What initial assessments should I perform for a patient presenting with chronic fatigue to rule out underlying medical conditions?

For a patient presenting with chronic fatigue, initial assessments should include:

• A thorough medical assessment covering symptoms, history, comorbidities, and overall physical and mental health.
• A physical examination to identify any clinical signs that may indicate underlying conditions.
• Investigations to exclude other diagnoses, including but not limited to: urinalysis (for protein, blood, glucose), full blood count, urea and electrolytes, liver function tests, thyroid function tests, erythrocyte sedimentation rate or plasma viscosity, C-reactive protein, calcium and phosphate, HbA1c, serum ferritin, coeliac screening, and creatine kinase.
• Use clinical judgement to consider additional tests such as vitamin D, vitamin B12 and folate levels, serological tests if there is a history of infection, and 9am cortisol for adrenal insufficiency.

These assessments help exclude other medical conditions that could explain the fatigue before considering diagnoses like ME/CFS.