Why do I get stomach pain after eating gluten?

Stomach pain after gluten has three main explanations, and sorting them matters because one of them is a lifelong autoimmune disease. Celiac disease: gluten triggers an immune attack on the small intestine lining - NIDDK lists belly pain, bloating, diarrhea or constipation, plus the quieter signs: iron-deficiency anemia, fatigue, mouth ulcers, and weight loss. It affects about 1 in 100 people, runs in families, and does real cumulative damage untreated. Non-celiac gluten sensitivity: real symptoms after wheat, negative celiac tests, no intestinal damage - a diagnosis of exclusion. And coincidence: wheat-based meals are often big, fast, and fatty, and indigestion or IBS gets blamed on the gluten. The rule everyone gets wrong: do not go gluten-free before testing. Celiac blood tests and biopsy only detect the disease while gluten is still in your diet - quit first and the tests come back falsely clean, leaving you in diagnostic limbo. The right order: note the pattern, book the blood test, keep eating gluten until it is done. If celiac is excluded and symptoms persist, a structured trial of gluten-free eating with your provider or dietitian is reasonable, and FODMAPs - the fermentable carbs in wheat itself - are often the real culprit in the sensitivity group. Pain with blood in the stool, weight loss, or anemia symptoms moves everything faster. Pymander is a free AI doctor, 24/7 by text. Describe the pattern, and it can help you plan the test before you change your diet.