Does L-Carnitine work?

Does supplementation with L-Carnitine really lose fat?

L-Carnitine is one of the best known supplements when it comes to losing fat, whether in ampoules or capsules, liquid or powder, if you haven't taken it, you're sure you know someone who's already taken it.

The big question is… Works?

First of all, L-Carnitine has several benefits, but let's rely only on one: fat loss.

That is, it may even be effective for several things, but here we will only evaluate its effectiveness in this respect.

Let's get started.

What is L-Carnitine?

L Carnitine is a compound that is synthesized by the body through lysine and methionine.

In addition to being able to be synthesized through these amino acids, it is naturally found in some foods, especially in meat.

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Food Amount L-Carnitine per 100g
Beef 95mg
Pork 27.7mg
Bacon 23.3mg
Cod 5.6mg
Chicken breast 3.9mg


The great theory behind the use of this supplement by those who want to lose weight, is that this compound promotes a greater use of fats.

This on paper makes sense, as L Carnitine binds to fatty acids and allows them to enter the mitochondria to be used as energy.

Theoretically by increasing carnitine levels, we would get more fatty acids used as energy, and thus more fat to be burned.

But it doesn't always make sense in theory, it's confirmed in practice.

l-carnitine ampoules


The absorption of L-Carnitine through feeding is 54% to 87%, while through supplementation it is only 14% to 18%. (1)

That is, when you drink that ampoule with a horrible taste, only 14% to 18% is actually absorbed.

Besides, it's important that this L-Carnitine gets to the muscle, and that's not exactly what happens. (9)

But let's get to the point that really matters, fat burning.

Does Not Work

Unfortunately there are not many studies regarding L-Carnitine in fat loss, but we will use what exists.

According to this study, a low-calorie diet with L-Carnitine supplementation had no advantage in terms of fat loss over a low-calorie diet without L-Carnitine. (2)

This study was done in rats.

Now let's move on to humans.

In this study, moderately obese women were compared, in which one group used 4g of L-Carnitine per day for eight weeks, while the other group did not. (3)

There was no difference between groups in terms of results.

In this study, they analyzed whether L-Carnitine could actually promote greater use of fats, and the results indicate that it did not. (4)

In this study, it was evaluated whether L-Carnitine could promote fat loss in medicated bipolar people.

Two groups were created, both following similar diets, in which one group used an L-Carnitine supplement and the other did not, for 26 weeks.

The results were similar between the two groups. (5)

It's complicated.

Doesn't L-Carnitine really work?



In this study, 66 people were recruited to test the efficacy of this supplement. (6)

These 66 people were separated into two groups, one of them received 2g of L-Carnitine per day, while the other did not.

The results were positive, with not only a decrease in body fat, but also an increase in muscle mass.

The only problem is, the people used in this study were centenarians, that is, people over 100 years old.

If you are over 100 years old, this study shows that this supplement works.

This study proves the same, loss of fat mass and increased muscle mass. (7)

For the end, we left the best.

In 2011 a study was presented that showed that supplementation with this compound may actually be effective.

This study shows that L-Carnitine supplementation, together with carbohydrates, leads to a significant increase in carnitine in muscle, and a consequent increase in fat oxidation.

The form of Carnitine used in this study was L-Tartrate, in a dose of 2g together with 80g of carbohydrates, twice a day. (8)

The bad news is that efficacy only exists in the long run, it takes 6 months for L-Carnitine to show good results.


L-Carnitine if it works in healthy people, in a fat loss component, it will only be long-term.

Those who may also benefit from this supplement are people with low carnitine values, such as the elderly, in which studies show that there is benefit, and vegetarians, who do not have a significant source of L-Carnitine.

The balance we can do is, if you're thinking of using this supplement for a month to get some nice abs, good luck, you're going to need it.

The typical approach of buying a box of ampoules, or a bottle of L-Carnitine, and taking for a few weeks, does not work.

If, on the other hand, you are willing to use this supplement in the long term, or have low carnitine values, L-Carnitine can be a good bet.

The big problem of this supplement to move from theory to practice seems to be absorption, and carnitine levels in muscles in most studies have not increased.

Insulin seems to favor the absorption of L-Carnitine into the muscle, so it will be a good strategy to use this supplement in conjunction with a high carbohydrate meal.

Oh, and use for at least 6 months!


(1) CJ Rebouche. Kinetics, pharmacokinetics, and regulation of L-carnitine and
acetyl-L-carnitine metabolism. Ann N Y Acad Sci. 2004 Nov;1033:30-41.

(2) Brandsch C, Eder K. Effect of L-carnitine on weight loss and body composition 
of rats fed a hypocaloric diet. Ann Nutr Metab. 2002;46(5):205-10.

(3) Villani RG, Gannon J, Self M, Rich PA. L-Carnitine supplementation combined
with aerobic training does not promote weight loss in moderately obese women. Int
J Sport Nutr Exerc Metab. 2000 Jun;10(2):199-207.

(4) Broad EM, Maughan RJ, Galloway SD. Carbohydrate, protein, and fat metabolism
during exercise after oral carnitine supplementation in humans. Int J Sport Nutr 
Exerc Metab. 2008 Dec;18(6):567-84.

(5) Elmslie JL, Porter RJ, Joyce PR, PJ Hunt, Ji Mann. Carnitine does not improve 
weight loss outcomes in valproate-treated bipolar patients consuming an
energy-restricted, low-fat diet. Bipolar Disord. 2006 Oct;8( 5 Pt 1):503-7.

(6) Malaguarnera M, Cammalleri L, Gargante MP, Vacante M, Colonna V, Motta M.
L-Carnitine treatment reduces severity of physical and mental fatigue and
increases cognitive functions in centenarians: a randomized and controlled
clinical trial. Am J Clin Nutr. 2007 Dec;86(6):1738-44.

(7) Pistone G, Marino A, Leotta C, Dell'Arte S, Finocchiaro G, Malaguarnera M.
Levocarnitine administration in elderly subjects with rapid muscle fatigue:
effect on body composition, lipid profile and fatigue. Aging Drugs.

(8) Bt Wall, 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. Physiol J. 2011 Feb 15;589(Pt 4):963-73.

(9) Barnett C, Costill DL, Vukovich MD, Cole KJ, Goodpaster BH, Trappe SW, Fink
Wj. Effect of L-carnitine supplementation on muscle and blood carnitine content
and lactate accumulation during high-intensity sprint cycling. Int J Nutr Sport. 
1994 Sep;4(3):280-8.
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