If you’re looking to get into bodybuilding, you may have heard of L-carnitine and its reported benefits. But what is it really, what are those benefits, and how much evidence is there to back up the claims?
This complete guide to L-Carnitine for bodybuilding breaks down the basics of this compound and explores the evidence behind it so that you can make an educated decision about whether or not it’s right for you.
What is L-Carnitine?
L-Carnitine is a naturally occurring amino acid byproduct that is commonly taken as a dietary supplement.
It plays a significant role in processing fatty acids, helping to transport them into the cells to be used as energy. It is commonly used to improve exercise performance, increase weight loss, and reduce muscle damage. It can also be used to treat certain conditions such as heart disease and diabetes.
However, more research is necessary to confirm its effectiveness for any of these uses, but more on that in a minute.
Why Do Bodybuilders Take L-Carnitine?
Bodybuilders and other athletes often take L-carnitine supplements to help improve exercise performance and muscular endurance, burn fat quicker and recover faster.
Since L-carnitine helps transport fatty acids into the cells to be used as energy, in theory, this should help increase endurance and reduce muscle damage during intense exercise.
On a similar note, L-carnitine may also help reduce muscle soreness and improve muscle recovery after exercise, which is why many bodybuilders and athletes use it as a supplement.
However, despite some studies suggesting that L-carnitine does all these things, there are also several other studies that have failed to show any significant benefits.
At this point, the scientific evidence is mixed and more research is needed.
What are the Benefits of L-Carnitine Supplements for Bodybuilding?
The benefits, or at least assumed benefits, of L-carnitine for bodybuilding are numerous.
Here are a few of them:
Helps with muscle recovery
The first benefit of L-carnitine for bodybuilding is its potential to aid in muscle recovery.
While studies on this have been inconclusive, some research indicates that L-carnitine supplementation may reduce muscle damage, soreness, and recovery time from intense exercise.
For example, a 20-year-old study suggests that L-carnitine L-tartrate supplementation can reduce the amount of exercise-induced muscle tissue damage and increase IGFBP-3 concentrations prior to and after acute exercise.  This supports the use of LCLT as a recovery supplement and suggests that it may help to mediate quicker recovery through some hormone interactions.
However, not many studies align with this result.
Reduces muscle soreness
It is also believed that L-carnitine can help reduce soreness and improve recovery time after exercise, which is the reason why many athletes or bodybuilders often include L-carnitine in their supplement stack.
A few studies support its potential as a muscle soreness reducer, with one finding that supplementing with 3 grams of L-carnitine for seven weeks resulted in reduced muscle soreness. 
As results suggest, this is thought to be the result of L-carnitine’s impact on vasodilation which translates to improved energetic metabolism of the damaged muscle.
But once again, not every study has been able to confirm this benefit.
Speaking of vasodilation, it’s also thought that L-carnitine can improve stamina and exercise performance.
You see, by promoting better blood flow and increasing oxygen delivery to the muscles, L-carnitine can help extend the time until exhaustion and thus improve overall performance in the gym.
Studies have also shown a decrease in heart rate and lactate levels during endurance tests on professional footballers supplementing with 3-4 grams of L-carnitine, indicating that taking L-carnitine before exercise has a beneficial effect on stamina and endurance, effectively prolonging exhaustion. 
Is L-Carnitine Good for Bulking?
In theory, L-carnitine can be beneficial for bulking. However, simply supplementing with L-carnitine won’t yield any noticeable results on its own.
Despite popular claims and theories, there is little scientific evidence to support the use of L-carnitine for bulking and gaining mass.
While studies suggest that L-carnitine can improve exercise performance in the aforementioned ways, none of them has provided evidence that it directly increases muscle size.
As far as we know, eating in a caloric surplus while feeding your muscles with an adequate amount of protein and training regularly is still the most effective way to bulk up.
Does L-Carnitine Help with Weight Loss?
On its own, L-carnitine won’t have any noticeable effect on weight loss or fat burning despite being one of the most popular “fat burners.”
In theory, L-carnitine’s effects on the body should contribute to the weight loss process. If taken alongside a proper diet and exercise regimen, it may help to reduce fat mass and improve performance, which can, in turn, aid in weight loss. Right?
Unfortunately, it’s not that simple.
The effectiveness of L-carnitine supplementation for weight loss has rarely been shown to be significant.
For instance, a study conducted on moderately obese adults supplemented with 2 grams of L-carnitine daily for eight weeks showed no difference in body fat mass or weight loss compared to the placebo group. 
To this day, the most efficient way to lose weight is to cut down on calories and just work out.
Does L-Carnitine Boost Testosterone?
L-carnitine won’t boost testosterone, despite the fact we’ve already established that it can have an effect on hormone levels.
While there has been a study confirming the positive effects of L-carnitine on symptoms of male aging , which are often associated with low testosterone levels, there haven’t been any studies suggesting that supplementing with L-carnitine could lead to an increase in overall testosterone.
What’s the Best Dosage for L-Carnitine?
The best dosage for L-carnitine is usually considered to be 2 grams or less per day.
These dosages have been shown to be easily tolerated and produce minimal side effects.
However, some studies have used up to 3 grams per day without any adverse effects, but we still can’t say for sure what the optimal dosage is for each individual.
Can You Take L-Carnitine Every Day?
While studies suggest that L-carnitine is safe to take every day in doses of up to 2 grams, it’s important to remember that everyone’s body is different and that individual tolerances may vary. Not to mention the fact that more research is needed to fully understand the long-term effects of supplementing with L-carnitine on a daily basis, as some studies suggest that prolonged usage could put you at risk of arteriosclerosis.
When is the Best Time of Day to Take L-Carnitine
The best time of day to take L-carnitine is typically shortly before exercise, before a meal, or first thing in the morning.
But, once again, this is purely based on anecdotal evidence as there isn’t any scientific proof (nor have there been any studies on the subject) indicating that taking L-carnitine at a certain time of day could have any profound effect on its effectiveness.
How Long Does it Take for L-Carnitine to Start Working?
There is a ton of debate and conflicting results on this particular subject, but it is generally accepted that the effects of L-carnitine start to manifest after about 6-8 weeks of daily supplementation.
However, some studies suggest that it could take around 100 days of continuous supplementation before you experience a 10% increase in muscle carnitine content.
Whatever it may be, the only certain thing is that it takes time for carnitine to work, but we still need more research to fully understand the specifics of its effects and how long it takes for them to start showing.
Can You Have an L-Carnitine Deficiency?
Yes, you can have an L-carnitine deficiency.
Carnitine deficiency is a rare disorder that is caused by a genetic mutation. However, it could also occur due to an array of different health issues.
The symptoms of L-carnitine deficiency can vary from person to person and may include muscle weakness, fatigue, or irritability.
Methods of Taking L-Carnitine
There are four main ways to take L-carnitine:
- L-carnitine Powder
- L-carnitine Liquid
- L-carnitine Capsule
- L-carnitine Injections
To take L-carnitine powder, simply add the recommended dosage of powder to a glass of water or smoothie and mix it well. The powder is tasteless, so there is no need to worry about the flavor.
Liquid L-carnitine is also easy to take and can be consumed directly from the bottle and is considered by many as the most effective form of L-carnitine. However, once again, there is only anecdotal evidence supporting this theory.
L-carnitine capsules are also a great option, as they’re easy to swallow and don’t taste bad.
Injections of L-carnitine are also available, but they’re generally reserved for those with severe carnitine deficiency and are rarely used by the general population or bodybuilders. Also, they’re essentially prescription only.
Which Method is Best for Taking L-Carnitine?
The best method for taking L-carnitine is definitely intravenous (IV) injection, as this is generally considered to be the most effective and quickest way for it to get into your system.
However, since you can’t quite rely on it, any of the other three methods should be sufficient.
Does Taking L-Carnitine with Coffee Have Any Additional Benefits?
Taking L-carnitine with coffee does (not) have any additional benefits.
Studies have shown that these two together work better than carnitine alone. However, that doesn’t necessarily mean that taking one with the other has anything to do with it.
In reality, it is simply the effects of caffeine that lead to further improved performance.
Caffeine is a well-known stimulant with proven performance-enhancing effects, so it doesn’t really matter if it’s taken with L-carnitine or not.
Can I Mix L-Carnitine with a Protein Shake?
Yes, you can take L-carnitine with a protein shake.
In fact, some would suggest mixing L-carnitine with a post-workout protein shake for improved recovery. But once again, the evidence supporting that claim is not very strong.
Be that as it may, taking L-carnitine with a protein shake should not cause any harm.
Are There Any Side Effects of Taking L-Carnitine?
Yes, there could be side effects of taking L-carnitine, although they are generally mild and rarely occur unless the dose of L-carnitine is 3 grams or more.
The most common side effects include nausea, stomach cramps, vomiting, and diarrhea.
In rare cases, muscle weakness and seizures could occur, alongside an increased chance of developing arteriosclerosis due to prolonged usage.
Who Should Not Take L-Carnitine?
Women who are pregnant or breastfeeding shouldn’t take L-carnitine supplements. Children, also.
Apart from those two, people with thyroid, kidney, or liver problems, seizures, or high blood pressure are advised against using L-carnitine without consulting their healthcare provider first.
Is L-Carnitine Safe to Take?
L-carnitine is generally considered to be safe when taken in the recommended dosages – up to 2 grams per day for up to 12 months.
As long as you don’t exceed the recommended dosage or take it for a prolonged period of time, taking L-carnitine should be perfectly safe.
That said, the emphasis is on should as you never know what could happen. Therefore, it is always best to consult your doctor and get their approval before taking any supplements.
What are the Different Types of L-Carnitine?
There are four different types of L-carnitine, each with its own unique benefits:
- L-carnitine L-tartrate
This form is the basic form of carnitine and is found naturally in food and supplements. It helps shuttle fatty acids into the mitochondria, where they can be broken down for energy, and is recommended to take in doses ranging from 500-2500 mg a day.
This acetylated form of carnitine has higher bioavailability than the basic form, making it more efficiently absorbed and utilized by the lower intestines.
ALCAR also has antioxidant effects, which help protect cells from damage caused by oxidative stress.
Its recommended dose ranges from 600-2500 mg per day.
This form is important for creating energy in the body, aiding in heart functions and muscular movements. Additionally, it can improve circulation throughout the body.
Some studies have shown that PLC could help with endurance for people with cardiovascular issues, but its dose should never be greater than 1 gram a day.
L-Carnitine L-Tartrate (LCLT)
This highly bioavailable form combines both l-carnitine and l-tartrate molecules together.
Studies suggest that this version may reduce muscle soreness after exercise, allowing athletes to train harder and longer.
But also, its effectiveness is somewhat limited when taken in doses lower than 1 gram a day, so it is recommended to stay in the 1-4 gram range if supplementing with LCLT.
How Does D-Carnitine Compare to L-Carnitine?
The differences between the two are not only difficult to explain, but they are also incredibly hard to study due to carnitine’s nature. But we’ll try to outline the most important stuff.
D-carnitine is an optical isomer of L-carnitine, facilitating long-chain fatty acid transport into the mitochondria. So, it performs in a very similar way to L-carnitine.
However, D-carnitine isn’t to be used as a supplement as it is not utilized by the body in the proper way. Instead, it is treated as a foreign compound leading to oxidative stress, inflammation, and lipotoxicity, a process ultimately leading to cellular dysfunction and death.
L-Carnitine vs. L-Arginine
While both of these compounds are important for biological processes and are often used as supplements – they work in very different ways.
L-arginine is an amino acid that helps with the production of nitric oxide, which widens and relaxes blood vessels and improves circulation.
On the other hand, L-carnitine is an amino acid derivative made from lysine and methionine and helps with the transportation of fatty acids into cells for energy production.
While L-carnitine is shown to aid with vasodilation, its effects are much less powerful than those of L-arginine.
However, L-arginine isn’t “that” powerful as a supplement, so if your goal is improved vasodilation and greater pumps, you’re much better off going with L-citrulline.
L-Carnitine vs. Creatine
Comparing the two in terms of which supplement is better is difficult as the two are used for entirely different purposes. Also, it’s not a fair game.
Creatine is easily the most studied supplement in all of sports nutrition, and it has been found to help with strength gains, power output, and muscle growth.
L-carnitine, on the other hand, mostly helps with increased energy metabolism and muscle recovery, and even those effects aren’t studied enough to be accurately quantified.
In fact, creatine’s effects on muscle recovery are (in)arguably better than L-carnitine’s.
So, if you’re looking for a supplement to aid your bodybuilding journey and it has come down to these two – creatine wins every single time.
Can You Take CLA and L-Carnitine Together?
You can take CLA and L-carnitine together to aid weight loss.
That said, you probably shouldn’t do it.
Neither CLA nor L-carnitine has been shown to be particularly effective weight loss aids. So, the combination isn’t likely to have much of an effect on helping you lose weight.
Some studies have linked CLA to a negligible difference compared to a placebo, but nowhere near enough where you could expect significant weight loss results.
Best L-Carnitine Supplements
If you’d like to give L-carnitine a try, these two supplements are more than decent:
Dr. Martin’s Nutrition Extra Strength L-Carnitine
Probably the best bang for the buck, this product contains 100 servings for just above $20.
You get 200 capsules, each with 500 mg of L-carnitine in its natural form, with no other added ingredients, ensuring you only what you need.
Marketed as a product to reduce muscle soreness and improve recovery, this supplement’s probably the only one with an “honest” marketing policy.
The bottle contains 250 half-gram capsules, which does mean you might have to pop at least two for a potent dose, which does make this one a bit more expensive than the others.
However, you’re getting L-carnitine L-tartrate (Carnipure®), the one most commonly associated with positive effects on physical fitness.
Foods That Are High in L-Carnitine
Several foods are somewhat rich in L-carnitine, such as:
- Beef (95 mg per 100 g)
- Pork (28 mg per 100 g)
- Milk (8 mg per 250 ml)
However, as you can see, the amounts of L-carnitine in these foods aren’t all that impressive compared to supplements.
That said, some studies show that L-carnitine is 4-6 times better absorbed from food than from supplements, so eating a steak or two here and there could be better than swallowing capsules.
Is Taking L-Carnitine for Bodybuilding Worth It?
No, taking L-carnitine for bodybuilding is not worth it.
Despite some of the associated benefits of L-carnitine, such as improved energy metabolism and muscle recovery, studies have yet to conclusively prove its efficacy. But that’s not the only reason why you shouldn’t waste money on these supplements.
As said, L-carnitine is made from the amino acids lysine and methionine. Therefore, supplementing with or eating enough protein with a well-balanced amino acid profile is more than enough to provide you with all the L-carnitine your body might need.
In conclusion, while L-carnitine may be popular among bodybuilders looking to shed fat before a show and those wanting to simply lose weight, its effects on performance and/or weight loss are inconclusive at best.
Therefore, it’s best to focus your efforts on a healthy diet and exercise regimen alongside proven supplements rather than trying to supplement with L-carnitine.