Subtypes of Irritable Bowel Syndrome (IBS)
IBS is not a one-size-fits-all condition. It affects people differently, and doctors classify it into four main subtypes based on your usual stool consistency and bowel habits. This helps tailor the right treatment approach for each person.
The classification is based on the Bristol Stool Scale, a tool that groups stool forms into seven types, from very hard to entirely liquid.
IBS-C (CONSTIPATION-PREDOMINANT)
IBS-C (CONSTIPATION-PREDOMINANT)
IBS-C (CONSTIPATION-PREDOMINANT)
This type is diagnosed when:
- More than 25% of your bowel movements are hard or lumpy (Bristol types 1–2)
- Less than 25% are loose or watery (Bristol types 6–7)
People with IBS-C often experience:
- Abdominal pain or cramping
- Bloating
- Difficulty passing stool or infrequent bowel movements
IBS-D (Diarrhea-Predominant)
IBS-C (CONSTIPATION-PREDOMINANT)
IBS-C (CONSTIPATION-PREDOMINANT)
This type is diagnosed when:
- More than 25% of stools are loose or watery (types 6–7)
- Less than 25% are hard or lumpy
Common symptoms include:
- Sudden urges to go to the bathroom
- Frequent, loose stools
- Abdominal pain
Feeling of incomplete evacuation
IBS-M (Mixed Type)
IBS-C (CONSTIPATION-PREDOMINANT)
IBS-U (Unclassified)
This subtype involves a combination of both constipation and diarrhea, without one clearly dominating.
- In this case, more than 25% of stools are hard/lumpy and more than 25% are loose/watery.
Symptoms vary from day to day, and patients may switch between constipation and diarrhea episodes. Managing IBS-M can be especially challenging and usually requires a more individualized treatment plan.
IBS-U (Unclassified)
IBS-C (CONSTIPATION-PREDOMINANT)
IBS-U (Unclassified)
In this category, symptoms do not clearly fit into any of the other subtypes.
- Stool consistency does not meet the thresholds for IBS-C, D, or M, but other IBS symptoms like abdominal pain and bloating are still present.
This classification can change over time as symptoms evolve.
(Lacy et al., 2021; Chey et al., 2021)
Bristol Stool Chart and Differential Diagnosis of IBS-C
The Bristol Stool Chart: A Simple But Powerful Tool
The Bristol Stool Chart is a visual guide that helps you and your doctor describe the form and consistency of your stool. It divides stool into seven types, from very hard lumps (Type 1) to entirely liquid (Type 7). This tool is not just for description—it's actually key in identifying patterns and guiding diagnosis, especially in IBS.
Why is this important? Because IBS with constipation (IBS-C) is often difficult to distinguish from other conditions that also cause bowel changes. For example:
Differential diagnosis of IBS-C includes:
- Functional constipation
- Inflammatory Bowel Disease (IBD)
- Colorectal cancer
- Celiac disease
- Small Intestinal Bacterial Overgrowth (SIBO)
(Morales, 2020; Lacy et al., 2021; Chey et al., 2021)
These conditions can overlap in symptoms, but their treatment and implications are very different. That’s why doctors may ask you to track your bowel movements using the Bristol Stool Chart, keeping a stool diary for several weeks.
In some cases, further tests—like anorectal manometry (to evaluate muscle function) or colonic transit studies (to see how fast stool moves through your colon)—may be needed to get a clear picture.
(Choi, Y. et al. 2025)
Welcome!
Curious about your gut health? Meet Gutti our friendly chatbot designed to guide you through IBS-C symptoms, answer your questions, and help you make sense of what you're feeling.
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Note: Gutti is not a substitute for medical advice — it’s a support tool to help you better understand your condition.