Hydrochlorothiazide for hypertension: what to know

This medicine is a thiazide diuretic, often called a water tablet. It increases urine production, reducing fluid in the bloodstream; with regular use, it also helps blood vessels remain less tense. The aim is to reduce the strain on the heart and lower the long-term risks associated with hypertension, including stroke and heart complications.

Take it exactly as prescribed, usually earlier in the day so increased urination is less disruptive at night. Do not double a missed dose. Your clinician may check blood pressure, kidney function and salts such as sodium or potassium, especially after starting or changing the dose. Tell them about other medicines, vomiting, diarrhoea, heavy sweating or a history of kidney disease. Do not stop treatment without advice, even when readings improve.

Seek urgent help for fainting, severe weakness, confusion, chest pain, severe breathlessness or sudden neurological changes such as facial drooping or difficulty speaking. Contact your prescriber promptly for persistent dizziness, troublesome muscle cramps, a racing heartbeat, a marked change in urination or an allergic reaction with swelling or breathing difficulty.

Ask what blood-pressure target applies to you, when your blood and kidney checks are due, how to handle a missed dose, and whether any painkillers or supplements could affect the medicine.