What Is Metolazone? Uses, Dosage, and What You Need to Know in 2026

Metolazone is a prescription diuretic — often called a "water pill" — that helps the body remove excess fluid and salt through urine. It's been used for decades to treat conditions including congestive heart failure, kidney disease, and high blood pressure. Here's a comprehensive guide to what metolazone is, what it does, how it's taken, and what makes it unique compared to other diuretics.

What Is Metolazone?

Metolazone is a quinazoline diuretic that belongs to the thiazide-like class of medications. It was originally sold under the brand names Zaroxolyn, Mykrox, and Diulo — all of which have been discontinued. Today, metolazone is available only in generic tablet form in the United States, in three strengths: 2.5 mg, 5 mg, and 10 mg.

Metolazone is manufactured by several pharmaceutical companies including Mylan, Sandoz, and Aphena Pharma Solutions. It's FDA-approved and has been on the U.S. market since the 1970s.

What Is Metolazone Used For?

The FDA has approved metolazone for two primary indications:

Edema (fluid retention) — caused by congestive heart failure or chronic kidney disease; used to reduce swelling in the legs, ankles, feet, and lungs

Hypertension (high blood pressure) — used alone or in combination with other antihypertensive drugs; especially useful in resistant hypertension

Off-label uses include edema from liver disease (cirrhosis/ascites) and as an adjunct to loop diuretics in patients who are resistant to furosemide or bumetanide alone.

What Makes Metolazone Different From Other Diuretics?

Metolazone has one critical difference from standard thiazide diuretics like hydrochlorothiazide (HCTZ): it works even when kidney function is significantly reduced. While HCTZ loses effectiveness when the glomerular filtration rate (GFR) falls below 30 mL/min, metolazone continues to produce meaningful diuresis even at GFR levels below 20 mL/min.

This makes metolazone especially valuable for:

Patients with chronic kidney disease (CKD stage 3–5) who have fluid retention

Heart failure patients who don't respond adequately to loop diuretics alone

Patients with diuretic-resistant edema or ascites from liver disease

Metolazone Dosage: How Is It Taken?

Metolazone comes as an oral tablet taken once daily. The dose your doctor prescribes depends on your condition:

Hypertension: 2.5–5 mg once daily

Edema (heart failure or kidney disease): 5–20 mg once daily

Maximum daily dose: 20 mg

Metolazone begins working within 1 hour of taking a dose, and the effects can last 24 hours or longer. Most doctors recommend taking it in the morning to prevent frequent nighttime urination.

Is Metolazone a Controlled Substance?

No. Metolazone is not a controlled substance. It has no DEA schedule, meaning there are no special restrictions on how it's prescribed, how many refills you can get, or which providers can prescribe it. This also means it can be prescribed by telehealth platforms without any special DEA requirements.

Key Drug Interactions to Know

Always tell your doctor and pharmacist about all your medications before starting metolazone. Important interactions include:

Lithium: Metolazone reduces lithium clearance, which can raise lithium levels to toxic ranges

Digoxin: Low potassium from metolazone increases the heart's sensitivity to digoxin, raising arrhythmia risk

Furosemide: Combined use can cause profound fluid and electrolyte losses — requires careful monitoring

NSAIDs (ibuprofen, naproxen): Can reduce metolazone's blood pressure-lowering effects

Who Should Not Take Metolazone?

Metolazone is contraindicated in patients with:

Anuria (inability to produce urine)

Hepatic coma or pre-coma

Known hypersensitivity to metolazone, sulfonamides, or thiazide diuretics

Want to understand how metolazone does what it does? Read: How Does Metolazone Work? Mechanism of Action Explained. Need to find a pharmacy that has metolazone in stock? medfinder can help.