body weight) | 1.8-4 g | 30 to 360 days |
| Muscle soreness and recovery | 1-3 g; about 2 g in the tartrate trials | 3 to 5 weeks, every day |
| More carnitine in muscle | 1.36 g twice a day, with 80 g of carbohydrates each time | 12 weeks or more |
| What you already get from food | 24-145 mg on a diet that includes meat; 1.2 mg on a vegan diet | Every day |
Sources: US NIH Office of Dietary Supplements; Kazeminasab et al., 2025; Stefan et al., 2021; Stephens et al., 2013; Australian Institute of Sport, 2021.
For fat loss
This is the most searched-for use, because L-carnitine is one of the most widely known stimulant-free fat burners. According to physiology studies, it carries long-chain fatty acids into the mitochondria, where they are oxidised to produce energy 1. You can see it in a diagram in what L-carnitine is good for.
In a meta-analysis of 9 trials with 911 adults, those who took it lost 1.33 kg more weight than the control group 2. Those trials used 1.8 to 4 g a day for 30 to 360 days 1. The effect was larger in the shorter studies 2.
For muscle soreness and recovery
Here the dose is more precisely defined. A meta-analysis of 14 trials with 284 adults, using 1-3 g a day, found less muscle soreness 24 and 48 hours after exercise and lower markers of muscle damage 3.
Do you need to go up to 3 g? One trial compared 1 g and 2 g of L-carnitine tartrate for 3 weeks. Both doses reduced muscle soreness and markers of muscle damage; with 2 g, blood carnitine rose more 4.
In a 5-week trial, 73 adults aged 21 to 65 took 2 g of L-carnitine a day. In the placebo group, creatine kinase (CK), a marker of muscle damage, was 28% higher 5.
To load your muscles with carnitine
This is the most demanding goal. In one trial, 1.36 g of L-carnitine twice a day, with 80 g of carbohydrates each time, raised muscle carnitine by 20% in 12 weeks. The group that took only the carbohydrates did not change 6.
The Australian Institute of Sport sums it up like this: 1.4-3 g of L-carnitine a day, split into two doses with a carbohydrate-containing meal, for 12 weeks or more. In 4 weeks or less, no changes in muscle carnitine have been seen 7. The effects on muscle soreness, on the other hand, were measured after 3 to 5 weeks 4 5.
Count the L-carnitine
What each 20 ml serving provides
Count the L-carnitine, not the tartrate
When you read a label, check the form. Tartrate is L-carnitine bound to tartaric acid: 3 g of tartrate provides 2 g of L-carnitine 5. If a product advertises 3,000 mg of tartrate, you are getting about 2 g of L-carnitine, not 3.
It is the form most used in sport 7 and the one used in many recovery studies. You will find its trials one by one in L-carnitine tartrate and recovery.
The Australian protocol uses a range of 1.4-3 g of L-carnitine a day, split into two doses with carbohydrates 7.
Absorption
The more you take at once, the less you absorb
More is not better
Only 14-18% of the L-carnitine in supplements is absorbed, compared with 63-75% of the L-carnitine in food 1. And the percentage drops the more you take at once.
In an absorption study, 16% was absorbed with 2 g taken at once; with 6 g, only 5%. The amount that reached the bloodstream was similar with both doses 8.
On top of that, at around 3 g a day, nausea, vomiting, abdominal cramps, diarrhoea and a fishy body odour can appear 1. The US NIH has not set an upper limit 1, so the practical rule is simple: stick to the dose used in the studies and do not double the one on the label. We cover it in L-carnitine side effects.
When to take it and for how long
- Once a day, every day. In the 5-week trial, it was taken 30 minutes before training and, on non-training days, with the first meal 5.
- With carbohydrates, if it suits you. Muscle takes up carnitine better alongside a carbohydrate-containing meal 6 7. If you train after a meal, the pre-workout serving fits in well.
- Weeks, not days. The effects on muscle soreness were measured after 3 to 5 weeks 4 5; changes in muscle, after 12 weeks or more 6 7.
Does it change with your weight, sex or age?
- Your weight: studies use a fixed daily amount, not an amount per kilo. Of the trials in the weight meta-analysis, only one calculated the dose per kilo: 15 mg per kilo a day 1.
- If you are a woman: the 5-week trial included men and women, with similar results 5.
- Over 40: that same trial included adults up to 65, with less muscle damage (CK) in the 41-65 age group too 5.
- If you are vegetarian or vegan: on a vegan diet you get barely 1.2 mg a day 1, and vegetarians may respond better to supplementation 7. Even so, carnitine deficiency is rare, including in vegans 7.
If you are pregnant or breastfeeding, take medication or have kidney disease, check with your doctor first.
Frequently asked questions
How much L-carnitine should you take a day?
Between 1 and 3 g a day is what comes up most in the studies; trials on body weight used 1.8 to 4 g.
How much L-carnitine should you take to lose fat?
In a meta-analysis of 9 trials with 911 adults, 1.8 to 4 g a day was used for 30 to 360 days, and those who took it lost 1.33 kg more than the control group. It is taken as a stimulant-free fat burner, alongside a moderate calorie deficit.
Can you take 3 g of L-carnitine a day?
It has been used in studies, but at around 3 g a day, nausea, digestive discomfort, diarrhoea and a fishy body odour have been reported. The US NIH has not set an upper limit: the practical approach is not to exceed the dose on the label.
How much L-carnitine is in L-carnitine tartrate?
About two thirds of its weight: 3 g of tartrate provides 2 g of L-carnitine. When comparing products, count the grams of L-carnitine, not the grams of tartrate.
Should you take L-carnitine on days you do not train?
Yes: its effects were measured with daily servings over several weeks. In the 5-week trial, on non-training days it was taken with the first meal of the day.
Sources
- Office of Dietary Supplements, National Institutes of Health. Carnitine: fact sheet for health professionals. View publication
- Pooyandjoo M, Nouhi M, Shab-Bidar S, Djafarian K, Olyaeemanesh A. The effect of (L-)carnitine on weight loss in adults: a systematic review and meta-analysis of randomized controlled trials. Obes Rev. 2016;17(10):970-976. View publication
- Kazeminasab F, Miraghajani M, Ahmadinejad S, et al. Effects of L-carnitine supplementation on markers of exercise-induced muscle damage in healthy adults: a systematic review and meta-analysis of randomized controlled trials. Adv Exerc Health Sci. 2025;2(2):94-107. View publication
- Spiering BA, Kraemer WJ, Vingren JL, Hatfield DL, Fragala MS, Ho JY, et al. Responses of criterion variables to different supplemental doses of L-carnitine L-tartrate. J Strength Cond Res. 2007;21(1):259-264. View publication
- Stefan M, Sharp M, Gheith R, Lowery R, Ottinger C, Wilson J, et al. L-carnitine tartrate supplementation for 5 weeks improves exercise recovery in men and women: a randomized, double-blind, placebo-controlled trial. Nutrients. 2021;13(10):3432. View publication
- Stephens FB, Wall BT, Marimuthu K, Shannon CE, Constantin-Teodosiu D, Macdonald IA, et al. Skeletal muscle carnitine loading increases energy expenditure, modulates fuel metabolism gene networks and prevents body fat accumulation in humans. J Physiol. 2013;591(18):4655-4666. View publication
- Australian Institute of Sport. AIS Sports Supplement Framework: carnitine (L-carnitine). Supplement fact sheet. Updated March 2021. View publication
- Harper P, Elwin CE, Cederblad G. Pharmacokinetics of bolus intravenous and oral doses of L-carnitine in healthy subjects. Eur J Clin Pharmacol. 1988;35(1):69-75. View publication
Information based on published studies. It does not replace the advice of a doctor or registered dietitian. The results describe what was measured in each study, not the properties of any specific product. A varied and balanced diet and a healthy lifestyle are important.
