In 30 seconds
- Follow your product's label: the usual approach is one serving 30 minutes before training.
- Consistency matters more than timing: muscle carnitine only increased after months of daily use.
- Carbohydrates help: in the study that achieved it, it was taken with 80 g of carbohydrates twice a day.
- Only 14-18% of the carnitine in supplements is absorbed. At around 3 g a day, digestive discomfort may appear.
It is the classic question about L-carnitine: before or after training? The short answer is that timing matters less than it seems. Here is what does matter.
What the label says
Start there. Follow your product's label and do not exceed the recommended dose.
Wall's study
Consistency and carbohydrates, more than timing
What matters more than timing
Consistency
Taking it does not mean it reaches your muscles straight away. In Wall's study, muscle carnitine rose by 21%, but after 24 weeks of taking it every day 1. It is an effect built over months, not from one serving before a training session. We take you through it week by week in how long L-carnitine takes to work.
Carbohydrates
In that same study, L-carnitine was taken with 80 g of carbohydrates twice a day, and the group that took only the carbohydrates did not change 1. The reason: muscle takes up carnitine better when insulin rises.
So if you train after a meal with carbohydrates, the pre-training serving fits in well.
How much is absorbed
Much less than it seems 2:
| Source | Absorption |
|---|---|
| From food | 63-75% |
| From supplements | 14-18% |
Source: US NIH Office of Dietary Supplements.
Amount a day
How much L-carnitine the studies use
How much the studies use
Most studies use between 1 and 3 g a day. In studies on recovery after exercise, around 2 g a day was linked to fewer markers of muscle damage and less muscle soreness 3.
For body weight, a meta-analysis of 9 trials found 1.33 kg more weight loss than with placebo, with an effect that decreased over time 4. You have it all in L-carnitine: what the studies say.
Side effects
At around 3 g a day, nausea, digestive discomfort, diarrhoea and a fishy body odour may appear 2. If you take medication, have a cardiovascular or kidney condition, or are pregnant or breastfeeding, check with your doctor first.
And on days you do not train?
The usual approach is one serving a day: on training days, 30 minutes before, and on rest days, with a meal. If you do not exercise, we explain what to expect in L-carnitine without exercise.
Frequently asked questions
When should you take L-carnitine?
Follow your product's label. More than the exact time, what counts is taking it consistently.
Can you take L-carnitine fasted?
You can, but muscle takes up carnitine better when insulin rises. In the study that managed to increase muscle carnitine, it was taken with carbohydrates. If you train after a meal, it fits in well.
Should you take L-carnitine on days you do not train?
Yes, the usual approach is one serving a day: on training days, 30 minutes before, and on rest days, with a meal.
Is liquid L-carnitine better than capsules?
We have not found studies showing that one form is absorbed better than the other. The advantage of the liquid is that a dose of several grams is taken in one go, without swallowing several capsules.
Does L-carnitine have side effects?
At around 3 g a day, nausea, digestive discomfort, diarrhoea and a fishy body odour may appear. If you take medication or have a cardiovascular or kidney condition, check with your doctor.
Sources
- Wall BT, Stephens FB, Constantin-Teodosiu D, Marimuthu K, Macdonald IA, Greenhaff PL. Chronic oral ingestion of L-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans. J Physiol. 2011;589(4):963-973. View publication
- Office of Dietary Supplements, National Institutes of Health. Carnitine: fact sheet for health professionals. View publication
- Fielding R, Riede L, Lugo JP, Bellamine A. L-Carnitine supplementation in recovery after exercise. Nutrients. 2018;10(3):349. 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
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.
