What Is the Bristol Stool Form Scale?

The Bristol Stool Form Scale sorts stools into seven types, from separate hard lumps (type 1) to entirely liquid (type 7). It’s used by doctors and in research because stool form is a good guide to how quickly food moves through your gut: slow transit gives hard stools, fast transit loose ones. Types 3 and 4 are usually considered the ideal.

This article is general information, not medical advice. See a doctor about blood in your stool, black stools, unexplained weight loss, a lasting change in your bowel habits, or symptoms that wake you at night.

The Seven Types

Type	Description	Usually means
1	Separate hard lumps, like nuts, hard to pass	Constipation, slow transit
2	Sausage-shaped but lumpy	Constipation
3	Like a sausage with cracks on its surface	Normal
4	Like a sausage or snake, smooth and soft	Normal
5	Soft blobs with clear-cut edges, passed easily	Tending to loose
6	Fluffy pieces with ragged edges, a mushy stool	Diarrhoea
7	Watery, no solid pieces, entirely liquid	Diarrhoea, fast transit

Why Form Matters

Lewis and Heaton developed the scale at Bristol Royal Infirmary. In their 1997 study of 66 volunteers, stool form predicted how long it took food to pass through the gut (whole-gut transit time) better than how often people went or how much they passed. When the volunteers took a laxative, transit sped up and stool types rose; with an anti-diarrhoeal medicine, they fell. So the scale can show change in bowel function over time, which is why it’s used to follow treatments.

How Doctors Use It

The Rome IV criteria for functional bowel disorders (Lacy and colleagues, 2016) use the scale to classify irritable bowel syndrome (IBS) by its predominant stool form on days with abnormal bowel movements:

• IBS with constipation: more than a quarter of abnormal stools are types 1 or 2, and less than a quarter types 6 or 7.
• IBS with diarrhoea: the reverse.
• IBS with mixed bowel habits: more than a quarter of each.

Rome IV’s definitions of functional constipation also include straining, a sense of incomplete emptying or blockage, and manual manoeuvres to help, in more than a quarter of bowel movements, so a useful bowel diary records those too.

Keeping a Bowel Diary

• Note each bowel movement’s type and time.
• Note urgency, straining, a sense of incomplete emptying or of blockage, manual manoeuvres, mucus, and visible blood.
• Keep it for at least two weeks, longer if your pattern varies, and bring it to appointments.

Following It in Kaizora

On Symptoms, each bowel movement is logged with its Bristol Stool Form Scale Type and whether it came with urgency, straining, incomplete emptying, blockage, manual manoeuvres, mucus, or visible blood, as Rome IV and IBS diaries record. Bowel Movements Logged counts them. On Correlations, put the daily average stool type beside Dietary Fiber or Dietary Water to see how your diet moves it.

The Short Version

• The Bristol scale has seven types; 3 and 4 are usually ideal.
• Hard types (1 and 2) mean slow transit; loose types (6 and 7) fast transit.
• Rome IV uses the types to classify IBS; a diary also records straining, urgency, and blood.

Sources

• Lewis SJ, Heaton KW, “Stool form scale as a useful guide to intestinal transit time,” Scandinavian Journal of Gastroenterology 32, no. 9 (1997): 920–924. doi:10.3109/00365529709011203
• Lacy BE et al., “Bowel disorders,” Gastroenterology 150, no. 6 (2016): 1393–1407. doi:10.1053/j.gastro.2016.02.031