The Direct Answer: No Evidence of Semen Colour Change

There is no scientific evidence or clinical reporting that GLP-1 medications like Mounjaro (tirzepatide) or Wegovy (semaglutide) cause semen colour changes. This side effect does not appear in FDA adverse event databases, clinical trials, or medical literature.​

What research does show is that GLP-1 medications can significantly improve semen quality and sperm health—a positive effect often overlooked.​

What Actually Happens to Semen on GLP-1 Medications

Improved Sperm Parameters Through Weight Loss

Men using GLP-1 medications for obesity experience remarkable improvements in sperm health:

Sperm concentration: Increased approximately 1.71-fold after weight loss​

Total sperm count: Increased 1.41-fold after sustained weight loss​

Sperm motility: Improved significantly with better swimming ability​

Sperm morphology: Higher percentage of normally shaped sperm​

Sperm DNA fragmentation: Decreased by approximately 2.5%, reducing genetic damage​

These improvements correlate directly with weight loss achievement, particularly when men maintain at least 12 kg weight loss.​

Why This Happens: The Obesity-Fertility Connection

Obesity causes:

GLP-1 medications reverse these mechanisms by promoting weight loss and improving metabolic health.​

Direct Effects on Testosterone and Fertility

Testosterone levels: Increase significantly with GLP-1 treatment in obese men, with liraglutide showing +46% testosterone increase in one clinical trial​

Sperm production: Liraglutide improved sperm concentration from ~6 million/mL to 16 million/mL (nearly tripling sperm counts) in infertile men​

Erectile function: Improvements tracked via standardized sexual function questionnaires (IIEF-5), with GLP-1 users showing better erectile performance​

FDA safety analysis: Among millions of GLP-1 users, only 182 reports of sexual dysfunction occurred from 2003-2024, indicating a reporting odds ratio below 1—meaning sexual dysfunction was less common than expected statistically.​

Semen Colour: What's Normal

Normal semen colour ranges from white to translucent grey, varying based on:

Abnormal colours requiring evaluation:

GLP-1 medications do not alter pigmentation or cause discolouration.​

Important Fertility Consideration

Critical warning: Discontinue GLP-1 medications at least 2-3 months before attempting conception. However, the fertility improvements from weight loss often persist even after discontinuation if weight loss is maintained.​

Bottom Line

GLP-1 medications do not cause semen colour changes. Instead, they improve male fertility through weight loss-induced improvements in sperm concentration, motility, morphology, and testosterone levels. For obese or diabetic men with fertility concerns, GLP-1 medications represent a potentially beneficial treatment strategy that addresses underlying metabolic dysfunction rather than harming reproductive health.​

If you notice actual semen colour changes while on GLP-1 medication, this likely reflects an unrelated medical condition requiring urological evaluation—not a medication effect.​

  1. https://mensreproductivehealth.com/glp-1-agonists-in-men-effects-on-testosterone-sperm-and-sexual-function/
  2. https://www.mensreproductivehealth.com/post/glp-1-agonists-in-men-effects-on-testosterone-sperm-and-sexual-function
  3. https://www.sciencedirect.com/science/article/pii/S2772973725007076
  4. https://pmc.ncbi.nlm.nih.gov/articles/PMC10820247/
  5. https://www.ics.org/2025/abstract/166
  6. https://www.givelegacy.com/resources/semaglutide-weight-loss-medications-ozempic-wegovy-mounjaro-sperm-health/
  7. https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2024.1496416/full
  8. https://www.jackfertility.co.uk/post/can-ozempic-affect-your-sperm-the-truth-about-glp-1s-and-male-fertility
  9. https://www.conceivio.com/resources/can-weight-loss-drugs-affect-male-fertility
  10. https://onlinedoctor.superdrug.com/glp-1-medications-for-weight-loss.html

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