L-carnitine, Antioxidants & Male Infertility

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What you will learn

How long and how much L-carnitine a man needs to take to improve the quality of his sperm

Why you need to take vitamin E with it

There are several studies that have shown the positive effect of L-carnitine supplementation in men with sub-fertility problems. 

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In 2003, Lenzi and colleagues found that 2g per day of L-carnitine could improve sperm motility and concentration within as little as two months1.

During this placebo-controlled, double-blind crossover trial, 100 participants aged between 20 and 40 underwent L-carnitine/placebo therapy. The study involved two months of therapy/placebo, followed by two months of washout before another two months of crossover placebo/therapy.

There was a statically significant improvement in forward sperm motility, especially in men with lower baseline levels.

Early studies have supported the findings of Lenzi and colleagues, although using slightly higher doses of L-carnitine. Vitali and colleagues found that sperm count and motility could be improved in 79% of patients treated with 3g of L-carnitine over three months2.


In a four month study by Costa and associates, sperm count increased by 15% and sperm motility by 40% in patients administered 3g of L-carnitine daily3.

antioxidants protect sperm cells

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This enzyme reduces oxidative stress which can lead to infertility.

Given the importance of antioxidants in reducing free radical induced oxidation, it’s reasonable to anticipate an improvement in fertility associated with higher antioxidant concentrations.

Wang and associates investigated the effects of L-carnitine supplementation together with vitamin E4. A potent antioxidant, it was expected that together with L-carnitine, male fertility would significantly improve.

During this three month trial, 135 infertile males were randomly separated into two groups, one receiving 2g L-carnitine and vitamin E per day, the other only receiving vitamin E.  Sperm motility was found to increase by 59% in men taking the L-carnitine and vitamin E combination.

However, there were no changes in density and morphology. Subsequent pregnancy rates were much higher in association with men treated with both L-carnitine and vitamin E, compared with those only taking vitamin E.


L-carnitine supplementation in association with vitamin E may help infertile men improve sperm health. Although the results are not instantaneous, daily supplementation over several months has been proven effective. 

Male fertility supplements are a popular method to ensure availability of the rights in the male system to ensure optimal sperm production. However, these supplements differ significantly in their price and quality. Menfertility.org has carefully compared the ten most popular male fertility supplements in the UK marketplace:



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Related studies:

  1. Lenzi A, Lombardo F, Sgrò P, Salacone P, Caponecchia L, Dondero F, Gandini L. Use of carnitine therapy in selected cases of male factor infertility: a double-blind crossover trial. Fertility and Sterility. 2003. 79(2): 292-300
  2. Vitali G, Parente R, Melotti C. Carnitine supplementation in human idiopathic asthenospermia: clinical results. Drugs Under Experimental and Clinical Research. 1995. 21(4): 157-9
  3. Costa M, Canale D, Filicori M, D’lddio S, Lenzi A. L-carnitine in idiopathic asthenozoospermia: a multicenter study. Italian Study Group on Carnitine and Male Infertility. Andrologia. 1994. 26(3): 155-9
  4. Wang YX, Yang SW, Qu CB, Huo HX, Li W, Li JD, Chang XL, Cai GZ. L-carnitine: safe and effective for asthenozoospermia. Zhonghua Nan Ke Xue. 2010. 16(5): 420-2
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