IBS-D, or diarrhea-predominant irritable bowel syndrome, is one possible explanation for recurring diarrhea, abdominal cramps, and an urgent need to use the bathroom. But these symptoms can also stem from other digestive conditions, and not everyone with frequent diarrhea has IBS.
Understanding how IBS-D is diagnosed, what conditions can look similar, and which treatments may help can give you a clearer idea of what to discuss with your doctor.
What Is IBS-D?
IBS is a disorder involving communication between the gut and brain. Standard tests may look normal even when bowel habits and pain sensitivity have changed.
In IBS-D, stool may move through the bowel too quickly for enough water to be absorbed. Some people are also more sensitive to normal stretching from gas or stool, which can cause cramping. Stress can worsen symptoms, but it doesn't mean stress alone causes IBS.
How Is IBS-D Diagnosed?
Doctors assess your symptoms, medical history, and whether other conditions need to be ruled out. The Rome V criteria, updated in 2026, provide a framework for diagnosing IBS.
The criteria include recurring abdominal pain or discomfort at least three days a month over the past three months, linked to at least two of the following: bowel movements, a change in how often you go, or a change in stool form. Symptoms must have started at least six months before diagnosis under the formal criteria.
Doctors also use the Bristol Stool Form Scale to identify the IBS subtype. IBS-D involves loose or watery stools (types 6 and 7) making up more than 25% of abnormal bowel movements, with hard or lumpy stools (types 1 and 2) making up less than 25%.
Recurring loose stools without the abdominal pain or discomfort associated with IBS may instead point to functional diarrhea. These criteria guide a doctor's assessment. They aren't a substitute for a diagnosis.
What Causes IBS-D Flares?
Some people develop IBS after a stomach infection, while others have no clear starting point. Symptoms may also be influenced by meals, certain foods, stress, and sleep.
Meals. Eating naturally stimulates colon activity. With IBS-D, this can trigger cramps or urgency soon after eating.
Certain foods. FODMAPs are carbohydrates that can draw water into the bowel or produce gas during digestion. Onions, garlic, some fruits, wheat products, and sugar alcohols are common sources. Triggers vary from person to person.
Stress and poor sleep. Both can worsen symptoms. They don't mean the symptoms are imaginary or that stress is the sole cause.
What Else Can Cause Similar Symptoms?
Several conditions can resemble IBS-D. Doctors choose tests based on your symptoms, medical and family history, and warning signs. The ACG guideline supports targeted testing rather than testing everyone for every possible condition.
Celiac disease. This immune reaction to gluten can cause diarrhea similar to IBS-D. The ACG recommends celiac blood testing for people with suspected IBS and diarrhea.
Bile acid diarrhea. Bile acids help digest fat. When too many reach the colon, they draw in water and cause loose stools. This condition can occur after gallbladder removal and may be mistaken for IBS-D. A doctor may consider specific tests or a treatment trial.
Inflammatory bowel disease. Crohn's disease and ulcerative colitis cause intestinal inflammation, unlike IBS. Stool tests such as fecal calprotectin, sometimes alongside blood tests, can help determine whether further investigation is needed. Normal results make inflammation less likely but don't rule out every condition.
Colorectal cancer and other conditions. These are less common in younger people with typical IBS symptoms, but age, family history, screening status, and new symptoms matter. The ACG advises against routine colonoscopy solely for IBS symptoms in people under 45 without warning signs. This doesn't replace recommended cancer screening or investigation of new symptoms.
An IBS diagnosis also doesn't explain every future symptom. New or changing symptoms still deserve medical attention.
