What causes a fishy odor in semen?

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Last updated: March 5, 2025View editorial policy

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Differential Diagnosis for Semen Smelling Fishy

  • Single Most Likely Diagnosis
    • Bacterial vaginosis or other infections in the partner: This is often associated with a fishy odor in the semen after ejaculation, due to the exchange of bodily fluids during sexual intercourse.
  • Other Likely Diagnoses
    • Urinary tract infection (UTI): A UTI can cause a strong, unpleasant odor in the urine and semen.
    • Prostatitis: Inflammation of the prostate gland can lead to changes in semen odor, including a fishy smell.
    • Epididymitis: Inflammation of the epididymis, a tube at the back of the testicle that stores and carries sperm, can cause changes in semen odor.
    • Poor hygiene: Infrequent showering or bathing, especially after engaging in sexual activity, can contribute to a fishy odor in the semen.
  • Do Not Miss Diagnoses
    • Sexually transmitted infections (STIs) such as gonorrhea or chlamydia: These infections can cause changes in semen odor and are important to diagnose and treat to prevent long-term complications.
    • Diabetes: Uncontrolled diabetes can lead to changes in bodily fluids, including semen, which may result in a strong, unpleasant odor.
  • Rare Diagnoses
    • Maple syrup urine disease (MSUD): A rare genetic disorder that can cause a sweet, maple syrup-like odor in urine and semen.
    • Trimethylaminuria: A rare genetic disorder that affects the body's ability to break down trimethylamine, a compound found in certain foods, which can cause a strong, fishy odor in bodily fluids, including semen.
    • Certain medications: Some medications, such as those used to treat cancer or HIV, can cause changes in semen odor as a side effect.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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