Generally, doctors can diagnose cellulitis by looking at or touching the area affected. However, sometimes they can request other tests:

  • Blood tests
  • Wound or skin culture; in rare instances, a skin biopsy may be warranted to identify an underlying skin condition
  • X-rays, ultrasound, CT, or MRI

Diagnostic Tests

Blood test

Blood tests can identify the kind of bacteria that are causing the infection. Blood tests can also show whether the infection has spread to the blood, which can potentially be a life-threatening occurrence.


A biopsy is an analysis of a tissue or fluid sample from the infected area. This test can rule out other skin disorders, so that patients are more likely to receive more effective treatment. Again, more commonly, a skin culture or fluid would be taken to test the infected area.

X-rays, ultrasound, CT or MRI

X-rays, ultrasound, CT scans, or MRI scans can show how far the infection has spread through the tissues.

How is cellulitis diagnosed?

Doctors can diagnose cellulitis by examining the area affected, generally simply by looking or touching the area. However, sometimes they may request further diagnostic tests, such as blood tests, a biopsy, x-ray, ultrasound, CT scans, or MRI scans.

These diagnostic tests can:

  1. provide more information about the kind of bacteria causing the infection,
  2. the extent of the infection, and
  3. can help rule out other conditions.

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