Primary care or Internal Medicine is typically the best first step because fatigue has many possible causes. After history and exam, clinicians often order baseline tests (CBC, ferritin/iron, B12/folate, TSH, glucose, kidney/liver markers). Based on results, you may be referred to cardiology (palpitations/shortness of breath), sleep clinic/pulmonology (snoring/daytime sleepiness), mental health care (anxiety/depression), rheumatology (inflammatory symptoms), or other specialties. The practical pathway: start with primary care/internal medicine, then targeted referral.