Boils - Diagnosing boils and carbuncles

Your GP will usually be able to diagnose a boil or carbuncle by examining it.

Further testing is usually only required if you have:

• a boil or carbuncle that doesn't respond to treatment – it may be caused by bacteria other than staph bacteria
• multiple boils or carbuncles
• a weakened immune system caused by a condition such as diabetes, or if you're having a treatment such as chemotherapy

In these circumstances, your GP will probably use a cotton swab to take a tissue sample from the boil so it can be examined under a microscope.

You may also be referred for a blood test to see if you have an undiagnosed underlying health condition, such as diabetes, which could be increasing your risk of developing boils and carbuncles.