How long should I wait before seeing a doctor?

A change that lasts more than two weeks should be assessed. If the change comes with bleeding, unexplained weight loss, persistent pain or a lump, see a doctor immediately.

Is a change in bowel habit always serious?

No. Most changes have a benign explanation such as diet, medication, infection or irritable bowel syndrome. Assessment is recommended because the small number of cases with a more serious cause are much easier to treat when found early.

I have piles. Could that explain it?

Piles can cause bleeding and discomfort and are very common. They do not usually cause a lasting change in the shape or frequency of your stool. Some symptoms of piles are similar to those of colon cancer, and where there has been bleeding the colon above the rectum should be examined as well, to rule out other causes. Bleeding should be assessed rather than attributed to piles without examination.

What test will I need?

That depends on your symptoms, age and history. It may be blood tests, a stool test, or a colonoscopy. Dr Chen will explain which is appropriate for you and why at your consultation.

Patient guide

Change in Bowel Habit

A change in bowel habit means a lasting change from what is normal for you: looser, harder, narrower or more frequent stools, or a new urgency. Most causes are benign, but a change lasting more than two weeks should be assessed, and sooner if there is bleeding or weight loss.

Medically reviewed by Dr Chen Chung Ming, FRCS (Edin), FAMS · Colorectal Surgeon

BUILD NOTE: this page was drafted for the refresh and has NOT yet been read by Dr Chen. Clinical content, and the medical-review byline above, must be confirmed by him before the domain cutover.

What Counts as a Change in Bowel Habit

There is no single normal. Some people open their bowels three times a day and others three times a week, and both can be perfectly healthy. A change from what is normal for you, and whether it persists, is what counts.

A change worth assessing includes:

Stools that have become looser, harder, narrower or more frequent
Needing to open your bowels more urgently than before
A feeling that the bowel has not emptied completely
Alternating constipation and diarrhoea

As a general guide, a change that persists should be looked at, particularly if you are over 50. A change in bowel habits lasting more than two weeks, other than constipation alone, is a recognised reason for a colonoscopy, as is abdominal bloating or pain lasting more than two weeks that has not responded to treatment.¹

Common Causes

Most changes in bowel habit have a benign explanation. Common causes include:

A change in diet, fibre intake or fluid intake
Medication, including painkillers, iron supplements and some blood pressure tablets
Gastrointestinal infection, which usually resolves within days
Irritable bowel syndrome
Stress, travel or a change in routine
Piles or an anal fissure, which can change how comfortable it is to pass stool

A persistent change can also be caused by inflammatory bowel disease, a polyp, or colorectal cancer. These are far less common, but they are the reason a persistent change is worth assessing.

Symptoms That Should Be Assessed Sooner

Speak to a doctor immediately if a change in bowel habit comes with any of the following:

Bleeding from the back passage or blood mixed in the stool
Unexplained weight loss
Persistent abdominal pain or bloating
A lump in the abdomen or back passage
Anaemia
A family history of colorectal cancer

The same applies to anyone assuming their symptoms are piles, since some symptoms of piles are similar to those of colon cancer.² See a doctor if things are no better after 7 days or are getting worse. Also see a doctor if there is unexplained loss of appetite or weight, bleeding between bowel movements, a change in the colour or shape of stools, or a hard lump at the anus.²

What Assessment Involves

Dr Chen will take a history of what has changed and for how long. He will ask about diet, medication and family history, then examine your abdomen and back passage. Depending on what is found, he may recommend blood tests, a stool test, or a colonoscopy to look directly at the lining of the large bowel.

The purpose is to explain the change, treat what is treatable, and rule out the conditions that need early attention.

When to See a Doctor

While a short-lived upset that resolves on its own is rarely a concern, see a doctor if the change has lasted more than two weeks, or if it comes with bleeding or weight loss.

References

Ministry of Health, Singapore, Claims Management Office. MediShield Life Claims Rules for Gastrointestinal (GI) Endoscopy and Related Procedures (PDF). August 2022. The document states that the claim rules are not clinical practice guidelines. Accessed 22 September 2026.
HealthHub, Health Promotion Board. Piles. Article last reviewed 12 June 2024. Accessed 22 September 2026.
National University Hospital. Haemorrhoids or Piles. Last updated 12 March 2025. Accessed 22 September 2026.

BUILD NOTE: every figure on this page carries a numbered citation. All three sources were fetched and checked on 22 September 2026. Reference 1 is a claims document rather than a clinical guideline, and the page says so where it is used.