The physician has several ways of diagnosing necrobiosis lipoidica diabeticorum (NLD) and ruling out other skin disorders associated with diabetes that may have similar symptoms. These methods include:

• Medical history. People with diabetes or a family history of the condition are at a higher risk of developing NLD than people with no personal or family history of diabetes.
  
  
• Physical examination. The presence of NLD may be apparent upon visual inspection. The physician will look for the characteristic lesions of the condition, such as yellowish lesions, skin damage and other symptoms.
  
  
• Biopsy. A tissue sample from the lesion may be examined to differentiate NLD lesions from other conditions such as granuloma annulare. A tiny sample may be drawn by a needle or scraped or sliced by a blade. If necessary, a larger sample may be taken in a punch biopsy using a small device to extract the skin sample. A punch biopsy may involve an injection of local anesthesia and stitches after the biopsy, in some cases.
  
  
• Glucose tests. The physician may check the patient’s level of glucose (blood sugar).