What causes change in bowel habits?

A change in bowel habits can be caused by diet, medicines, infection, constipation, diarrhoea, inflammation, or a bowel condition. The change may involve frequency, stool consistency, urgency, difficulty passing stool, or narrower stools. A symptom alone cannot identify its cause.

A sudden change may follow a stomach infection, travel, stress, altered eating, or reduced fluid intake. Iron tablets, opioid pain medicines, antibiotics, and some cancer treatments can affect bowel movements. Irritable bowel patterns can cause alternating constipation and diarrhoea. Inflammatory bowel conditions may cause ongoing diarrhoea, pain, or blood. A change in bowel habits can also be a presentation of colorectal or rectal cancer, particularly when it persists or occurs with bleeding, anaemia, weight loss, or abdominal pain. Immunotherapy can trigger bowel inflammation that needs prompt attention.

Record when the change began, stool appearance, frequency, urgency, pain, blood, fever, recent travel, and medicines. Drink fluids unless a clinician has restricted them, and make gradual food changes rather than using repeated laxatives or anti-diarrhoeal medicines without advice. Contact your clinician if the change persists, keeps returning, or follows cancer treatment. Bring your symptom record and medicine list to the appointment.

Seek urgent care for heavy rectal bleeding, black stools, severe or worsening abdominal pain, repeated vomiting, a swollen abdomen with inability to pass stool or gas, faintness, or signs of dehydration. During immunotherapy, report new or worsening diarrhoea promptly because bowel inflammation may require treatment. A persistent change with bleeding, unexplained weight loss, fever, or marked tiredness also needs timely medical assessment.

Could my medicines or recent treatment explain this change? Do I need stool tests, blood tests, or a bowel examination? What symptoms should make me seek urgent help? Is it safe for me to use a laxative or anti-diarrhoeal medicine?