BACKGROUND: A gluten-free diet is the only available treatment for celiac disease. Our aim was to investigate the effect of a gluten-free diet on celiac disease related symptoms, health care consumption, and the risk of developing associated immune-mediated diseases. METHODS: A questionnaire was sent to 1,560 randomly selected members of the Swedish Society for Coeliacs, divided into equal-sized age- and sex strata; 1,031 (66%) responded. Self-reported symptoms, health care consumption (measured by health care visits and hospitalization days), and missed working days were reported both for the year prior to diagnosis (normal diet) and the year prior to receiving the questionnaire while undergoing treatment with a gluten-free diet. Associated immune-mediated diseases (diabetes mellitus type 1, rheumatic disease, thyroid disease, vitiligo, alopecia areata and inflammatory bowel disease) were self-reported including the year of diagnosis. RESULTS: All investigated symptoms except joint pain improved after diagnosis and initiated gluten-free diet. Both health care consumption and missed working days decreased. Associated immune-mediated diseases were diagnosed equally often before and after celiac disease diagnosis. CONCLUSIONS: Initiated treatment with a gluten-free diet improves the situation for celiac disease patients in terms of reduced symptoms and health care consumption. An earlier celiac disease diagnosis is therefore of great importance.