Acetyl-L-carnitine to maximize testosterone and erections

Acetyl-L-carnitine might have a positive influence on your androgens.

Carnitine is a naturally found compound in the body that’s involved in energy metabolism and removing products of metabolism from cells.

In the body, 75% of carnitine is ingested from the diet, and 25% is synthesized internally (roughly 11–34mg per day). It’s created from two essential amino acids lysine and methionine and requires vitamin C, vitamin B6, niacin, and iron as cofactors. L-carnitine is then stored in skeletal muscles, heart, brain, and testes.

The bioavailability of l-carnitine from dietary sources is estimated to be 54–86%, whereas the absorption from supplements is roughly 9–25% from a single oral dose of 2g dose.

Signs of carnitine deficiency

  • Can’t sleep through the night
  • Brain fog
  • Exercise intolerance
  • Fatigue
  • Hypoglycemia
  • Decreased or floppy muscle tone or muscle weakness
  • Shortness of breath

Supplemental forms of carnitine include:

  • L-carnitine
  • Acetyl-L-carnitine
  • L-Carnitine-L-tartrate
  • Propionyl-L-carnitine
  • Glycine propionyl-L-carnitine

Most people know carnitine as the compound that boosts fat burning, but it does so much more than that. Let’s dive in.

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Carnitine on testosterone

People with kidney disease have low carnitine levels, due to enhanced excretion.

In men with kidney disease, low carnitine levels were independently associated with low free testosterone (R).

In aminals with diabetes or that were poisoned, carnitine is able to increase LH, FSH, various steroidogenic enzymes (StAR and CYP11A1) as well as testosterone (R, R)

Carnitine is also able to prevent testicular damage and the drop in testosterone induced by heat stress (R). Hot baths, saunas, seat warmers, tighty whities, prolonged sitting, etc., increase testicular temperature too much and lowers testosterone. Carnitine can help to prevent this.

Carnitine and androgen receptors

Carnitine might strengthen the effect of testosterone and DHT by upregulating androgen receptors.

According to this study, supplementing 2944mg of L-carnitine-L-tartrate (yielding 2g carnitine) increased androgen receptor content (in the vastus lateralis) after 3 weeks, only if it was consumed with a carb-heavy drink (R).

As you can see in the graph below, AR didn’t increase when L-carnitine-L-tartrate was taken with water, but only with a carb-heavy drink (8 calories/kg/BW and 1.1g/kg carbs).

Additionally, the L-tartrate was added to help stabilize L-carnitine and there are no known biological effects of tartaric acid. Thus, it likely doesn’t matter which carnitine you use to increase AR.

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Carnitine might help with building muscle

Carnitine might be able to help with muscle growth as it:

  • Increases IGFBP-3, a transporter for IGF-1 into cells (R). IGF-1 enhances insulin sensitivity and is anabolic.
  • Prevents excess muscle damage from exercise, thus preserving androgen receptors (R).
  • Speeds up muscle recovery after exercise (R).
  • Enhances blood flow and oxygen supply to the muscle tissue via improving endothelial function (R).

Although studies have shown that carnitine doesn’t improve aerobic exercise performance, it might enhance anaerobic exercise performance.

This study found that 2g of carnitine increased bench press and leg press reps to failure on the 1st and 3rd sets, more than the placebo.

It appears that the main benefit of carnitine is from delaying fatigue more than anything else, as well as reducing oxidative stress and muscle soreness.

This 35 days study found that 3g L-carnitine-L-tartrate (about 2g carnitine) supplementation improved recovery and reduced fatigue following exercise across gender and age (R).

As you can see in the graph, it reduced creatine kinase (a marker of muscle damage) and CRP (a marker of acute inflammation) and increase SOD (superoxide dismutase; an anti-oxidant enzyme that deactivates superoxide, a free radical).

All of this helps to speed up recovery so that you can train more frequently and with more volume.

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Carnitine for better erections

The people carnitine will help the most are people with diabetes, obesity, sleep apnea and inflammation.

The reason why is because carnitine is a powerful anti-oxidant and lowers oxidative stress and inflammation. That’s how it improves vascular health and function and increases nitric oxide (R).

This study found that 2g propionyl-L-carnitine + 50mg Viagra twice a week vs Viagra alone improved erections (improvement was seen in 68% vs. 23% of users) and successful intercourse attempts (76% vs. 34%) significantly more (R).

Propionyl-L-carnitine is a strong endothelial anti-oxidant, similar to pycnogenol. Thus, when you have healthier blood vessels, you can respond better to something like Viagra.

Propionyl-L-carnitine (PLC) and acetyl-L-carnitine (ALC) have recently demonstrated an antifibrotic activity that reduces the size of plaques seen in acute and chronic Peyronie’s disease (R). Less plaque will result in better erections.

Carnitine vs testosterone

In this study, they compared 160mg oral testosterone undecanoate taken daily vs 2g propionyl-L-carnitine and 2g acetyl-L-carnitine per day for 6 months (R).

Total and free T increased from 9.89 to 13.96 (285 to 402.6ng/dl) and 4.4 to 23.7 in the testosterone group, but didn’t change in the carnitine group.

Despite not increasing testosterone, carnitine was significantly more effective than testosterone in improving nocturnal erections and erections in general.

Additionally, propionyl-L-carnitine and acetyl-L-carnitine dramatically improved the effectiveness of Viagra in restoring erections after bilateral nerve-sparing radical retropubic prostatectomy (R).

Carnitine for fertility

One of the main reasons why people become infertile is because they have oxidative stress in the Sertoli cells (where sperm is produced), which then damages the Sertoli cell and sperm. This leads to low sperm count, low motility and infertility.

Carnitine is a powerful anti-oxidant and lowers free radicals, thus protecting the sperm.

This meta-analysis showed that carnitine is just as effective as NAC (N-acetylcysteine) at increasing sperm motility and normal morphology. However, NAC increased sperm concentration and ejaculate volume whereas carnitine did not (R).

Carnitine also provides energy for the sperm, which improves their health. In fact, low levels of carnitine have been suggested as one of the contributing factors for sperm disorders such as azoospermia and asthenospermia (R).

ALCAR on dopamine, serotonin, noradrenaline, etc.

Acetyl-L-carnitine has many beneficial effects on the brain, by improving energy production (better glucose and fat oxidation), reducing oxidative stress and preventing stress-induced brain dysfunction.

ALCAR has been shown to:

  • Protect dopaminergic neurons and protect against Parkinson’s disease (R).
  • Prevent the decrease in dopamine receptor D1 expression with age (R).
  • Enhance the release of dopamine in the brains (cortex, hippocampus, and striatum) of old animals to the same level as young animals (R).
  • Increase noradrenaline levels, which enhances focus, motivation, energy, libido, etc. (R)
  • Promote acetylcholine release, which helps with focus, vasodilation, sleep, etc. (R)
  • Enhance glucose oxidation (reduce glucose to lactate conversion) and ATP production (R).
  • Prevent the decrease in cortisol receptors in the hippocampus (R). Reduced hippocampal cortisol receptors may be involved in depression, forgetfulness, etc. (R)
  • Increase the NMDA glutamate binding site density to promote neuronal plasticity, focus, memory formation, etc. (R)
  • Prevent stress-induced neuroenergetics dysregulation that leads to neurological damage and depression (R)

Carnitine restores insulin sensitivity and glucose oxidation

A lot of people think that carnitine is only useful for boosting fat oxidation. However, it actually helps to promote proper glucose disposal and oxidation (R).

Studies in humans and animals demonstrate that “lipid over supply” causes or worsens insulin resistance via multiple mechanisms involving the accumulation of intracellular lipids in multiple tissues. In particular, the accumulation of fatty acyl CoA derivatives/metabolites in muscle inhibits both insulin signaling and glucose oxidation. Therefore agents that ameliorate the accumulation of fatty acyl CoA derivatives and/or their metabolites would be beneficial in the treatment or prevention of insulin resistance and T2D.” (R)

Carnitine is also used to shuttle acetylcarnitine out of the mitochondria, thus allowing proper glucose oxidation, because acetylcarnitine inhibits proper glucose oxidation.

Carnitine switches energy substrate preference in the heart from fatty acid oxidation to glucose oxidation. Shocker isn’t it?

By converting acetyl-CoA to its membrane permeant acetylcarnitine ester, CrAT regulates mitochondrial and intracellular carbon trafficking. Several studies have indicated that CrAT combats nutrient stress and enhances insulin action by permitting mitochondrial efflux of excess acetyl moieties that otherwise inhibit key regulatory enzymes such as pyruvate dehydrogenase and enhance metabolic flexibility.” (R)

Why it’s low

The most common causes of carnitine deficiency are:

  • Impaired absorption due to IBD or another inflammatory bowel condition (colitis, Celiac disease, etc.)
  • Low dietary intake of carnitine
  • Low precursor intake (lysine and methionine)
  • Low cofactor intake (vitamin C, vitamin B6, niacin, and iron)


Carnitine doesn’t directly stimulate testosterone production, but it can help to prevent testosterone from declining due to excess oxidative stress and inflammation. Carnitine might be able to increase free testosterone, as low carnitine is independently associated with free testosterone.


  • Might help build muscle
  • Improves fertility
  • Improves erections. People that don’t respond very well to Cialis or Viagra might benefit from adding an anti-oxidant such as acetyl-L-carnitine or propionyl-L-carnitine to their stack.
  • Improves insulin sensitivity
  • Enhances brain health

I personally don’t supplement with carnitine as I do get a lot from my diet (I regularly eat 500g of red meat daily). I have used it in the past to see how I would respond, but haven’t noticed anything.

Some people do have an increased requirement for carnitine despite eating a diet high in carnitine. This is likely due to impaired absorption or another genetic factor where they don’t synthesize enough.

Here you can see the amount of carnitine in various foods.

Interestingly, kangaroo meat (637 mg) and horse meat (423mg) are much higher than beef (139 mg per 100 g of dry weight) (R). The regular consumption of Kangaroo meat must be what’s giving the All Blacks rugby team the upper hand to win so many world championships. Jk everyone! 😀

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4 thoughts on “Acetyl-L-carnitine to maximize testosterone and erections”

    • Chris Masterjohn did a good writeup on TMAO and he’s only 3/10 concerned about it. I changed my mind on carnitine when I found out it actually lowers excessive fatty acid oxidation while restoring glucose oxidation.


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