Which IBS subtype
does your pattern fit?
The Rome IV criteria classify Irritable Bowel Syndrome into four subtypes, IBS-C, IBS-D, IBS-M, and IBS-U, based on the percentage of stools that fall into the abnormal-form bands. This classifier applies the criteria to your stool-type log and returns the matching subtype with a confidence indicator based on log length.
rome iv ibs subtype self-test
Important. This classifier applies the Rome IV symptom criteria to your stool-type log. It does not diagnose IBS, that requires a clinician to rule out organic causes. Use this tool after a doctor has indicated IBS as a working diagnosis, to clarify which subtype fits your pattern best.
your bristol stool log
Log period (days)
Enter how many stool entries fell into each band over your 14-day log. Total across all bands should equal the number of stools you logged.
Types 1-2 (separate hard lumps / sausage but lumpy)
Types 3-4 (cracked sausage / smooth soft sausage)
Type 5 (soft blobs with clear edges)
Types 6-7 (mushy/fluffy / liquid)
Total: 14 entries
rome iv thresholds
Types 1-2 above 25% = constipation-predominant signal. Types 6-7 above 25% = diarrhoea-predominant signal. Both above 25% = mixed. Both below 25% = unsubtyped.
classification
IBS-M (Mixed)
Mixed pattern. Both type 1-2 stools AND type 6-7 stools each exceed 25% of total. Day-to-day variability is high.
Confidence: 100% (based on 14 entries; 14+ entries gives higher confidence)
distribution
Source: Rome Foundation, Rome IV Diagnostic Criteria for Disorders of Gut-Brain Interaction (2016), IBS section. Available at theromefoundation.org. The 25% threshold applies only to abnormal-form stools, types 3-5 are considered “normal” in the criteria.
The four Rome IV IBS subtypes
Constipation predominant
>25% types 1-2 AND ≤25% types 6-7
Diarrhoea predominant
>25% types 6-7 AND ≤25% types 1-2
Mixed
>25% types 1-2 AND >25% types 6-7
Unsubtyped
≤25% types 1-2 AND ≤25% types 6-7
Why subtype matters for treatment
IBS treatment is subtype-directed. Soluble fibre and osmotic laxatives help IBS-C; loperamide and bile-acid sequestrants help IBS-D; low-FODMAP eating helps all subtypes but the specific triggers differ. Antispasmodics and gut-brain axis treatments (low-dose tricyclics, gut-directed CBT) help across subtypes.
Knowing your subtype lets your clinician pick the right first-line treatment instead of working through trials. The classifier output is meant for you to take to that conversation, “my 14-day pattern shows IBS-M with 28% type 1-2 and 42% type 6-7” gives your GP or gastroenterologist a much faster starting point than “sometimes constipated, sometimes loose”.
Important: this is a classifier, not a diagnosis
IBS is a diagnosis of exclusion. Blood in stool, unexplained weight loss, family history of bowel cancer or inflammatory bowel disease, persistent symptoms over age 50, or any change from a long-standing baseline all need clinician investigation. This tool is for clarifying which subtype fits your pattern once IBS is already a working diagnosis, not for determining whether you have IBS in the first place.