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Gram stain of urethral discharge

A Gram stain of urethral discharge is a test used to identify bacteria in fluid from the tube that drains urine from the bladder (urethra).

How the Test is Performed

Fluid from the urethra is collected on a cotton swab. A sample from this swab is applied in a very thin layer to a microscope slide. A series of stains called a Gram stain is applied to the specimen.

The stained smear is then examined under the microscope for the presence of bacteria. The color, size, and shape of the cells help identify the type of bacteria causing the infection.

How to Prepare for the Test

This test is often performed in the health care provider's office.

How the Test will Feel

You may feel pressure or burning when the cotton swab touches the urethra.

Why the Test is Performed

The test is performed when an abnormal urethral discharge is present. It may be performed if a sexually transmitted disease is suspected.

Normal Results

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

Abnormal results may indicate gonorrhea or other infections.


There are no risks.


A culture of the specimen (urethral discharge culture) should be performed in addition to the gram stain. More sophisticated diagnostic tests (such as PCR tests) are sometimes also done.

Alternative Names

Urethral discharge Gram stain


Augenbraum MH, McCormack WM. Urethritis. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 109.

Cohen MS. Approach to the patient with a sexually transmitted disease. In: Goldman L, Ausiello D, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 293.

Update Date 12/2/2014

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