L-Carnitine And Testosterone | Can It Replace TRT?
I've been keeping a pulse on injectable L-carnitine for the last couple of years, both in my own body and in clients I coach. What I've seen is interesting enough that I finally decided to put it all together. This is my own theory based on anecdotal experience and the research I've come across, so take it for what it's worth.
The short version. L-carnitine seems to be doing something real with androgen receptor density and sensitivity, and it can meaningfully raise free testosterone in some people without any exogenous hormones involved.
What the androgen receptor actually is
Androgen receptors are nuclear hormone receptors that get activated when androgens like testosterone or DHT bind to them. Once activated, they regulate genes involved in muscle growth and other anabolic processes.
Two things matter here. Density and sensitivity.
Density is how many androgen receptors you have on a given cell. This gets influenced by hormone levels, exercise (especially resistance training), age, and genetics. Higher androgen levels can upregulate density. Aging tends to decrease it.
Sensitivity is how effectively those receptors respond when an androgen binds to them. This is influenced by post-translational modifications, co-activators and co-repressors, ligand affinity, and most importantly for our purposes, inflammation. Chronic inflammation in the body lowers how sensitive your receptors are to binding.
So you can have plenty of testosterone floating around, but if your receptors are low in number or low in sensitivity, you won't get the full effect.
Where injectable L-carnitine comes in
L-carnitine is a naturally occurring amino acid derivative. Its main job is shuttling fatty acids into the mitochondria for energy production.
Why injectable. Oral L-carnitine has maybe 10% bioavailability. Injectable is closer to 100%. To match the same effect orally, you'd have to take so much that you start running into TMAO and liver stress issues. Injectable wins, like with most things.
L-carnitine does three things that matter here.
- Improves mitochondrial efficiency, which improves muscle function and recovery.
- Boosts fatty acid oxidation, which helps fat loss and energy production.
- Has strong anti-inflammatory effects.
That third one is the key to the testosterone connection.
How L-carnitine ties to receptor density and sensitivity
Better mitochondrial function and lower inflammation create a better environment for muscle growth, which can upregulate androgen receptor density in muscle tissue. Studies suggest L-carnitine supplementation enhances muscle recovery, which indirectly supports androgen receptor activity.
There's also some research indicating L-carnitine may increase the expression of genes related to androgen signaling, which improves how responsive the receptor is when testosterone binds to it.
When you stack L-carnitine with resistance training, the two work together. You get the stimulus from training and the cellular support from L-carnitine.
I can attest to this firsthand. When I take injectable L-carnitine before cardio fasted or before a lift, I get better gas mileage. More reps with the same weight, more focus, less fatigue. That intensity itself drives more receptor stimulation.
Free testosterone and SHBG
Here's where it gets interesting. I've watched people who weren't on TRT double their free testosterone using injectable L-carnitine. Not total testosterone necessarily. Free testosterone, which is the active form.
Quick refresher. Total testosterone is everything in your blood. SHBG (sex hormone binding globulin) binds to testosterone and takes it out of play. Free testosterone is what's left over to actually go do work in your tissues. Higher SHBG means lower free testosterone. Inverse relationship.
SHBG goes up with age. SHBG goes up with body fat. The fatter you are, the higher your SHBG, and the less benefit you get from any testosterone in your system, whether natural or therapeutic. This is why a guy at 25% body fat doesn't respond to TRT the same way I do at sub 10%.
L-carnitine influences SHBG through a few mechanisms.
Anti-inflammatory effects bring inflammation down, which brings SHBG down. Improved fat metabolism and insulin sensitivity bring body fat down, which also brings SHBG down. Better workout performance means more fat loss from the same training, which compounds the effect.
When I first saw L-carnitine bringing down SHBG and bumping free testosterone in people's bloodwork, I had to sit with it for a minute. But the mechanism is there. Reduce inflammation, improve insulin sensitivity, drop body fat, lower SHBG, raise free testosterone.
Why this matters for younger guys
A lot of younger men are scared to inject. They want testosterone benefits but won't pull the trigger on TRT.
Injectable L-carnitine is a good bridge for those guys. It gets them comfortable with the needle. It raises their free testosterone naturally. And it's just an amino acid, so the risk profile is very different.
For a 21-year-old who isn't ready to commit to therapeutic testosterone, this is a real option for the next several years.
This works for women too
Testosterone matters for women. Muscle mass, bone density, mood, libido. Same androgen receptors, same mechanisms.
L-carnitine improves energy production, supports better workouts, helps with body composition, and lowers SHBG the same way it does in men. For women in fitness or sports, this means better performance and recovery.
For women going through menopause, L-carnitine helps manage hormonal changes by reducing inflammation and supporting hormonal balance. It can also help maintain bone density, which lowers osteoporosis risk. I'd still recommend bioidentical hormone replacement for most women in that phase, but L-carnitine is a useful tool in the kit.
My protocol
Simple. Start at 200 mg injected intramuscularly once per day. You can do this every day or four or five times a week.
Titrate up by 200 mg per week if you want more.
For most women, 500 mg per day is probably the ceiling. For men, you can go up to 1,000 mg per day and see real benefit. The only real limit is injection volume, which gets cumbersome at higher doses.
You can take it fasted or with food. The whole "must be taken with insulin" idea comes from bodybuilding circles where guys are pushing maximum muscle mass. For our purposes, timing isn't critical. Pre-workout works well in my experience.
My take
Injectable L-carnitine is doing something real with androgen receptor density and sensitivity. I can't prove it under a microscope, but I've watched it raise free testosterone in natural lifters, lower SHBG in bloodwork, and dramatically improve workout output in myself.
It's not a replacement for TRT, especially as you age. But it's a strong bridge for younger guys not ready for testosterone, and it stacks well on top of TRT if you're already on it. 200 mg per week of testosterone goes further when you're running 200 mg per day of injectable L-carnitine alongside it.
For an amino acid, it's punching way above its weight class.
Full transcript click any paragraph to jump video
Hey everybody, this is Hunter Williams. I hope you are doing amazing wherever you at in the world. Today's video is going to be about L-carnitine and testosterone. So selfishly, This is something that I have kind of kept my pulse on just over the last couple of years since I started experimenting with injectable L carnitene. And I finally decided to put this together into my own comprehensive thesis slash theory, not a scientific theory but my on just rampant speculation theory and I was able to come up with some data information just based on my anecdotal experience of myself and clients that I coach and then also some scientific
research that came across. So what I am going to do today is examine the connection between L-carnitine and testosterone, particularly injectable L carnitin. And the reason I do this is because in myself I notice that injectable l-carnitine is hugely beneficial. And in starting to understand this more, what I noticed is that there is something going on with androgen receptor sensitivity and density in l carnitene. Now obviously I can't prove this scientifically or under a microscope or anything like that, but I've noticed this in my own life.
And then I noticed people that I started to coach that were not using therapeutic testosterone, especially younger men that used injectable oil carnitine, that it was raising their free testosterone and their total testosterone. Now, does it do it effectively as therapeutic testosterone? Of course not. But for someone that's 21 years old that probably doesn't want to start looking into therapeutic, testosterone I think, even though you could make the case for that, I think injectable L-carnitine is a good bridge, at least for those few years, or several years before someone starts testosterone.
So what I want to do today is examine L carnitin and testosterone, and then we're going to look at androgen receptor sensitivity and density, what that even means, because that's thrown around a lot in the fitness world, then kind of examine that. I also want it to be clear that this video is for men and for women, so testosterone is important for Really is just as important for women as it is for men. Obviously men have it in a different quantity But I'm going to talk about this specifically in the context as women for woman as well So I know this is
a little off topic from most of the peptides and stuff But as relates to hormones and everything I really wanted to do a deep dive on this because something's going on there and I wanted To quantify it and put it into my own unique take on so You know, I also want to be clear that this helpful L carnitine is helpful if you're using therapeutic testosterone, and if you are not using therapy testosterone. So it's really good to use. Obviously it just an amino acid. That's what we're going to look at today. Before I jump in, share my screen. If you like topics like this, because I don't know of anyone else that's at least like comprehensively talking about it on the internet like,
this manner, definitely check out Fully Optimized Health. that is our private membership group. It's $99 a month. You can cancel anytime. Jay and I talk about stuff like this all the time, and there's tons of threads in the form and everything with people talking about topics such as these. Obviously, too, if you're into peptides and things like that, there are plenty of that in there for you. That being said, If you want to check out the peptide cheat sheet, that's going to be down in a link in all of the descriptions of all my videos. So check that out. I'll sign you up for my email list and you'll get all that amazing content, written content that goes out on my e-mail list. Without further ado, I'm going show my screen and we are going jump into L-carnitine and testosterone.
All right, so today's video is all about L-carnitine and testosterone, and we're going to jump into as well androgen receptor sensitivity and density and really try to get a grasp on what those actually mean. So let's first look at the andogen receptor. What is the Androgen Receptor? You hear this again thrown around all the time, but basically the endogen receptors are nuclear hormone receptors that are activated by binding androgens like testosterone and dihydrotestosterone, otherwise known as DHT. So basically, once activated, androgen receptors regulate the expression of genes involved in the development and maintenance of male characteristics,
such as muscle growth and overall anabolic processes, which just means muscle building. So let's also look at andogen receptor density. Basically, Androgen receptor Density refers to the number of androgens receptors present in a given cell or tissue. So, if you think about cells or tissue, we basically have androgen receptors on them and we will all have a different amount of receptors in the cell. So basically, factors that can influence these are hormone levels.
High levels of androgens, i.e. testosterone, can upregulate the number of antigen receptors of the cells. Also, exercise. So this is why also exercise is crucial as it relates to hormone production because resistance training has been shown to increase androgen receptor density in muscle tissue. Now, you can't rely on exercise alone, but it's very important in that respect. Also age. Androgen and receptor may decrease with aging, contributing to age-related muscle loss. And then also genetics, so obviously sometimes people are just freakishly big and some people were just wiry, skinny, small.
And genetic variations can affect the baseline of androgen receptor density in individuals. This is in men and women. Obviously it's going to be different in man. Now, so we have the androgen receptor. We have androgens receptor density, which basically means the number of andogen receptors on the cell. So based on our environment and our lifestyle, that amount, the amount of Androgen receptors can be higher or lower. Now let's look at the sensitivity. Once we had the Androgen receptor, we'd have a number Of Androgyne receptors. Let's Look at The sensitivity and what that means of the receptors in the cells.
Basically, The sensitivity refers to how effectively androgen receptors on the cell respond to andogen binding. So what that means is that basically we have all of these factors get an influence how sensitive that receptor is to being bound to Androgen. And so basically, we first have post-translational modifications, which is just kind of like a scientific term. But so, basically phosphorylation, acetylation and other modifications can affect androgyn receptor function.
We also have the presence of co-activators and co repressors can modulate androgen receptor activity. And we also ligand affinity. So different androgens have varying affinities for andrin receptors and influencing sensitivity. Then lastly, but definitely not least inflammation, obstructive stress can influence andridge receptor function. Basically we have chronic inflammation in the body through everything that we do through our diet lifestyle. and all that stuff can affect how sensitive the androgen receptors are to binding to androgens at the cell level.
Now, let's move gears for a second and look at injectable L-carnitine. So now that we understand, basically we have the sell, we had the Androgen receptor on the sale, and then we the sensitivity of that receptor to bind to Androgenes. Let's look how injectible L carnitene comes in the picture. So L-carnitine is a naturally occurring amino acid derivative that plays a crucial role in the transport of fatty acids into the mitochondria for energy production.
So injectable L carnitin is used for its higher bioavailability compared to oral supplementation. My guess is that you're probably getting somewhere in the neighborhood of like 10% of the bioavailability if you take oral L-carnitine versus injectables close to 100%. So it's not that that couldn't simulate the same effects with oral l-Carnatine, but because of how it is metabolized, you'd have to take much higher dose, which gets into TMAO and potentially being stressful to the liver.
So injectable is always going to be better as with most things, Injectable's always better, and how does this work? So L-carnitine enhances mitochondrial efficiency, which potentially improves muscle function and recovery. It's also, this is where it really, really helps with fat loss, it helps fatty acid oxidation. So by increasing the transport of fatty acids into the mitochondria, L carnitin aids in fat-loss and energy production. Basically, l-Carnatine helps shuttle fatty-acids in our cells into mitochondrion which helps us expend energy at a higher rate and thereby lose fat more
effectively with the same amount of work that we would be putting in otherwise. It also has strong anti-inflammatory effects. So L-carnitine has been shown to reduce the markers of inflammation, which like we just talked about with androgen receptor sensitivity, is going to help with Androgen Receptor Sensitivity so that, as you're gonna see in a second, our testosterone levels can potentially improve. Now let's look at, here's the meat and potatoes. How does L-carnitine relate to androgen receptor density and sensitivity?
So first, let's look at this. So enhanced muscle recovery and growth. Improved mitochondrial function and reduced inflammation can create a more favorable environment for muscle growth, which can up-regulate androgens receptor-density in muscle tissue. And remember, androgyn receptor intensity is how many of those receptors we have on the cell. When we improve mitochondrial function, we improved androgen receptor density, which again, puts more of those receptors on the cell.
So what's the evidence behind that? So studies suggest that L-carnitine supplementation can enhance muscle recovery after exercise, indirectly supporting AR activity. Then we also have an improved hormonal environment. So, L-carnitine can modulate hormonally responses to exercise. Basically, we exercise that creates, among other things, a hormono cascade in our body. When we use injectable L carnitin particularly before a workout, it's going to modulated the expression hormontally after that workout.
which is going to influence the androgen receptor sensitivity. So some research indicates that L-carnit may increase the expression of genes related to androgens signaling, which enhances the receptiveness or the responsiveness of the antigen receptor. Now, how does this work with exercise? So when we combine L-Carnitine with resistance training, it synergistically increases androgen receptor density and sensitivity by providing both the stimulus and the support needed for optimal muscle adaptation.
It also improved performance, so enhanced energy production and reduced fatigue from L-carnitine supplementation can enhance workout intensity, which is going to allow us to stimulate the androgen receptor pathways even more. I can attest to this firsthand, when I take L carnitin, whether it's before cardio in a fasted state or whether its before a resistance training session. It absolutely increases energy expenditure for the same amount of work I'm doing. So think about getting better gas mileage out of your car.
If I take L-Carnitine before a lift, I get more reps with the amount weight that I would normally use. I train more intensely. More focused too, which is a huge benefit because I am more able to stay on task. um, and not get distracted by things or not, get tired as easily. So it improves my workout performance thereby kind of having this hormonal cascade that influences engine and receptor density and sensitivity. And that leads us to athletic performance and age-related muscle loss. So athletes and bodybuilders may benefit from L-carnitine's effects on androgen receptor sensitivity and density which aids in muscle hypertrophy which
is basically the enlargement of our muscle cells and recovery. And then also to older adults can use L carnitines to combat sarcopenia which has muscle lost because it helps enhance andogen receptor signaling in the muscle tissue which huge. Now, let's look at this connection between injectable or carnitine free testosterone and SHBG. So this is also to, as I mentioned, I have seen people's free testosterone double. Now I can't promise that for you, but I've seen. People that are not using therapeutic testosterone, uh, double their free Testosteron while using injectible or quarantine,
which is kind of crazy because there's all of these, um, supplements that were sold to young men to try to increase their testosterone. Um, and none of them have injective or Carnitin. But it's kind of funny because just as a side note before I go into this, most of the time people won't use testosterone, I'd say not all the times, not most the the, but there's a good chunk of people that won' use testosterone because they're scared to inject. And so it was like you show them injectable l-carnitine and it kind elucidates or like exposes that beer because if l carnitene is able to raise your testosterone levels,
why would you not use it? It's naturally occurring amino acid. Why would not you use that? And a lot of times it is because people are scared And then I think once people, I take L-Carnitine can be a bridge, meaning that people can use it. They get comfortable with injecting. they realize they're not going to die or have any sort of like, you know, massive trauma to them, uh, from injectting. And they were like oh, okay, that's pretty good. That works. Maybe now I can try testosterone. So that why I, think it's a Bridge. But basically. I wanted to explore this connection between L-carotene free testosterone and SHBG, which I'm going to explain. So free-testosterone is the fraction of total testosterone that is not bound to proteins like SHPG otherwise known as sex hormone binding globulin.
I am just going refer to that from SH-B-G henceforth. which makes it bioavailable for tissues to use for muscle protein synthesis, libido and all the things that we know testosterone for. So basically free testosterone is the active form of testosterone that interacts with the androgen receptor and exerts these anabolic effects influencing muscle growth, and overall vitality. So in the body we have testosterone and a lot of that gets bound up to SHBG, but the free testosterone is actually what is going to go to the muscle tissue
and increase muscle size, uh, and do all the other effects that, you know, we'd love and no testosterone for. So, um, Now, secondarily, SHBG is a glycoprotein that binds to sex hormones, including testosterone and estrogen, which regulates their bioavailability. And by binding to testosterone, S-HB-G controls the amount of free testosterone in the bloodstream. So basically the higher our SH-Bg, the lower our free-testosterone would be. Think of it as an inverse relationship. Higher SHPG equals lower free testosterones, lower SHHPg equals higher free testosterones.
And when we look at SHBG, this is what it's influenced by. So estrogen increases SHPG levels, while androgens, like testosterone, tend to decrease it. Also SH-B-G-levels tend increase with age, so as we age it is harder to produce the same amount of free testosterone because a lot of it gets bound up. And obviously this the big one. Typically the fatter someone is, the higher their SHbG will be. So someone like me, who I'm not at my leanest right now by any means, but is sub 10% body fat is going to have much less SHBG just from the jump than someone
that is 25% fat. And the reason is, this is the outside scope of this video, basically the fatter you are, the more SHPG you will have, which decreases free testosterone. So even if someone is using therapeutic testosterone, they're not going respond as well to it as I will as a leaner person, because they have higher levels of SHG. which means more of the testosterone that they inject gets bound up and then they don't get the benefits of free testosterone. So that's why we say like, you know, testosterone can help you lose weight. Absolutely. But if you're 25 to 30% body fat as a man, don' think that you are going to get all the benefit that someone that is 12% fat will.
Obviously lifestyle factors are huge when it comes to SHBG and this is why testosterone is not a panacea. Peptides are not pancea because it's going back to like how much fat we have in our body. Let's look at how this works. So when we introduce injectable L-carnitine, it's going to improve mitochondrial function, which helps enhance exercise capacity and recovery. And this supports anabolic processes that increase free testosterone levels. Basically, L carnitin is going upregulate our ability to have more free-testosterone in the body.
Studies have shown that athletes using L-carnitine experience better performance and quicker recovery, leading to more favorable hormonal profile, including higher free testosterone. Also, inflammation plays a big part in SHBG, so chronic inflammation can lead to elevated SHPG levels and decreased free-testosterone. So L carnitines anti-inflammatory properties help mitigate this effect. So a lot of people will think, okay, well, if I can manipulate my SHBG, I'll increase free testosterone, right? Yes. In theory, yes, you can. And L-carnitine is kind of a catalyst for that.
I'm not saying it's going to work directly to do that, but it is going kickstart a cascade of process in the body to help do it. So research indicates that L carnitin reduces markers of inflammation, which will maintain higher levels of free testosterone by lowering SHPG because it has ridden the bottom of the inflammation. Now, let's look at fat metabolism and insulin sensitivity. So, improved fat metabolism and insulin sensitivity through L-carnitine supplementation can lead to lower SHBG levels, thus increasing the amount of free testosterone. What I didn't realize at first, until I saw it through people's blood work, is that L-carnitine was bringing down SHBG for people because of the anti-inflammatory effects,
because the mitochondrial-enhancing effects. So it was bring down the SHPG. It was taking people that were exercising and allowing them to burn more fat from the exercise that they were already doing, thus increasing their freestyle testosterone. When I first saw this, I was like, how could All other variables aside, L-carnitine enhance someone's free testosterone without supplementing with testosterone, right? Like for a natty person, and this is what was going on. So clinical trials have demonstrated that L carnitin improves insulin sensitivity and body composition, which is going to bring down that SHBG,
thereby raising free-testosterone, there by giving us all the beneficial and therapeutic effects of having higher free testosterones in the body. Hopefully this starting to come full circle now. I also wanted to talk about this for women, because up until this point, you're probably thinking this in the context of men. So let's look at testosterone in women. While testosterone is often associated with men, it is also an important hormone for woman, which contributes to muscle mass, bone density, mood, and libido. And just as in men androgen receptors are proteins that bind to testosterone and other androgens, that allow them to exert their effects on various tissues,
including muscle. It does the same thing for a woman as for men so let us look in working for the women as it's a little bit different. L-carnitine improves the transport of fatty acids into mitochondria which boosts energy production and reduces fatigue and this supports more effective workouts which can naturally enhance hormonal balance. We also have, as in men, the androgen receptor density and sensitivity. So increased energy availability supports cellular functions including this upregulation of androgens receptors and improves sensitivity to andogens which
for women can benefit muscle health and overall vitality. So fatty acid oxidation and body composition. As for men, L-carnitine facilitates the breakdown of fats for energy leading to reduced body fat levels. Lower body fats associated with improved hormonal profiles as excessive body fact can disrupt hormone levels and in women, this can maintain a healthier testosterone and estrogen levels which are very important. and reduce body fat and improve insulin sensitivity, can lower SHBG levels, increasing the availability of free testosterone and other androgens.
So what does this mean for women? So women involved in fitness, sports, and athletics can benefit from enhanced muscle health and recovery, obviously, as well as the optimized hormonal environment provided by L-Carnitine. And by improving free testosterone levels in women and androgen receptor function, L-carnitine supports better performance, muscle tone, and overall vitality, which is just health and energy. And then also too, one of the biggest things as women age is menopause and bone density. So L carnitin can help manage hormonal changes associated with menipause by reducing inflammation and supporting hormon imbalance.
And improved hormonal health can help maintain bone density, reducing the risk of osteoporosis in post-menopausal women. So as it relates to that, again, this is, I would recommend for everyone, especially a woman that is going through that to be supplementing with bioidentical hormone replacement therapy, but L-Carnitine is definitely a tool in the toolkit that I will use to help combat some of those things that are typically associated with aging and age-related disease in women Now, what is my protocol? Because everyone wants to know the protocol, right? Well, for injectable carnitine, it's very simple.
I would start with 200 milligrams injected intramuscularly once per day. And you could do that every day, you can do it four or five times a week. Um, and then I would titrate up by 200 milligrams per week. And then this is, you know, for men can go this high. I don't think women would need to go as high, You know for most women, I think the most they would go is high as 500 milligrams for a week, but for me, And you can get up to tie. At that point, it just becomes such a burdensome thing to inject because there's so much volume that you're injecting, but you can go as high as 1,000
milligrams per day and you will see a lot of benefit for that. Injectable oil carnitine is amazing. It gives you all these amazing benefits, that's my protocol. Again, like I said, the only downside is the injection volume. It's very easy. You can buy it. I'm not here to recommend where to buy or anything like that. But basically that is the protocol. So you can kind of start out from there. And again, you could take it fasted. Take it with food. There is this whole idea that you need to take in the presence of insulin. It has amazing benefits.
That's from the bodybuilding world where you have people trying to put on a ton of muscle mass. That is the protocol, and that is it for the slides. That's the summary and comprehensive look at L-carnitine testosterone. In theory, it can help raise testosterone levels. It definitely will affect how you feel for certain. I would never recommend it as a replacement for testosterone therapy, especially on someone that's aging, but I do think It can be a bridge. And if you're looking at testosterone therapy and you want to introduce yourself to something that potentially has the benefits before you go full-bore
into testosterone, therapy, definitely injectable oil carnitine. But again, it's something even if are using testosterone. I think it gives you more bang for your buck when it comes to testosterone so I you know, 200 milligrams per week of testosterone goes further if your using 200 mg per day of injectible oil So, again, as it relates to the androgen receptor density and sensitivity, it's definitely doing something there. Again, this is my best attempt to kind of explain and summarize that. So hopefully this video has helped you guys. I'd love to hear your feedback, questions, comments, and concerns. And if you'd like me to do more videos like this, I know I talk about peptides a lot, but I can talk all things biohacking and stuff because this what
I do. Thanks to you, guys, that I have the ability to this now. Appreciate you all. Much love. Don't forget to check out all the links in the description,
