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Lasix Patient Tips

Medically reviewed on Sep 27, 2017 by C. Fookes, BPharm.

How it works

  • Lasix is a brand (trade) name for furosemide.
  • Furosemide significantly increases urination by inhibiting the reabsorption of salts in the kidneys.
  • Lasix belongs to the class of medicines known as loop diuretics.


  • Used to relieve the body of excess fluid caused by heart failure, kidney failure, cirrhosis of the liver and other conditions.
  • May be used in addition to other medicines for the treatment of high blood pressure.
  • An injectable form is available.
  • Lasix is available as a generic under the name furosemide.


If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • Dry mouth, thirst, weakness, muscle pains or cramps, muscular fatigue, dizziness on standing, gastrointestinal disturbances, changes in blood counts, and alterations in cholesterol levels or liver function.
  • Lasix's effect is very strong. It can lead to a significant depletion of electrolytes which may lead to side effects such as muscle cramps and an irregular heartbeat. The risk is greater in people with a restricted salt intake or taking certain medications.
  • Tinnitus and reversible or irreversible hearing impairment have been reported. The risk is greater with higher dosages, injectable Lasix, severe renal impairment, low protein levels, and concomitant therapy with other drugs that are also toxic to the ears.
  • May increase blood glucose levels and affect laboratory test results.
  • Older people may not respond as well to the initial diuretic effect of Lasix.
  • May not be suitable for some people including those with cirrhosis of the liver or ascites, kidney disease, or who are already electrolyte depleted or dehydrated.
  • May interact with a number of other drugs including those that also lower blood pressure or potassium, lithium, corticosteroids, digoxin, phenytoin, and methotrexate.

Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.

Bottom Line

Lasix increases urination which relieves excess fluid but may also lead to the depletion of certain electrolytes in the body (such as potassium).


  • Dosages vary from individual to individual; higher dosages need extra monitoring by a doctor. Some individuals may only need Lasix two to four times per week.
  • You may be more sensitive to sunlight while taking Lasix; use an SPF 30-50+ sunblock when outside.
  • Tell your doctor if you develop diarrhea or vomiting while taking Lasix.
  • Get up slowly when going from a lying down or sitting position to standing because Lasix may make you feel dizzy.
  • Your electrolyte levels will need regular monitoring and your blood may need occasional testing for diabetes. If you already have diabetes, be aware that Lasix may increase your blood glucose levels.
  • Potassium supplements or extra dietary potassium may be needed to counteract the effects of low potassium levels caused by Lasix.

Response and Effectiveness

  • The onset of diuresis (increased urination) is within an hour.
  • Peak effects are seen within one to two hours and the effects of Lasix last for 6 to 8 hours.


Lasix (furosemide) [Package Insert]. Validus Pharmaceuticals LLC. Revised: 04/2016.

  • Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Lasix only for the indication prescribed.
  • Disclaimer: Every effort has been made to ensure that this information is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. This drug information does not endorse drugs, diagnose patients or recommend therapy. It is an informational resource designed as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of this information. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.

Copyright 1996-2018 Revision Date: 2017-09-27 02:33:08