6 Best L-Carnitine Supplements To Boost Your Training 2024

L-carnitine supplementation is used to boost your exercise performance, reduce muscle soreness, to promote weight loss, and to improve brain health, such as in Alzheimer’s Disease^[1].  

The most common use of L-carnitine is as an ingredient in fat burners. A fat burner often has a combination of ingredients that can help you lose weight. 

Those are the known uses for carnitine supplements; how much those claims are true depends on who you ask or how much research you do. The manufacturer may claim that their L-carnitine supplements are the ones that will get your energy levels high to boost performance and promote weight loss, but is that what the literature says? 

Science, on the other hand, may not always agree, and understanding how L-carnitine is made and used in the body can help clarify the use of L-carnitine supplements.

The amino acids don’t just make one type of carnitine. The amino acids, during different processes, can create four forms of carnitine: pure L-carnitine, pure acetyl L-carnitine, propionyl-L-carnitine, and L-carnitine L-tartrate. Each form has its own varying degrees of absorption. The most researched is acetyl-L-carnitine for its increased absorbability and ease of passing through the blood-brain barrier (passing into the brain tissue^[2]). Acetyl L-carnitine will be what you will often come across, but you may also have a combination of others included. 

Its most important role is in energy production, which helps transport fatty acids to make energy, specifically the long-chain fatty acids, into the powerhouse within our cells, the mitochondria. 

The mitochondria are like a power plant, and the long-chain fatty acids are crude oil. The crude oil is converted to fuel like gasoline or diesel in the power plant. So if you need that fuel to be made in the body, you send fatty acids into the mitochondria to create that energy.

6 Best L-Carnitine Supplements For Bodybuilding In 2024  

Benefits of Carnitine

There is extensive research that L-carnitine helps in the areas of aging, cardiovascular health, cancer, type 2 diabetes, HIV and AIDS, End-Stage Renal Disease, and athletic performance. 

A study^[10] suggests that the benefits of L-carnitine supplements in the form of acetyl-L-carnitine can improve cognitive function and reduce deterioration in older adults that have cognitive impairment or that have Alzheimer’s. 

In relation to cardiovascular diseases such as peripheral arterial disease (poor blood circulation in the legs), which can significantly reduce the ability to walk. The use of propionyl-L-carnitine has been shown to significantly improve walking distance^[11] by improving blood flow, thus providing a cardiovascular benefit. 

People with cancer can experience fatigue from chemotherapy and low appetite that may result in poor nutrition; they have also been shown to be carnitine deficient^[12].  Providing a cancer patient that is on chemotherapy with a carnitine supplement has shown to help with fatigue, improve mood, and normalize L-carnitine levels in the blood^[13]. 

A person with type 2 diabetes has difficulty with insulin levels and controlling sugar levels. There is early research that indicates that taking a carnitine supplement can improve insulin sensitivity^[14]. The use of acetyl-L-carnitine as a supplement for one year resulted in diabetes symptoms like reduced nerve pain and improved perception of vibrations for people with diabetic neuropathy^[15].  

In a person with HIV/AIDS, the accumulation of fat varies in locations and can increase the amount of fat in the blood and insulin resistance. This combination is known as lipodystrophy syndrome; this syndrome plus the HIV and antiretroviral drugs can cause toxicity to the mitochondria and lead to carnitine deficiency^[16]. This deficiency creates a loop that does not allow for fat metabolism, but the way it works is unknown. 

A person diagnosed with End-Stage Renal Disease (ESRD), where the kidneys are no longer doing their job to regulate waste and excess fluids, or a person on hemodialysis, a treatment to help regulate waste and fluids from ESRD may result in depleted carnitine levels^[17]. 

The most popular use is usually for athletic purposes, to boost exercise performance, and aid in weight loss; therefore, the reason supplement companies sell L-carnitine supplements. The reasoning is that carnitine plays a role in making energy, which in theory, if supplemented, could provide the necessary extra boost needed for exercise performance.

Carnitine has been studied extensively^[18], and many studies record blood level changes of carnitine. Yet many questions remain unanswered; some questions to be answered, How do L-carnitine supplements get used in the body versus the L-carnitine made by the body? How much do you really need? What is an appropriate dosage? Also, how real are its claims that by supplementing, you can boost energy, lose weight or improve exercise performance?  

Best Time to Take L-Carnitine Supplements

There isn’t an official recommendation of when to take L-carnitine; each manufacturer has its own recommendations based on the additional ingredients in the supplement. 

In supplements that only have L-carnitine, the recommendation on average is to take 30-60 minutes before a workout, and on non-workout days it can be taken in the morning. 

What to Look For in the Best L-Carnitine Supplement

Dosage

The Food and Nutrition Board (FNB) of the National Academies concluded that carnitine is not an essential nutrient; therefore, there aren’t any Dietary Reference Intakes (DRI)^[19] which means that the supplement industry may not have a reliable or credible source to base their dosage amounts on. Carnitine is deemed a “conditionally essential” nutrient meaning that although our body can make it, there are some circumstances where it can’t keep up with the need; thus, it becomes essential to get it from an outside source such as the diet or a supplement.

The standard dose found in L-carnitine supplements is between 500 mg to 2000 mg per day. At doses of three grams per day, you may notice a fishy odor, have nausea or vomiting, and become weak.

Conditions that may require a carnitine supplement^[20] include anorexia, chronic fatigue, coronary vascular disease, Diphtheria, hypoglycemia, muscular disorders, and male infertility.

Price

A supplement with L-carnitine added can range in price from $22.50 to $39.99. The range can mean many things related to the different types of ingredients added or the quality of the ingredients. Unfortunately, it’s hard to tell what the reasoning is for the pricing. 

Third-Party Testing 

Supplements are not regulated by the FDA (Food and Drug Administration) and are not required to provide any third-party testing. Some supplement companies, in good faith, will opt to provide third-party testing. The most popular third-party testing companies will be USP (United States Pharmacopeia), (National Sanitation Foundation), NSF International, and ConsumerLabs.com.

Conclusion

It’s important to know that L-carnitine supplementation is not recommended for healthy individuals; the body makes the amount that you need through the amino acids lysine and methionine. If you follow a healthy diet, you should be able to get the amino acids you need to make L-carnitine. 

An L-carnitine deficiency is rare and is only seen in two situations: a genetic disease called primary carnitine deficiency and a secondary carnitine deficiency related to a chronic condition.  It is also seen in the conditionally essential disorders mentioned above under “Dosage.”.

Also, because L-carnitine is not considered an essential nutrient, a Recommended Dietary Intake is not established; therefore, no known upper limit has been set by the government or scientific institutions.  There is extensive research on L-carnitine for all of its possible benefits, but for fat loss and muscle recovery, more research is still needed.

Frequently Asked Questions

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