Tips for taking diuretic medications

Often called water pills, these drugs help lower blood pressure and are a mainstay for treating heart failure.

Diuretics, commonly called "water pills," are the oldest and some of the least expensive class of drugs used to treat high blood pressure. They help the kidneys eliminate sodium and water from the body. This process decreases blood volume, so the heart has less to pump with each beat, which in turn lowers blood pressure. People with heart failure, who often gain weight because their bodies hold onto excess fluid (a condition called edema), are often prescribed diuretic medications.

Not surprisingly, one of the most common side effects of taking water pills is frequent urination. Other possible side effects include lightheadedness, fatigue, bowel changes, and muscle cramps. Men may occasionally experience erectile dysfunction.

In addition to getting rid of extra salt in your body, diuretic medications also affect levels of potassium. This mineral plays a key role in controlling blood pressure, as well as nerve and muscle function. In general, your kidneys help regulate potassium levels in your blood. But age, diabetes, heart failure, and certain other conditions may impair kidney function. And while some water pills tend to lower potassium levels, others have the opposite effect.

Thiazide diuretics, such as chlorothiazide (Diuril), chlorthalidone (Hygroton), and hydrochlorothiazide (Esidrix, HydroDiuril, Microzide) tend to deplete potassium levels. So do loop diuretics, such as bumetanide (Bumex) and furosemide (Lasix). If you take these medications, your doctor will likely encourage you to eat more potassium rich foods and beverages and limit salt intake.

Potassium-sparing diuretics, which include amiloride (Midamor), spironolactone (Aldactone), and eplerenone (Inspra), avoid the potential problem of potassium loss. But the opposite problem can occur. If potassium levels become too high, it can cause dangerous heart rhythm problems and even cardiac arrest.

People with high blood pressure or heart failure are often advised to limit how much salt or sodium they consume. One way to do that is to use salt substitutes, but these products are high in potassium—a quarter teaspoon of one brand contains about 800 mg of potassium. So, people who take potassium-sparing diuretics should avoid these products.

If you take any diuretic medication, ask your doctor whether you need periodic testing of your potassium and kidney function.

To learn more about managing hypertension, buy "Controlling Your Blood Pressure: What to do when your doctor says you have hypertension."

– By Julie Corliss
Executive Editor, Harvard Heart Letter