Is L-Carnitine Good For Weight Loss? What Experts Think

Dr. Harshi Dhingra, MBBS, MD
Published by Dr. Harshi Dhingra, MBBS, MD | Medical Doctor
Last updated: December 14, 2023
FACT CHECKED by Dr. Kristy Dayanan, BS, MD
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As a practicing physician, I frequently receive inquiries on how to lose weight and get results fast.

One of the supplements that gets brought up regularly is carnitine, so I decided to take a deeper look into l-carnitine supplementation and get the science-backed facts on its effectiveness as a weight-loss tool.

After a few weeks of online research and multiple conversations with my colleagues, I am ready to share what I learned.

Quick Summary

  • L-carnitine aids in weight loss by transporting fatty acids to cells, where they are burned for energy, making it a popular weight loss supplement.
  • Carnitine also presents the following health benefits; relieving muscle soreness, delaying muscle pain, and improving post-exercise muscle recovery.
  • In a 12-week NIH study, participants taking L-carnitine burned more calories during low-intensity exercises and did not gain weight, demonstrating its effectiveness in weight management​​.
  • My personal opinion is that while L-carnitine can support weight loss, it should be combined with healthy diet changes and regular exercise for optimal results​.

How Does Carnitine Work?

Pouring pills on hand

As someone who's used carnitine, I know it transports fatty acids to cells for energy.

It is a naturally occurring amino acid made in the brain, liver, and kidneys and is found in foods like beef, pork, fish, poultry, and milk.

Carnitine is a general term that refers to a few different compounds.

I will mention them briefly below, but this article focuses on l-carnitine, a common additive in sports drinks and supplements.

Other Types of Carnitine

  • D-carnitine is the inactive mirror image of l-carnitine and may impede the absorption of the other forms, potentially causing carnitine deficiency.
  • Acetyl-l-carnitine, also known as ALCAR, is believed to be the best for brain function and has a role in metabolism.
  • Propionyl-l-carnitine may be best for circulatory issues by boosting nitric oxide, improving blood flow and oxygen supply, and imparting some pain-relieving properties.
  • L-carnitine l-tartrate helps the cells create energy and aids the removal of waste from the cells, keeping them healthy and efficient. It is commonly found in sports drinks and supplements because it quickly absorbs into the human body.

“Carnitine is responsible for fueling the fires of energy production at the cellular level. Without this valuable nutrient, the mitochondria are unable to burn dietary fats to create the energy we need to live.”

- Dr. Julius G. Goepp, M.D

Essentially when you exercise, there are a lot of biochemical reactions going on in your body, and one of these is breaking down stored fat and converting it to energy, in which l-carnitine seems to play a significant role [1].

This reaction allows you to burn more fat during exercise, enhances muscle recovery, increases oxygen supply, and combats physical and mental fatigue, all essential when your goal is to lose weight.

Is Carnitine Effective for Weight Loss?

Measuring waist using measuring tape

Based on my experience and backed by NIH research, L-carnitine effectively reduces BMI and fat mass in overweight adults [2]. Further studies, including one noting increased fat oxidation with L-carnitine supplements, align with its weight loss benefits, especially with a healthy lifestyle [3].

Even though each study I came across seems to support l-carnitine weight-loss benefits, the research is ongoing to determine to what degree l-carnitine supplementation is effective in terms of fat loss.

Another 12-week study conducted by the National Institutes of Health (NIH) had participants taking l-carnitine supplements and a high carbohydrate beverage twice a day. At the beginning and the end of the 12 weeks, participants performed 30 minutes of low-intensity exercise.

Related articleFat Burner vs L-Carnitine

Interestingly, those on l-carnitine burned more calories during the study's final low-intensity exercise, had 20% more muscle carnitine, and maintained their weight. Conversely, the non-l-carnitine group, who drank the high-carb beverage, gained weight and had reduced calorie burn. The l-carnitine and high-carb drink combo possibly improved l-carnitine's cellular absorption and fat metabolism.

These findings collectively indicate the potential efficacy of l-carnitine supplementation in weight loss efforts [4].


Other Uses

Man using a treadmill to run

Carnitine seems to have several other health benefits besides helping your body burn fat.

Some of these health issues are treated with carnitine in supplement form and sometimes administered by a healthcare provider by IV.

Athletes taking l-carnitine show improved post-exercise muscle recovery, which can help with muscle soreness and delayed muscle pain [5].

L-carnitine is believed to improve cardiac health in several ways, including reducing blood pressure and helping symptoms of cardiovascular disease like chest pain and arrhythmia [6].

“It’s been suggested that L-carnitine has the ability to move more fatty acids into your cells to be burnt for energy, making it an effective performance enhancer, and it may also be beneficial for fat burning and weight loss.”

- Claire Muszalski, Registered Dietician

It’s interesting to note that taking l-carnitine supplements alone or with acetyl-l-carnitine may aid male fertility issues by increasing sperm count [7].

Also, people with decreased liver function or kidney disease may be more susceptible to l-carnitine deficiency because the liver and kidney are two places where the compound is produced in the human body.

In hemodialysis patients, taking l-carnitine supplements improved muscle weakness, muscle cramps, anemia, and cardiomyopathy (heart muscle disease). Hemodialysis, or simply dialysis, purifies the blood of a person whose kidneys are not working correctly [8].

Side Effects and Precautions

Woman vomiting from nausea

Taking carnitine supplements is considered generally safe, but there is the potential for side effects with any supplement or medication.

I always advise my patients to talk to their healthcare provider when considering any supplement to address any concerns or possible interactions.

Commonly reported side effects of l-carnitine can include nausea, vomiting, abdominal cramps, and diarrhea [9].

Seizures may occur more often and with increased severity in people who have a history of seizures.

L-carnitine also interacts with Warfarin and Acenocoumarol, two anticoagulant medications or blood thinners [10].


How Much L-Carnitine Should I Take for Weight Loss?

The usual recommendation is to take 2-4g (2000-4000 mg) of l-carnitine per day for weight loss. Many advise dividing this total into two or three even doses throughout the day is best, usually with or just after a meal.

How Long Does It Take for L-Carnitine to Work?

L-carnitine can work in as little as an hour to enhance exercise performance which is why many athletes take it as part of their pre-workout routine. In supplement form, it can take weeks of prolonged l-carnitine administration to reap its full health benefits.

Can I Take L-Carnitine before a Workout?

Yes, you can take l-carnitine before a workout to potentially improve exercise performance.

Taking l-carnitine with fast-acting carbohydrates gives you the most benefit as it aids the body in producing energy, which equates to greater physical exertion and improved exercise performance.

Can Carnitine Accelerate Your Weight Loss?

There is no arguing the potential health benefits of l-carnitine are numerous, with fat-burning at the forefront.

Some of my patients take natural fat burners containing l-carnitine, and most of them reported more rapid weight loss and significantly improved energy output. Here are some you should consider for your weight loss process:

If you are looking to lose weight, I encourage you to adopt healthy habits like improving your diet and implementing an exercise routine. There is no quick fix for weight loss, and these two are crucial.

Go ahead and include a fat burner into the mix; you’ll be pleasantly surprised how all three work together to get you to your goal.


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About The Author

Dr. Harshi Dhingra, MBBS, MD is a published peer-reviewed author and renowned physician from India with over a decade of experience. With her MBBS from Bharati Vidyapeeth and an MD from Rajiv Gandhi University, she actively ensures the accuracy of online dietary supplement and medical information by reviewing and fact-checking health publications.
Learn more about our editorial policy
Dr. Kristy June Dayanan, BS, MD is an author with a BS degree from University of the Philippines and an MD from University of Perpetual Help System. Her ability to simplify medical science complexities and dietary supplement jargon for the average reader makes her a valued medical fact checker and reviewer.
Learn more about our editorial policy

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