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Lasix dosage, forms, and strengths

Lasix treats high blood pressure or edema. Learn what the recommended dosage recommendations are for these conditions.

Forms and strengths | Lasix for adults | Lasix for children | Lasix dosage restrictions | Lasix for pets | How to take Lasix | FAQs

Lasix is a brand-name prescription diuretic that is often called a water pill since it helps to remove water from the body through urination. Lasix can be used to treat high blood pressure or edema. 

High blood pressure, also called hypertension, can happen when the force of blood is too high in the artery walls. Edema, also called fluid retention, is the swelling caused by too much fluid trapped in different parts of the body. Swelling can be due to congestive heart failure, liver cirrhosis, or kidney disease. 

Furosemide, the active ingredient in Lasix, is a loop diuretic that acts on specific parts of the kidneys. Lasix is available as a tablet, but generic furosemide can also be found as an oral solution or injection common in hospital settings.

RELATED: Learn more about furosemide | Get furosemide discounts

Lasix forms and strengths

Lasix tablets are available in three different dose strengths.

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

Lasix dosage for adults

Lasix dosing will depend on the condition being treated and is often individualized to the patient. A person’s dose will depend on his or her response to Lasix. The goal is to get the best therapeutic effect with the smallest dose to prevent dehydration and decreases in electrolytes (such as sodium, potassium, and chloride).

  • Standard Lasix dosage: 40–120 mg per day taken in one or two daily doses (edema) or 10-40 mg taken twice per day (hypertension) 
  • Maximum recommended Lasix dosage: 600 mg per day for the most severe cases of edema
Indication Starting dosage Standard dosage Maximum dosage
Edema 20–80 mg given once per day 40–120 mg per day divided into 1 or 2 daily doses 600 mg per day
Hypertension 40 mg twice per day 10–40 mg twice per day Not specified

Lasix dosage for edema

Lasix 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 cirrhosis of the liver. Furosemide affects parts of the kidneys—the loop of Henle and nearby tubules—that reabsorb water and salt from the urine and return them to the bloodstream. As a result, more water and salt (sodium, chloride, magnesium, and calcium) are eliminated from the body, reducing the buildup of fluid in the body’s tissues.

When using Lasix, after the first dose there is a quick increase in urination. It is important for people to have quick and easy access to a bathroom. If necessary and part of the treatment plan, people can have their second Lasix dose six to eight hours after their first dose. Since Lasix doses are individualized for each person, some people may benefit from taking Lasix for edema a few days per week instead of daily.

It is important for people managing edema with Lasix to keep track of their body weight. Changes in the body’s fluid can impact a person’s weight. These weight changes can often be the first sign of edema. Having a bathroom scale can help people check their weight at home and allow them to report any significant changes to their healthcare provider. The Lasix dose can be adjusted based on these weight changes.

  • Standard dosage: 40–120 per day divided into one or two daily doses
  • Maximum dosage: 600 mg per day

Lasix dosage for hypertension

Lasix is prescribed alone or with other blood pressure lowering medications to adults with high blood pressure (hypertension). Typically Lasix is used along with other medications to lower blood pressure. As a diuretic, Lasix lowers the amount of salt and water in the bloodstream, reducing overall blood volume and blood pressure. Furosemide also widens blood vessels and this helps to lower blood pressure. Most adults with hypertension under consideration to begin a diuretic will start a thiazide diuretic such as hydrochlorothiazide or chlorthalidone. Loop diuretics, such as Lasix, are great options for treating high blood pressure in people with moderate to severe kidney disease or people experiencing symptoms due to heart failure.

Since Lasix dosages are individualized for each person, the Lasix dose may need to be adjusted based on any other blood pressure medications that person is taking. Healthcare providers may make these adjustments to prevent excessive drops in blood pressure. 

  • Standard dosage: 10–40 mg twice daily
  • Maximum dosage: Not specified

Lasix dosage for children

Furosemide is FDA-approved to treat edema in children with congestive heart failure, kidney disease, or liver disease. Newborns and infants will usually be given furosemide injections or oral solution, whereas Lasix is only available as a tablet. The dose for newborns, infants, and children is determined by body weight, typically starting at mg of furosemide for every one (1) kilogram (kg) of body weight This dose should not exceed 6 mg per kilogram of body weight. A kilogram is equal to 2.2 pounds.

  • Standard oral dosage for newborns: 1–4 mg/kg of body weight given once to twice per day
  • Standard oral dosage for infants and children: 1–6 mg/kg of body weight every 12 or 24 hours
  • Maximum oral dosage for newborns, infants, and children: No more than 6 mg/kg per dose

Lasix dosage restrictions

Lasix will not be given to people whose kidneys do not produce urine (anuria), who are depleted of electrolytes, or who are in a hepatic coma (loss of brain function due to liver disease). 

People older than 65 will receive the same doses as other adults, but they will be started with the lowest recommended doses. Unlike some medications, lower doses are not necessary for people who can still safely receive Lasix with liver problems or impaired renal function. However, people with cirrhosis of the liver or ascites (abdominal fluid retention) will require close monitoring. Overdose is possible with Lasix so it is important to take this medication as directed by a healthcare professional. If an overdose is suspected, people should contact their doctor immediately for treatment.

Lasix dosage for pets

In veterinary practice, furosemide is commonly used as tablets, oral solutions, or injections in all mammal species including cats and dogs. Veterinarians use furosemide to treat edema due to congestive heart failure, liver disease, or kidney disease, as well as to treat high blood pressure, pulmonary edema, hyperkalemia (excess potassium), and hypercalcemia (excess calcium) in animals. It’s also used as an emergency treatment for exercise-induced pulmonary hemorrhage (EIPH) in horses. 

If determined necessary by a veterinarian, most pets will receive IV injections of furosemide, but some conditions may involve maintenance therapy with furosemide tablets or oral solution. The dose will depend on the condition and the animal. Similar to humans, pets will need to be monitored for electrolyte changes, low blood pressure, and signs of dehydration. Please do not give human medications like Lasix to an animal. Allow a professional veterinarian to determine the proper furosemide dose, dosing schedule, and format to best treat a pet. 

How to take Lasix

Lasix is taken as a tablet one to two times a day with or without food.

  • Take medicine as directed by a healthcare professional
  • Try to avoid taking Lasix late in the day to prevent waking up at night to go to the bathroom
  • Swallow the tablet with water
  • Take the medicine with food if it causes stomach upset
  • If Lasix is being given to a child, monitor the child’s weight carefully since the dose is based on weight. The prescribing physician will need to be updated about any significant weight change.
  • Lasix reduces potassium levels in the body, potentially causing low blood potassium (hypokalemia). Talk to a doctor or healthcare provider about taking potassium supplements along with Lasix.
  • Store Lasix in a closed, light-resistant container away from any moisture or heat at room temperature (68º––77ºF)
  • Lasix tablets are white and will discolor when exposed to light. Do not take discolored Lasix tablets.

Lasix dosage FAQs

How long does it take Lasix to work?

Diuresis (increased urine production and excretion) will begin about 1 to 1½ hours after taking a single dose of oral Lasix. The most diuresis will happen in about two hours. It is okay to take Lasix on an empty stomach or with food, but taking Lasix with food may affect how the body absorbs the medication. However, don’t hesitate to take Lasix with food if it causes stomach upset when taken on an empty stomach. It is important to stay consistent with how the medicine is taken each day.

How long does Lasix stay in your system?

The diuretic effects of oral Lasix last for about six to eight hours. Furosemide is mainly removed from the body through urination. In those with impaired kidneys, it may take longer for their bodies to remove Lasix. 

What happens if I miss a dose of Lasix?

Take a missed dose as soon as it’s remembered. If it is almost time for the next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose. Keep in mind that diuretics like Lasix can disrupt sleep if taken too close to bedtime. Talk to a doctor, pharmacist, or another healthcare provider for advice about taking a missed dose late in the day.

How do I stop taking Lasix?

In most patients, Lasix can either be safely stopped or replaced by a substitute therapy without serious adverse effects. However, Lasix is prescribed for serious and health-threatening medical conditions, so don’t stop taking the medication until a doctor or other healthcare professional has been consulted. 

Loop diuretics such as Lasix do cause temporary withdrawal symptoms. Diuretics affect the body’s regulation of urination (diuresis), water volume, and salt concentration. When the drug wears off, the body may overcompensate by retaining too much sodium chloride and fluids, causing fluid build-up or high blood pressure. In patients with serious health conditions, such as congestive heart failure, diuretic withdrawal may require monitoring.

A doctor or healthcare provider may discontinue Lasix treatment in people who experience ringing in the ears (tinnitus), hearing loss, kidney damage, pancreatitis, hepatic encephalopathy, hyperuricemia (excess uric acid), severe dehydration, severe electrolyte imbalance, or a serious hypersensitivity reaction when taking the drug. Pregnant women may also need to stop taking Lasix. Furosemide is present in breast milk and decreases lactation, so either the drug or breastfeeding may need to be discontinued. If for any reason furosemide must be stopped, other similar loop diuretics include bumetanide, torsemide, and ethacrynic acid. Thiazide diuretics and potassium-sparing diuretics are other alternatives. 

What is the maximum dosage for Lasix?

No more than 600 mg of oral furosemide should be taken in a single day. High doses are rarely used for hypertension but are possible in severe cases of edema. If Lasix is not working sufficiently well for either edema or hypertension, healthcare professionals may add other diuretics or blood pressure medications before prescribing high doses of Lasix.

What will need to be monitored while taking Lasix?

In order to make sure Lasix is being effective for patients without causing unwanted side effects, their doctor will often have them regularly examined. Depending on the condition being treated, patients may need to check their blood pressure, body weight, fluid intake, and urine output. Additionally, patients will need to have regular lab tests to check their electrolytes and kidney function.

Do patients require supplements while taking Lasix?

Since Lasix can lower the amount of potassium in the body, some patients may need to take potassium supplements while taking Lasix. People will often take a potassium supplement such as Klor-Con. Another option for patients treating heart failure or hypertension is a potassium-sparing diuretic such as spironolactone. Healthcare professionals could also make recommendations for changes in a person’s diet to increase the amount of potassium from food.

Can patients with diabetes take Lasix?

 Lasix may increase blood glucose levels. People with diabetes that start Lasix may need dose adjustments for their diabetes medications. Patients with diabetes should continue to test their blood sugar levels regularly. It is important for all patients to tell their healthcare providers about their medical history to determine if Lasix is the best option for them. 

What medications interact with Lasix?

Prescription drugs such as sucralfate (ulcer medication) and bile acid sequestrants may prevent Lasix from working correctly and the dose should be separated.

Lasix has several drug interactions that may affect treatment. In particular, Lasix therapy requires close monitoring if other diuretics are also being used. Caution should be taken when combining Lasix with NSAIDs or other drugs like phenytoin (seizure medication), methotrexate (cancer and rheumatism medication).

Many prescription drugs lower blood pressure. When combined with diuretics like Lasix, these drugs raise the risk of lowering blood pressure too much, a condition called hypotension.

Lastly, some prescription drugs are particularly hazardous when combined with Lasix and should be avoided. These include desmopressin, Marplan (isocarboxazid), and platinum-based cancer drugs such as cisplatin. The toxicity of some drugs, like lithium (bipolar disorder medication) or aminoglycosides ( antibiotics), is increased when taken with Lasix. Doctors, pharmacists, and healthcare professionals are well-versed in these drug interactions and will try to avoid combining Lasix with these drugs.

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