What Is a Diuretic? Uses, Warnings, Side Effects, and More

Diuretics are a class of medications commonly known as "water pills." There are several different classes of diuretics, each of which works differently in the kidneys to help rid the body of extra water and salt.

Most diuretics help your kidneys release more sodium into your urine, according to Mayo Clinic. The sodium helps remove water from your blood, decreasing the amount of fluid that flows through your veins and arteries, which in turn reduces blood pressure.

Each type of diuretic affects a different part of your kidneys, notes Mayo Clinic. Some medications combine more than one type of diuretic, or combine a diuretic with another blood pressure medication.

Diuretics are recommended as a first-line treatment for high blood pressure, per Mayo Clinic.

They are also commonly recommended for people who have the following conditions:

• Heart failure
• Liver failure
• Tissue swelling (edema)
• Kidney disorders, such as kidney stones

There are three main types of diuretics, per Mayo Clinic. These include:

• Thiazide diuretics, like chlorthalidone, chlorothiazide, hydrochlorothiazide, indapamide, and metolazone.
• Loop diuretics, such as furosemide, bumetanide, ethacrynic acid, and torsemide.
• Potassium-sparing diuretics, including amiloride, eplerenone, triamterene, and spironolactone.

You should not take any type of diuretic if you have severe dehydration, anuria (lack of urine production), or an electrolyte abnormality, per StatPearls.

Avoid taking any diuretic drug to which you have a known hypersensitivity.

If you have gout, do not take loop or thiazide diuretics.

Avoid taking loop diuretics if you have certain conditions, including hypokalemia (low potassium levels), severe hyponatremia (low sodium levels), hypotension (low blood pressure), oliguria (low urine output), or if you are expecting to have fluid depletion, such as during surgery.

Take loop diuretics instead of thiazides (except metolazone) if you have chronic kidney disease and extra urine production is required.

Do not take potassium-sparing diuretics if you have hyperkalemia (high potassium levels), advanced kidney failure, or chronic kidney disease. Certain potassium-sparing diuretics should also be avoided during pregnancy.

Ask your doctor about the best type of diuretic for you if you have severe chronic obstructive pulmonary disease.

If you’re being treated with diuretics, your doctor should carefully and regularly assess your urine output, electrolyte level, body weight, blood pressure and other vials, especially if you are elderly or if you have cardiovascular, liver, kidney, or metabolic disorders.

If you are taking loop diuretics, baseline auditory tests are recommended to avoid hearing or balance problems.

If you are using any diuretic and it does not increase your urine output, you should stop taking the medication, as it could be a sign of undiagnosed, underlying kidney disease.

According to Mayo Clinic, side effects of diuretics include:

• Increased urination
• Sodium loss
• Hypokalemia (low potassium levels): Thiazide diuretics can cause hypokalemia, which can cause life-threatening problems with your heartbeat.
• Hyperkalemia (too much potassium in your blood): Potassium-sparing diuretics can cause hyperkalemia.

Other possible side effects of diuretics include:

• Dizziness
• Headache
• Dehydration or increased thirst
• Muscle cramps
• Joint disorders (gout)
• Impotence
• Digestive problems, upset stomach, or abdominal pain

According to an article published in StatPearls, rare side effects of diuretics include:

• Impotence
• Skin reactions
• Anemia
• Muscle cramps

Side effects are more likely with loop diuretics, notes StatPearls.

Nonsteroidal anti-inflammatory drugs (NSAIDs) can suppress kidney production when used simultaneously with loop or thiazide diuretics, which can lead to acute kidney failure.

Take care when using loop diuretics along with other drugs that can cause hearing or balance issues, such as aminoglycoside antibiotics.

Avoid taking diuretics that may induce hypokalemia in combination with digoxin (used for heart failure) or quinidine (used for arrhythmias).

Bendroflumethiazide, a thiazide diuretic, can cause calcium retention, so take care when using the drug along with calcium supplements or vitamin D.

Potassium-sparing diuretics should not be taken at the same time as another potassium-sparing diuretic to avoid the risk of hyperkalemia.