Could taking paracetamol impair male fertility?


LIFE research

The National Institutes of Health has conducted a long-term study in the United States called the Longitudinal Investigation of Fertility and the Environment (LIFE). This research has been investigating fertility data associated with 501 couples from Texas and Michigan. The study was conducted between 2005 and 2009. Now researchers have began analyzing this data and publishing their findings.

One area of investigation has focused on a potential link between reduced male fertility and high levels of urinary paracetamol (acetaminophen)1. This preliminary study assessed whether taking paracetamol could influence the time it takes for couples to conceive.  Although more research is necessary, the preliminary findings highlight the influence of lifestyle and environmental chemical exposure on reproductive health.

What is paracetamol?

Paracetamol is also known as acetaminophen and sometimes branded as Tylenol. This non-prescription drug is widely used to reduce fever and offer pain relief.  Acetaminophen is also produced when the body processes aniline2. This compound is widely used in colouring agents, pesticides, rubber, food, clothing and cosmetics. People are regularly exposed to aniline through both occupational and environmental sources.  The more frequent the exposure to aniline, the higher the concentration of acetaminophen in the body.

The LIFE findings

Women and men aged over the age of 18 participated in the study. Each member provided a single urine sample at the start of the LIFE project. As part of the urinary analysis, acetaminophen concentrations were measured.

The researchers found that overall women had more than double the concentration of acetaminophen in their urine. Women averaged 26.6 ng/mL of acetaminophen compared with men who average 13.2 ng/mL.  However, this high level of acetaminophen did not reduce the female partner’s ability to conceive.

Conversely, couples in which the male partner had very high concentrations of acetaminophen (over 73.5 ng/ml) were less likely to conceive by 35% compared with couples where the male had low levels of acetaminophen (less than 5.4 ng/ml.). These findings suggest that paracetamol may negatively impact male reproductive health.

How does paracetamol negatively influence male fertility?

Several studies have looked at the effects of administration of analgesics on sperm quality. Researchers have found that analgesics such as paracetamol can cause sperm head abnormalities3, 4. Although the direct cause is still to be confirmed, it’s believed that it stems from genetic, cytotoxic and/or physiological mechanisms. Alterations in testicular DNA and spermogenesis due to chemical exposure may account for the structural and functional impairment of sperm cells. Consequently, overall male fertility is impaired.

Should men avoid analgesics such as paracetamol?

The short answer is no. The high levels of paracetamol found in the urine of study participants cannot be attributed to paracetamol consumption alone. Instead, these high concentrations are more consistent with environmental exposure to aniline and/or paracetamol.

However, these findings may provide a starting point to determine the baseline of acceptable paracetamol exposure. Much larger studies are required before any conclusions can be drawn. It’s also important to note that these findings were based on a single urine sample from each participant. For stronger statistical meaning several samples would be required for analysis.

Nevertheless, this study does highlight that the regular consumption of socially acceptable medications can pose health risks. Analgesics should be used sparingly. Not only may they negatively impact reproductive health, they also have implications for kidney and liver function.


  1. “Smarr, M. et al. (2016).Urinary paracetamol and time-to-pregnancy. Human Reproduction. Published online July 13, 2016 doi: 10.1093/humrep/dew172.”
  2. Modick, H. et. al.  (2014). Ubiquitous presence of paracetamol in human urine: sources and implications. Reproduction. Volume 147, Issue 4.”
  3. “Lister, C. and McLean, A. (1997). Inhibition of DNA synthesis by paracetamol in different tissues of the rat in vivo. Toxicology. Volume 116, Issues 1-3, (pp. 49-57).”
  4. “Ekaluo, U. et al. (2005). Comparative toxicity of five commonly used analgesics on sperm count and sperm head abnormalities. Global Journal of Pure and Applied Sciences. Volume 11, (pp. 81-84).”
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