People with lactose intolerance experience digestive symptoms due to intestinal bacteria consuming the undigested lactose. Symptoms vary widely from person to person, and can include flatulence and bloating (from the excess gas produced by intestinal bacteria), borborygmus (a delightful word that refers to tummy rumbling from gas and liquid sloshing around), diarrhea (caused by osmotic pressure due to undigested lactose), abdominal pain, and nausea. Symptom onset is usually 30 minutes to 2 hours after ingesting lactose.[1]
What are the main signs and symptoms of lactose intolerance?
Written by:
Fact-checked
by:
•Last Updated: May 16, 2025
Lactose intolerance leads to various digestive symptoms, including flatulence, bloating, borborygmus, diarrhea, abdominal pain, and nausea, which typically occur 30 minutes to 2 hours after consuming lactose. The symptoms arise from intestinal bacteria that ferment undigested lactose.