Reviewed on 8/24/2021

What Is Furosemide and How Does It Work?

Furosemide is known as a diuretic (like a "water pill"). It helps your body get rid of extra water by increasing the amount of urine you make. Getting rid of extra water decreases the strain on your heart and blood vessels, thereby lowering high blood pressure and reducing your risk of strokes, heart attacks, and kidney problems. This effect can also improve symptoms such as trouble breathing and swelling (edema). This injectable form of furosemide is used when the drug cannot be taken by mouth, especially in patients with severe medical conditions.

  • Furosemide can also be used to decrease calcium in the blood (hypercalcemia).
  • Furosemide is available under the following different brand names: Lasix.

What Are Dosages of Furosemide?

Dosages of Furosemide:

Adult and Pediatric Dosage Forms and Strengths

Injectable solution

  • 10mg/mL

Oral solution

  • 10 mg/mL


  • 20 mg
  • 40 mg
  • 80 mg

Dosage Considerations – Should be Given as Follows:


Edema associated with congestive heart failure (CHF), liver cirrhosis, and renal disease, including nephrotic syndrome

  • 20-80 mg orally once daily; may be increased by 20-40 mg every 6-8 hours; not to exceed 600 mg/day
  • Alternative: 20-40 mg intravenously/intramuscularly (IV/IM) once; may be increased by 20 mg every 2 hours; individual dose not to exceed 200 mg/dose

Refractory CHF may necessitate larger doses

  • Infants and children: 1-2 mg/kg IV/IM/orally once initially; increased by 1-2 mg/kg every 6-8 hours (orally) or 1 mg/kg every 2 hours (IV/IM); individual dose not to exceed 6 mg/kg

Neonates (younger than 28 days):

  • 0.5-1 mg/kg IV/IM every 8-24 hours; individual dose not to exceed 2 mg/kg


  • 20 mg/day orally/IV/IM initially; increased slowly until the desired response is obtained

Hypertension, Resistant

  • Adult: 20-80 mg orally divided every 12 hours
  • Children less than 1 year: Safety and efficacy not established
  • Children 1-17 years: 0.5-2 mg/kg orally every 24 hours or every 12 hours; individual dose not to exceed 6 mg/kg/dose

Acute Pulmonary Edema/Hypertensive Crisis/Increased Intracranial Pressure

  • 0.5-1 mg/kg (or 40 mg) intravenously (IV) over 1-2 minutes; may be increased to 80 mg if there is no adequate response within 1 hour; not to exceed 160-200 mg/dose

Hyperkalemia in Advanced Cardiac Life Support (ACLS)

  • 40-80 mg intravenously (IV)

Hypermagnesemia in ACLS

  • 20-40 mg intravenously (IV) every 3-4 hours as needed

Dosing Modifications

  • Acute renal failure: 1-3 g/day may be necessary to attain desired response; avoid use in oliguric states
  • Hepatic impairment: Monitor, especially with high dosages

Dosing Considerations

  • Use for fluid retention refractory to thiazides or impaired renal function

Overdose management


  • Excessive diuresis may cause dehydration and electrolyte loss in the elderly; lower initial dosages and more gradual adjustments are recommended (e.g., 10 mg/day orally)

An increase in blood urea nitrogen (BUN) and loss of sodium may cause confusion in the elderly; monitor renal function and electrolytes


In the U.S., 1 in every 4 deaths is caused by heart disease. See Answer

What Are Side Effects Associated with Using Furosemide?

Side effects associated with the use of Furosemide, include the following:

Other side effects of furosemide include:

Postmarketing side effects of furosemide reported include:

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

What Other Drugs Interact with Furosemide?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Severe interactions of furosemide include:
    • None
  • Serious Interactions of furosemide include:
  • Furosemide has moderate interactions with at least 161 different drugs.
  • Furosemide has mild interactions with at least 142 different drugs.

This information does not contain all possible interactions or adverse effects. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns, or for more information about this medicine.


Heart Disease: Symptoms, Signs, and Causes See Slideshow

What Are Warnings and Precautions for Furosemide?


  • The agent is a potent diuretic that, if given in excessive amounts, may lead to a profound diuresis with water and electrolyte depletion
  • Careful medical supervision is required; dosing must be adjusted to the patient's needs
  • This medication contains furosemide. Do not take Lasix if you are allergic to furosemide or any ingredients contained in this drug
  • Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately


  • Documented hypersensitivity to furosemide or sulfonamides
  • Anuria

Effects of Drug Abuse

  • The agent is a potent diuretic that, if given in excessive amounts, may lead to a profound diuresis with water and electrolyte depletion

Short-Term Effects

  • See "What Are Side Effects Associated with Using Furosemide?"

Long-Term Effects

  • See "What Are Side Effects Associated with Using Furosemide?"


  • Use caution in systemic lupus erythematosus, liver disease, renal impairment
  • Concomitant ethacrynic acid therapy (increases risk of ototoxicity)
  • Risks of fluid or electrolyte imbalance (including causing hyperglycemia, hyperuricemia, gout), hypotension, metabolic alkalosis, severe hyponatremia, severe hypokalemia, hepatic coma and precoma, hypovolemia (with or without hypotension)
  • Do not commence therapy in a hepatic coma and electrolyte depletion until improvement is noted
  • The Intravenous (IV) route is twice as potent as the oral route
  • Food delays absorption but not diuretic response
  • May exacerbate lupus
  • Possibility of skin sensitivity to sunlight
  • Prolonged use in premature neonates may cause nephrocalcinosis
  • Efficacy is diminished and the risk of ototoxicity increased in patients with hypoproteinemia (associated with nephrotic syndrome); ototoxicity is associated with rapid injection, severe renal impairment, use of higher than recommended doses, concomitant therapy with aminoglycoside antibiotics, ethacrynic acid, or other ototoxic drugs
  • To prevent oliguria, reversible increases in BUN and creatinine, and azotemia, monitor fluid status and renal function; discontinue therapy if azotemia and oliguria occur during treatment of severe progressive renal disease
  • FDA-approved product labeling for many medications have included a broad contraindication in patients with a prior allergic reaction to sulfonamides; however, recent studies have suggested that cross-reactivity between antibiotic sulfonamides and non-antibiotic sulfonamides is unlikely to occur
  • In cirrhosis, electrolyte and acid/base imbalances may lead to hepatic encephalopathy; before initiation of therapy, correct electrolyte, and acid/base imbalances, when hepatic coma is present
  • High doses (greater than 80 mg) of furosemide may inhibit the binding of thyroid hormones to carrier proteins and result in a transient increase in free thyroid hormones, followed by an overall decrease in total thyroid hormone levels
  • In patients at high risk for radiocontrast nephropathy furosemide can lead to a higher incidence of deterioration in renal function after receiving radiocontrast compared to high-risk patients who received only intravenous hydration before receiving radiocontrast
  • Observe patients regularly for the possible occurrence of blood dyscrasias, liver or kidney damage, or other idiosyncratic reactions
  • Cases of tinnitus and reversible or irreversible hearing impairment and deafness reported
  • Hearing loss in neonates has been associated with the use of furosemide injection; in premature neonates with respiratory distress syndrome, diuretic treatment with furosemide in the first few weeks of life may increase the risk of persistent patent ductus arteriosus (PDA), possibly through a prostaglandin-E-mediated process
  • Excessive diuresis may cause dehydration and blood volume reduction with circulatory collapse and possibly vascular thrombosis and embolism, particularly in elderly patients
  • Increases in blood glucose and alterations in glucose tolerance tests (with abnormalities of the fasting and 2-hour postprandial sugar) have been observed, and rarely, precipitation of diabetes mellitus reported
  • Patients with severe symptoms of urinary retention (because of bladder emptying disorders, prostatic hyperplasia, urethral narrowing), the administration of furosemide can cause acute urinary retention related to increased production and retention of urine; these patients require careful monitoring, especially during the initial stages of treatment

Pregnancy and Lactation

  • Use furosemide with caution during pregnancy if benefits outweigh risks
  • Animal studies show risk and human studies are not available or neither animal nor human studies done
  • Treatment with furosemide during pregnancy necessitates monitoring of fetal growth because of the risk for higher fetal birth weights
  • Furosemide is excreted into breast milk; use with caution if breastfeeding; may inhibit lactation
Medscape. Furosemide.

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