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Diuretics (Water Pills) for High Blood Pressure

Medically Reviewed by Brunilda Nazario, MD on September 17, 2021

What Are Diuretics?

Commonly known as "water pills," these drugs help your kidneys get rid of extra water and salt from your body through your urine. Because you have less total fluid in your blood vessels, like a garden hose that's not turned on all the way, the pressure inside will be lower. This also makes it easier for your heart to pump.

They're usually the first type of medication that your doctor will try to control your blood pressure.

Examples of diuretics include:

Diuretics come in different categories:

  • Thiazide-like. These get rid of a moderate amount of water. They can be used for a long time.
  • Loop. They’re more powerful and are very useful in emergencies.
  • Potassium-sparing. They help you keep potassium as you’re getting rid of water and salt.

Different diuretics can be taken together, and you can take them with other medications, sometimes in the same pill.

Who Should Take Them?

Your doctor may recommend a diuretic if you have:

  • Edema. Diuretics lessen swelling that usually happens in the legs.
  • High blood pressure. Thiazide diuretics lower blood pressure. That lowers your chance of a stroke or heart attack.
  • Heart failure. Diuretics ease swelling and congestion in the lungs. You’ll usually get a loop diuretic for heart failure.
  • Kidney problems. You’ll keep less water.
  • Liver problems. If you have cirrhosis, a diuretic will ease the fluid buildup you’ll get with it.
  • Glaucoma. They’ll reduce the pressure in your eye.

How Should I Take Them?

Before you’re prescribed a diuretic, tell your doctor if you have diabetes, kidney disease, liver disease, or gout.

Follow the directions on the label. If you’re taking one dose a day, take it in the morning with your breakfast or right after. If you’re taking more than one dose a day, take the last one no later than 4 p.m.

The number of doses you take each day, the time allowed between doses, and how long you need to take a diuretic will depend on the type prescribed, as well as your condition.

Weigh yourself at the same time every day (on the same scale) and write down your weight. Call your doctor if you gain 3 pounds in one day or 5 pounds in one week.

While you’re taking these, have your blood pressure and kidney strength tested regularly. Diuretics can change your blood potassium and magnesium levels.

Keep all your doctor and lab appointments so your response to this medicine can be tracked.

What Foods or Drugs Interact With Them?

To avoid a potential problem, tell your doctor and pharmacist about all the medicines you are taking, including:

Diuretics are often prescribed with other drugs. If you have more side effects when you take them together, contact your doctor. You may need to change the times you take each one.

Before a diuretic is prescribed, tell your doctor if you’re taking:

Some diuretics may require you to avoid or eat certain foods. Follow your doctor's advice, which may include:

  • A low-salt diet
  • A potassium supplement or high-potassium foods such as bananas and orange juice.

As always, talk with your doctor.

While You're Taking Diuretics

Let your doctor know what medications (prescription and over-the-counter), supplements, and herbal remedies you use. Also, tell them about other medical problems you have.

They may want to regularly check your blood pressure as well as test your blood and urine for levels of specific minerals and to see how well your kidneys are working. They'll probably tell you to follow a low-sodium diet and limit how much salt you eat.

Because some diuretics also pull potassium out of your body, you might need to eat more foods like bananas, sweet potatoes, spinach, and lentils, or take a potassium supplement. On the other hand, if you're taking a potassium-sparing diuretic, such as amiloride (Midamar), spironolactone (Aldactone), or triamterene (Dyrenium), they may want you to avoid potassium-rich foods, salt substitutes, low-sodium milk, and other sources of potassium.

If you only need one dose a day, you might want to take your diuretic in the morning so you can sleep through the night instead of getting up to go to the bathroom.

Avoid alcohol and medicines to help you sleep. They may make side effects worse.

Side Effects

The water that comes out of your body has to go somewhere, so you can expect to be peeing more and more, often for several hours after a dose. If you’re taking two doses each day, take the second dose no later than late afternoon so you can sleep through the night without waking up to urinate.

You also run the risk of getting dehydrated, and simply drinking more fluids may not be enough. Call your doctor if you're very thirsty or have a very dry mouth, your pee is a deep yellow, you aren't peeing much or get constipated, or you have a bad headache.

You may have extreme tiredness or weakness. These should ease as your body gets used to the medicine. Call your doctor if these symptoms hang around. That could mean your dose needs to be adjusted.

You may feel dizzy or lightheaded, especially when you stand up, if your blood pressure has dropped too low, or you're getting dehydrated.

Your blood chemistry can get thrown off. You could have too little or too much sodium or potassium in your system. This can make you tired or weak or give you muscle cramps or a headache. It's rare, but your heart may speed up (over 100 beats a minute) or you might start throwing up because of a dangerously low potassium level.

Diuretics may make it harder for you to control your blood sugar, which can lead to diabetes if you don't already have it. You might be more likely to get gout.

Taking combination pills or multiple medicines could boost these side effects. To help lower those odds, ask your doctor when during the day you should take each medication.

If you have constant or severe blurred vision, confusion, headache, increased sweating, or restlessness, call your doctor.

Call your doctor or nurse if you have:

Also call them if you have any other symptoms that concern you.

Who Shouldn't Take Them?

Some diuretics are sulfa drugs, so they could cause a reaction if you're allergic.

Older people tend to have more side effects such as fainting and dizziness from dehydration. You'll need to work closely with your doctor.

Most diuretics are fine to take if you’re breastfeeding, with some precautions. Talk with your doctor.

Kids can safely take them, but they need smaller doses. The side effects are similar to adults. But potassium-sparing diuretics can cause low levels of calcium, which could hurt bone development.

WebMD Medical Reference

Sources

SOURCES: 

American Heart Association: "Types of Blood Pressure Medications."

Blood Pressure UK: "Diuretics - blood pressure medication."

Mayo Clinic: "High blood pressure (hypertension): Diuretics."

European Heart Journal: "Adverse reactions to diuretics."

Consumer Reports: "What to Know About Diuretics for High Blood Pressure."

HeartHealthyWomen.org: "Diuretics in Heart Failure."

MayoClinic.com: "Diuretics."

Texas Heart Institute: "Diuretics."

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