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Metolazone

Brand names: Zaroxolyn (brand discontinued)

Metolazone is a strong water pill, often added to furosemide or other loop diuretics when swelling won't go down.

Brand namesZaroxolyn (brand discontinued)
Type of medicineThiazide-like 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

Together with a loop diuretic it can remove a lot of fluid quickly, so labs and weight are watched closely.

What it's used for

  • Stubborn fluid buildup in heart failure or kidney disease
  • High blood pressure

How to take it

  • Take it exactly as directed; it's often used only on certain days.
  • Usually taken 30 minutes before the loop diuretic.
  • Weigh yourself daily.

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
  • Low potassium, sodium, or magnesium
Call your provider todayExtreme thirst, confusion, cramps, or very little urine
Call your provider todayLosing more than 2 to 3 pounds a day
Call 911Fainting or an irregular heartbeat

Warnings

  • Don't switch between metolazone products; they're absorbed differently.

Other medicines, foods, and alcohol

  • Loop diuretics greatly increase its effect.
  • Lithium levels can rise.
  • Digoxin toxicity is more likely with low potassium.

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

Pregnancy and breastfeeding

Talk with your provider.

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.