The mainstays of lactose intolerance diagnosis in adults are dietary history and the lactose breath test (LBT).[1] Infants suspected of having congenital lactase deficiency (CLD) who respond well to elimination of dietary lactose should have genetic testing for mutations in the LCT gene.[1]
How is lactose intolerance diagnosed?
Written by:
Fact-checked
by:
•Last Updated: May 16, 2025
Lactose intolerance in adults is primarily diagnosed through dietary history and the lactose breath test. For infants who are suspected of congenital lactase deficiency, genetic testing for mutations in the LCT gene is recommended if they respond well to lactose elimination.