: Sputum Gram Stain

: What This Test Is

: A sputum Gram stain is a microscopy test performed on a sample of sputum, the thick mucus brought up from the lungs and airways when you cough deeply. A laboratory professional places the sample on a glass slide, applies special stains, and examines it under a microscope to look for bacteria and to see how they react to the stain.

: Why It Is Ordered

: Your healthcare provider may order a sputum Gram stain when you have symptoms of a respiratory infection such as a persistent cough, fever, chest discomfort, or coughing up colored mucus. The test can help confirm that an infection is present and provide early information about the general type of bacteria involved.

: How the Sample Is Collected

: You will usually be asked to cough deeply and spit the mucus into a sterile container. In some cases a healthcare professional may help collect the sample. Collecting a good-quality specimen from deep in the airways, rather than saliva from the mouth, is important for accurate results. Follow any instructions you are given about rinsing your mouth or timing the collection.

: How to Understand the Results

: The report describes whether bacteria were seen, their shape and staining characteristics, and the presence of other cells such as white blood cells. These findings are interpreted together with your symptoms and other tests. A Gram stain alone does not identify a specific organism or determine antibiotic susceptibility, so it is often paired with a sputum culture. Ask your provider to explain what your results mean for your care.