Written by Slawomir Gromadzki, MPH


L-carnitine is an amino acid the body uses to turn fat into energy. Our body makes it in the liver and kidneys storing it in the heart, brain, skeletal muscles, and sperm. L-carnitine transports fatty acids into mitochondria, the powerhouses of cells.


Although normally our body can manufacture L-carnitine yet supplementation is often recommended as it may improve the ability of our cells to burn more fat cells and produce more energy.

In addition, in infancy, and in situations of high energy needs, such as excessive physical activity, stress, pregnancy and breast-feeding, the need for L-carnitine often exceed production by the body. Therefore, L-carnitine is considered a conditionally essential nutrient.

Some individuals may not have enough L-carnitine also due to kidney or liver problems (L-carnitine is manufactured in these two organs), angina or intermittent claudication. Also some medications can lead to deficiency of this amino acid.


It is also important to be aware of the fact that L-carnitine, which is needed to release energy from fat, is made in the liver and kidneys from the amino acids methionine and lysine.

Also vitamin C, B3, B6, and iron are required in this process. It means that deficiency of these nutrients will lead to insufficient production of L-carnitine I the body while their supplementation should increase L-carnitine synthesis.


Acetyl-L-Carnitine is also a powerful super antioxidant which is very effective in fighting with dangerous free radicals preventing them from damaging cell’s DNA, mitochondria or lining of arterial walls. In this way Acetyl-L-Carnitine, like many other antioxidants, slows down ageing process and reduces risk of various associated with damaging effects of free radicals health problems including cancer, heart attack, stroke, fatigue or conditions caused by weak immune system.


Acetyl-L-Carnitine has been shown in clinical studies to benefit cognitive ability, memory and mood as it helps supply the brain with more energy by improving efficiency of mitochondria, brain cell power stations. Acetyl-L-Carnitine also promotes biosynthesis of acetylcholine, a key neurotransmitter for brain and nerve function.


Supplementation with L-carnitine for two months resulted in significant 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 up to 4 grams per day.


A study of 60 participants with mild depression has shown that treatment with 3 g of Carnitine daily for two months significantly reduced symptoms as compared to placebo. Similar results were seen in another study as well.


L-carnitine is very beneficial in weight control as it transports fatty acids into the mitochondria to facilitate a fat-burning process called beta oxidation. Studies prove that to use the fatty acids as energy, your body needs l-carnitine.


L-carnitine is exceptionally highly concentrated in the heart, the organ to which fat oxidation and proper metabolism is most crucial for energy. For this reason normal heart function greatly depends on adequate concentrations of this amino acid. In one study patients with high blood pressure and heart problems received 4 grams of L-carnitine per day, and after 11 months, irregular heartbeat decreased significantly compared to non-supplemented patients.

L-carnitine also exerts positive effect on blood lipids by lowering cholesterol LDL, total cholesterol and triglycerides (another bad fat which contributes to heart attacks and strokes) while raising good HDL-cholesterol.


L-carnitine is highly concentrated in the epididymis (a tube that connects testicle to vas deferens in the male reproductive system) and plays a key role in sperm metabolism and maturation. Some studies support the idea that at total daily amounts of at least 3 g per day of either L-carnitine or Acetyl L-carnitine can significantly improve both total sperm count and sperm concentration among men diagnosed with infertility.

One study found evidence that Acetyl-L-Carnitine may be beneficial in Peyronie’s disease, a condition which affects penis.


L-carnitine levels are often depleted in various neuromuscular disorders such as Down Syndrome. There is also some evidence that Acetyl-L-carnitine can improve visual memory and attention in people with Down Syndrome.


Patients with high blood glucose levels or hypoglycaemia (low blood sugar) have been reported to have insufficient blood L-carnitine concentrations, and supplementing with it has shown improvements in blood sugar regulation, in peripheral vascular function, and nerve damage prevention. For this reason both L-carnitina and Acethyl L-carnitine can be recommended together with Alpha lipoic acid and sublingual Methylcobalamin (highly bioavailable form of vitamin B12) to prevent and even reverse neurological problems such as peripheral neuropathy, usually caused by chronic high blood sugar levels and statins.


Taking 2g of L-carnitine two times a day for 4 weeks has been shown to improve energy production and athletic performance in endurance athletes. Studies also demonstrated that L-carnitine supplementation has improved cardiovascular function and significantly reduced the time heart needs to return to the resting rate after exercise.

Research also shows that those who supplement with L-carnitine while engaging in an exercise regimen are less likely to experience muscle soreness as it has been shown to reduce lactic acid production. L-carnitine helps athletes run faster for longer before they start to feel like they are running in porridge.


L-carnitine can increase the activity of phagocytic cells such as macrophages as well as lymphocytes including killer cells. In addition, being a powerful antioxidant it strengthens immune system cells by preventing free radical from damaging mitochondria, their power stations.


A six months study comparing L-carnitine to placebo in 50 female participants with hyperthyroidism demonstrated that daily dose of 2 to 4 grams of L-carnitine was effective in preventing and reducing the nine hyperthyroid related symptoms. In addition, it also had a beneficial effect on bone mineral density.


L-carnitine has a protective effect against liver damage. Studies have found that valproate and other similar anti-convulsant drugs significantly reduce the body’s carnitine levels, resulting in liver damage. L-carnitine supplementation in such individuals may prevent or reduce the severity of liver damage. In brain issues (encephalopathy) caused by liver problems (cirrhosis), carnitine was able to lower ammonia and improve brain function. One of the most important benefits of L-carnitine with regards to PCOS is that it is best deposited into muscles when blood insulin levels are high (which is almost all the time for most PCOS women).


A study with PCOS women taking 2000mg per day of L-carnitine found that compared to placebo group, they managed to reduce body weight in 12 weeks. It has been found that women with PCOS are often deficient in L-carnitine, even if they consume animal foods on a regular basis. L-carnitine helps in PCOS because one of the key causes of this problem is insulin resistance and L-carnitine, like Alpha lipoic acid, improves insulin sensitivity thus helping to lower blood glucose.


Scientists have discovered that teamwork between Alpha lipoic acid and Acetyl L-carnitine can increase energy in muscle cells allowing to lead a more active lifestyle. According to a study conducted at the University of California, Berkeley, Research Institute Alpha lipoic acid together with
Acetyl L-carnitine were able to impose a huge energising and rejuvenating effect on ageing rats, and might do the same for ageing humans. A team of scientists led by Bruce N. Ames, professor of molecular and cell biology at UC Berkeley, supplemented old rats with ALA and Acetyl-L-carnitine. As a result, not only the memory of the rats was significantly improved, but they also had much more energy. According to Professor Ames, “With the two supplements together, these old rats got up and did the Macarena. The brain looked better, they were full of energy – everything we looked at looks more like a young animal!

Also another scientist associated with the same study, Professor Tory M. Hagen, suggested that they actually observed “a reversal in loss of memory” and “a dual-track improvement which was significant and unique that is really starting to explode and move out of the realm of basic research into people. We significantly reversed the decline in overall activity typical of aged rats to what you see in a middle-aged to young adult rat. This is equivalent to making an 80-year-old individual act as middle-aged person!
Both chemicals are normally used in mitochondria, which is regarded as the “weak link in ageing”, because deterioration of mitochondria, triggered mainly by free radicals, is an important cause of ageing, fatigue and impaired cognitive functions of the brain. The study, however, demonstrated that the two chemicals are able tofix the energy-producing mitochondria and greatly improve its function thus increasing the efficiency of mitochondria in empowering all cells, including brain cells. Ageing is caused by oxidizing certain proteins in mitochondria causing them to lose their activity. Supplementation with ALA and Acetyl L-carnitine, however, can reduce or even reverse the process to certain extent, because Acetyl L-carnitine at higher concentrations can even enable them to work again, while ALA does not allow radicals to damage them. It means each antioxidant solves a different problem and therefore when they are used together they produce better results than either one alone.
In another experiment the same group of scientists fed old rats a similar diet with the two supplements and looked at memory function. They found that supplementation improved both spatial and temporal memory, and reduced the amount of oxidative damage to RNA in the brain’s hippocampus, an area important in memory. In electron microscope pictures of cells from the hippocampus and mitochondria showed less structural decay in old rats that had received the two supplements.


L-Carnitine is most commonly used for its potent fat burning effects. Unlike Acetyl L-Carnitine it is characterised with rather poor ability to cross the blood-brain barrier and therefore is much less beneficial for maintaining and improving brain health.

Acetyl L-Carnitine on the other hand is associated with the improvement of cognitive functions of the brain, preventing and treating dementia such as Alzheimer’s, anti-ageing benefits, antioxidant effects, and improving memory.

Studies have shown that supplementing with L-Carnitine greatly increases body’s ability to oxidise (burn) fat-cells in order to produce energy. Without enough L-Carnitine in the system the body is unable to effectively transport fat cells into the mitochondria, which can therefore lead to the accumulation of fat. Acetyl L-Carnitine seems to be less effective in producing this benefit. L-Carnitine has also been shown to be more effective in increasing body’s sensitivity to insulin.

L-Carnitine has also been shown to reduce the amount of muscle oxidation during intense exercise, which means it increases the ability to train harder and longer.

Carnitine is actually available and used in three forms: L-Carnitine (for heart, fat-burning, athletic performance and other conditions), Acetyl-L-Carnitine (for Alzheimer’s disease, brain health and neurological problems), and Propionyl-L-Carnitine (for heart conditions). The dosage is the same for all three forms.


Acetyl L-carnitine may help improve mental abilities in people who are alcoholic.


1 to 4g per day in divided doses.

For weight loss: 1 – 3 grams of L-carnitine.

If for better results you decide to take L-carnitine or Acetyl L-carnitine together with Coenzyme Q10 and Alpha lipoic acid, take them all two times a day in the beginning of meals which should include some oil such as coconut oil, flax oil, or olive oil as it will greatly improve absorption.

Athletes usually take it in separate dosages, one of L-carnitine before a workout and one in the evening.


Elevated blood triglycerides and cholesterol,

Muscle weakness,

Weight control,

Cardiovascular conditions (angina, intermittent claudication, arrhythmias, congestive heart failure, recovery from a heart attack, etc.)

Fatty liver congestion (due to alcoholism),

Kidney support,

Alzheimer’s disease,

Parkinson’s disease

Downs Syndrome,

Male infertility,

Sports performance,

Vegans and vegetarians are encouraged to take supplements as plant foods are lower in carnitine than animal products.




Safety for use during pregnancy has not been established.


The following medications may increase the need for l-carnitine: Chemotherapy, Anticonvulsants, AZT, Doxorubicin, Valproic Acid, Gabapentin, Phenobarbital.


L-Carnitine is extremely safe, with no significant side effects ever being reported in any of the human clinical studies. Studies have shown that taking up to 3-4 grams per day l-carnitine is safe, showing no side effects.


L-Carnitine works best when combined with CoQ10. Carnitine and coenzyme Q10 work synergistically through supporting fat metabolism and increasing ATP production.

Another antioxidant which proved to give excellent results together with Acetyl-L-Carnitine is Alpha lipoic acid.


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