Can immunotherapy side effects change bowel habits?

Immune checkpoint medicines can activate immune cells against healthy tissue as well as cancer cells. In the bowel, this may lead to looser stools, urgency, cramps or mucus; some people instead notice constipation or a new pattern. The timing can vary, including during treatment or after an infusion. Infection, diet, other medicines and the cancer itself can also alter bowel habits, so the symptom needs clinical assessment rather than self-diagnosis.

Tell your oncology team when the change began, how often it happens, whether there is blood or pain, and which medicines you take. Keep fluids going if stools are loose, unless a clinician has given you fluid restrictions. Do not take anti-diarrhoea medicine or laxatives without checking first, because treatment may need adjusting. See [Change in Bowel Habits](/symptoms/change-in-bowel-habits/) for symptom details.

Contact your cancer team promptly for repeated diarrhoea, increasing cramps, blood or black stools, fever, vomiting, or reduced urination. Seek urgent help for severe abdominal pain, faintness, confusion or inability to keep fluids down.

Could this be immune-related bowel inflammation? Should my next dose wait? What fluid plan and symptom log should I use?