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The story of L-Carnitine began in 1905 when Russian scientists Gulevich and Krimberg isolated it from meat extracts, naming it after the Latin word carnis, meaning "meat." For decades, carnitine was simply a chemical compound without clear application.
In the 1950s, scientists uncovered L-Carnitine’s vital role in energy metabolism—it helps transport fatty acids into the mitochondria, where fats are transformed into energy. This discovery opened the door to medical applications, especially in metabolic and cardiovascular support.
Soon, this supplement gained popularity among athletes for its ability to enhance endurance and support recovery. Since the 1980s, L-Carnitine has been a staple in strength and endurance sports, and today, it's also valued for its benefits to heart health, brain function, and reproductive wellness.
WHAT IS L-CARNITINE AND HOW IS IT BENEFICIAL FOR ATHLETES
L-Carnitine is a natural amino acid derivative that our bodies produce to help convert fat into energy. Thanks to this function, L-Carnitine supplements help improve three important metrics for athletes:
- Fat burning. Research and user experiences demonstrate L-Carnitine's effectiveness in fat burning, especially when you combine it with intense workouts doi.org/10.1016/j.clnesp.2020.03.008).
- Energy boost. The more actively the body burns fat and utilizes fuel reserves, the more strength and energy a person gains.
- Recovery after workouts. By delivering fatty acids to the mitochondria in muscle cells, L-Carnitine reduces inflammation and helps the body recover more quickly from micro-injuries and muscle damage (doi.org/10.3390/nu10030349).
Since L-Carnitine supplements do not have serious side effects like most other medications, it is an excellent choice to get noticeable effects and support for the body at the slightest risk.
WHAT OTHER EFFECTS CAN YOU GET FROM L-CARNITINE
At the core of all L-Carnitine's effects is its ability to enhance and accelerate fat metabolism, which ultimately benefits the function of various organs. Below, we list the effects that are most studied and recognized within the scientific community:
- Cardiovascular endurance and protection: L-Carnitine enhances heart function by improving fat metabolism within cardiac muscle, which provides a steady source of energy for the heart during prolonged activity. This not only supports overall endurance but also helps protect the heart from exercise-induced stress, which is important for long-duration or high-intensity athletes (doi.org/10.2169/internalmedicine.1055-18).
- Neuroprotective effects: L-Carnitine reduces oxidative damage in neurons, which can protect against neurodegenerative conditions and mental fatigue. This makes it a valuable supplement for both younger athletes looking to optimize mental sharpness and older people seeking to preserve cognitive function (doi.org/10.1021/acs.chemrestox.0c00479).
- Metabolic health and insulin sensitivity: L-Carnitine has been shown to improve metabolic function in overweight individuals and those with insulin resistance. By promoting the oxidation of fats, it helps reduce fat buildup in the liver and muscle tissues, which can enhance insulin sensitivity and overall metabolic health. This supplement can be really supportive for individuals looking to manage type 2 diabetes or prevent metabolic syndrome (doi.org/10.17179/excli2019-1447).
- Male fertility support: L-Carnitine sometimes can be used in fertility treatments for men due to its ability to improve sperm motility and quality. Overall, evidence supports that L-Carnitine positively impacts male fertility, even at a relatively low dose of 2 g/day. This supplementation enhances sperm parameters, regulates hormone levels, reduces reactive oxygen species (ROS) levels, and subsequently improves fertility rates (doi.org/10.3390/jcm12185796).
- Fatigue-related disorders and chronic conditions: L-Carnitine is often prescribed to individuals suffering from chronic fatigue syndrome (CFS) or fibromyalgia. By improving mitochondrial efficiency and reducing oxidative stress, L-Carnitine helps alleviate symptoms of fatigue, muscle pain, and cognitive fog (doi.org/10.1016/j.amsu.2021.103145, doi.org/10.3389/fendo.2024.1358404).
INJECTIONS VS ORAL FORM
When comparing L-Carnitine injections to oral form, there are some clear advantages in terms of how much your body actually absorbs and uses:
- Bioavailability differences: L-Carnitine taken orally has a bioavailability of about 15-20%, meaning only about 15-20% of the dose actually reaches your bloodstream and muscles after digestion. In contrast, injections offer nearly 100% bioavailability, as the entire dose goes directly into the bloodstream (doi.org/10.1093/ckj/sfu082).
- Tablet vs. injection dosage: to get the same effect as a 500 mg injection of L-Carnitine, you would need to take roughly 2,500-3,000 mg of L-Carnitine in tablet form - that’s about 5-6 standard 500 mg tablets.
- Consistent levels for performance: with injections, L-Carnitine levels remain steady and consistent in the bloodstream, which boosts recovery and provide a more reliable source of energy. Tablets, with their lower bioavailability, may cause fluctuations in L-Carnitine levels, making the effect less predictable.
HOW MUCH TO TAKE AND HOW OFTEN
Dosage and timing
Typically users choose a daily dose of injectable L-Carnitine around 400-800mg, often taking it before training or morning cardio on an empty stomach, or combining it with carbohydrates to stimulate insulin. Each approach has distinct goals:
- Before training on an empty stomach: this is commonly done to maximize fat utilization as energy during workouts, particularly effective in fasted states. It supports fat-burning and energy output, making it ideal for those who want to lose fat or improve endurance without relying heavily on stored glycogen.
- Combining with carbohydrates to stimulate insulin: this method targets muscle gain and performance by leveraging insulin's ability to transport L-Carnitine into muscle cells. Insulin assists in efficient nutrient uptake, allowing muscles to use L-Carnitine and other nutrients more effectively. This approach can be used by those who want to grow muscle, increase strength, or improve recovery after workouts (doi.org/10.70252/JGGV7814).
Injections are mostly administered intramuscularly (usually in the glutes), although some prefer subcutaneous injections despite occasional tissue thickening, which typically subsides over time.
Injection frequency
Injection timing and frequency vary: some use L-Carnitine daily, while others administer it up to three times per week, occasionally combining it with B12 vitamins or glutathione in a single syringe for convenience.
Next we will look at the most popular protocols and combinations with injectable L-Carnitine that people use to achieve more pronounced results.
L-CARNITINE LOADING PROTOCOL
The L-Carnitine loading phase spans two weeks, with the dosage tailored to body weight. Generally, users take 200 mg for every 25 kg. For instance, someone at 100 kg would take 800 mg daily.
During this phase, having insulin in the bloodstream is essential, as it helps transport L-Carnitine from the blood into cells, where it supports energy production in the mitochondria. This insulin can come from either a natural spike through carbs or an external source.
The timing of L-Carnitine injections can be done as a single dose pre-workout or split between pre- and post-workout. Many users find splitting the dose (e.g., 400 mg pre-workout with 2-4 IUs of fast-acting insulin) effective, combining it with intra-workout carbs to avoid low blood sugar.
Alternatively, if skipping an insulin shot, increasing carbs in the intra-workout shake can help create an insulin response, though insulin is generally more reliable for L-Carnitine transport.
After two weeks, you can enter a maintenance phase, cutting the dose by half since cells are now saturated and less insulin-dependent for L-Carnitine transport. However, keeping carbs around workouts remains beneficial for most users.
One of the common challenges is that many L-Carnitine solutions are low-concentration (e.g., 200 mg/ml), which requires higher injection volumes, making the process uncomfortable. Opting for higher-concentration solutions (like 500 mg/ml) offers a more practical and cost-effective option, making it easier to manage both loading and maintenance doses with fewer injections.
GROWTH HORMONE (GH) AND L-CARNITINE COMBINATION
It has also been noted that L-carnitine can increase the density of androgen receptors, which allows for better absorption of anabolic drugs such as growth hormone (GH) (doi.org/10.1249/01.mss.0000227314.85728.35).
Growth hormone, a potent lipolytic agent, boosts fat breakdown and increases the release of free fatty acids into the bloodstream for energy. L-Carnitine facilitates the transport of these fatty acids into the cells' mitochondria for oxidation, making it an ideal complement to GH, promoting sustained energy and endurance.
- Morning GH and L-Carnitine for cardio. Many athletes inject GH in the morning to initiate lipolysis before fasted cardio. GH combination with L-Carnitine accelerates fat breakdown, making it especially useful during cutting phases to preserve muscle mass.
- GH and L-Carnitine pre-workout. Administering L-Carnitine and GH before strength training enhances anabolic and energetic effects, enabling higher training intensity. L-Carnitine’s role in fat utilization provides valuable energy for endurance-focused workouts.
- Dosing GH and L-Carnitine throughout the day. You may split GH doses in the morning and before sleep to maintain stable levels, with L-Carnitine taken in the morning and pre-training. This schedule allows GH’s anabolic effects to support nighttime recovery, while L-Carnitine accelerates metabolism and sustains activity during the day.
For optimal absorption of L-Carnitine and GH, a small dose of fast-acting insulin (8-10 units) with carbohydrates (60-90g) is recommended pre-training.
ARE THERE ANY DOWNSIDES TO L-CARNITINE
L-Carnitine is generally safe for most people, but like any supplement, it can have a few potential side effects. Here’s what you might want to know:
- Fishy odor: one of the most common things people report with L-Carnitine is a slight fishy smell in their sweat or breath. This happens because, during digestion, L-Carnitine can produce trimethylamine, which has a fishy scent. However, it’s pretty rare and usually only occurs with high doses. Drinking more water and sticking to the recommended amount can help prevent it. Additionally, taking a garlic supplement (like allicin) or adding chlorophyll to your routine can help neutralize the odor by reducing trimethylamine production.
- Mild digestive issues: some people may feel mild stomach discomfort, like nausea, diarrhea, or cramps, especially when they’re just starting out or if they take a higher dose all at once. To prevent this, you can start with a lower dose and see how your body responds before gradually increasing it if needed.
- Possible side effects with high doses: at higher doses, L-Carnitine could cause more noticeable side effects - increased heart rate or blood pressure, but this is uncommon. Sticking to the recommended dose generally keeps these issues at bay.
In general, L-Carnitine is very safe when taken as directed, and side effects are typically mild or rare. But if you do notice any unusual symptoms, lowering the dose or switching to injections might help lessen these effects.
PLEASE NOTE THAT L-CARNITINE IS INTENDED FOR INTRAMUSCULAR INJECTIONS ONLY!
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