Your primary care doctor is the starting line. They can order the initial blood work at any standard lab, like Quest or LabCorp. If you need a gastroenterologist for the endoscopy, they’re typically covered by insurance if your blood test is positive or if symptoms are severe.
Some people try at-home test kits, but these are not a replacement for a doctor’s evaluation. Home kits only check blood antibodies (and you still need to be eating gluten). Plus, they don’t include the biopsy, which is crucial for a definitive diagnosis.