Does hyperthyroidism cause diarrhoea?

An overactive thyroid can increase the pace of several body processes. In the digestive system, food may pass through the intestine more quickly, leaving less time for water to be absorbed. Stools can therefore become loose, frequent, or urgent. Diarrhoea may occur alongside weight loss, a fast or pounding heartbeat, tremor, sweating, heat intolerance, or feeling unusually restless. These features can support a thyroid assessment, but diarrhoea also has many other causes, including infection, food intolerance, medicines, and bowel conditions.

Replace fluids regularly, especially after each loose stool, and choose simple foods that you tolerate. Avoid alcohol and notice whether caffeine or particularly rich meals make urgency worse. Record how often stools occur, whether there is blood or mucus, and any associated palpitations or weight change. A clinician can review your symptoms and arrange thyroid blood tests when appropriate; do not start or change thyroid medicine without advice.

Seek urgent medical help for severe weakness, fainting, confusion, inability to keep fluids down, or signs of significant dehydration such as very little urine. Prompt assessment is also needed for bloody or black stools, severe abdominal pain, or a very fast heartbeat with fever or marked agitation. Arrange a routine appointment if diarrhoea keeps returning or continues, particularly when it occurs with weight loss, tremor, sweating, or a neck swelling.

Could my symptoms fit an overactive thyroid, and which blood tests would help check it? Could any medicine, supplement, infection, or food trigger be contributing? What fluid replacement is suitable for me, and which changes should prompt earlier review?