Lasix Medication Information:

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Lasix medication comes in several different strengths; click on the strength you need to view prices from pharmacies competing to earn your business.

Lasix 20 mg
Lasix 40 mg
Lasix 80 mg
Lasix 500 mg

About Lasix

What Lasix is used for

LASIX has been prescribed to you by your health provider to treat your edema (water retention) or hypertension (high blood pressure).

What Lasix does

LASIX belongs to a group of medicines known as diuretic drugs which improve the elimination of water and salts (electrolytes) in the urine.

When Lasix should not be used

Do not use LASIX if you are allergic to it or to any of the components of its formulation (for list of components see What the important nonmedicinal ingredients are:), or to any sulfonamide-derived drugs. Ask your physician or pharmacist if you are not sure what sulfonamide-derived drugs are.

Before using LASIX, tell your health provider if you have any of the following conditions so he can carefully consider the risks and benefits of a treatment with LASIX:

  • Kidney disease

  • Any liver disease

  • Urinary retention (difficulty to urinate)

  • Hypokalemia (low potassium blood levels)

  • Hyponatremia (low sodium blood levels)

  • Low blood pressure

  • Breast feeding

  • Dehydration

  • Your newborn baby has jaundice (yellowing of the skin and/or eyes) or Rh incompatibility.

Do not use LASIX if you are pregnant or breastfeeding.

What the medicinal ingredient is


What the important nonmedicinal ingredients for Lasix are

20 mg tablets: colloidal silicon dioxide, lactose monohydrate, magnesium stearate, purified water, starch and talc.

40 mg tablets: colloidal silicon dioxide, D&C Yellow #10, FD&C Yellow #6, lactose monohydrate, magnesium stearate, purified water, starch and talc.

10 mg/mL, oral solution: alcohol, butylated hydroxyanisol, butylated hydroxytoluene, glycerine, methylparaben, natural orange flavour, polysorbate 80 non-animal, potassium sorbate, purified water, sodium hydroxide and sorbitol.

What dosage forms Lasix comes in

Tablets of 20 mg or 40 mg

Oral solution of 10 mg/mL

Warnings and Precautions


BEFORE you use LASIX talk to your health provider if:

  • You have liver disease or disorder

  • You have kidney disease or disorder

  • You are diabetic (high blood sugar)

  • You had an organ transplant

  • You have gout

  • You have recently suffered from excess vomiting or diarrhea

  • You intend to have a surgery and general anesthesia (even at the dentist’s office), as there may be a sudden fall in blood pressure associated with general anesthesia.

  • You are breast feeding, pregnant, or think you might be pregnant

  • You intend to change your eating habits

  • You are less than 18 years old

  • You are older than 61 years old

When administered to children, LASIX therapy should be started in the hospital, in carefully selected patients, under close observation with frequent blood tests to measure electrolytes such as sodium, potassium, chloride, magnesium and calcium.

For elderly patients, (over 61 years old), the dose selection should be cautious, usually starting at the low end of dosage range, reflecting the greater frequency of decreased liver, kidney or heart function.

The administration of LASIX to diabetic patients may result in possible decrease of diabetic control. Dosage adjustments of the antidiabetic agent may be needed.

There have been cases of ringing in the ears, reversible and non-reversible deafness especially in children. This is most true when the patient has severe kidney disease or is taking drugs that are known to sometimes damage the ears while they are taking LASIX. Your doctor will decide if LASIX is the right medication for you/your child based on your particular condition.

LASIX should not be used in pregnant women or in women of childbearing potential unless in the opinion of the attending physician the benefits to the patient outweigh the possible risk to the fetus. Treatment during pregnancy requires monitoring of fetal growth by your doctor.

If you are suffering from hyperuricemia (high uric acid levels in your blood), taking LASIX can sometimes make a gout attack more likely.

Almost all patients can drive or operate machinery while taking LASIX, but you should not perform these tasks, which may require attention, until you know how you tolerate your medicine.

Interactions with Lasix

Before using LASIX, tell your health provider about medication you are currently taking. This way appropriate adjustment and decision can be taken for your treatment with LASIX.

Below are drugs or drug classes that may interact with LASIX. These include:

  • Drugs to reduce blood pressure (e.g. ACE inhibitors, angiotensin II receptor antagonist)

  • Diuretics (waterpills), including ethacrynic acid

  • Pressor amines such as epinephrine (a medication used to treat life-threatening allergic reactions)

  • Medication to treat diabetes, including insulin. The administration of LASIX to diabetic patients may result in possible decrease of diabetic control. Dosage adjustments of the antidiabetic agent may be needed.

  • Theophylline, a medication used to treat asthma, chronic bronchitis, and other lung diseases

  • Cisplatin (anti-cancer drug)

  • Probenecid (medicine used to treat gout)

  • Antibiotics (e.g. cephalosporines, aminoglycosides)

  • Certain pain and anti-inflammatory drugs (e.g. non-steroidal anti-inflammatory drugs [NSAIDs], acetylsalicylic acid, indomethacin)

  • Drugs used in the treatment of rheumatoid arthritis (methotrexate, cyclosporin)

  • Drugs used to treat epilepsy (e.g. phenytoin, carbamazepine, phenobarbital)

  • Lithium (medicine used to treat bipolar depression)

  • Sucralfate (antacid drug)

  • Sedatives such as phenobarbital or chloral hydrate

  • Stimulant laxatives and drugs which may induce low potassium levels (hypokalemia) such as glucocorticoids, and medicine derived from licorice (e.g. carbenoxolone)

  • Drugs known to be harmful to the ear (ototoxic) as for instance aminoglycosides antibiotics, ethacrynic acid (a “water pill”) and cisplatin (a drug used to treat some types of cancer)

  • Drugs known to be harmful to the kidney

  • Substances used during certain radiological investigations (radiocontrast agents)

  • Digitalis (digoxin)

  • Certain steroids.

Proper Use of Lasix

During long-term therapy a high-potassium diet may be recommended. You should not be on a strict salt restricted diet. Potassium supplements may be required. Your doctor will monitor your blood tests for blood sugar, potassium and other electrolytes and to monitor liver and kidney function. This is especially important if you have other medical conditions such as diabetes, take other medications or the patient is an infant or child.

Usual dose

Adults (oral) for edema and high blood pressure

It is important that you take LASIX as prescribed by your doctor.

Usually your doctor will prescribe LASIX tablets at a dose of 20 to 80 mg per day, which you could take as single or 2-3 divided doses, based on the type of administration your physician considers to be the most appropriate for your condition.

Maximum daily dose: 200 mg.

Swallow the tablets whole with a glass of water.

When prescribed to children, LASIX is usually administered in the form of a solution and at a dose that will be determined by the health care provider. The oral solution should be taken on an empty stomach.

You should always respect the prescribed interval between the doses. Never change the dose of LASIX you are taking unless your doctor tells you to.

This drug is specifically prescribed for you or a child in your care. Do not give it to others, even if they have the same symptoms, and you yourself must not use it for any condition than the one for which it was prescribed.

Pediatrics (oral)

LASIX therapy should be instituted in the hospital, in carefully selected patients, under close observation with frequent monitoring of blood tests including electrolytes. The doctor will decide what is the best dose for each child.

Orally, the initial dose should be in the range of 0.5 to 1 mg/kg body weight.

The total daily dose (given in divided doses of 6 to 12 hours apart) should not exceed 2 mg/kg orally. In the newborn and in premature babies, the daily dose should not exceed 1 mg/kg.


If you have accidentally taken too much LASIX contact your doctor or nearest hospital emergency department immediately, even if you do not feel sick. If you go to the doctor or the hospital, take the LASIX container with you.

Side Effects for Lasix and What to Do About Them

Along with its beneficial effects, LASIX like all other drugs may sometimes cause undesirable effects. These may include: blurring of vision, constipation, diarrhea, dizziness, dry mouth, fatigue, tachycardia, arrhythmia (heart rhythm disturbance), feeling of pressure in the head, increase in the amount and frequency of your urine, leg cramps, mental confusion, nausea, sweating, thirst, vomiting, hepatic encephalopathy (altered mental state due to liver disease). Talk to your doctor or pharmacist if you experience any of the above.

Stop taking LASIX and contact your doctor immediately if you experience an allergic reaction or any severe side effect.

Serious Side Effects, How Often They Happen and What to Do About Them
Symptom/Effect Talk with your doctor or pharmacist
Only if severe In all cases
Hearing problems  
Skin rash and/or blistering  
Hives and/or itching  
Abdominal pain  
Difficulty to urinate  
Low blood pressure (hypotension): dizziness when rising to a standing position, impaired concentration and lightheadedness  
Yellow coloration of the skin (jaundice)  
Dehydration and/or abnormal blood tests: dryness of the mouth, thirst, weakness, dizziness, lethargy, drowsiness, restlessness, muscle pain or cramps, muscular fatigue, hypotension, racing or irregular heartbeats, nausea and vomiting, sweating, increases in blood sugar levels, increased urination, mental confusion, headache  
Blurred vision  
Allergic reactions: eyes sensitive to light, tingling of fingers or toes, fever  

Although not all of the above side effects are common, if you experience one of these while you are in the hospital or at home, talk to your doctor or pharmacists immediately.

This is not a complete list of side effects. For any unexpected effects while taking LASIX, contact your doctor or pharmacist.


Technical Information