Harvard Health Letter

By the way, doctor: Will thiazide diuretics increase my chances of getting diabetes?

Q. Thiazide diuretics are often recommended as the first medication to use to control blood pressure, but I've heard that a large study called ALLHAT found an association between thiazide diuretics and diabetes. Is this something to be concerned about?

A. You're right about thiazide diuretics being the first choice if you need to take a drug to bring high blood pressure under control. National guidelines recommend them as initial therapy for most people with hypertension — that's another term for high blood pressure — although often more than one medication will be needed to bring blood pressure under control. Numerous studies have shown that thiazide diuretics are effective for preventing heart attacks, strokes, and other cardiovascular consequences of hypertension, and it's reducing the risk of those complications that makes control of hypertension so important. In this country, hydrochlorothiazide is the most commonly prescribed thiazide diuretic.

The ALLHAT study you mention is probably the most influential study of blood pressure medication ever conducted. The study included 33,000 people who were randomized to take one of three blood pressure–lowering medications: a thiazide diuretic, a calcium-channel blocker, or an ACE inhibitor. The rate of heart attacks and deaths from heart disease was similar in all three groups, but the thiazide group had a lower rate of heart failure.

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