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L-Carnitine: The Benefits And Side Effects

Jason Hughes
Published by Jason Hughes
Fact checked by Markus Oliver, BHSc FACT CHECKED
Last updated: July 3, 2022

Levocarnitine (L-carnitine) is an amino acid structure produced naturally by the body. However, the body doesn't always produce L-carnitine in beneficial amounts, so many people can benefit from taking supplements or eating foods that contain L-carnitine.

Why is L-carnitine important? L-carnitine plays a crucial role in the production of energy, and it converts the fat in the foods we eat into energy. Additionally, L-carnitine helps to maintain general brain function and reduce the risk of some disorders.

What Exactly Is L-carnitine?

Carnitine is a derivative of amino acids, and L-carnitine is just one type of carnitine. When combined, amino acids make proteins that are responsible for several different essential bodily tasks.

Most significantly, carnitine works to break down the fatty acids we consume and turn those fatty acids into energy that helps to power our body's cells and mitochondria.

The body uses the kidneys and liver to create L-carnitine from methionine and lysine, two amino acids. Additionally, the kidneys—along with the blood, liver, and muscles—are able to store L-carnitine to eliminate excess supply through urine and save needed L-carnitine for use later as needed. Excess concentrations are released through urine.

Note that for the human body to produce enough L-carnitine, you also need to be sure you have sufficient vitamin C.

Types of Carnitine

There are four different types of carnitine.

  • D-carnitine: can be toxic to the human body because it keeps other carnitine forms from absorbing
  • Acetyl L-carnitine (ALCAR): good for metabolism, neurodegenerative diseases, and protects the central nervous system
  • Propionyl-L-carnitine: antirheumatic properties, pain relief, circulatory issues, high blood pressure, and heart health
  • L-carnitine L-tartrate: absorbs rapidly, minimizes muscle soreness after exercise, and aids recovery

L-carnitine Benefits

There are several possible health benefits of L-carnitine, and some of them are backed by science.

1. Cancer Treatment

Some cancer treatments like chemotherapy can cause people to become L-carnitine deficient. Therefore, some doctors may recommend that patients take L-carnitine to help with weakness and fatigue. 

2. Cardiovascular Health

Some studies with carnitine show potential for reducing the inflammatory process and blood pressure that is often associated with heart disease. In one study, a 10-point drop in blood pressure was noted. 

In patients with severe heart disorders such as chronic heart failure and coronary heart disease, L-carnitine has been shown to offer improvements. Another study observed that there was a reduction in deaths and heart failure among study participants who consumed L-carnitine supplements. 

3. Healthy Brain Function

Animal studies indicate that acetyl-L-carnitine (ALCAR) may help prevent mental decline caused by aging. Also, supplementing with ALCAR can improve learning markers

Specifically, supplementing with ALCAR can help reverse brain function decline that is often associated with brain diseases such as Alzheimer's. Moreover, adults who don't have Alzheimer's can also experience the same benefits

4. Exercise Performance

Studies show that L-carnitine can help with all of these exercise issues:

5. Type 2 Diabetes

Some studies indicate that L-carnitine can reduce type 2 diabetes symptoms and its risk factors. One study showed a significant reduction in blood sugar levels in patients with type 2 diabetes. 

6. Weight Loss

Most studies didn't prove that L-carnitine leads to weight loss, but one study did show a weight loss of about 2.9 pounds in older adults and obese people. 

While more research is needed in human trials, L-carnitine may help with weight loss. 

7. Increased Testosterone

One study demonstrated that L-carnitine significantly increases testosterone receptor concentration. This can play a role in the unadulterated development and growth of muscles. 

Additionally, this study showed that L-carnitine increased the mobility of sperm. 

L-carnitine Side Effects

Although the majority of people tolerate L-carnitine well, there are some side effects experienced by some individuals.

L-carnitine Sources

You can get L-carnitine via the food you eat or with supplements. 

Food Sources

One study showed that L-carnitine absorbs better in the human body when it is consumed via food sources. In that study, 57-84% of the L-carnitine in the food was absorbed by the body. On the other hand, only 14-18% of L-carnitine consumed via a supplement was absorbed by the body.

These foods are excellent sources of L-carnitine.

  • Pork
  • Beef
  • Chicken
  • Fish
  • Milk

People who don't eat meat or animal products may benefit from taking L-carnitine supplements. 


For most people, the body makes sufficient L-carnitine because L-carnitine is a conditionally essential nutrient. However, if your body doesn't make enough L-carnitine, you may need to take supplements.

Also, vegans may not get enough L-carnitine from their diet. If you're vegan or vegetarian, you may need to consider taking L-carnitine supplements.


Here are some answers to some of the most frequently asked questions about L-carnitine.

Is L-carnitine good for weight loss?

L-carnitine weight loss results vary because of the complexity of the human body. Scientific studies show mixed results in terms of weight loss with L-carnitine, with some studies showing no significant weight loss. Another study determined that L-carnitine had no effect on fat burning.

However, one study did show some weight loss when obese individuals supplemented with L-carnitine.

What are the dangers of L-carnitine?

While there are side effects to taking too much carnitine, the kidneys filter out what the body doesn't need.

Does L-carnitine work without exercise?

While L-carnitine benefits the cells during both rest and exercise, research shows that carnitine is most effective when combined with intense exercise.

When is it best to take L-carnitine?

To optimize workout energy, take L-carnitine about one hour before you work out.

How much L-carnitine should I take?

The recommended dosage for L-carnitine is between 1 and 3 grams every day. Speak with your doctor to learn more about how much L-carnitine you should take. 

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