To diagnose blood in the semen the doctor will take a complete medical history. That will include a history of any recent sexual activity. The doctor will also perform a physical examination. This will include examining the genitals for lumps or swelling and a digital rectal examination to check the prostate for swelling, tenderness and other symptoms. The doctor may also arrange the following tests:

Urinalysis or urine culture to identify infection or other abnormalities.
STI testing if a sexually transmitted infection is suspected.

The "condom test" if there’s a possibility that blood in the semen is actually coming from a sexual partner’s menstrual cycle. The man will be told to wear a condom and then examine the "protected" semen for blood.

PSA testing, to help determine prostate cancer by measuring a substance called prostate-specific antigen in the blood.

Other urological tests such as cystoscopy, ultrasound, CT and MRI to further evaluate the patient.