Furosemide dosage, forms, and strengths

Furosemide, known by the brand name Lasix, is a generic prescription drug used to treat hypertension (high blood pressure), pulmonary edema (fluid buildup in lungs), or edema (fluid retention) due to congestive heart failure, liver cirrhosis, or renal disease, including nephrotic syndrome. As a loop diuretic, furosemide increases the amount of water and salt excreted in the urine. Its mechanism of action is especially suitable for people with impaired renal function. Depending on the condition, furosemide is taken orally or administered as an intravenous or intramuscular injection.

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Furosemide forms and strengths

Depending on the medical condition, furosemide is given as an injection, tablet, or liquid. 

• Tablet: 20 milligrams (mg), 40 mg, 80 mg

• Oral solution: 8 mg per milliliter (mL), 10 mg/mL

• Injection: 10 mg/mL

Furosemide dosage for adults

Furosemide dosing depends on the condition being treated. Some conditions are only treated using furosemide injections. Intramuscular (IM) and intravenous (IV) injection doses will often be determined by weight.

Furosemide dosage for edema

Furosemide is used alone or in combination with other diuretics to relieve fluid retention (edema) in children and adults with congestive heart failure, kidney disease, or liver damage. Furosemide increases the urinary excretion of water and salt from the body, drawing off excess extracellular fluid. Furosemide injections are not therapeutically equivalent to oral doses. Because more of the drug is used by the body and peaks earlier, furosemide injections are given in smaller doses and often repeated at shorter intervals than oral doses. Injections typically stop when therapeutic goals have been met. In some cases, furosemide injections may continue to be administered as one or two daily doses.

• Standard oral dosage for edema: 40-120 mg divided into one or two daily doses

• Standard injection dosage for edema: 20-40 mg initial injection followed by additional injections increased by 20 mg every two hours

• Maximum dosage for edema: 600 mg per day

Furosemide dosage for hypertension

For adults with high blood pressure (hypertension), furosemide is used alone or with other blood pressure medications. Diuretics are a staple of blood pressure management. By reducing water and salt, they lower blood volume and pressure. Current guidelines recommend loop diuretics such as furosemide only be prescribed for hypertension in people with advanced kidney disease.

• Standard dosage in adults with hypertension: 10-40 mg twice daily

• Maximum dosage in adults with hypertension: Not specified

Furosemide dosage for acute pulmonary edema

Furosemide is FDA approved to treat acute (abrupt-onset) pulmonary edema, or fluid build-up in the lungs. Immediate response is required, so furosemide is injected intravenously every hour until the lungs are sufficiently cleared of fluid. In addition to reducing water and salt, furosemide also widens veins, helping to draw off more water from the lungs.

• Standard dosage in adults with pulmonary edema: 80 mg injected once per hour

• Maximum dosage in adults with pulmonary edema: Not specified

Furosemide dosage for children

Children are given furosemide only to treat fluid retention due to heart disease, kidney disease, or liver disease. The oral dose for newborns, infants, and children is determined by weight, starting at 1 mg/kg for newborns (0-2 months old) and 2 mg/kg for infants and children (greater than 2 months old). The maximum recommended dose is 6 mg/kg of body weight. Consult the furosemide dosage table for initial and standard doses for children.

Furosemide dosage restrictions

Furosemide may not be right for every person. Contraindications include anuria (not producing urine), electrolyte depletion, and hepatic coma. People with liver problems or abdominal fluid retention (ascites) will be closely monitored when treated with furosemide.

• Renal impairment: No dose adjustment

  • Creatinine clearance < 60 ml/min: No dose adjustment 

  • Hemodialysis or parenteral dialysis: No dose adjustment, no supplement

  • Anuria: Do not use

• Hepatic impairment: No dose adjustment

Seniors will not require dose adjustments. Doctors are advised, however, to start with the lowest possible furosemide doses when treating people older than 65. 

Furosemide dosage for pets

Veterinarians commonly use furosemide to treat edema due to congestive heart failure, liver disease, or kidney disease, and to treat high blood pressure, pulmonary edema, ascites (abdominal swelling), hyperkalemia (excess potassium), and hypercalcemia (excess calcium) in all common species of household pets. Most conditions will require injections, but some may involve giving the animal furosemide tablets or oral solution. Dosing will depend on the condition, and the animal’s species, and body weight.

How to take furosemide

For some conditions, furosemide will be injected by a healthcare provider. However, when taking furosemide tablets or oral solution, follow these useful tips:

• Take the medicine as directed.

• If taking a tablet, swallow the tablet whole with water. Do not crush, break, or chew the tablet.

• If taking the oral solution, shake the bottle well before measuring out a dose.

• Measure the oral solution with the metered measuring syringe or cup provided with the medicine.

• Take the medicine with food if it causes stomach upset.

• Store furosemide in a closed, light-resistant container at room temperature (68–77 degrees Fahrenheit).

Furosemide dosage FAQs

How long does it take furosemide to work?

When taken orally, furosemide begins to work in 60 to 90 minutes and reaches its peak concentration in two hours. Furosemide can be taken with or without food, but food may delay and reduce its peak concentration. Furosemide injections are not therapeutically identical to oral doses. When injected, furosemide begins to work in five minutes and achieves peak diuretic effects in 20–60 minutes.  

How long does furosemide stay in your system?

When taken orally, furosemide is effective for four to six hours, but the effects may last for up to eight hours in some people. When injected, furosemide is effective for about two hours. With a half-life between four and four and a half hours, furosemide falls to undetectable levels in the blood and urine in about 24 to 48 hours.

What happens if I miss a dose of furosemide?

Take a missed dose as soon as possible. If it is almost time for the next dose, skip the missed dose and take the next scheduled dose. Never take extra medicine to make up for a missed dose. Many people will be instructed not to take furosemide too late in the day. Increased urination can interfere with sleep. Talk to a healthcare provider about what to do about taking a missed dose late in the day.

How do I stop taking furosemide?

Taken as directed, furosemide can be safely discontinued without serious side effects or withdrawal. Though sometimes abused by athletes, furosemide does not cause physical or psychological dependence. However, when the drug is abruptly discontinued, it can cause the body to overcompensate by temporarily retaining too much water and salt. This may require monitoring in people with serious health conditions.

Furosemide might have to be discontinued in people who experience serious adverse effects such as kidney damage, tinnitus (ringing in the ears), hearing loss, liver dysfunction, pancreatitis, hyperuricemia (excess uric acid), severe dehydration, severe electrolyte depletion, or a serious hypersensitivity reaction. 

What is the maximum dosage of furosemide?

No more than 600 mg of furosemide should be taken in a single day. High doses, however, are only used to treat the most severe cases of edema. Children should not receive doses greater than 6 mg for every kilogram (2.2 pounds) of body weight.

Can you overdose on furosemide?

Taking too much furosemide will cause dehydration, electrolyte depletion, low blood pressure, and low potassium levels (hypokalemia), all potentially hazardous medical conditions. Look for symptoms such as dry mouth, muscle cramps, tiredness, vomiting, or constipation when taking furosemide. These symptoms may indicate possible drug interactions or that the furosemide dose is too high. 

What interacts with furosemide?

Some prescription drugs, such as sucralfate and bile acid sequestrants interfere with furosemide absorption. Also, some drugs and herbal remedies reduce the beneficial effects of furosemide, such as NSAIDs, ginseng, and phenytoin.

Combining furosemide with diuretics, over-the-counter laxatives, or alcohol increases this risk. In addition, blood glucose levels could drop to hazardously low levels in patients with diabetes mellitus who drink alcohol while taking furosemide. 

Furosemide also lowers blood pressure, so any medication that reduces blood pressure could cause hypotension when combined with furosemide. Some antihypertensives, particularly angiotensin-converting enzyme inhibitors (ACE inhibitors) and angiotensin II receptor blockers (ARBs), may cause a dangerous drop in blood pressure when used with furosemide.

Furosemide can cause hearing loss. Furosemide ototoxicity (ear damage) could be amplified when the drug is combined with other ototoxic drugs such as aminoglycoside antibiotics or cisplatin. Furosemide can also increase the toxicity of some drugs such as cephalosporin antibiotics or lithium.

Is it safe to take furosemide during pregnancy or while nursing?

The safety of giving furosemide to pregnant or nursing women has not been determined. Women who are pregnant or considering pregnancy should consult with a healthcare provider. Furosemide is present in breast milk and reduces lactation, so it may need to be discontinued or reduced in women who are breastfeeding

Related resources:

• 2017 Guideline for the prevention, detection, evaluation, and management of high blood pressure in adults

• Effect of food on the absorption of furosemide and bumetanide in man

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