Most people are diagnosed with acid reflux or GORD by their GP, on the basis of their typical symptoms and their response to treatment. Further tests may be needed if:

• Symptoms are severe
• Symptoms do not improve with treatment
• Symptoms are not typical of GORD
• There are "flag symptoms" (e.g. difficulty swallowing, worsening symptoms, unexplained weight loss, chest pain or shortness of breath on exertion)

If further investigation is required a gastroscopy (also sometimes referred to as an "OGD") is usually the next step. This is where a thin, flexible telescope is passed down the oesophagus into the stomach. This can help to rule out more serious causes of reflux symptoms, particularly stomach cancer.