Why can antibiotics cause diarrhoea?

Loose stools may begin during a course or after it has finished. Because significant diarrhoea can also reflect bowel inflammation or the original infection, the pattern and accompanying symptoms matter.

Antibiotics act against susceptible bacteria, including some organisms that normally live in the digestive tract. The altered gut environment can lead to looser or more frequent stools, cramping, and urgency. The exact effect varies with the medicine and the person taking it.

A more concerning pattern includes frequent watery stool, worsening abdominal pain, fever, blood or mucus, or symptoms that continue after treatment. Certain bacteria can multiply after antibiotic exposure and inflame the colon, so these features should not be dismissed as an ordinary side effect.

Sip water regularly and consider an oral rehydration solution if fluid losses are ongoing. Choose foods you tolerate and avoid large, rich meals while the bowel is unsettled. Keep track of stool frequency, appearance, fever, pain, and when the antibiotic doses were taken.

Continue the antibiotic as prescribed unless the prescriber advises a change. Contact a pharmacist or clinician before using an anti-diarrhoeal medicine or probiotic, particularly if there is fever, blood in the stool, severe pain, reduced immunity, pregnancy, or a complex medical history.

Seek timely medical advice for persistent or worsening diarrhoea, fever, blood or black stool, substantial abdominal pain, repeated vomiting, or symptoms beginning after a recent antibiotic course. Contact the prescriber if diarrhoea makes it difficult to take or retain your medicine.

Get urgent help for fainting, confusion, unusual drowsiness, very little urine, severe weakness, a rapidly swollen abdomen, or intense abdominal pain. These can accompany serious dehydration or bowel inflammation and need direct assessment.

Tell the clinician which antibiotic you take, when diarrhoea started, what the stool looks like, and whether you have pain or fever. Ask whether to continue the current course, whether testing is needed, and which hydration or symptom-relief products are appropriate for you.