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.
Questions about the scale
What we can and cannot answer
This site is an educational reference. It is not medical advice, it is not a diagnosis, and we will not interpret your own symptoms for you. Blood in the stool, unexplained weight loss, a change in bowel habit that has persisted, or pain that is severe or ongoing should be taken to a GP or doctor promptly. Those belong in a consulting room rather than an inbox, and waiting on a reply here would only put the appointment back. Please do not send personal medical details; the tracker keeps its entries on your own device and we would rather they stayed there.
Reference questions we will take
- How the scale is defined, what each of the seven types describes, and where the scale came from.
- What the Rome IV criteria actually say about the IBS subtypes and how the percentages are counted.
- How the tracker works, where its entries are held, and how to clear them.
- Which NHS or NICE wording a page on this site is following, and where to read it in full.
How a reply is handled
A person reads every message, and an answer names the source it rests on, whether that is the Lewis and Heaton paper behind the scale, NICE guidance or the Rome IV criteria themselves.
Where an answer would be useful to other readers we ask your permission first, and only an anonymised version of the question is ever published.