Sometimes, no cause can be found. Prevention is related to the cause. For instance, avoiding drugs known to cause a loss of appetite can prevent cases due to drugs. Proper control of diabetes can prevent cases due to this cause. Many cases cannot be prevented.
Diagnosis starts with a history and physical exam.
This may be all that is needed to make the diagnosis. In other cases, further tests will be needed. The specific tests ordered depend on the suspected cause. For instance, blood tests can help diagnose diabetes, hormone imbalances, and liver disease. Urine tests can help diagnose kidney infections or pregnancy.