Symptoms and when to see a doctor
Change in bowel habit: what counts, and when to see a doctor
By Dr Wong Nan-Yaw, MBBS (NUS), FRCS (Edinburgh). Published . 6 min read.
A significant change in bowel habit is a shift from your own usual pattern, such as looser stools, constipation or more frequent trips, that keeps going instead of settling within a week or so. A change with blood, black stools, weight loss or tiredness needs a doctor's check (NHS). Dr Wong Nan-Yaw is a colorectal surgeon who assesses these changes.
What is a normal bowel habit?
There is no single normal. HealthHub notes that a normal bowel habit can range from two or three times a day to three times a week. What matters is your own pattern: how often you go, how your stool looks, and how easy it is to pass. A change is measured against that baseline.
Stool form matters as much as frequency. The NHS describes constipation as going less than three times in a week, or passing stool that is unusually large or small and dry, hard or lumpy, with straining or a feeling that the bowel has not fully emptied.
Many everyday things shift bowel habits for a few days: a change in diet or routine, less fluid, less activity, stress, and some medicines. Iron and calcium supplements and certain blood pressure medicines are examples HealthHub lists as causes of constipation.
What counts as a significant change?
A change becomes significant when it lasts, keeps coming back, or comes with other symptoms. A stomach bug usually causes diarrhoea that stops within 5 to 7 days (NHS). Looser or harder stools, a new urgency to go, or a feeling of incomplete emptying that persists beyond that deserves attention, even if it does not hurt.
Persistent diarrhoea has many possible causes besides infection. The NHS lists medicines, food intolerance, irritable bowel syndrome, inflammatory bowel disease, coeliac disease, diverticular disease and anxiety. Constipation is also more common during pregnancy, after giving birth and over the age of 65, and is rarely caused by a condition such as bowel cancer (NHS).
None of these on its own means cancer. The NHS stresses that these symptoms are very common and usually have other causes, but that they are worth checking because a cause found early is easier to treat.
- Stools that are softer or looser than usual for you, or diarrhoea that does not settle
- Constipation that is new for you, or that keeps returning despite fibre and fluids
- Needing to go more or less often than your usual pattern
- Often feeling you need to go again, even straight after the toilet
Which symptoms with a bowel change need a prompt check?
Book a prompt check if a bowel change comes with blood in the stool, black or dark red stools, tummy pain or a lump, bloating, weight loss without trying, or tiredness and breathlessness from anaemia. The NHS lists all of these as possible symptoms of bowel cancer, although most people with them turn out to have another cause.
| What you notice | What it may suggest | How soon |
|---|---|---|
| Diarrhoea after a meal out, settling within a week | A stomach bug or food poisoning | Home care and fluids; see a doctor if it lasts more than 7 days |
| New constipation that does not improve with fibre and fluids | Diet, medicines or a bowel problem | See a doctor |
| Bowel change with blood, weight loss or tiredness | Needs investigation, including for bowel cancer | See a doctor soon |
| Black or dark red stools, or bloody diarrhoea | Bleeding that needs prompt assessment | Urgent same-day advice |
| Heavy bleeding, large clots, or severe sudden pain | Significant blood loss or an emergency | Emergency department or call 995 |
The time frames in this table follow NHS guidance on diarrhoea, constipation and bowel cancer symptoms. They are a guide, not a diagnosis.
Does age change how seriously a bowel change is taken?
Age raises the level of concern but never removes it. UK NICE guidance offers a stool test for blood (FIT) to adults of any age with a change in bowel habit, and lowers the threshold for testing from age 50 when bleeding, pain or weight loss is unexplained. In Singapore, screening invitations start at 50.
Under Singapore's national programme, Singaporeans and permanent residents aged 50 and above are invited to screen for colorectal cancer every year with a faecal immunochemical test (FIT) kit, or may choose colonoscopy once every 10 years instead (Ministry of Health).
Screening is meant for people without symptoms. If you already have a lasting bowel change, a screening kit is not a substitute for seeing a doctor. NICE guidance makes a related point: when there is strong clinical concern because symptoms remain unexplained, referral should not be delayed even after a low FIT result.
What happens when you see a doctor about a bowel change?
The doctor asks about your symptoms, general health and family history, may examine your tummy, and may do a gentle rectal examination. Depending on the findings, the next step can be blood tests, a stool test, or a colonoscopy, which looks at the whole large bowel and can remove polyps during the same test.
The NHS notes that most of the time a colonoscopy does not find anything to worry about, and many causes of a bowel change, such as piles, a fissure or irritable bowel syndrome, are treatable. If a colonoscopy is advised, your clinic will explain the bowel preparation and what the result means for future checks.
- Keep a short diary for a week: how often you go, what the stool looks like, and any blood
- List your medicines and supplements, including iron, calcium and painkillers
- Note any close relative with bowel cancer or polyps, and their age at diagnosis
- You can ask for a chaperone during any examination
Sources
Medically reviewed by Dr Wong Nan-Yaw
MBBS (NUS), FRCS (Edinburgh). 33 years in medicine (since 1993), 23 years as an accredited specialist (since 2003) and 18 years in private practice at Mount Elizabeth (since 2008). Last reviewed 6 November 2026.
How this article is prepared
Statements are checked against the sources listed above. This article is general education and does not replace a consultation. It is reviewed and updated when guidance changes. In an emergency, call 995.