Cannabis Science

Does Weed Kill Sperm?

fruit and sperm going towards it

Smoking a blunt is often linked to being horny and enhancing sexual experiences for some people. However, weed may cause fertility problems for stoners. We know that weed should be avoided during pregnancy.  However, smoking could affect the paternal parent too. There is evidence that smoking cigarettes affect semen and sperm. Since there are similar components in both weed and cigarette smoke, could weed affect sperm and semen? Does weed kill sperm? 

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Does Smoking Weed Kill Sperm? 


According to a study done, people who use weed have lower sperm concentrations than non-users. 

THC seems to be the culprit. The study found that when a greater concentration of THC was found in urine, there were more pronounced genetic changes to the sperm.

With the amount of THC in weed higher than it used to be, this is concerning. 

In addition to that, THC seems to alter DNA methylation. Cells use DNA methylation to control gene expression. The study says, “If sustained, the changes in DNA methylation could increase risk of later cancer development”. However, this claim was only speculative. 

The researchers are also uncertain if these changes will be passed on to the offspring. According to Susan Murphy, Ph.D, the lead researcher, it’s unknown whether or not the sperm affected by THC is healthy enough to fertilize an egg and continue developing into an embryo. 

However, Dr. Nelson Bennett, MD, FACS and Associate Professor of Urology at Northwestern Medicine, tells Men’s Health that research is pointing to these changes as being permanent. 

Other Studies On Marijuana and Sperm

While the study we mentioned above is really small, there have been a number of other studies suggesting that weed affects sperms negatively. 

According to 1979 report, there was a significant decline in sperm concentration and total sperm count after marijuana exposure. The study recorded these results after the 5th or 6th week of exposure to cannabis.

A UK study reported that poor sperm morphology was associated with cannabis use. Sperm morphology refers to the size and shape of sperm. Poor sperm morphology was seen in men aged 30 and under, who reported use of cannabis in the 3 months prior to sample collection.

A Danish study revealed that using weed was associated with lower sperm count. The study said, “Regular marijuana smoking more than once per week was associated with a 28% lower sperm concentration and a 29% lower total sperm count (after adjustment for confounders).

Does Weed Affect Fertility In Other Ways? 

According to Harvard Health Publishing, marijuana may cause:

  • Inability to perform sexually
  • Diminished fertility
  • Increased levels of female hormones in men
  • Development of abnormally shaped sperm

Using weed may also be linked to lower testosterone levels

Ways To Boost Male Fertility 

There are steps you can take to boost your fertility as a stoner.

For example, Murphy suggests taking a cannabis break for 6 months before trying to conceive. 

In addition to that, since THC seems to be the culprit, maybe opting for weed with lower levels of THC could help. 

Healthline also offers some tips on improving fertility in men:

  • Consider taking D-aspartic acid supplements to increase testosterone levels. 
  • Exercise on a regular basis for better sperm quality and an increase in testosterone. 
  • Take a vitamin C supplement to improve sperm count, sperm motility and reduce the impact of reactive oxygen species.
  • Get some sun or take a vitamin D supplement. Vitamin D can improve testosterone levels. 
  • Reduce stress and anxiety. Lower levels of testosterone may be a result of high stress. You can work on stress management through meditation. You can also deal with anxiety with medication, therapy, or both. 
  • Take Tribulus terrestris. It’s a medicinal herb that may improve erectile function and libido.
  • Stock up on zinc. People low in zinc can increase testosterone levels and sperm count with zinc supplements. 
  • Limit the amount of soy you eat. Soy may cause lower semen quality.


Research indicates that weed impacts male fertility negatively. Smoking weed may result in lower sperm concentration. So by that logic, weed does kill sperm. THC seems to be the cannabinoid responsible for the negative effects. With the potency of weed increasing over the years, this is definitely something to pay attention to. At the same time, there are ways to boost fertility in men such as taking a break for a few months before trying to conceive. Having a conversation with your doctor is always a great idea. 


About Trevann

Trevann is Stoner Rotation’s Jamaica-based lead writer for the Science section of our cannabis blog. She graduated with honors receiving her Bachelor of Science degree in Molecular Biology from the University of West Indies, Mona. For the last three years, she has covered some of the biggest questions around cannabis and health underpinned with research from supporting studies, medical journals and scholarly articles. Got something on your mind? You can reach her at [email protected].