Allergies to gluten are relatively common. According to studies, one in 167 seemingly healthy children and one in 111 adults have some type of allergy to gluten. Celiac disease, one of the more severe and common gluten allergies, is said to affect one in every 100 people, with an increased risk for those who have a family member diagnosed with the disease. Gluten allergy symptoms and the severity and frequency of these symptoms can range dramatically in different people. Therefore, making a diagnosis of this allergy can be difficult and is often missed.

Some people suffer for many years from gluten allergies before a diagnosis is made. Most doctors have to see severe gastrointestinal problems before they'll consider ordering an intestinal biopsy to diagnose celiac disease. An intestinal biopsy, considered the "gold standard" for diagnosing celiac disease, is a procedure that involves placing a camera into the digestive tract and taking a sample of the small intestine to send for a biopsy. Celiac disease is diagnosed based on the biopsy of the intestine, and it is determined by the presence of damage to the villi (finger-like hairs that absorb nutrients in the small intestines). However, not all people with gluten allergies, or even celiac disease, will present with gastrointestinal symptoms.

Other tests to determine an allergy to gluten include a range of blood tests to measure the levels of antibodies to gluten. These tests include the anti-tissue transglutaminase Antibody (tTG) test, the anti-gliadin antibodies (AGA) test, the anti-endomysial antibodies (EMA) test, and the anti-reticulin antibodies (ARA) test. These tests vary in their reliability and sensitivity to detecting gluten allergies and will often be accompanied by a full blood count to check for other possible symptoms, such as anemia, electrolytes, renal function and liver enzymes.