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Furosemide

Brand names: Lasix, Furoscix

Furosemide is a strong water pill that removes extra fluid from the body. It's used for swelling and fluid buildup from heart, liver, or kidney problems.

Brand namesLasix, Furoscix
Type of medicineLoop diuretic (water pill)
Prescription?Prescription
ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

It makes the kidneys pass more salt and water, usually within an hour.

What it's used for

  • Fluid buildup and swelling (edema) from heart failure, liver disease, or kidney disease
  • High blood pressure

How to take it

  • Take it in the morning (and early afternoon if you take a second dose) to avoid peeing at night.
  • Weigh yourself daily at the same time if your provider asks.
  • Get up slowly to avoid dizziness.

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

  • Peeing a lot
  • Dizziness
  • Thirst
  • Low potassium
  • Muscle cramps
Call your provider todayExtreme thirst, dry mouth, very little urine, confusion, or fainting (dehydration)
Call your provider todayMuscle weakness or cramps with an irregular heartbeat
Call your provider todayRinging in the ears or hearing loss

Warnings

  • Your provider will check potassium, sodium, and kidney function.
  • Tell your provider if you're allergic to sulfa drugs.

Other medicines, foods, and alcohol

  • Lithium levels can rise.
  • Some antibiotics (aminoglycosides) raise the risk of hearing damage.
  • NSAIDs can weaken its effect.
  • Digoxin side effects are more likely with low potassium.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Use only if your provider decides it's needed.

Missed doses, overdose, and storage

If you miss a dose

Take it as soon as you remember, unless it's almost time for your next dose. Then skip the missed dose. Don't take two doses at once.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.

Conditions it's used for

Sources

Last updated 2026-11-13.