Prostatitis: This is often the most common cause of hematospermia (blood in semen), especially in younger men. Prostatitis, which is inflammation of the prostate gland, can cause bleeding into the semen.

Benign Prostatic Hyperplasia (BPH): Enlargement of the prostate gland can lead to bleeding into the semen due to the increased vascularity and potential for minor trauma during ejaculation.
Urethritis: Inflammation of the urethra can cause bleeding, which may then appear in the semen.
Seminal Vesiculitis: Inflammation of the seminal vesicles can lead to hematospermia.

Prostate Cancer: Although less common, prostate cancer can cause bleeding into the semen. It is crucial to rule out this potentially life-threatening condition.
Testicular Cancer: Though rare, testicular cancer can also lead to hematospermia and must be considered to ensure timely diagnosis and treatment.
Urethral or Bladder Cancer: These cancers can also cause bleeding that appears in the semen and are critical to diagnose early.

Ejaculatory Duct Obstruction: This condition can lead to hematospermia due to the potential for bleeding from the obstruction site.
Amyloidosis: A rare condition where abnormal proteins (amyloid) accumulate in various organs, including the prostate and seminal vesicles, potentially causing bleeding.
Vascular Malformations: Rare vascular abnormalities in the genital area can lead to bleeding into the semen.
Infections (e.g., Tuberculosis, Schistosomiasis): Certain infections, though uncommon in many parts of the world, can cause inflammation and bleeding in the genital tract, leading to hematospermia.