Blood in semen (hematospermia) can be frightening, but the vast majority of time, it's not cause for serious concern. Blood in semen is uncommon, and, most often, it goes away on its own.

Often, no cause can be found for blood in semen. For men under age 40, infection is the most common cause. Infection is usually accompanied by other signs and symptoms, such as fever, genital or urinary pain, difficulty urinating, or blood in your urine.

For men age 40 and older, blood in semen is a slight predictor of a cancer (malignancy), most often prostate cancer. So a more careful evaluation is merited when this sign appears in this age group. But the risk is low. In follow-up studies of more than 800 men who had blood in their semen, cancer was found in less than 4 percent (on average).

More common causes of blood in semen:

1. Brachytherapy
2. Chlamydia
3. Epididymitis
4. Genital herpes
5. Gonorrhea
6. Interrupted sex
7. Prolonged sexual abstinence
8. Prostate biopsy
9. Benign prostatic hyperplasia (BPH)
10. Prostatitis
11. Testicular trauma
12. Vasectomy
13. Vigorous sex

Less common causes

1. Amyloidosis
2. Benign growths (cysts, polyps) in the bladder, urethra or prostate
3. Prostatectomy
4. Fragile blood vessels
5. Hemophilia
6. Prostate cancer
7. Schistosomiasis
8. Testicular cancer
9. Thrombocytopenia
10. Tuberculosis
11. Von Willebrand disease
12. Warfarin side effects

Causes shown here are commonly associated with this symptom. Work with your doctor or other health care professional for an accurate diagnosis.

Source: mayoclinic.org

• You have no other symptoms
• You've had a recent prostate exam or vasectomy, which could explain short-term bleeding
• There isn't a lot of blood in the semen and it happens infrequently, then goes away

Make an appointment with your doctor if:

• You're 40 or older
• Blood in semen persists longer than three to four weeks
• You have other signs and symptoms, such as genital or urinary pain, pain during ejaculation, fever, difficulty urinating, or blood in your urine
• You have other risk factors, such as a history of cancer, bleeding disorders, trauma, or genital or urinary system malformation, or you've recently engaged in behaviors that put you at risk of sexually transmitted infections

Source: mayoclinic.org