Semen consists of sperm and fluids released by the prostate and other glands. The fluids, also called ejaculate, join the sperm as they pass through a series of tubes to the urethra for ejaculation. A number of things can break blood vessels along this route or along the urinary route to the urethra. Broken vessels then leak blood into the semen, urine or both.

Your doctor will ask if you've had prostate surgery or a prostate biopsy recently, since these procedures can cause blood in semen for several weeks afterward.

Most often, no cause can be found for blood in semen. In some cases, particularly among men under age 40, infection is a possible cause. Infection is usually accompanied by other signs and symptoms, such as painful urination.

Severe or recurrent blood in semen and blood in semen in men age 40 and older might, in rare cases, be a warning sign for conditions such as cancer. As a result, a more careful evaluation might be needed. But the risk is low. In follow-up studies of men, mostly over 40, who had blood in their semen, prostate cancer developed in between 4 and 6 percent of participants.

Possible causes of blood in semen:

• Brachytherapy
• Chlamydia trachomatis
• Epididymitis (When the coiled tube at the back of the testicle becomes inflamed.)
• Excessive sexual activity or masturbation
• External beam radiation for prostate cancer
• Genital herpes
• Gonorrhea
• Hemophilia
• Orchitis (A condition in which one or both testicles become inflamed.)
• Prolonged sexual abstinence
• Prostate biopsy
• Prostate cancer
• Prostatitis (Infection or inflammation of the prostate.)
• Testicular trauma
• Vasectomy

Rare causes of blood in semen:

• Amyloidosis (buildup of abnormal proteins in your organs)
• Benign growths (cysts, polyps) in the bladder, urethra or prostate
• Schistosomiasis
• Testicular cancer (Cancer that starts in the testicles.)
• Tuberculosis
• Warfarin side effects

Blood in semen (hematospermia) can be frightening, but the cause of this uncommon condition is usually benign. Typically, blood in semen goes away on its own.

If you're under age 40 and see blood in your semen, chances are it will resolve without treatment. However, it's a good idea to make an appointment with your doctor for a physical exam and simple tests to rule out a cause, such as a sexually transmitted infection.

If you have certain risk factors and symptoms, further testing may be necessary to rule out a more serious underlying disorder. Call your doctor about blood in semen if you:

• Are 40 or older
• Have blood in semen that persists longer than three to four weeks
• Have repeatedly recurring blood in semen
• Have other symptoms, such as painful urination
• Have other risk factors — such as a history of cancer, bleeding disorders, or genital or urinary system malformation — or have recently engaged in behaviors that put you at risk of sexually transmitted infections