L-Carnitine Benefits, Side Effects & Dosage

L-Carnitine Benefits, Side Effects & Dosage

People use carnitine as an energy booster, antioxidant, and to encourage mood and cognition. Is the evidence to support these applications? Keep reading to discover more about the health effects and side effects of carnitine.

What is Carnitine?


Carnitine is an amino acid found in nearly every cell of the body. It is a generic name for a number of compounds such as L-carnitine, acetyl-L-carnitine, and propionyl-L-carnitine. The three are similar and a number of their gains stinks. However, they have some distinct mechanisms of actions and uses.

  • Acetyl-L-carnitine is generally used to improve brain functioning and cognition.
  • L-carnitine is used to increase vitality levels and physical performance.
  • Propionyl-L-carnitine is used to boost flow.

Scientists think that all forms of carnitine play a very important role in the creation of energy. Carnitine is believed to help burn body fat into energy. It might also get rid of toxic chemicals from the mitochondria to prevent their buildup. Carnitine is made by the liver and kidneys and stored in muscle, brain, and heart tissue — all of which utilize fatty acids as energy.

L-Carnitine: Benefits, Side Effects, Dosage, Interactions

You are going to receive carnitine from meat, poultry, fish, and milk. Individuals with genetic disorders, chronic ailments, and people on a vegetarian diet can frequently benefit from supplemental carnitine. The exact same goes for underweight and premature babies. Other conditions that cause carnitine deficiency include angina (chest pain) and intermittent claudication (cramping leg pain from obstructed arteries).

The FDA has approved the use of L-carnitine (by mouth or intravenously) treating L-carnitine deficiency due to specific genetic diseases, end-stage kidney disorder, and other disorders. It’s known under the brand name Carnitor.

However, other medical uses of carnitine supplements have not been accepted by the FDA. Supplements generally lack strong clinical study. Regulations set manufacturing criteria for them but do not ensure that they’re safe or effective. Speak with your physician before supplementing.



  • Effective for L-carnitine deficiency
  • Supports mitochondrial health and energy function
  • Allegedly supports liver and brain health
  • May enhance PCOS in women and semen quality and fertility in men


  • Many popular uses are not supported by evidence
  • Might contribute to heart disease by metabolizing TMAO
  • Can cause nausea or stomach upset
  • Long-term use may cause oxidative stress from the liver and bloodstream
  • Affects thyroid function

Health Benefits of Carnitine

Effective for:

L-Carnitine Deficiency (Genetic)

Oral and intravenous L-carnitine is effective for treating primary and secondary L-carnitine lack due to inborn errors of metabolism (genetic).

Probably Effective for:

L-Carnitine Deficiency in Bipolar Disorder

Dialysis reduces carnitine levels in people with end-stage kidney disease. The FDA has accepted intravenous (by IV) L-carnitine for preventing and treating L-carnitine lack in these patients.

Despite being FDA-approved for this indication, some studies have had mixed results. Evidence indicates that l-carnitine enhances nausea and inflammation in people with this condition. However, it does not appear to affect the patients’ wellbeing, muscle cramping, low blood pressure, breathing, or exercise performance.

Carnitine taken by mouth isn’t accepted for carnitine deficiency in kidney patients undergoing dialysis.

Possibly Successful for:

Chest Pain from Heart Disease (Angina)

Evidence indicates that carrying carnitine by mouth or intravenously can improve exercise tolerance in people with chronic stable angina. As an addition to traditional treatment, l-carnitine may also reduce the frequency of chest pain (angina) in people with angina (microvascular type) [8, 9].

Scientists believe carnitine and its derivatives can protect heart functioning by increasing glucose metabolism, increasing blood flow, correcting abnormal heart rhythms, and reducing oxidative stress. These mechanisms have to be confirmed in people.

Heart Failure

Accepting L-carnitine by mouth or intravenously (by IV) seems to improve symptoms and increase exercise capacity in people with heart failure. 1 study suggests that a combination of l-carnitine using ubiquinol, a form of CoQ10, may also improve symptoms of heart failure (the mixed product is called Carni Q-Gel, by Tishcon Corporation).

In a 3-year-long study on patients with heart failure, L-carnitine appeared to increase survival rates in comparison with the placebo.

Scientists are exploring the effects of a combination of taurine and L-carnitine on heart cells.

Heart Infection (Myocarditis)

Carnitine (D-L-carnitine) by mouth appears to decrease death rates from myocarditis associated with diphtheria, based on clinical trials.

Overactive Thyroid (Hyperthyroidism)

Some clinical evidence indicates that l-carnitine may improve symptoms of high thyroid hormones, such as rapid or pounding heartbeat, anxiety, and weakness.

In one randomized trial, 2 and 4 grams daily of L-carnitine reversed hyperthyroid symptoms. In a different research, L-carnitine relieved that a”thyroid storm”.

Some scientists think that l-carnitine may inhibit both triiodothyronine (T3) and thyroxine (T4) entrance into the cell nuclei. This is important because thyroid hormone action is mostly mediated by specific nuclear receptors.

Infertility in Men

Despite some mixed findings, many clinical studies suggest that L-carnitine increases sperm count and sperm motility in men with infertility.

Some researchers have indicated that the quantity of carnitine in semen is directly related to sperm count and mobility. Carnitine seems to provide greater energy for sperm cells and it may decrease cell death in the testes, based on the preliminary findings.

An analysis of 100 infertile men demonstrated that the intake of carnitine supplements increased sperm motility.

Infertile men with varicose veins in the scrotum (varicocele) required carnitine for 6 weeks (250 mg, 4x per day). Results showed increased sperm count, freedom, and concentration.

Scientists are also investigating the antioxidant effects of carnitine on sperm in cells and in animals.


Clomiphene is the typical remedy for infertility treatment in women with PCOS. However, some women don’t respond to this medicine independently. Clinical research indicates that adding L-carnitine from day 3 of the cycle until the afternoon of pregnancy testing to some clomiphene treatment cycles increases ovulation and pregnancy rates in comparison with placebo in these women.

Valproic Acid Side Effects

Valproic acid is an anticonvulsant drug that could decrease the body’s carnitine levels, possibly leading to high nitrate levels, and brain or liver damage. L-carnitine supplementation in these individuals may prevent or reduce high ammonia levels (hyperammonemia) and the severity of liver and brain damage, based on clinical trials.

Insufficient Evidence for:

The subsequent purported benefits are only supported by restricted, low-quality clinical studies.

There is inadequate evidence to support the use of carnitine for any of those below-listed uses.

Don’t forget to talk with a health care provider prior to taking carnitine supplements. Carnitine shouldn’t ever be utilized as a replacement for accepted medical therapies.

Weight Reduction

L-carnitine is frequently marketed as a weight reduction support and performance enhancer, but there’s inadequate evidence to back up these supposed benefits.

The evidence so far has been mixed and inconsistent. According to one analysis of clinical trials, L-carnitine can reduce weight by approximately 1.3 kg and decrease body mass indicator by about 0.5 kg/m2 compared to control both nonobese and obese adults.

1 trial suggests it might help reduce weight in obese people with diabetes when utilized as an add on to this anti-obesity medication orlistat.

In a different study of obese women diagnosed with polycystic ovary syndrome, carnitine supplements decreased their weight, body mass index, and waist and hip size (circumference).

However, L-carnitine does not seem to influence weight loss in overweight or obese individuals without diabetes or PCOS. The effects of carnitine on weight loss also appear to weaken with time. Larger trials on more diverse populations are required.

Body Piercing and Performance Enhancement

According to an unproven hypothesis, younger folks have a sufficient quantity of carnitine in the human body, unlike elderly people. In accord with this, carnitine was researched for enhancing body composition and muscle mass in elderly individuals. The results have been mixed.

The existing research suggests that L-carnitine might be beneficial in weak patients over 75 decades old but that it probably isn’t advantageous in healthy older women.

Others claim that carnitine may improve exercise endurance in all ages by raising muscle carnitine levels, but data are lacking to support this claim.

Some evidence suggests that maximal exercise in trained athletes is linked with lower L-carnitine blood levels.

Initial studies have indicated that dietary carnitine stimulates the breakdown of fats into energy, lowers the amount of lactic acid produced through exercise, and speeds up recovery from exercise stress. Further studies failed to demonstrate any advantage of L-carnitine on athletic performance or endurance in men athletes or wholesome guys.

Although it’s unsure what caused these contradictory effects, all these clinical trials suffered from defects such as small sample sizes and short period. Larger, more, higher-quality trials are needed to ascertain the consequences of L-carnitine on athletic performance.

Fatigue From Disease and Aging

Infection is common in cancer patients following treatments from chemotherapy, radiation therapy, and bad nutrition. Some scientists think that low carnitine levels can contribute to fatigue.

Nevertheless, there isn’t enough evidence to rate the effectiveness of L-carnitine on exhaustion from aging and disease.

In a study of elderly subjects, acetyl-L-carnitine therapy decreased physical and mental fatigue, reduced muscle pain, and enhanced cognitive functioning.

In 1 study, 250 mg of carnitine 3 times a day enhanced fatigue and quality of life in terminal cancer patients.

One group of scientists has been investigating the effects of acetyl-l-carnitine and lipoic acid on metabolic function in old rats. This combination has not yet been researched in people [39].

In Dialysis Patients

Patients with kidney disease undergoing dialysis frequently have anemia with deformed red blood cells. The deformity prevents the blood cells from carrying enough oxygen into the body’s tissues, causing muscle fatigue and tiredness.

A study after dialysis patients discovered that carnitine supplements reduced red blood cell deformity and enhanced general red blood cell count in 3 months.

Another research on dialysis patients discovered that carnitine injections helped sustain elevated levels of oxygen use (improved endurance), such as through exercise and additionally reduced overall tiredness.


Evidence is lacking to ascertain the effects of carnitine in your mood.

Initial studies suggested that acetyl-L-carnitine has some antidepressant possible in older patients using age-associated depression.

A study found that supplementing the diets of fibromyalgia patients using acetyl-L-carnitine enhanced depressive symptoms and reduced muscle pain.

More human studies are required.

Scientists are also investigating the consequences of acetyl-L-carnitine on mice with depression [44].


It’s uncertain how L-carnitine affects cognition since clinical trials are limited.

Some scientists proposed that carnitine levels slowly decline as Alzheimer’s progresses, suggesting that patients with Alzheimer’s may potentially gain from acetyl-L-carnitine therapy.

In a small study, acetyl-L-carnitine enhanced memory in elderly individuals and in Alzheimer patients. The authors suggested it could slow the development of the disease, but appropriate trials would need to determine its mechanism and effectiveness.

Theoretically, consuming carnitine helps the body create acetylcholine. According to a hypothesis, this neurotransmitter declines as memory loss advances.

Thus, carnitine might hypothetically increase energy production in brain cells which are starting to”slow down” and activate memory reduction. However, this is but a scientific hypothesis that hasn’t been confirmed in clinical trials.

Insulin Resistance

Insulin resistance has been linked with obesity and increased amounts of fat in lean tissues.

Some researchers suggest that carnitine can improve insulin sensitivity by changing fat oxidation in lean muscles and tissue. However, data are lacking to back up their theory.

In a study of obese women with polycystic ovary syndrome, carnitine supplements reduced sugar and insulin blood levels and decreased insulin resistance.

Far more research is needed.

Sleep Disorders

One hypothesis claims that sleep-disordered breathing is associated with heart damage and shifted heart carnitine metabolism. Although carnitine levels are low in heart tissue in those with chronic heart failure, carnitine blood levels may be increased because of”leakage” from damaged heart cells and modified carnitine metabolism.

Thus, some scientists think that carnitine supplementation might help patients suffering from obstructive sleep apnea, a condition where breathing repeatedly stops and starts during sleep. Carnitine helped improve airways for breathing and improved overall sleep quality in patients in one small study.

In a study of older subjects, the byL-carnitine treatment improved sleep quality.

However, a study of fibromyalgia patients found no improvement in sleep disturbances from L-carnitine.

Further clinical trials are needed to rate the efficacy of L-carnitine for sleep disorders.

Alertness at Narcolepsy
Acylcarnitine levels are abnormally low in narcolepsy patients. L-carnitine supplements can improve daytime alertness in these patients. L-carnitine treatment improved acylcarnitine and decreased blood lipids. Large-scale trials are required.


HIV patients may develop complications like fat, muscle, and nerve degeneration. Carnitine supplements are being researched as a potential add-on strategy. In HIV positive individuals L-carnitine and acetyl-L-carnitine, as an add-on to conventional therapy, increased CD4 counts, reduced heart tissue damage, and reduced the number of triglycerides (fat) in the blood [52].

According to a scientific hypothesis, L-carnitine may block the enzyme acidic sphingomyelinase, which prevents sphingomyelin breakdown in cells.

However, the first study on patients using HIV-associated fat tissue degeneration didn’t detect any evidence for using L-carnitine to reverse the effects of fat tissue degeneration. This research found that L-carnitine lowered cholesterol amounts from the bloodstream, but not the amounts of triglycerides.

Large-scale trials are required before we can draw any sound conclusions.

Lacking Evidence (Animal and Mobile Studies)

No clinical evidence supports the use of carnitine for any of the conditions listed in this section.

Below is a list of the existing animal and cell-based research, which should guide further investigational efforts. However, the research listed below shouldn’t be interpreted as supportive of any health advantage.

Kidney Function

In a rat model of chronic kidney disease, the management of carnitine improved kidney function. Carnitine reduced the levels of creatinine and BUN in the blood, decreased kidney tissue damage and abnormal kidney enhancement.

Bone Health

At a mouse model of osteoporosis, L-carnitine and isovaleryl-L-carnitine stimulated bone formation, improving bone regeneration, bone density, bone size, and bone structure.

Another study found that dietary L-carnitine may enhance bone mineral content and bone mineral density in a female mouse model of postmenopausal bone loss. Results suggested slowed bone loss and enhanced bone structure.

Some scientists discovered that carnitine might encourage bone mineralization, in part by inhibiting thyroid hormone action.

The effects of carnitine on bone health in humans are still unknown.


In mouse studies of drug-induced seizure, pre-treating the mice using L-carnitine suppressed seizures dose-dependently.

A rat model of hyperthyroidism induced by L-thyroxine shots suggested that L-carnitine may have dose-dependent protective effects against liver damage.

L-carnitine suppresses the onset of neuromuscular degeneration and increases the lifespan of mice with familial amyotrophic lateral sclerosis (ALS).

It’s unknown how carnitine affects seizures, liver health, and ALS in people.

L-Carnitine Side Effects & Precautions

Side Effects

In general, the adverse effects of oral or intravenous L-carnitine are rare and mild. It’s been reported to induce vomiting, diarrhea, a fishy body odor, abdominal cramps, and nausea. More severe and rarer side effects are seizures and muscle weakness in people prone to heart disease [38].

Pregnant women should avoid L-carnitine; insufficient data are available.

Preclinical Safety Data

These side effects have never been confirmed in people.

Some research indicates that carnitine is metabolized into TMAO, which affects cholesterol metabolism and might promote plaque build-up in the blood vessels. Theoretically, this contributes to the degeneration of artery walls, restricted blood circulation, and blood clots. Yet, no human studies indicate that L-carnitine worsens cardiovascular wellness.

Carnitine appears to block both triiodothyronine (T3) and thyroxine (T4) entrance to the cell. Long-term use of L-carnitine hastened the creation of reactive oxygen species from the liver and bloodstream in mice.

L-carnitine may disturb kidney function by changing ion transporters in mice.

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