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What is Lasix?

Lasix (furosemide) is a diuretic that prevents the body from absorbing too much salt. It’s used to treat patients with edema (fluid retention), liver disease, kidney disorders, hypertension, and congestive heart failure.

What are the most important things I should know about Lasix?

Large doses of furosemide may cause irreversible hearing loss. Therefore, all your doses should be closely monitored by a healthcare provider. You should also not use Lasix if you have trouble urinating.

Prior to commencing treatment, tell your doctor if you have kidney disease, enlarged prostate, urination problems, cirrhosis, liver disease, an electrolyte imbalance, high cholesterol, gout, lupus, diabetes, or an allergy to sulfa drugs.

In addition, tell your doctor if you’ve recently had an MRI or any type of scan using radioactive dye injected into your veins.

Tell your doctor if you are pregnant or plan to become pregnant while undergoing treatment. Also, inform your healthcare provider if you are breastfeeding or plan to breastfeed — the medication can pass into your breast milk and harm your baby. It is not currently known whether Lasix can harm an unborn baby.

Lasix will make you urinate more often — making dehydration a possibility. Follow your healthcare provider’s instructions regarding hydration and potassium supplements. You may also need frequent blood tests. Avoid getting up too fast from a sitting or lying position — this could make you feel dizzy.

Avoid drinking alcohol while taking Lasix, as it could cause side effects. If you need to undergo surgery, tell the surgeon ahead of time that you are using Lasix.

Medications to avoid while using Lasix

Using certain drugs can increase side effects or make Lasix less effective. Prior to starting treatment, let your doctor know if you’re currently on any other medications, especially if you’re taking any of the following:

  • Chloral hydrate
  • Lithium
  • Phenytoin
  • Cisplatin or any other cancer medications
  • Heart or blood pressure medications
  • Any other diuretics — especially ethacrynic acid

What are the common side effects of Lasix?

Some of the most serious side effects of Lasix include:

  • Ringing in your ears
  • Hearing loss
  • Easy bruising
  • Unusual bleeding
  • Fever
  • Chills
  • Weakness
  • Painful or difficult urination
  • Numbness
  • Tingling
  • Burning pain
  • Feeling light-headed
  • Muscle spasms
  • Pale skin

You may also develop additional health conditions, such as:

  • High blood sugar — symptoms include increased thirst, increased urination, dry mouth
  • Liver or pancreas problems — symptoms include loss of appetite, stomach pain that may spread to the back, nausea, vomiting, dark urine, yellowing of the skin or whites of eyes
  • Kidney problems — symptoms include little to no urination, swollen feet or ankles, tiredness, feeling short of breath
  • Electrolyte imbalance — symptoms include dry mouth, increased thirst, mood changes, weakness, drowsiness, lack of energy, muscle pain, fast heartbeat, nausea, and vomiting
  • Allergic reaction — symptoms include hives, breathing difficulties, swelling of face or throat, a severe skin reaction, fever, eyes burning, skin pain, blistering, and skin peeling

If you experience any of the above-listed symptoms, seek emergency help immediately. Other side effects may include:

  • Diarrhea
  • Constipation
  • Numbness
  • Tingling
  • Headache
  • Dizziness
  • Blurred vision

These are not all of the possible side effects of Lasix. Talk to your doctor about any side effects that you experience. You are encouraged to report negative side effects of prescription drugs to the FDA. Visit, or call 1-800-FDA-1088.