Lactose intolerance in adults can be diagnosed by a careful dietary history. Keeping a written record of both food and digestive symptoms can reveal a relationship between lactose-containing foods and symptoms. The digestive symptoms of lactose intolerance usually develop 20 minutes to two hours after consuming lactose.[1]
How is a dietary history used for diagnosing lactose intolerance?
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•Last Updated: May 16, 2025
A careful dietary history, including a written record of food intake and digestive symptoms, can help diagnose lactose intolerance by identifying a correlation between lactose-containing foods and symptoms. Symptoms typically arise 20 minutes to 2 hours after consuming lactose.