What should you know about vomiting, diarrhoea and high blood pressure?

Fluid loss from vomiting and diarrhoea may cause weakness, dizziness and a lower reading, while pain, stress or some medicines may raise it temporarily. High blood pressure itself often causes no symptoms, so vomiting and diarrhoea should not automatically be attributed to hypertension. Kidney disease, heart failure and some treatments can make fluid balance harder to manage. Obesity and obstructive sleep apnoea are associated with hypertension, but they do not explain a sudden stomach illness on their own.

Rest, take small frequent sips of water or oral rehydration solution, and measure blood pressure only after sitting quietly for several minutes. Record the reading, symptoms, fluid intake and medicines. Do not double a missed dose or stop prescribed treatment without medical advice; vomiting may prevent a tablet being absorbed, and some medicines need individual sick-day guidance. Ask a pharmacist or clinician what to do if you cannot keep medicines down.

Call emergency services for chest pain, severe breathlessness, new weakness or numbness on one side, trouble speaking, confusion, fainting, a severe headache or vision loss. Seek urgent medical advice for repeated vomiting, very little urine, marked dizziness, blood in vomit or stool, or a persistently very high blood-pressure reading with symptoms. Do not delay because the stomach symptoms seem mild.

Ask which medicines to continue during vomiting or diarrhoea, when to recheck blood pressure, how to replace fluids safely, and which readings or symptoms require same-day assessment.