Changes in bowel habit
Constipation, diarrhoea or both.Notice what has changed.
Your bowel habit is your usual pattern: how often you go, what the stool is like, how easy it is to pass, and whether urgency or accidents occur. A short-lived change can follow food, travel, infection or medicine. A persistent or unexplained change deserves assessment, especially when it comes with bleeding, weight loss, abdominal pain or marked tiredness. [1] [3]
What counts as a change in bowel habit?
There is no single “normal” frequency for everyone. What matters is a clear change from your own usual pattern. That may mean going much less often, passing harder stools, having looser or more frequent stools, alternating between constipation and diarrhoea, or developing new urgency or difficulty emptying.
The duration matters too. A stomach infection can cause a few days of diarrhoea. A medicine can change stool frequency. Constipation can also cause overflow diarrhoea when liquid stool leaks around impacted hard stool. A pattern that keeps returning or does not settle should be considered in context rather than treated as one isolated symptom. [1] [2]
Harder stools, straining, going less often or feeling that you have not fully emptied.
Loose or watery stools, often with greater frequency or urgency.
Moving between constipation and diarrhoea can occur, but the cause still needs to be assessed from the wider history.
Track the change, not just the label.
A useful history is more than “I am constipated” or “I have diarrhoea”. Note what changed and what came with it. This helps a clinician decide whether the problem looks temporary, medicine-related, functional, inflammatory or in need of another investigation.
| What to notice | Why it matters | What not to assume |
|---|---|---|
| Duration | A few days after a stomach bug differs from a change that persists for weeks or keeps returning. | A long-lasting change should not be dismissed because you have had similar symptoms before. |
| Stool pattern | Hard stools, watery stools, urgency, straining or incomplete emptying point to different questions. | Alternating stool types do not by themselves prove IBS. |
| Blood or colour change | Blood in the stool, bloody diarrhoea or black/dark-red stool needs medical assessment. [5] | Do not assume visible blood is only haemorrhoids without appropriate assessment. |
| Pain, weight and energy | Abdominal pain, unexplained weight loss or unusual tiredness can change the urgency and type of investigation. [1] | Dietary change alone may not be the right response. |
| Medicines and recent antibiotics | Medicines can cause constipation or diarrhoea. Recent antibiotics matter because some infections need specific assessment. [6] | Do not stop prescribed medicine without advice. |
Common causes are varied.
Constipation may be related to low fibre intake, dehydration, inactivity, changes in routine or medicines. Diarrhoea is commonly caused by infection, but can also occur with medicine side effects, food intolerance, IBS, inflammatory bowel disease, coeliac disease and other conditions. [1] [2]
The same symptom can have different causes in different people. Age, medical history, recent travel, antibiotic use, family history and previous investigations can all matter. If the change is persistent or unexplained, the aim is not to order every test. It is to identify which questions need answering first.
Why might a clinician discuss a FIT test?
NICE recommends quantitative faecal immunochemical testing, or FIT, to guide referral for suspected colorectal cancer in adults with a change in bowel habit and in several other symptom groups. FIT looks for tiny amounts of blood in stool that may not be visible. [3]
A FIT result is not the whole decision. NICE says people with a result below the usual referral threshold still need safety-netting, and referral should not be delayed when ongoing unexplained symptoms create strong clinical concern. [3]
A test supports assessment; it does not replace it.
If a clinician recommends FIT, ask what the result will help decide and what happens if symptoms continue. Blood in the stool, weight loss, a new abdominal mass, persistent pain or worsening symptoms should be assessed in context. Do not use a home test result as a reason to ignore ongoing symptoms.
What should you bring to an assessment?
A short record can make the consultation more useful. Bring existing results rather than repeating tests automatically. Include medicines and supplements, because both constipation and diarrhoea can be treatment-related.
- When the change started and whether it is continuous or intermittent.
- Your usual pattern compared with the new pattern.
- Stool consistency, urgency, straining or a feeling of incomplete emptying.
- Any visible blood, black stool, abdominal pain, fever or vomiting.
- Unexplained weight loss, reduced appetite or unusual tiredness.
- Recent travel, infection, antibiotics or new medicines.
- Previous blood tests, stool tests, scans, endoscopy or specialist letters.
For a broader review of persistent digestive symptoms, read the gut health and persistent digestive symptoms guide. If targeted testing is being considered, the functional medicine testing and diagnostics page explains how to think about whether a test could change the next step.
What patients say about the consultation experience.
Patient reviews can help you understand how a consultation feels. They do not prove that a treatment works. These short excerpts come from Dr Stavy’s existing public Google review profile.
Individual reviews reflect personal experiences and do not predict your diagnosis, treatment response or outcome.
“patient, understanding and kind”
Google reviewer
“warm and compassionate bedside manner”
Google reviewer
“takes incredible care to get to know her patients”
Google reviewer
Questions about changes in bowel habit
How long should a change in bowel habit last before I see a doctor?
There is no single safe waiting period for every person. Seek assessment sooner if the change is sudden, persistent, keeps returning, or comes with blood in the stool, unexplained weight loss, abdominal pain or significant tiredness. NHS constipation guidance specifically advises seeing a GP for sudden bowel-habit changes or constipation that is not improving. [1]
Can constipation cause diarrhoea?
Yes. Long-term constipation can lead to faecal impaction, where hard stool builds up in the rectum and liquid stool can leak around it. This is one reason an alternating pattern should be assessed rather than assumed to be IBS. [1]
When is diarrhoea urgent?
Contact NHS 111 urgently if you have bloody diarrhoea, cannot keep fluids down, have diarrhoea for more than 7 days, or still have signs of dehydration after using oral rehydration treatment. Call 999 or go to A&E for sudden severe abdominal pain, severe breathing difficulty, confusion or signs of shock. [2] [4]
What is a FIT test?
FIT is a stool test that measures tiny amounts of blood. NICE recommends it to help guide referral for suspected colorectal cancer in adults with a change in bowel habit and several other symptom groups. A low result does not automatically close the case if symptoms continue and there is strong clinical concern. [3]
Does a change in bowel habit mean bowel cancer?
No. Many more common conditions can change bowel habit. But persistent or unexplained change is one of the symptoms clinicians use to decide whether further assessment is needed. The purpose of red-flag guidance is to avoid missing important disease, not to imply that most people with a bowel change have cancer. [3]
Should I stop a medicine if I think it is affecting my bowels?
Do not stop a prescribed medicine without advice. Some medicines can cause constipation or diarrhoea, so bring a current list to the consultation and explain when the bowel change started in relation to treatment. A clinician can help decide whether the medicine is relevant and what to do next. [1] [2]
Medical sources and further reading
- NHS: Constipation. Covers common causes, medicine-related constipation, sudden bowel-habit change, blood in the stool and complications such as faecal impaction. Media reviewed 12 May 2026.
- NHS: Diarrhoea and vomiting. Covers common causes, hydration and urgent or emergency assessment routes.
- NICE NG12: Suspected cancer, recognition and referral. Includes quantitative FIT for adults with a change in bowel habit and safety-netting when symptoms persist. Guideline last updated 15 April 2026.
- NHS: Dehydration. Covers symptoms of dehydration and urgent or emergency escalation. Page reviewed 1 May 2026.
- NHS: Rectal bleeding. Covers visible blood, black or dark-red stool, bloody diarrhoea and when to seek assessment.
- NHS: Clostridioides difficile. Covers diarrhoea associated with current or recent antibiotics and when urgent assessment is needed.
A bowel change is information. The pattern tells you what to do next.
If constipation, diarrhoea or an alternating pattern is persisting, start by recording what changed and any accompanying symptoms. Then use the wider gut-assessment guide to understand the next step.