Harvard Heart Letter

Ask the doctors: High BP and diabetes?

Q. I am a 47-year-old man with diabetes being treated with insulin and high blood pressure treated with lisinopril and low-dose hydrochlorothiazide (HCTZ). I have read that HCTZ can actually cause diabetes. My physician says not to worry about it, but I do.

A. HCTZ can cause modest elevations in blood glucose levels. However, a low dose of HCTZ will have very little effect on your body's chemical balance, whether or not you have diabetes, or whether your diabetes is well controlled. The single most important thing you can do to prevent complications from diabetes is to control your blood pressure. This will lower your risk of kidney and heart disease, as well as stroke. Lisinopril is an ACE inhibitor, a class of drugs that lowers blood pressure and helps protect the kidneys. Adding a low dose of HCTZ to your lisinopril is a good idea, and I often use this combination in my own patients.

— Thomas Lee, M.D. and Richard Lee, M.D.
Co-Editors in Chief, Harvard Heart Letter

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