The U.S. Centers for Disease Control and Prevention (CDC) has noted that there is no gold standard for diagnosing acanthosis nigricans (AN). In diagnosing this condition, a physician will perform a complete physical examination. AN may be apparent on visual inspection.

In addition, the physician will compile a thorough medical history, including a family history. People who have relatives with type 2 diabetes (condition characterized by the body’s inability to use the hormone insulin effectively) tend to be more prone to AN.

Other methods a physician may use to examine a patient for AN include:

• Blood tests. An elevated fasting blood insulin (hormone that regulates blood sugar) level suggests the hyperinsulinemia (accumulation of insulin) that is usually present in AN. Results of blood glucose tests are often normal in people with insulin resistance.
  
  
• Biopsy. Sometimes a small tissue sample may be taken and examined under a microscope to rule out other skin conditions.

When AN is diagnosed, the possibility of prediabetes or diabetes should be investigated.