novembris 10, 2025 Merike Pulk

L-Carnitine - a Supporter of Effective Fat Burning and Energy Levels

L-Carnitine is probably best known for its properties among active athletes. Namely, L-Carnitine helps burn fat and produce energy. Let's talk more about how it works in the body.

What is L-Carnitine and How does it Work in Our Body?

Chemically, Carnitine exists in two forms – L-Carnitine and D-Carnitine. However, only L-Carnitine is the biologically active form that the body produces and uses and that participates in metabolic processes. Body synthesizes L-Carnitine from the amino acids lysine and methionine and it plays an important role in energy production in the body by helping to transport fatty acids into the mitochondria of cells, where they are converted into energy. L-Carnitine synthesis occurs mainly in the liver and kidneys, but it is also transported to other tissues, especially the muscles and heart, where it is needed most – as much as 95% of our L-Carnitine reserves are located in the muscles. Our body can synthesize L-Carnitine itself, but only in limited quantities. Carnitine is also found in smaller quantities in animal products such as meat and dairy products. Although the body can synthesize L-Carnitine itself, supplementing it may be beneficial in the following cases:

Inherited or acquired deficiency – e.g. in kidney or liver diseases
The diet is entirely plant-based or vegan – plant-based foods contain very little Carnitine
The energy requirement is higher than usual – e.g. in people who do intense sports

The Role in Burning Fat and Maintaining Energy Levels

One of the main reasons for L-Carnitine’s popularity among athletes and health-conscious individuals is its ability to support the use of fat as an energy source.

L-Carnitine is not a conventional “fat burner,” which speeds up metabolism, but rather helps the body use the fat it already has more efficiently. L-Carnitine supports energy production by transporting fatty acids into the mitochondria of cells. Mitochondria act as the engines in cells, burning these fats for usable energy. This helps increase endurance both in the gym and in everyday life.

The Scientific Effects of L-Carnitine

The effects of L-Carnitine have been scientifically studied. The most evidence found is its positive effects on exercise performance and fat loss. But how can you make it work for you?

Improved Exercise Performance and Recovery

L-Carnitine helps the body use fat as an energy source, preserve muscle energy stores, and reduce lactic acid buildup. Studies have shown that it can support endurance and reduce fatigue during exercise, improve oxygen consumption, and speed up recovery from exercise.

A 2018 review of 11 clinical trials with 251 well-trained athletes found that regular use of L-Carnitine (1–4 g per day for up to 6 months) improved energy expenditure and physical performance in some athletes.

Although the results are somewhat mixed, several studies suggest that L-Carnitine may help improve exercise performance and recovery, especially in endurance events.

Those interested can read the study HERE .

Iconfit L-Carnitine with CLA and green tea extract 90 capsules

Discover ICONFIT L-Carnitine here

Effects on Fat Mass Reduction

L-Carnitine is also used to support weight loss due to its ability to participate in fat metabolism.

A review of 37 studies published in 2020 concluded that L-Carnitine supplementation has a modest effect on weight, BMI (body mass index), and fat mass, especially in overweight/obese adults. A non-linear dose-response relationship was observed between L-Carnitine supplementation and weight loss, suggesting that 2000 mg of L-Carnitine daily provides the maximum effect in adults.

Another review of 10 studies published in Frontiers in Nutrition in 2021 concluded that L-Carnitine has a potential but modest effect on weight loss in patients with type 2 diabetes. Regular intake of 2 g per day for at least two weeks can produce a small but significant decrease in BMI (~1.5%). Other forms of Carnitine did not show a similar effect. However, larger and longer-term studies are needed to confirm the results.

Although L-Carnitine may help with weight loss in some people, it works best when combined with exercise and a balanced diet.

Supporting Heart and Brain Function

L-Carnitine helps the body produce energy, but not only. While research is still ongoing, several findings suggest that L-Carnitine may have a potential role in supporting heart and brain health, especially as we age.

Different Forms of L-Carnitine and How to Choose the Right One

L-Carnitine also comes in several different forms, each with slightly different properties and therefore supporting different goals. Let’s take a closer look at them:

L-Carnitine tartrate – the most popular form in sports supplements, is quickly absorbed and is well suited for consumption before a workout.
Acetyl-L-Carnitine – has a greater effect on brain function and mental energy.
Propionyl-L-Carnitine and other forms – less common, with more specific goals, such as supporting blood circulation.

How, When and How Much L-Carnitine Should You Take

In healthy adults, the body produces enough L-Carnitine on its own and it is usually not necessary to take it as a supplement. L-Carnitine is found naturally in animal foods, especially red meat, fish and poultry.

However, if you are an active athlete and want to support your body during training and recovery or contribute to weight loss, it is worth considering taking L-Carnitine as a supplement.

Studies on the potential benefits of L-Carnitine have used a wide range of doses. Doses vary between studies and may differ depending on the form of Carnitine used:

Acetyl-L-Carnitine – 500 to 3000 mg per day
L-Carnitine L-tartrate – 1000 to 4500 mg per day
Propionyl-L-Carnitine – approx. 2000 mg per day.

When and In What Form Should You Take L-Carnitine?

There is no single best time to take L-Carnitine, as it depends primarily on your goals:

More energy and better training performance – take 30–60 minutes before exercise.
Recovery and reducing muscle damage – take after exercise.
Weight loss – take before physical activity.

A systematic review of 11 studies published in MDPI in 2021 concluded that L-Carnitine may help improve high-intensity exercise performance, reduce muscle fatigue and support recovery, especially when taken at 3–4 g about an hour before exercise or as a long-term supplement (2–2.72 g per day for 9–24 weeks) with carbohydrates. For moderate exercise, the effect is more limited.

But in what form should you take L-Carnitine? L-Carnitine is available in both capsule and liquid forms. Both have the same effect, so the choice depends on your preferences. Let's take a closer look at what speaks in favor of one option and what speaks in favor of the other.

Iconfit_L-carnitine capsules versus liquid

Meet ICONFIT L-Carnitine products here

L-Carnitine should be taken with a meal rich in carbohydrates or protein, which helps it to be better absorbed, as insulin supports the transport of L-Carnitine into muscle cells. Consistency is more important than exact timing – the effect of L-Carnitine will manifest itself within a few weeks, not immediately after the first dose. In summary, regular use in combination with a balanced diet will provide the most stable results.

Combining L-Carnitine with Other Supplements

L-Carnitine can be successfully combined with other natural supplements that support energy metabolism and fat burning. For example, with caffeine and green tea extract. Green tea extract contains natural antioxidants and the compound EGCG, which helps to make fat metabolism even more efficient.

These combinations are also common in high-quality supplements, such as ICONFIT L-Carnitine + CLA & Green Tea, where the ingredients complement each other's effects and support both energy levels and fat burning in a natural way. Check out the product HERE .

However, it is important to remember that although combinations can enhance the effect, they do not replace a healthy diet or regular exercise – they simply help the body work at its best.

L-Carnitine Safety and Drug Interactions

Before starting a supplement, it is always a good idea to research the safe upper intake levels and whether there may be interactions with medications you are taking. The European Food Safety Authority (EFSA) has not set a safe upper intake level for L-Carnitine.

However, L-Carnitine is considered safe when taken in doses of 1–3 grams per day. It is recommended to consult a doctor before taking it, especially if you have health problems or are taking certain medications, such as antibiotics and anticonvulsants. L-Carnitine may interact with certain medications.

For most people, taking 2 grams or less per day is relatively safe and does not cause serious side effects. Some people may experience mild side effects such as heartburn and indigestion.

It is worth noting that L-Carnitine in supplements can increase blood levels of trimethylamine-N-oxide (TMAO) over time, high levels of which are associated with a risk of atherosclerosis (clogging of the arteries).

Additionally, L-Carnitine should not be taken by children, pregnant women, or breastfeeding women, as safety in these target groups has not been adequately studied.

L-Carnitine is not a miracle cure, but it does help to efficiently use the body's own fat stores for energy. If you want better endurance during exercise and recovery, taking L-Carnitine as a supplement is a great help. However, if it were enough to just swallow a tablet, it would be too easy, and therefore the best results will still come in combination with a healthy diet and regular exercise.

Links to Sources:

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