Can lactose intolerance cause constipation?

By Katy Brodski-Quigley, MD Jun 30, 2022 • 2 min

Constipation is not usually associated with lactose intolerance, a condition where the gut cannot process a sugar in milk called lactose. However, the condition frequently causes diarrhea, bloating, flatulence and abdominal cramping.

What happens when you’re lactose intolerant?

When someone is lactose intolerant, their small intestine does not produce enough lactase, the enzyme that digests lactose. Instead, lactose has to be broken down by bacteria that live in the large intestine. This process produces gas and other by-products, leading to the unpleasant symptoms of lactose intolerance such as bloating, abdominal pain, flatulence and diarrhea. 

If you’re constipated, it’s best to discuss the issue with your healthcare provider to make sure that the constipation is not being caused by irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), diverticulosis, thyroid disease or any other condition.

Symptoms of lactose intolerance can be managed by limiting or avoiding milk products, eating lactase-fortified foods or taking lactase supplements.

Published June 2022.