Diuretics are medicines that help reduce fluid buildup in the body. They are sometimes called water pills. Most diuretics help the kidneys remove salt and water through the urine. This lowers the amount of fluid flowing through the veins and arteries. As a result, blood pressure goes down.

Types of diuretics used to treat high blood pressure include:

• Thiazide.
• Loop.
• Potassium sparing.

Some water pills combine more than one type of diuretic. Others combine a diuretic with a different medicine, such as one to treat blood pressure. Which type is best for you depends on your health and the condition being treated.

Examples of thiazide diuretics include:

• Chlorothiazide.
• Chlorthalidone.
• Hydrochlorothiazide.
• Indapamide.
• Metolazone.

Examples of loop diuretics include:

• Bumetanide (Bumex).
• Ethacrynic acid (Edecrin).
• Furosemide (Lasix).
• Torsemide (Soaanz).

Examples of potassium-sparing diuretics include:

• Amiloride (Midamor).
• Eplerenone (Inspra).
• Spironolactone (Aldactone, Carospir).
• Triamterene (Dyrenium).

Thiazide diuretics are recommended as one of the first medicines to treat high blood pressure.

If diuretics aren't enough to lower your blood pressure, you may receive additional medicine.

Diuretics also are used to prevent, treat or improve symptoms in people who have:

• Heart failure.
• Liver failure.
• Fluid buildup in the body.
• Certain kidney disorders, such as kidney stones.

Diuretics are generally safe. Side effects include:

• Urinating more often.
• Too little sodium in the blood.
• Too little potassium in the blood.

Thiazide diuretics may cause very low levels of potassium, called hypokalemia. Hypokalemia can cause life-threatening heartbeat problems. To prevent potassium loss, you may be given a potassium-sparing diuretic. Your health care team checks your potassium levels if you take these medicines.

Other possible side effects of diuretics include:

• Dizziness.
• Headaches.
• Dehydration.
• Muscle cramps.
• A type of arthritis called gout, which causes severe joint pain, usually in the big toe.
• Trouble getting erections, also called erectile dysfunction or impotence.

Talk to your health care team if you have any questions about the medicines you take.