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All drugs have a powerful impact on male fertility, and it’s easy to measure this with semen testing. They have such a significant effect because sperm and their DNA aren’t like normal cells. Sperm cells are tiny, and their DNA is on single (rather than double) helix strands which are much less stable in a vulnerable environment as they form in the testes.

Drugs are, by their very nature, chemicals that alter how the body works, and this can include sperm function and production. Some of the drugs not only affect sperm and a man’s fertility, but they can also affect the health of the baby. It’s worth remembering that many medications are essential for health, and there are possible severe consequences to stopping them. Therefore if you’re concerned about the prescription drugs you take, we strongly recommend discussing your concerns with your MD/GP.

Many commonly prescribed drugs have a significant but temporary effect on male fertility, and men can sometimes stop taking them, which results in: i

  • Improvements in semen quality by 93%
  • 85% of their partners became pregnant


It’s known that men with epilepsy are less fertile, which could be due to their medication more than their epilepsy. A study of men taking the anti-epileptic drugs carbamazepine, oxcarbazepine and valproate all had high levels of abnormal sperm. Men taking valproate also had smaller than normal testes, which reduced the number of sperm they produced. ii


Serotonin Re-uptake Inhibitors (SSRIs) such as Prozac and Seroxat are the most widely prescribed type of antidepressants. These are linked to problems with male sexual performance, and many men taking them experience:

  • A loss of sex drive
  • Inability to maintain an erection
  • Inability to ejaculate
  • A continuation of these issues after they’ve stopped taking the drugs

The sperm of men taking SSRIs look normal. However, research iii shows that after four weeks of taking them, the average DNA fragmentation levels rise from 13.8% to 30.3%. DNA fragmentation rates increase the chances of implantation failure, miscarriage or abnormalities in children. iv


Only 6% of male smokers produce normal sperm samples (compared to 37% of non-smoking, non-alcoholic men). Smoking cigarettes reduces both the number of normally shaped sperm a man produces, as well as their ability to swim forward. Unsurprisingly, the effect of smoking increases with the number of cigarettes smoked. v Additionally, when fathers smoke over 20 cigarettes a day, there’s a greater risk of their child having leukaemia. vi Smoking over 20 a day also shortens the reproductive life span of any daughters he has, compared to smoking less or not at all. vii

Drinking alcohol

Alcohol damages sperm and only 12% of alcoholic men produce normal sperm samples (compared to 37% of non-drinking, non-smoking men). Alcohol is a toxin, and it causes weight gain (especially abdominal fat), which raises a man’s estrogen levels. Drinking alcohol significantly reduces the:

  • The volume of semen samples
  • Sperm concentrations
  • Sperm numbers in samples
  • Percentages of normally shaped sperm
  • Sperm motility viii-ix

The man drinking alcohol also significantly increases the chances of his partner having a miscarriage, which is rather sobering.

Recreational drugs

Non-prescription drugs such as marijuana, amphetamines and cocaine have been linked to significant reductions in libido for many years. They may also diminish testosterone and luteinizing hormone (LH) levels, which are essential for healthy sperm production. There’s more information on drugs and fertility in the Lifestyle section.