Test guide
Gram Stain
A Gram stain is a test that checks to see if you have a bacterial infection . A sample is taken from the site of a suspected infection, such as your throat, lungs, genitals, or a skin wound . Gram stains may also be used to check for bacteria in certain body fluids, such as blood or urine.
What it is for
A Gram stain is most often used to find out if you have a bacterial infection. If you do, the test will show whether the bacteria in your infection is Gram-positive or Gram-negative. This may help your provider decide what other tests are needed to help identify which bacteria are causing your infection and how to treat it. A Gram stain may also be used to diagnose fungal infections . Source: MedlinePlus, National Library of Medicine. Medical test information is public domain. Source identity and definition checked automatically on 2026-10-18. No individual clinical interpretation or human reviewer is asserted.
Limitations
Reference intervals and interpretation depend on the laboratory, specimen, method and clinical context. This source definition is educational information; it does not establish a diagnosis, product approval or suitability for an individual.
Also known as
- Gram's stain
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