There is no test to diagnose IBS-D, so doctors often use blood and stool tests to rule out other diseases before reaching an IBS-D diagnosis. Rome IV criteria can be used to diagnose IBS-D based on the proportion of bowel movements rated as diarrhea compared to those rated as normal.[1] Symptoms need to occur at least once per week for at least three months to be considered IBS.[2]
How is IBS-D diagnosed?
Written by:
Fact-checked
by:
•Last Updated: May 16, 2025
IBS-D (diarrhea-predominant IBS) is diagnosed by ruling out other diseases through blood and stool tests because there is no specific test for IBS-D. The Rome IV criteria can be applied, which require symptoms to occur at least once per week for 3 months, with a focus on the proportion of diarrhea compared to normal bowel movements.