Hereditary fructose intolerance (HFI) is an under-recognized, preventable life-threatening condition. It is an autosomal recessive disorder with subnormal activity of aldolase B in the liver, kidney and small bowel. Symptoms are present only after the ingestion of fructose, which leads to brisk hypoglycemia, and an individual with continued ingestion will exhibit vomiting, abdominal pain, failure to thrive, and renal and liver failure. A diagnosis of HFI was made in a 50-year-old woman on the basis of medical history, response to IV fructose intolerance test, demonstration of aldolase B activity reduction in duodenal biopsy, and molecular analysis of leukocyte DNA by PCR showed homozygosity for two doses of mutant gene. HFI may remain undiagnosed until adult life and may lead to disastrous complications following inadvertent fructose or sorbitol infusion. Several lethal episodes of HFI following sorbitol and fructose infusion have been reported. The diagnosis can only be suspected by taking a careful dietary history, and this can present serious complications.