L-Carnitine has become a popular topic of discussion in the health and fitness community due to its potential health benefits and wide-ranging applications. As an amino acid derivative involved in energy production, it’s essential to understand the various aspects of L-carnitine, from its health benefits and forms to its recommended dosage and real-life experiences.

Table of Contents

In this comprehensive guide, we will cover the health benefits associated with L-carnitine, including its impact on weight loss, erectile dysfunction, and athletic performance. We’ll also discuss the different forms of L-carnitine available, optimal dosages for various applications, and the best times to take it. Additionally, we’ll touch upon potential side effects, recent studies, and a Q&A section addressing common questions about L-carnitine. To provide a well-rounded perspective, we will also share a fact sheet, publications, and reviews from real users who have shared their experiences on platforms like Reddit.


The name of L-Carnitine is derived from the Latin word “carnus,” meaning “flesh,” due to its prevalence in animal-based foods, particularly meat. It was first delivered from bull semen in 1905 by Russian scientists Gulewitsch and Krimberg. L-carnitine is naturally produced in the body, mainly in the liver and kidneys, from the amino acids lysine and methionine. Red meat, especially lamb and beef, is a rich source of L-carnitine, but it can also be found in smaller quantities in dairy products, fish, and poultry.

Early research established L-Carnitine’s role in fatty acid metabolism and its importance in conditions like primary and secondary L-Carnitine deficiencies. As a result, supplementation became an effective treatment option for those with these deficiencies.

Later, studies began to investigate L-Carnitine’s potential benefits for athletic performance, recovery, and muscle damage reduction. While some studies reported positive effects, others showed little to no improvement, leading to mixed conclusions.

In more recent years, the scope of research has expanded to assess L-Carnitine’s potential benefits in various clinical settings, such as cardiovascular health, weight management, cognitive function, and ageing. However, results have been inconsistent, and researchers continue to refine their methods to better understand L-Carnitine’s true benefits and any potential side effects.


L-carnitine is an amino acid derivative that plays a crucial role in energy production in the human body. It is primarily known for its potential benefits in various aspects of health and fitness, including:

  • Fat metabolism. L-carnitine helps transport long-chain fatty acids into the mitochondria of cells, where they are burned for energy. This process can contribute to weight loss and improved fat metabolism.
  • Exercise performance. Some research suggests that L-carnitine may enhance exercise performance by increasing oxygen supply to muscles, reducing muscle soreness, and promoting recovery after intense workouts.
  • Heart health. L-carnitine has been shown to support heart health by reducing oxidative stress, improving endothelial function, and potentially reducing symptoms of angina (chest pain) and peripheral arterial disease.
  • Brain function. Some studies indicate that L-carnitine may help improve cognitive function, focus, and memory, particularly in older adults and those with cognitive decline or Alzheimer’s disease.
  • Male fertility. L-carnitine has been linked to improved sperm quality and motility, potentially aiding in male fertility.
  • Diabetes management. L-carnitine may help improve insulin sensitivity and glucose utilization in people with type 2 diabetes, contributing to better blood sugar control.
  • Chronic fatigue syndrome. Some research suggests that L-carnitine may help alleviate symptoms of chronic fatigue syndrome by increasing energy production in cells.
  • Kidney function. L-carnitine supplementation may be beneficial for people with kidney disease, as it can help reduce symptoms of fatigue and improve overall kidney function.
  • Hyperthyroidism. Some evidence suggests that L-carnitine may help manage symptoms of hyperthyroidism by reducing thyroid hormone activity.
  • Immune system support. L-carnitine may play a role in supporting immune function, as it has been found to have antioxidant and anti-inflammatory properties.
  • Detoxication. L-carnitine supports the level of free CoASH, which is involved in the detoxification of organic acids and xenobiotics, is necessary for the functioning of certain enzymes, and for the normal operation of the Krebs cycle.
  • Anti-aging. L-carnitine has been studied for its potential anti-aging effects, as it may help reduce oxidative stress and improve mitochondrial function, which can decline with age.
  • Liver health. L-carnitine may help protect the liver from damage caused by various toxins and support overall liver function.
  • Muscular dystrophy and anabolic effects. Some studies suggest that L-carnitine supplementation may improve muscle strength and function in people with certain types of muscular dystrophy. The anabolic effect of L-carnitine was established experimentally; during trials with the use of this supplement, scientists noticed that the subjects not only lost fat but also increased their lean muscle mass. The mechanism of this action is not yet fully understood, but there are several theories that explain the anabolic effect of carnitine through its involvement in phospholipid metabolism, optimization of the Acetyl-CoA/CoASH balance, increased utilization of fat as an energy source, and improved neurotransmission.
  • Cholesterol level. L-carnitine has been studied for its potential effects on cholesterol levels, with some research suggesting that it may help lower total cholesterol and LDL cholesterol (often referred to as “bad” cholesterol) levels while increasing HDL cholesterol (or “good” cholesterol) levels. The mechanism behind these effects is thought to be related to L-carnitine’s role in transporting fatty acids into the mitochondria for energy production, which may help regulate lipid metabolism and reduce the buildup of cholesterol in the blood.

Forms of L-carnitine

There are several forms of L-carnitine available as supplements, each with its unique properties and potential applications. The most common forms include:

  1. L-Carnitine L-Tartrate (LCLT). This form of L-carnitine is quickly absorbed and often used to enhance exercise performance and recovery. It is commonly found in sports supplements and is considered the most effective form for muscle recovery and reducing exercise-induced muscle damage.
  2. Acetyl-L-Carnitine (ALCAR). Acetyl-L-carnitine has an additional acetyl group, which allows it to cross the blood-brain barrier more easily. As a result, ALCAR is considered the best form for supporting cognitive function, memory, and overall brain health. It is also used for neurological conditions and age-related cognitive decline.
  3. Propionyl-L-Carnitine (PLC). Propionyl-L-carnitine is primarily used for its potential benefits on cardiovascular health, as it may help improve blood flow and reduce symptoms of peripheral arterial disease. This form is also studied for its potential effects on erectile dysfunction.
  4. D-Carnitine. This form is a biologically inactive isomer of L-carnitine and is not recommended for supplementation, as it may interfere with the natural function of L-carnitine in the body.

The most universal form of L-carnitine is L-Carnitine L-Tartrate (LCLT). This form is widely used due to its quick absorption and versatility. LCLT is commonly found in sports supplements and is considered effective for supporting exercise performance, muscle recovery, and reducing exercise-induced muscle damage. Additionally, it has been studied for its potential effects on weight management and overall health.

While LCLT is the most universal form, it’s essential to consider your specific health goals and needs when choosing an L-carnitine supplement. Other forms, such as Acetyl-L-Carnitine (ALCAR) and Propionyl-L-Carnitine (PLC), may be more suitable for specific purposes, like cognitive function or cardiovascular health, respectively.


Determining the optimal dosage of L-carnitine depends on individual factors and specific health goals. Generally, for weight loss and exercise performance, 1,000 to 3,000 mg daily is recommended. For erectile dysfunction, studies suggest a dosage of 2,000 mg daily, often combined with other supplements like L-arginine. L-carnitine has also been studied for male fertility, with a suggested dosage of 2,000 to 3,000 mg daily. Limited research on PCOS recommends a dosage of 250 to 500 mg per day. Although there is no specific dosage for reducing belly fat, following the general weight loss guidelines may help.

When to Take

The optimal time to take L-carnitine depends on individual preferences and specific health goals. For weight loss and general health, L-carnitine can be taken with meals to improve absorption, and splitting the daily dosage into smaller doses throughout the day may be effective. When focusing on exercise performance and recovery, L-Carnitine L-Tartrate can be taken 30 to 60 minutes before a workout or immediately post-workout. For cognitive function and brain health, Acetyl-L-Carnitine (ALCAR) is best taken in the morning or early afternoon, as it may have a stimulating effect. Individual responses to L-carnitine supplementation can vary, so monitor your response and adjust the timing accordingly under the guidance of a healthcare professional.

Side Effects

L-carnitine is generally considered safe for most people when taken in appropriate doses. However, some individuals may experience side effects, particularly if they exceed the recommended dosage or have pre-existing medical conditions. Common side effects of L-carnitine supplementation may include:

  • Gastrointestinal issues. Some people may experience stomach discomfort, nausea, vomiting, or diarrhea.
  • Fishy body odor. High doses of L-carnitine can cause a fishy body odor due to the production of trimethylamine, a compound that emits a fishy smell when broken down.
  • Appetite changes. L-carnitine supplementation may cause a decrease in appetite in some individuals.
  • Insomnia. Some users have reported difficulty sleeping, particularly when taking Acetyl-L-Carnitine (ALCAR) later in the day due to its potential stimulating effects.
  • Allergic reactions. Though rare, some people may have an allergic reaction to L-carnitine, which could cause symptoms such as rash, itching, or difficulty breathing.
  • Increased blood pressure. Some people may experience a temporary increase in blood pressure, especially if they are sensitive to supplements or have pre-existing hypertension.
  • Heart palpitations. Although L-carnitine is generally considered safe for heart health, some individuals may experience heart palpitations or an irregular heartbeat after taking the supplement.
  • Headaches. Some users have reported headaches after taking L-carnitine, which may be related to changes in the body’s energy metabolism.
  • Dizziness. L-carnitine supplementation may cause dizziness in some individuals, particularly if taken in high doses or without sufficient hydration.

It’s essential to start with a low dose of L-carnitine and gradually increase it to assess your tolerance and monitor for any side effects.


There have been numerous studies conducted on L-carnitine, investigating its potential effects on various aspects of health and wellness. Here are a few examples:

  • Exercise Performance. A 2018 systematic review and meta-analysis published in the Journal of the International Society of Sports Nutrition analyzed the effects of L-carnitine on exercise performance. The study found that L-carnitine supplementation led to a significant improvement in exercise performance, particularly in endurance-related activities.
  • Weight Loss. In one study, 2 grams of L-carnitine were given daily to a group of participants to assess its effects on weight loss and overall health. After 12 weeks, the researchers observed significant improvements in various health markers, including a reduction in body weight, body mass index (BMI), and waist circumference. The study also noted improved insulin sensitivity, lower levels of triglycerides, and increased high-density lipoprotein (HDL) cholesterol levels, commonly known as “good” cholesterol.
  • Cognitive Function. A 2017 meta-analysis published in the journal Ageing Research Reviews investigated the effects of Acetyl-L-Carnitine (ALCAR) on cognitive function in older adults. The analysis concluded that ALCAR supplementation had a positive impact on cognitive function, particularly in individuals with mild cognitive impairment or Alzheimer’s disease.
  • Cardiovascular Health. A 2014 study published in the journal Mayo Clinic Proceedings analyzed the effects of L-carnitine on patients with acute myocardial infarction (heart attack). The study found that L-carnitine supplementation reduced the risk of subsequent cardiovascular events and improved overall heart health in these patients.
  • Male Fertility. A 2016 systematic review and meta-analysis published in the journal Reproductive Biology and Endocrinology examined the effects of L-carnitine on male fertility. The analysis found that L-carnitine supplementation significantly improved sperm motility and overall sperm quality in men with fertility issues.
  • PCOS. A 2016 study published in the journal Clinical Endocrinology explored the effects of L-carnitine on insulin sensitivity and lipid profiles in women with polycystic ovary syndrome (PCOS). The study found that L-carnitine supplementation improved insulin sensitivity and lipid profiles, suggesting potential benefits for women with PCOS.
  • Eye Health. Emerging research indicates that L-carnitine, specifically Acetyl-L-carnitine, might offer noteworthy advantages for ocular wellness, particularly in managing Age-Related Macular Degeneration (AMD). One compelling study underscored the potential of a nutrient blend consisting of Acetyl-L-carnitine, Omega-3 fatty acids, and Coenzyme Q10. The research found that this combination significantly enhanced visual functions and decreased fundus alterations — changes occurring at the rear part of the eye. This evidence is particularly crucial for those diagnosed with early AMD. Furthermore, this study observed a remarkable reduction in drusen, yellow deposits under the retina that escalate with AMD progression. L-carnitine’s potential extends beyond AMD, hinting at broader implications for overall eye health.

While many studies show potential benefits of L-carnitine supplementation, some research has reported limited or negative outcomes. For instance, certain studies have found L-carnitine to be ineffective in promoting weight loss or improving fatigue symptoms in chronic fatigue syndrome patients. Additionally, a study published in Nature Medicine suggested a possible link between high levels of L-carnitine in the blood and an increased risk of cardiovascular disease. However, individual responses to L-carnitine supplementation can vary, and further research is needed to fully understand its effects.

Questions and Answers

When should you take L-carnitine?

The optimal time to take L-carnitine may vary depending on your goals and individual needs. Here are some general guidelines:

  • For exercise performance: some studies suggest taking L-carnitine about 30 minutes to an hour before exercising. This timing may potentially enhance endurance, support energy production, and promote recovery.
  • For weight management: taking L-carnitine with a meal, especially one containing carbohydrates, might be more effective, as insulin levels are higher after a meal, which could help transport L-carnitine into muscle cells.
    For general health: if you’re taking L-carnitine for overall health benefits, the timing might be less critical. You can take it with or without food, according to your preference and convenience.

How long does it take to feel the effects of L-carnitine?

For exercise performance and recovery, some people may experience improvements in endurance and reduced muscle soreness within a few weeks of consistent L-carnitine supplementation. However, it’s important to note that results can vary, and some individuals may not see significant benefits.

In the case of weight management or general health, the effects of L-carnitine might be subtle and take longer to become noticeable. It could take several weeks to months of consistent supplementation to observe changes in these areas.

What should I combine L-carnitine with?

Combining L-carnitine with other supplements or nutrients can potentially enhance its benefits or support complementary goals. Some possible combinations include:

  • Carbohydrates. Consuming L-carnitine with a meal containing carbohydrates can increase insulin levels, which may help transport L-carnitine into muscle cells more effectively.
  • Omega-3 fatty acids. These healthy fats, found in fish oil, can support heart health and help reduce inflammation. Combining them with L-carnitine might have synergistic effects on cardiovascular health.
  • Alpha-lipoic acid. This powerful antioxidant can support mitochondrial function and energy production. Combining it with L-carnitine may enhance the body’s ability to utilize fatty acids for energy.
  • Coenzyme Q10 (CoQ10). CoQ10 is another compound involved in energy production within the mitochondria. Combining it with L-carnitine could provide additional support for mitochondrial function and overall energy levels.
  • B-vitamins. B-vitamins are essential for energy metabolism and nerve function. Taking L-carnitine with a B-vitamin complex may help support overall energy production and metabolism.
  • Minerals. Some minerals to consider include magnesium, which plays a vital role in energy production, muscle function, and nerve function, and zinc, which is important for immune function, protein synthesis, and wound healing. Combining these minerals with L-carnitine may help improve exercise performance, recovery, overall energy levels, and general well-being.

What can you not mix with L-carnitine?

Generally, L-carnitine can be safely combined with most vitamins, minerals, and amino acids. While L-carnitine is generally considered safe for most individuals, it is important to be cautious when combining it with certain medications or supplements to avoid adverse interactions. Some examples include thyroid hormone medications, like levothyroxine, which L-carnitine may decrease the effectiveness of, and anticoagulant medications, such as warfarin, as L-carnitine might interfere with their blood-thinning effects.

Does L-carnitine reduce belly fat?

The age-old quest for a miracle belly fat reducer! While L-carnitine has been touted as a potential weight loss aid, the evidence is not quite as clear-cut when it comes to banishing that stubborn belly fat. L-carnitine plays a role in transporting fatty acids into the mitochondria, where they’re burned for energy. However, simply taking L-carnitine supplements doesn’t guarantee a flatter belly.

Scientific evidence regarding the effectiveness of L-carnitine in reducing belly fat is mixed. Some studies have shown modest weight loss benefits, while others report no significant effects.

A 2016 systematic review and meta-analysis published in Obesity Reviews found that L-carnitine supplementation resulted in a small but significant decrease in body weight. However, the review did not specifically focus on belly fat reduction. Another study published in the Journal of Physiology and Biochemistry in 2014 found that L-carnitine supplementation combined with an aerobic training program helped reduce visceral fat (a type of fat found around internal organs, including the abdomen) in obese women.

On the other hand, some research has reported no significant impact of L-carnitine on weight loss or body fat reduction. For example, a study published in the International Journal of Sport Nutrition and Exercise Metabolism in 2000 showed that L-carnitine supplementation did not significantly alter body composition in moderately obese women.

User experiences and testimonials are also mixed. Some users may report positive effects, such as increased energy levels, improved exercise performance, and modest weight loss, including belly fat reduction. However, others might not experience any noticeable changes.

If you choose to take L-carnitine for weight management, you can consume it with a meal or 30 minutes to an hour before exercising to potentially enhance its effectiveness.

Is it good to take L-carnitine everyday?

L-carnitine is a substance that our bodies naturally produce, and it can also be found in certain foods or taken as a supplement. As a result, it’s possible to consume L-carnitine daily. Some individuals may find L-carnitine supplementation especially beneficial, such as those with specific medical conditions or those adhering to a vegetarian or vegan diet. There is no evidence to suggest that tolerance or addiction develops to L-carnitine with regular use.

Is L-carnitine good for female fertility?

There is some evidence suggesting that L-carnitine may have a positive effect on female fertility, particularly in women with certain fertility issues. L-carnitine plays a role in energy production within cells, and it has been studied for its potential to improve various aspects of reproductive health.

Some studies have shown that L-carnitine supplementation may improve egg quality and ovarian function in women with fertility problems, such as polycystic ovary syndrome (PCOS) or diminished ovarian reserve. It has also been suggested that L-carnitine may help reduce oxidative stress in the reproductive system, which can be detrimental to fertility.

Is L-carnitine good for PCOS?

L-carnitine has been studied as a potential supplement for women with polycystic ovary syndrome (PCOS). PCOS is a hormonal disorder that affects women of reproductive age and can lead to various symptoms such as irregular periods, acne, excess hair growth, and difficulties with fertility.

Some research suggests that L-carnitine may be beneficial for women with PCOS due to its role in energy production and metabolism. A few studies have found that L-carnitine supplementation may help improve insulin sensitivity, reduce inflammation, and manage weight in women with PCOS. Additionally, as mentioned previously, L-carnitine may have a positive impact on ovarian function and egg quality in women with fertility issues, including those with PCOS.

Does L-carnitine affect sleep?

There is limited research on the direct effects of L-carnitine on sleep. However, some studies and anecdotal reports suggest that it could have both positive and negative impacts on sleep, depending on the individual and the circumstances.

In some cases, L-carnitine has been reported to improve sleep quality and reduce fatigue. This could be due to its role in energy production and metabolism, which may help regulate sleep-wake cycles and improve overall energy levels.

On the other hand, some individuals have reported difficulty falling asleep or staying asleep after taking L-carnitine, particularly when taken close to bedtime. This could be because L-carnitine may increase alertness and make it harder for some people to relax and fall asleep.

Personal Experiences and Reviews

Understanding the real-world experiences of individuals who consume L-carnitine can provide valuable insights into the potential benefits and drawbacks of this supplement. In this chapter, we delve into typical reviews and personal accounts from people who have incorporated L-carnitine into their daily routines, highlighting common themes and patterns that emerge.

  • Enhanced Energy and Endurance. A significant number of L-carnitine consumers report experiencing increased energy levels and improved endurance during exercise (Fielding et al., 1998)1. One user shared, “Since I started taking L-carnitine, my stamina during workouts has definitely improved. I can push myself harder and recover faster.” This is consistent with the known role of L-carnitine in transporting fatty acids into the mitochondria for energy production.
  • Weight Management. Many users mention L-carnitine as a helpful tool in their weight loss or weight management journey. As one individual noted, “L-carnitine has been a game-changer for me. I’ve lost 10 pounds over the last two months and have been able to keep it off.” It’s important to note that individual experiences can vary and that L-carnitine should be used in conjunction with a healthy diet and exercise program for optimal results.
  • Cognitive Function. Some L-carnitine consumers report experiencing improved cognitive function, including enhanced focus, mental clarity, and memory. One user mentioned, “I’ve noticed that since taking L-carnitine, my concentration and memory have improved. I’m able to stay focused throughout the day and recall information more easily.” This may be due to the role of L-carnitine in brain energy metabolism and its potential neuroprotective effects.
  • Sleep and Relaxation. As discussed earlier, the effects of L-carnitine on sleep can be mixed. One user reported improvements in sleep quality, saying, “After starting L-carnitine, I’ve noticed that I sleep much better and wake up feeling refreshed.” However, others have experienced difficulty falling asleep or staying asleep. For instance, another user said, “I’ve had a harder time falling asleep since taking L-carnitine, especially if I take it in the evening.” The impact of L-carnitine on sleep may vary depending on individual factors and the timing of supplementation.
  • Side Effects. While many L-carnitine users do not experience any significant side effects, some individuals have reported gastrointestinal issues such as nausea, abdominal cramps, and diarrhea, particularly with high doses or when first starting supplementation. One user shared, “I experienced some stomach cramps and diarrhea when I first started taking L-carnitine, but after a week or so, my body adjusted, and the side effects went away.” A few users have also reported a fishy body odor, with one mentioning, “The only downside is the occasional fishy smell, but it’s manageable.”

My Personal Experience

L-carnitine is one of the few supplements that I take regularly and, in my subjective opinion, is one of the most effective. I find it to be even better than protein powders. It provides me with the energy I need for my workouts at the gym. I take it in the form of Acetyl L-Carnitine about 10 minutes before my training session, with a dose of approximately 750 mg. I also combine L-carnitine with GABA, which helps reduce the fatigue experienced by my central nervous system during workouts. This combination allows me to maintain a higher level of performance and focus throughout my training sessions. I am delighted with the results and positive impact L-carnitine has had on my fitness journey, making it an indispensable part of my daily routine.

I would love to hear about your experiences with L-carnitine. If you have used this supplement, please share your thoughts, insights, and any noticeable effects it has had on your well-being, workouts, or daily life.


The information provided in this article is for general informational purposes only. The content presented on this website should be considered solely as opinions and personal experiences. Read more