The full answer
Testing becomes unreliable once gluten is removed
Both blood tests and biopsies rely on the immune system actively reacting to gluten — once someone has been gluten-free for even a few weeks, antibody levels can drop and intestinal damage can begin healing, making both tests likely to come back falsely normal even if celiac disease is present.
The gluten challenge is the way around this
If someone has already gone gluten-free before testing, doctors may recommend a supervised gluten challenge — deliberately reintroducing gluten for a set period before retesting — to get an accurate result.
Important context
Individual symptoms, reactions, medical histories, food products, and local labeling rules can vary. Community experiences are not medical evidence.
For personal medical decisions, diagnosis, testing, or treatment, consult a qualified healthcare professional.