Dads-to-be: can using illegal drugs affect my fertility?

Hamed Al-Taher

Obstetrician and gynaecologist

There hasn't been much research into illegal drugs and fertility. But what little we do know suggests that certain drugs can make it more difficult to conceive. Here's what the evidence says about the three most common illegal drugs:

  • Cannabis. Also known as marijuana and weed, cannabis has been shown to affect fertility in men. Heavy use can decrease your testosterone levels, making you produce less sperm. THC (tetrahydrocannabinol), the active ingredient in cannabis, may also make your sperm move more slowly, so they're less able to reach and fertilise your partner's egg.
  • Cocaine. Cocaine use has been linked to reduced sperm counts and poorer quality sperm. Long-term users may also have problems getting or maintaining an erection.
  • Ecstasy. There has been little research into ecstasy use and fertility in humans. However, animal studies suggest that it can damage the DNA in sperm. This can make it more difficult to conceive in couples with existing fertility issues, and has also been linked with higher rates of miscarriage and birth defects.

Other drugs may also have an effect on your fertility, so if you're having trouble conceiving, it's always worth telling your GP about anything you're taking. He won't judge you, but will give you confidential advice and support. Your GP can also help if you're having any problems with cutting down or quitting.

For more information and help with tackling a drug habit, contact

Also discover which prescription drugs may affect your fertility.

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