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- L-Carnitine Deep Dive
Happy Tuesday!
Injectable L-carnitine has quietly been one of my favorite tools for years.
I realized I haven’t given it the attention it’s due as of late.
So today, I just dropped a brand new deep dive on injectable L-carnitine on Spotify.
I cover the mechanisms, human clinical data, real-world dosing, pros, cons, and all the nuances you will never hear in a 30-second TikTok clip.
Today’s email will be a written companion guide to that deep dive.
Let’s dig in!
What is L-Carnitine
When you think about L-carnitine, think about energy and fat transport.
Your body makes it from amino acids (lysine and methionine) in the liver and kidneys, then stores about 95% of it in skeletal muscle and the heart.
L-carnitine is the bus driver.
Fatty acids are the passengers.
Mitochondria are the power plants.
If you do not have enough buses, it does not matter how many passengers are waiting at the station, they are not getting to work.
L-carnitine binds long-chain fatty acids, puts them on the bus, and shuttles them into the mitochondria, where they can be burned for ATP.
I loved Magic School Bus as a kid, and I like to use that analogy to explain how it works.
When we inject L-carnitine, we bypass the gut (where oral absorption is only about 5–18%) and achieve near 100% bioavailability.
That means way higher plasma levels, more buses running, and more potential for fat and carbs to be used cleanly as fuel instead of sitting around as sludge.
It is a logistics upgrade for your metabolism.
Data
A lot of the serious research used IV L-carnitine in medical settings (dialysis patients, heart attack patients, people with true deficiencies). Still, it tells us what this molecule can do when you get enough of it into the system.
In dialysis patients, IV L-carnitine improved fatigue, muscle symptoms, and even reduced the dose of erythropoietin they needed for anemia.
When people were severely carnitine-deficient, supplementation improved their blood, muscles, and energy.
After heart attacks, high-dose IV L-carnitine (9 grams per day for 5 days) reduced arrhythmias and angina and was associated with about a 27% reduction in all-cause mortality post-MI.
Longer-term oral protocols with carbs (2–4 grams carnitine plus a carb drink over 12–24 weeks) increased muscle carnitine 10–20% and improved exercise performance, fat utilization, and perceived exertion.
Injectable L-carnitine is like a fast lane into the bloodstream.
But the real magic happens when you use it consistently and pair it with good training and nutrition, so the muscle actually starts storing more of it over time.
Who is a Good Candidate?
Although, L-carnitine is a staple in my pantry, it’s not a miracle.
It will not turn you into Mr. Olympia.
It will not grow your glutes by itself.
But for the right person, it can feel like a “cheat code” because of how it changes recovery and energy.
Athletes and lifters notice it first as a recovery and endurance tool.
You get less burn at the end of hard sets, less “I’m cooked” feeling deep into a workout, and you bounce back faster the next day.
Because carnitine buffers acetyl-CoA and helps carbs get used efficiently, you often see lower lactate, better pumps, and the ability to do more volume without feeling wrecked.
In the video I talk about how it reminds me of what people think steroids do, but in reality, steroids mainly allow you to recover faster.
Carnitine works in that same “recover faster, go harder” lane.
It also shines for fat loss and longevity.
It supports beta-oxidation during fasted cardio, helps overweight and insulin-resistant people use fat more effectively, and in older, frailer folks, the data is crazy.
In a study of centenarians, 2 grams of oral L-carnitine daily for 6 months increased muscle mass, reduced fat, and improved walking distance and mental function.
So if you are:
A younger athlete trying to squeeze more out of training,
Someone with 30–100 pounds to lose,
Or an older, more frail person trying to hold onto muscle and energy,
L-carnitine is one of those rare tools that helps all three groups, just in slightly different ways.
Dosing
I love injectable L-carnitine, but it can hurt.
I have had more post-injection pain from carnitine than from testosterone or most peptides.
It burns. It can welt. It can make your delt or glute feel like someone hit it with a hammer if you overdose on the volume.
For most people, the sweet spot is 200–600 mg intramuscular per injection.
If you are smaller or a woman, start at 200–250 mg and see how you feel.
My personal “everyday” sweet spot is 500 mg IM, three to four times per week before training.
I absolutely love 1,000 mg, but the post-injection pain at that dose can be rough, so I save that for workouts where I really want to be firing on all cylinders.
Practically, I use a 28–29 gauge, half-inch needle and inject into glutes or delts.
Anything smaller than 29 gauge and L-carnitine simply will not push through because it is too viscous.
You can do it subcutaneous, but I am not a fan.
The lumps in the abdomen hurt more than a lump in a glute in my experience. Go slow, massage the area, use a massage gun afterward if needed, and rotate sites.
For most people, 400–500 mg IM before training, 3–4 times per week, plus good nutrition, is more than enough.
And on top of that, I like 1 gram of acetyl-L-carnitine orally first thing in the morning for the cognitive and mood benefits.
Final Thoughts
If you stripped my entire protocol down and said, “Hunter, you get to keep a few things for performance, longevity, and feeling good in your own skin,” injectable L-carnitine makes that cut every time.
Not because it is the strongest thing in the world, but because carnitine quietly supports almost everything else you do.
It makes fasted cardio more productive.
It makes lifting sessions more efficient.
It makes fat-loss phases a little easier and muscle-retention phases a little more forgiving.
It helps the frail become less frail, and the already-optimized squeeze out a few extra percentage points of performance.
It touches heart, muscle, brain, and mitochondria all at once.
And outside of the occasional “fish market” body odor and some injection soreness, it is remarkably safe.
Most importantly, it is accessible and repeatable.
Your 16-year-old son trying to earn a college football scholarship, your 45-year-old self running a business and a family, your 75-year-old parent trying to stay independent can all potentially benefit from L-carnitine if it is dosed intelligently and paired with the right lifestyle.
Thank you, as always, for being the best audience in the world.
It is a blessing, privilege, and honor to share this with you.
My hope is that you take tools like injectable L-carnitine, use them wisely, and build a life you are proud to live!
Best,
Hunter Williams
P.S. I get my injectable L-carnitine from:
Further Reading