Lasix Drug Handout

What is Lasix?

Lasix is a diuretic (water pill). It helps the body get rid of water by increasing the kidneys production of urine.


  • Most important medication in the treatment of congestive heart failure
  • To treat fluid accumulation for reasons other than heart failure
  • Some forms of acute kidney failure
  • Elevated blood calcium levels
  • Used at low dosages in some dogs with chronic bronchitis

Adverse Effects

Please contact CVCA should any of these symptoms be noted

  • Increased thirst and urination (please contact us if this is not manageable)
  • Can cause dehydration in patients not drinking well, or with other diseases that cause fluid loss (kidney disease, vomiting/diarrhea)
  • May decrease levels of calcium, sodium, potassium, or magnesium, particularly In patients that are not eating well.
  • Low risk to increase blood sugar levels, altering the insulin need in diabetics
  • May cause low blood pressure and weakness in patients with pericardial effusion

Client Information

  • Can be given with or without food
  • Almost never used alone in the treatment of congestive heart disease
  • Can be given in pill form, liquid or made into chewable treats
  • Do not stop or lower the dose without the approval of a veterinarian
  • Monitor kidney values and electrolytes through blood work after starting or increasing the dose, and at least every 6 months thereafter
  • Often used in combination with an ACE inhibitor and/or spironolactone, decreasing the risk for low potassium

Interaction with Other Drugs

Standard Dosage Forms

Synonyms: (Lasix, Furosemide, Salix)