L-Carnitine

Uses

L-carnitine is made in the body from the amino acids lysine and methionine, and is needed to release energy from fat. It transports fatty acids into mitochondria, the powerhouses of cells. In infancy, and in situations of high energy needs, such as pregnancy and breast-feeding, the need for L-carnitine can exceed production by the body. Therefore, L-carnitine is considered a "conditionally essential" nutrient.1

What Are Star Ratings?

This supplement has been used in connection with the following health conditions:

Used forWhy
3 Stars
Angina
1 gram two or three times per day
Supplementing with L-carnitine may improve heart function and ease angina symptoms.

is an amino acid needed to transport fats into the mitochondria (the place in the cell where fats are turned into energy). Adequate energy production is essential for normal heart function. Several studies using 1 gram of L-carnitine two to three times per day showed an improvement in heart function and a reduction in symptoms of angina.Coenzyme Q10 also contributes to the energy-making mechanisms of the heart. Angina patients given 150 mg of coenzyme Q10 each day have experienced greater ability to exercise without experiencing chest pain. This has been confirmed in independent investigations.

3 Stars
Congestive Heart Failure
500 mg two to three times per day with a doctor's supervision
Supplementing with L-carnitine can improve heart function and exercise capacity and reduce heart muscle damage due to insufficient oxygen.

People with CHF have insufficient oxygenation of the heart, which can damage the heart muscle. Such damage may be reduced by taking supplements. L-carnitine is a natural substance made from the amino acidslysine and methionine. Levels of L-carnitine are low in people with CHF; therefore, many doctors recommend that those with CHF take 500 mg of L-carnitine two to three times per day.

Most L-carnitine/CHF research has used a modified form of the supplement called (PC). In one double-blind trial, people using 500 mg of PC per day had a 26% increase in exercise capacity after six months. In double-blind research, other indices of heart function have also improved after taking 1 gram of PC twice per day. It remains unclear whether propionyl-L-carnitine has unique advantages over L-carnitine, as limited research in animals and humans has also shown very promising effects of the more common L-carnitine.

3 Stars
Heart Attack
2 grams daily
Taking L-carnitine may help reduce damage and complications following a heart attack.
is an amino acid important for transporting fats that can be turned into energy in the heart. Clinical trials have reported that taking L-carnitine (4–6 grams per day) increases the chance of surviving a heart attack. In one double-blind trial, individuals with suspected heart attack were given 2 grams of L-carnitine per day for 28 days. At the completion of this study, infarct size, as well as the number of nonfatal heart attacks, was lower in the group receiving L-carnitine versus the placebo group. Double-blind research using L-carnitine intravenously also shows promise.
3 Stars
Intermittent Claudication
2 grams daily
In double-blind trials, supplementing with either L-carnitine or propionyl-L-carnitine (a form of L-carnitine) has increased walking distance in people with intermittent claudication.
In double-blind trials, supplementation with L-carnitine and propionyl-L-carnitine (a form of L-carnitine) has increased walking distance in people with intermitting claudication. Walking distance was 75% greater after three weeks of L-carnitine supplementation (2 grams taken twice per day), than after supplementation with a placebo, a statistically significant difference. In the study using propionyl-L-carnitine, improvement occurred on in the those who could not walk 250 meters to begin with. In that group, maximum walking distance increase by 78% with propionyl-L-carnitine supplementation compared with a 44% increase in the placebo group, also a statistically significant difference. The amount of propionyl-L-carnitine used was 1 gram per day, increasing to 2 grams per day after two months, and 3 grams per day after an additional two months, if needed. The results of this trial have been confirmed in a large European trial.
3 Stars
Obesity
250 to 2,000 mg per day
The amino acid L-carnitine is thought to be potentially helpful for weight loss because of its role in fat metabolism.
The amino acid L-carnitine is thought to be potentially helpful for weight loss because of its role in fat metabolism. L-carnitine has been found to reduce fatigue and hunger and improve weight loss effects of fasting. Multiple controlled trials and three meta-analyses have shown that supplementing with L-carnitine can lead to small reductions in body weight in people with overweight and obesity. In a placebo-controlled trial that included 60 overweight women with polycystic ovary syndrome, taking 250 mg of L-carnitine daily for 12 weeks resulted in weight loss, waist circumference reduction, and improved glucose regulation and insulin sensitivity.
2 Stars
Attention Deficit–Hyperactivity Disorder
100 mg per 2.2 lbs (1 kg) of body weight daily, up to a maximum of 4 grams per day
In a double-blind study, supplementing with L-carnitine resulted in improvement in 54% of a group of boys with ADHD, compared with a 13% response rate in the placebo group.

In a double-blind study, supplementation with for eight weeks resulted in clinical improvement in 54% of a group of boys with ADHD, compared with a 13% response rate in the placebo group. The amount of L-carnitine used in this study was 100 mg per 2.2 pounds of body weight per day, with a maximum of 4 grams per day. No adverse effects were seen, although one child developed an unpleasant body odor while taking L-carnitine. Researchers have found that this uncommon side effect of L-carnitine can be prevented by supplementing with riboflavin. Although no serious side effects were seen in this study, the safety of long-term L-carnitine supplementation in children has not been well studied. This treatment should, therefore, be monitored by a physician.

2 Stars
Autism
50 mg per kilogram of body weight per day (half in the morning, half in the evening)
In a double-blind trial, supplementing with L-carnitine resulted in a modest improvement in disease severity in children with autism spectrum disorders.
In a double-blind trial, supplementing with L-carnitine resulted in a modest improvement in disease severity in children with autism spectrum disorders. The amount of L-carnitine used was 50 mg per kilogram of body weight per day (half in the morning and half in the evening) for three months.
2 Stars
Chronic Fatigue Syndrome
1 gram three times daily
L-carnitine is an important nutrient for energy production. Supplementation can make up for a possible deficiency.

is required for energy production in the powerhouses of cells (the mitochondria). There may be a problem in the mitochondria in people with CFS. Deficiency of carnitine has been seen in some CFS sufferers. One gram of carnitine taken three times daily for eight weeks led to improvement in CFS symptoms in one preliminary trial. Supplementation with 6 grams of L-carnitine per day for four weeks also improved fatigue in a preliminary study of patients with advanced cancer. Similar improvements were seen in another study of patients with advanced cancer given up to 3 grams of L-carnitine per day for one week.

2 Stars
Chronic Obstructive Pulmonary Disease
2 grams taken twice per day
Studies have shown that when L-carnitine is given to people with chronic lung disease, breathing during exercise improves.

has been given to people with chronic lung disease in trials investigating how the body responds to exercise. In these double-blind trials, 2 grams of L-carnitine, taken twice daily for two to four weeks, led to positive changes in breathing response to exercise.

2 Stars
Erectile Dysfunction
2 grams of each daily
In one study, supplementing with the combination of propionyl-L-carnitine (a form of L-carnitine) and acetyl-L-carnitine significantly improved erectile function in elderly men.

In a double-blind study, supplementing with the combination of propionyl-L-carnitine (a form of ) and acetyl-L-carnitine (2 grams of each per day) for six months significantly improved erectile function in elderly men with erectile dysfunction associated with low testosterone levels. Propionyl-L-carnitine and acetyl-L-carnitine were significantly more effective than testosterone treatment.

2 Stars
High Cholesterol
2 to 3 grams per day
L-carnitine has been found in some, but not all, clinical trials to reduce high cholesterol levels.
is needed by cells, including heart muscle cells, to metabolize fat into energy, and numerous clinical trials show L-carnitine helps regulate cholesterol levels. A meta-analysis that included findings from 67 randomized controlled trials found L-carnitine appeared to lower total and LDL-cholesterol, increase HDL-cholesterol, and reduce triglyceride levels; however, these benefits disappeared when age, health status, and other parameters of trials and their participants were considered. Another meta-analysis that included 55 randomized controlled trials found only doses of L-carnitine higher than 2 grams per day improved total, LDL-, and HDL-cholesterol levels. Using results from eight randomized controlled trials in a combined total of 508 participants with type 2 diabetes, another meta-analysis found L-carnitine supplementation, at doses of 2–3 grams per day for at least 12 weeks, lowered total and LDL-cholesterol levels.
2 Stars
High Triglycerides
1 to 3 grams daily
Supplementing with L-carnitine may help normalize triglyceride levels.

is another supplement that has lowered TGs in several clinical trials. However, the effect of carnitine is unpredictable, and some individuals have experienced an increase in triglyceride levels after receiving this supplement. Some doctors recommend 1–3 grams of carnitine per day, in the form known as L-carnitine.

2 Stars
Intermittent Claudication
2 grams a day of proprionyl-L-carnitine
In double-blind trials, supplementation with either L-carnitine or propionyl-L-carnitine (a form of L-carnitine) has increased walking distance in people with intermittent claudication.

In double-blind trials, supplementation with either and propionyl-L-carnitine (a form of L-carnitine) has increased walking distance in people with intermittent claudication. Walking distance was 75% greater after three weeks of L-carnitine supplementation (2 grams taken twice per day), than after supplementation with a placebo, a statistically significant difference. In the study using propionyl-L-carnitine, improvement occurred only in those who could not walk 250 meters to begin with. In that group, maximum walking distance increased by 78% with propionyl-L-carnitine supplementation compared with a 44% increase in the placebo group, also a statistically significant difference. The amount of propionyl-L-carnitine used was 1 gram per day, increasing to 2 grams per day after two months, and 3 grams per day after an additional two months, if needed. The results of this trial have been confirmed in a large European trial.

2 Stars
Male Infertility
3 grams daily
L-carnitine appears to be necessary for normal functioning of sperm cells. Supplementing with it may improve sperm motility.

is a substance made in the body and also found in supplements and some foods (such as meat). It appears to be necessary for normal functioning of sperm cells. In preliminary studies, supplementing with 3–4 grams per day for four months helped to normalize sperm motility in men with low sperm quality. While the majority of clinical trials have used L-carnitine, one preliminary trial found that acetylcarnitine (4 grams per day) may also prove useful for treatment of male infertility caused by low quantities of immobile sperm.

2 Stars
Metabolic Syndrome
2 to 3 grams daily
L-carnitine supplementation may reduce cardiovascular risk by improving metabolic parameters such as body weight, blood glucose control, insulin sensitivity, and lipid levels.
The amino acid L-carnitine has been shown in clinical trials and meta-analyses to improve blood glucose control, insulin sensitivity, weight loss, and lipid metabolism, indicating its potential usefulness in treating metabolic syndrome and reducing cardiovascular risk. In one placebo-controlled trial, women with obesity and type 2 diabetes participated in a low-calorie diet program and received 2 grams of L-carnitine per day or placebo for about eight weeks. At the end of the trial, those receiving L-carnitine had greater improvements in blood glucose control, insulin sensitivity, cholesterol and triglyceride levels. In an uncontrolled trial, taking 3 grams of L-carnitine daily for three months led to decreased insulin resistance, LDL-cholesterol levels, and body-mass index (BMI), and increased HDL-cholesterol levels in 80 women with polycystic ovary syndrome, a condition associated with metabolic syndrome.
2 Stars
Multiple Sclerosis and Drug-Induced Fatigue
3 to 6 grams daily
Some drugs that are used to treat MS appear to deplete carnitine. In one trial, supplementing with L-carnitine significantly improved fatigue in 63% of drug-treated MS patients.

Some drugs that are used to treat MS appear to deplete carnitine. In a preliminary trial, supplementation with 3 to 6 grams of per day significantly improved fatigue in 63% of drug-treated MS patients.

2 Stars
Sickle Cell Anemia
50 mg per 2.2 lbs (1 kg) of body weight daily
In a study of children with sickle cell anemia, supplementing with L-carnitine reduced the number of painful crises and improved abnormal heart function and pulmonary hypertension.

In a preliminary study of children with sickle cell anemia, supplementing with (50 mg per 2.2 pounds of body weight per day for six months) significantly reduced the number of painful crises and significantly improved the abnormal heart function (diastolic dysfunction) that was present in most of the children. L-carnitine supplementation also significantly improved pulmonary hypertension in the children who had this abnormality prior to treatment.

2 Stars
Sprains and Strains and Exercise-Related Muscle Injury
3 grams per day
One trial showed that people who take L-carnitine for three weeks before engaging in an exercise regimen are less likely to experience muscle soreness.

One controlled trial showed that people who supplement with 3 grams per day for three weeks before engaging in an exercise regimen are less likely to experience muscle soreness.

2 Stars
Thalassemia
50 to 100 mg per 2.2 lbs (1 kg) of body weight daily
Studies have shown that propionyl-L-carnitine (a form of L-carnitine) protects red blood cells of people with thalassemia against free radical damage. Supplementing with it may reduce the need for blood transfusions.

Test tube studies have shown that propionyl-L-carnitine (a form of ) protects red blood cells of people with thalassemia against free radical damage. In a preliminary study, children with beta thalassemia major who took 100 mg of L-carnitine per 2.2 pounds of body weight per day for three months had a significantly decreased need for blood transfusions. Some studies have found people with thalassemia to be frequently deficient in folic acid, vitamin B12, and zinc. Researchers have reported improved growth rates in zinc-deficient thalassemic children who were given zinc supplements of 22.5 to 90 mg per day, depending on age.Magnesium has been reported to be low in thalassemia patients in some, but not all, studies. A small, preliminary study reported that oral supplements of magnesium, 7.2 mg per 2.2 pounds of body weight per day, improved some red blood cell abnormalities in thalassemia patients.

2 Stars
Type 1 Diabetes
1,500 to 2,000 mg daily
Supplementing with acetyl l-carnitine may reduce symptoms of diabetic neuropathy in people with type 1 diabetes.
Acetyl l-carnitine is an amino acid compound used to treat conditions affecting the brain and peripheral nervous system. Research reviews have concluded acetyl l-carnitine, in doses of at least 2 grams per day, can relieve pain and improve nerve function in those with diabetic nerve damage (neuropathy). A preliminary trial found 500 mg of acetyl l-carnitine three times daily for 24 weeks relieved symptoms of diabetic nerve damage (neuropathy) as effectively as vitamin B12.
2 Stars
Type 2 Diabetes
2 to 4 grams daily
Supplementing with L-carnitine may reduce glucose, cholesterol, and triglyceride levels, and support medical therapies for type 2 diabetes.
L-carnitine is an amino acid needed to properly utilize fat for energy. By supporting healthy fat metabolism, L-carnitine plays an important role in preserving normal insulin sensitivity and glycemic control. People with type 2 diabetes have been found to have lower levels of circulating L-carnitine than healthy people, and in people with type 2 diabetes, lower blood L-carnitine levels are correlated with higher blood glucose and triglyceride levels, lower free radical-quenching capacity, and greater risk of diabetes complications. Supplementing with L-carnitine has been shown in multiple human and animal studies to improve glucose tolerance and lipid metabolism in the context of insulin resistance. A meta-analysis of randomized controlled trials concluded 2–4 grams of L-carnitine per day can effectively reduce fasting blood glucose, total cholesterol, and LDL-cholesterol levels. Clinical trials further show the potential for 2–4 grams of L-carnitine per day to augment other therapies for improving metabolism in people with diabetes, including glimepiride, orlistat, sibutramine, simvastatin, and a low-calorie diet. In addition, a placebo-controlled trial found 600 mg per day of L-carnitine alleviated diabetes-related muscle cramps (a form of diabetic neuropathy) in people with type 2 diabetes.
1 Star
Asthma
Refer to label instructions
In a double-blind trial, supplementing with L-carnitine improved lung function and overall asthma control, compared with a placebo, in children with asthma.
In a double-blind trial, supplementing with L-carnitine (1,050 mg each morning for six months) improved lung function and overall asthma control, compared with a placebo, in Egyptian children with asthma.
1 Star
Athletic Performance
Refer to label instructions
L-carnitine has been popular as a potential aid in improving athletic performance because of its role in converting fat to energy. Some studies have found that it improves certain measures of muscle physiology.

, which is normally manufactured by the human body, has been popular as a potential ergogenic aid (i.e., having the ability to increase work capacity), because of its role in the conversion of fat to energy. However, while some studies have found that L-carnitine improves certain measures of muscle physiology, research on the effects of 2 to 4 grams of L-carnitine per day on performance have produced inconsistent results. L-carnitine may be effective in certain intense exercise activities leading to exhaustion, but recent studies have reported that L-carnitine supplementation does not benefit non-exhaustive or even marathon-level endurance exercise, anaerobic performance, or lean body mass in weight lifters.

1 Star
Cardiomyopathy
Refer to label instructions
Inherited forms of cardiomyopathy seen in children may be responsive to L-carnitine.

Deficiency of , an amino acid, is associated with the development of some forms of cardiomyopathy. Inherited forms of cardiomyopathy seen in children may be the most responsive to therapy with L-carnitine. Whether carnitine supplementation helps the average person with cardiomyopathy remains unknown. Nonetheless, some doctors recommend 1 to 3 grams of carnitine per day for adults of average weight.

1 Star
Liver Cirrhosis
Refer to label instructions
L-carnitine injections have been used to improve circulation to the liver in people with cirrhosis.

injections have been used to improve circulation to the liver in people with cirrhosis, but trials of the oral supplement are lacking.

1 Star
Mitral Valve Prolapse
Refer to label instructions
In one report, deficient levels of L-carnitine were found in five people with MVP. One person was given L-carnitine and experienced a complete resolution of MVP symptoms.

In one report, deficient levels of were found in five consecutive people with MVP. One of these people was given L-carnitine (1 gram three times per day for four months) and experienced a complete resolution of the symptoms associated with MVP.

1 Star
Raynaud’s Disease
Refer to label instructions
In one study, people with Raynaud’s disease who were given L-carnitine showed less blood-vessel spasm in their fingers in response to cold exposure.

In one study, 12 people with Raynaud’s disease were given (1 gram three times a day) for 20 days. After receiving L-carnitine, these people showed less blood-vessel spasm in their fingers in response to cold exposure.

Information about L-Carnitine

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