Skip to content
ClinCalc Pro
Menu
Calculators Drugs Pathways AI Dx Donate Get the App
Loop Diuretic

Furosemide 40–500mg oral / 20–200mg IV

Brand names: Lasix, Frusol (oral solution)

Furosemide given by the oral or intravenous route is a loop diuretic used to treat fluid overload in conditions such as heart failure, chronic kidney disease and nephrotic syndrome; the intravenous route is reserved for urgent decongestion or when gut absorption is unreliable.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It inhibits the sodium-potassium-chloride co-transporter in the thick ascending limb of the loop of Henle, producing potent natriuresis and diuresis.

Prescribing in practice

  • Rapid or high-dose intravenous administration can cause ototoxicity, so give IV doses slowly, especially in renal impairment where higher doses are often required.
  • Oral bioavailability is variable, so switching from oral to intravenous typically requires a reduction in the equivalent dose.
  • It can precipitate hypokalaemia, hyponatraemia, volume depletion and acute kidney injury, particularly when combined with other nephrotoxins or RAS blockers.

Monitoring

Monitor renal function, electrolytes, fluid balance and weight, and assess hearing if high intravenous doses are used.

Counselling the patient

  • You will pass urine more frequently, so time doses to avoid disturbing sleep.
  • Report dizziness on standing, muscle cramps or significant changes in weight.
  • Mention any ringing in the ears or hearing changes, especially after injections.

Evidence & guidelines

Loop diuretic use is supported by NICE heart failure and chronic kidney disease guidance for symptomatic fluid management.

Reference: ESC Heart Failure Guidelines 2021; NICE NG203; KDIGO AKI Guidelines; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

Calculators
Drugs
Pathways