Indigestion, also known as dyspepsia, is a condition of impaired digestion. Symptoms may include upper abdominal fullness, heartburn, nausea, belching, or upper abdominal pain. People may also experience feeling full earlier than expected when eating. Dyspepsia is a common problem and is frequently caused by gastroesophageal reflux disease (GERD) or gastritis. In a small minority of cases it may be the first symptom of peptic ulcer disease (an ulcer of the stomach or duodenum) and, occasionally, cancer. Hence, unexplained newly onset dyspepsia in people over 55 or the presence of other alarming symptoms may require further investigations.
Functional indigestion (previously called nonulcer dyspepsia) is indigestion "without evidence of an organic disease that is likely to explain the symptoms". Functional indigestion is estimated to affect about 15% of the general population in western countries.
As an indication, the market for indigestion remedies in the UK in 1986 was £28.4 million.