Is carnitine safe?

Is carnitine safe?

Dietary supplements have their fans but there are still people who are concerned about new and unknows substances. Surely even you know notorious comments and questions from friends why do you take protein, amino acids or other supplements. You also know the notorious comments and questions of friends why you are taking protein, amino acids or other supplements. A worse situation is when a report is published in the media with scientific evidence of the harmfulness of a substance. Due to a similar situation carnitine was also wrongly blacklisted.

What is carnitine?

Carnitine is ammonium compound which has its functions in the metabolism of mammals, plants and bacteria. In our body, carnitine is found in every cell and its main role is the transfer of fatty acids to mitochondria. In addition, it removes residual and noxious substances from mitochondria whose key function is the production of energy for the functioning of cells. The organism creates carnitine from two amino acids – lysine and methionine. In 1905, two Russian researchers managed to isolate carnitine from meat for the first time. Based on that its name was created. The name comes from the Latin word carnus, which means meat. [2] [3] [4] [6]

Carnitine is found in four forms [2] [5]:

  • L-carnitinethe most common form which is a component of dietary supplements for athletes and helps in muscle recovery after the workout.
  • acetyl-L-carnitinethe most effective form for the brain, useful for people with neurodegenerative diseases.
  • propionyl-L-carnitineuseful in problems with circulatory system such as vascular diseases and high blood pressure. It increases production of nitric oxide which improves blood flow.
  • D-carnitine – inactive form that can cause carnitine deficiency by inhibiting the absorption of its other active forms.
What is carnitine?


L-carnitine and its occurrence in food

The most common form of carnitine used by athletes and also by people with health problems, is called L-carnitine. It used to be incorrectly considered to be an amino acid, but it is compound similar to vitamin or amino acid that is classified as a B-group vitamin. In the 1950s, L-carnitine was scientifically analyzed for the first time and it was called as vitamin BT. [6]

L-carnitine is stored in the whole body, mostly in the muscles and brain. From the diet we get it mainly from red meat and animal products, but also from avocado and soy. The human body can produce enough carnitine if you consume a diet rich in lysine and methionine.  [6] [7] 

High amount of lysine can be found in these foods [7]:

  • cheese, yoghurt, milk
  • fruit from the trees
  • poultry, fish and other types of meat

Methionine is increasingly contained in these foods [7]:

  • meat (especially turkey), fish, crustaceans
  • dairy products, cheese, eggs 
  • soy and beans
  • nuts
L-carnitine and its occurrence in food

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Benefits of L-carnitine for athletes

L-carnitine is mostly known as a fat burner, but its benefits for the body do not end there. It is very important for muscle tissue because it relieves fatigue and muscle pain, but it also contributes to blood flow and regeneration of muscle tissue. It is one of the most popular supplements due to 4 key features. [6] 

1. It burns fat as a fuel

L-carnitine and its effects on performance enhancement of the athletes has been subject of several scientific studies. Research at the University of Nottingham followed two groups of athletes. The first group consumed every four hours 2 g of L-carnitine together with 80 g of high-glucose carbohydrates for 24 hours. The second group ate only carbohydrates. The results showed differences in performance in cycling, in both low and high intensity cycling.

Carnitine users burned 55 % less muscle tissue during slow cycling while increased body´s ability to burn 55 % of fat. In high intensity cycling, the carnitine group had a lower level of lactic acid and a higher amount of creatine phosphate which builds ATP. Adenosine triphosphate is the main source of energy in physical activity.

2. It improves fatigue resistance

Research in Nottingham also measured fatigue resistance during the cycling test. Subjects who consumed L-carnitine were able to cycle for 25% longer. The reason for the better results was fat burning while maintaining muscle glycogen.

3. It reduces muscle pain and speed up muscle regeneration

Several studies has confirmed the effects of L-carnitine on muscle regeneration. Already 1 – 2 g daily significantly reduced muscle damage and helped their recovery after strenuous workout. It was proven that L-carnitine relieves soreness after workout in healthy and active people.

4. It adjusts blood flow

The key feature of L-carnitine is not only the ability to burn more fat, but also to improve muscle perfusion. Better blood flow means better supply of nutrients and hormones that are needed during workout.

According to researches, carnitine has also other benefits. It is effective as prevention of diseases, it improves brain activity, reduces blood pressure and inflammatory processes associated with heart disease. [5] Do you want to know more about L-carnitine? Read our article L-carnitine and its 11 amazing side effects.

Benefits of L-carnitine for athletes

Is carnitine harmful?

In 2013, media reported that popular carnitive may cause cardiovascular disease. Reporters referred to a study which was published in magazine Nature Medicine, but conclusions presented in media were different that the research conclusions. [1]

What were the concerns about carnitine and what exactly did the study find out? Hoax was based on two information [1]:

  • research on mice – in one mouse strain, it was found that carnitine promotes the development of atherosclerosis. When digesting, it produces a substance called trimethylamine-N-oxide (TMAO) which damages the heart.
  • comparative study – 2595 participants were involved in the study to measure the possible incidence of heart disease and higher blood pressure with using carnitine. The results showed a higher incidence of cardiac attacks.

Why none of the reasons not indicated the harmfulness of carnitine?

  1. The first reason are the results of the research on mice that are not relevant to humans. The human organism is different in many aspects from the organism of rodents. Therefore, the results of research conducted on mice do not apply to humans. 
  2. The problem were also the mice themselves, on which the research was applied because they were genetically modified animals. They lacked a key enzyme that is important in fat metabolism and that was the reason for the increased susceptibility to atherosclerosis. [1]
  3. Another reason were the findings from a comparative study that revealed a link between carnitine and heart disease. The results of the study were not relevant because of wrong evaluation of the statistical data. When evaluating it is important to avoid the so-called multiple comparisons. What does it mean? Imagine you are throwing a coin. If you hit a character 5 times in a row, it will be a statistically important figure. However, if you throw a coin 100 times and only 5 times hit the character, it is very likely and statistically insignificant. Researchers later agreed that the association of carnitine with the development of heart disease was caused by a statistical error. [1]
Is carnitine harmful?

Carnitine and its safety

Carnitine and its forms have been studied since the 1950s and studies have studied its effect on athletes, but also on people suffering from carnitine deficiency or other diseases. In academic circles its use is being discussed and new studies are being introduced almost constantly. However, daily income of L-carnitine up to 2 grams is safe for most people and does not cause any side effects.

A research in 2001 studied the effect of 3 g of L-carnitine-L-tartrate per day on healthy men for 21 days. The aim of the research was to compare blood samples before and after taking carnitine. The researchers focused on the functioning of the liver, kidneys and also the content of minerals and electrolytes. The results of the study did not demonstrate statistically significant blood differences in participants receiving L-carnitine-L-tartrate and participants receiving placebo. It shows that L-carnitine-L-tartrate used as a nutritional supplement has no adverse effects on blood or metabolism in healthy men. [5] [8]

According to a study in 2006, the effects of carnitine on weight loss and energy balance have been addressed by several clinical studies. With regard to the safety of carnitine, the results of the investigations were evaluated and the term spotted safety level was introduced. The observation method of risks indicates a high level of safety with when taking a daily dose of L-carnitine of up to 2 g, even with long-term use. Studies have also tested higher doses without adverse reactions, which means that even higher doses can be considered as safe. The safety of long-term use of carnitine above 2000 mg per day can not be scientifically confirmed because we lack new studies. [9]

Side effects of L-carnitine

L-carnitine is safe when taking the recommended dosage. Minimal side effects were reported when taking 3 g per day and it was nausea, convulsions, diarrhea or body odor. L-carnitine increases blood flow and can therefore affect people at risk for cardiovascular disease. In addition, it increases the effects of medicines that help with blood clotting. [3] [7]

L-carnitine as a supplement is not regulated and that is why we can not confirm its suitability for pregnant women, breastfeeding women or kids. If you belong to these mentioned groups, it is better to consult with doctor the usage of L-carnitine as dietary supplement. [3] [7]

Side effects of L-carnitine

Who is the L-carnitine suitable for?

Carnitine content in the body depends on your diet and also carnitine production in the body. Especially athletes and people with an active lifestyle tend to add L-carnitine as a supplement because it brings them the benefits we mentioned above.

However, studies have confirmed that carnitine level also decreases in older people who can be benefit from supplementation of carnitine. Carnitine deficiency is a risk for patients suffering from liver cirrhosis and kidney disease. However, it is wise to consult income of carnitine with a doctor when having health problems. [5] 

Who is the L-carnitine suitable for?


Do you sport or do you need to lose excess kilograms? Supplementation of carnitine can be beneficial for you, but it is important to follow the recommended dosage. In this article, we have presented scientific evidence on the safety of carnitine and the benefits of carnitine usage. We believe you have learned something new and if you like the article, we would be happy if you support it with your like and sharing.


[1] Alan R. Gaby - Does Carnitine Really Cause Heart Disease? –

[2] Debra Rose Wilson - Carnitine: What are the benefits and risks? –

[3] Jayson Kroner - L-Carnitine: Metabolic Rocket Fuel –

[4] Carnitine –

[5] Rudy Mawer - L-Carnitine: Benefits, Side Effects, Sources and Dosage –

[6] Jim Stoppani - Your Expert Guide To L-Carnitine –

[7] Cathy Wong - Health Benefits of L-Carnitine –

[8] Rubin MR, Volek JS, Gómez AL, Ratamess NA, French DN, Sharman MJ, Kraemer WJ - Safety measures of L-carnitine L-tartrate supplementation in healthy men. –

[9] Hathcock JN, Shao A - Risk assessment for carnitine –

[10] CHEBI:17126 - carnitine –

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