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Everything you need to know about water pills

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These powerful medications may help keep your heart and kidneys healthy by lowering your blood pressure.
Written by Emily Shiffer
Updated on November 16, 2022

Don’t be fooled by their name — water pills pack a powerful punch. Doctors use them for all sorts of conditions. But water pills, also known as diuretics, are mostly used to lower blood pressure. And they’re excellent at doing just that.

That’s a good thing, because almost half of all adults in the U.S. have high blood pressure. When you have high blood pressure, your heart has to work harder to pump blood throughout the body. Your kidneys also have a tougher time removing salt and water from the body. That turns into a vicious cycle. More fluid in the body means your blood pressure keeps going up.

Diuretics help your kidneys flush out extra salt and water, explains Alyssa Wozniak, PharmD. She’s a clinical assistant professor at D’Youville School of Pharmacy in Buffalo, New York. And, yes, they make you pee more often as the body gets rid of the extra fluid. But when you have less fluid in your blood vessels, your heart doesn’t have to pump as hard. And that lowers your blood pressure.

Doctors also prescribe water pills when your legs or feet swell up from too much fluid in your body. That happens to people with kidney disease or heart failure.

There are 3 main types of water pills. They work in slightly different ways and for different conditions. Here’s what you need to know about each one. (Be sure to download our free mobile app to save on diuretics and any other medications you take.)

Types of diuretics

The 3 types of water pills work in slightly different ways. And doctors may prescribe them for different reasons, too.

Thiazide diuretics (hydrochlorothiazide, chlorothiazide, metolazone)

What they’re best for: High blood pressure

How they work: Thiazide diuretics stop the kidneys from reabsorbing sodium, says Wozniak. Instead, the sodium, along with the extra water and potassium, exits the body when you go to the bathroom. Potassium and sodium are electrolytes that help your kidneys work.

What you need to know: You’ll need to get regular blood tests. That way, your doctor can check your sodium and potassium levels to make sure you’re not losing too much of those electrolytes, Wozniak explains. If you are, your provider may put you on another type of diuretic or blood pressure medication.

Loop diuretics (bumetanide, ethacrynic acid, furosemide)

What they’re best for: Various conditions, depending on the type of diuretic

  • Bumetanide treats high blood pressure, congestive heart failure and kidney disease.
  • Ethacrynic acid treats high blood pressure, as well as fluid retention caused by medical problems such as cancer, heart disease, kidney disease or liver disease.
  • Furosemide is used to treat swelling caused by heart disease, kidney disease or liver disease.

How they work: Loop diuretics stop a specific area of your kidney (the loop of Henle) from reabsorbing sodium chloride. That helps the kidneys flush out salt, water and other electrolytes, such as potassium and magnesium, says Wozniak.

What you need to know: Your doctor will check your kidney function and electrolyte levels by giving you blood and urine tests from time to time, Wozniak notes.

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Potassium-sparing diuretics (amiloride, eplerenone, spironolactone)

What they’re best for: Various conditions, depending on the type

  • Amiloride treats high blood pressure and heart failure.
  • Eplerenone treats high blood pressure and can also be used to treat heart failure.
  • Spironolactone treats high blood pressure when other medications haven’t worked. It also treats heart failure and swelling, and it can help treat or prevent low potassium.

How they work: They help the kidneys get rid of the extra salt and water without losing potassium.

What you need to know: While too little potassium isn’t great for your heart, too much of it can cause an arrhythmia (irregular heartbeat), which could cause the heart to beat too fast. That’s why you’ll get regular blood tests to check your potassium levels.

Recommended reading: Why your legs swell up even when it’s cold out.

How to get the most out of diuretics

The biggest drawback to taking diuretics is that you’ll have to go to the bathroom more often. After all, when your body is flushing out more water, there’s only one way it can go. But you can minimize that side effect and others by doing the following:

Take them in the morning: If you take diuretics at night or right before you drift off, you’ll be waking up more often to empty your bladder, Wozniak explains. So do yourself a favor and take them in the a.m.

Check in regularly with your provider: Your doctor will give you regular urine and blood tests to make sure your kidneys are working well. Those tests can also check your potassium levels to ensure that they don’t get too low or high. You can help, too, by reporting side effects. Dizziness, for example, is a sign that you may be losing too much water and are dehydrated. Or it could signal a dangerous drop in potassium levels.

Keep taking them until your doctor says otherwise: Even if you feel well or the swelling goes down, keep taking your medications. Stopping them or cutting back can cause those conditions to return or get worse.

Tell your pharmacist about all your medications: That way, your pharmacist can check to see whether the diuretics are reacting with other medications, including over-the-counter ones, says Wozniak.

No matter which blood pressure medication you take, Optum Perks wants to help you save at the pharmacy. Here’s how it works.

Additional sources:
Blood pressure facts: Centers for Disease Control and Prevention
Salt and blood pressure: Cleveland Clinic
Low potassium: National Library of Medicine