What Is a Diuretic or "Water Pill" for High Blood Pressure?

How do water pills work to lower blood pressure?

Diuretics are sometimes known as "water pills.".

What Is a Diuretic or "Water Pill" for High Blood Pressure?

One of the most common types of blood pressure medications is known as a diuretic. These medicines lower your blood pressure by helping your body get rid of excess water and salt through your kidneys, allowing your heart to pump better. Diuretics are commonly known as "water pills" and they treat several conditions, including hypertension, heart failure, and kidney problems.

Thiazide diuretics, like hydrochlorothiazide, are used to treat blood pressure. Stronger diuretics are most frequently used to get rid of excess fluid, or edema, in patients with heart failure. Some common thiazide diuretics used to treat hypertension include:

  • Hydrochlorothiazide 
  • Indapamide
  • Chlorothiazide
  • Metolazone
  • Chlorthalidone

Lasix and Bumex are two common loop diuretics that are used to treat people in congestive heart failure. They work by blocking the reabsorption of fluid that passes through your kidneys, and that excess fluid is removed in your urine. Other loop diuretics are torsemid (Demadex) and ethacrynic acid (Edecrin.) Potassium-sparing diuretics like Aldactone are often used at the same time as other diuretics, to maintain the potassium balance in your body. They don't lower blood pressure significantly when used alone. Potassium-sparing diuretics include:

  • Spironolactone
  • Amiloride
  • Triamterene

What Are the Side Effects of Diuretics?

Diuretics can cause frequent urination. This effect usually lasts for several hours. Other side effects include electrolyte imbalance. You can lose electrolytes in your urine when you are taking a diuretic, so your doctor will monitor your blood chemistry while you are taking these drugs.

Some people experience weakness or fatigue when they start using a diuretic, but this usually resolves after a few weeks, as the person gets used to the drug. Muscle cramps also occur, particularly when a diuretic results in potassium loss.  Sometimes, you may have to add a daily potassium supplement if you are taking a diuretic. It's important to check with your doctor before you take any type of mineral supplement.

Dizziness or blurred vision can occur with diuretic use. This may be the result of dehydration. When you take a diuretic, you should watch for decreased urine output, excessive thirst or mouth dryness, or dark colored urine. Call your doctor if these occur.  Finally, if you experience rapid weight loss, fever, cough, ringing in your ears, bleeding or unusual bruising, contact your doctor right away. If you have an allergy to sulfa drugs, you should be aware that many diuretics have sulfa in them. Tell your doctor if you have an allergy to any medication.

Important Concerns for People Taking Diuretics

If your doctor prescribes a diuretic to control your hypertension, it's important to tell your doctor about any medications or supplements you are taking.

This includes herbal remedies and over the counter medicines. You should always tell your doctor about any medical conditions. Only take the diuretic as instructed. It may be helpful to take a diuretic in the morning, so you won't be up at night going to the bathroom. 

If you are taking a diuretic, your doctor should monitor your blood pressure and kidney function regularly, so be certain to keep all of your appointments as scheduled. 

Remember that diuretics can cause abnormal levels of potassium or sodium. Your doctor may tell you to avoid foods that are rich in potassium, if you are taking a potassium-sparing diuretic. These foods include some salt substitutes. Pregnant women and women who are breastfeeding should not use diuretics. 

There are dozens of different antihypertensive medications and each has pros and cons. If you are just beginning  blood pressure medication, remember that lifestyle factors, like smoking and salty foods, can keep your medicine from working effectively. If you have high blood pressure, you can reduce your need for medication by eating a healthy diet, maintaining a healthy weight, and exercising regularly. Take your medicines as prescribed and be certain to check your blood pressure at the same time each day.

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