Fructose intolerance is a hereditary disorder, in which affected persons develop hypoglycaemia (low blood sugar) and severe abdominal symptoms after taking foods containing fructose and cognate sugars. Continued ingestion of noxious sugars leads to hepatic and renal injury and growth retardation. The severity of clinical expression correlates well with the age, culture, and eating habits of affected subjects. It is absolutely different from glucose intolerance, where blood sugar is high.
Excess alcohol intake may cause low sugar in a diabetic if drugs are taken and food is not taken properly. It does not cause IBS.