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Loop diuretic · For Cats

Lasix dosage reference for cats (Furosemide)

This page's standard weight-based reference is 2 mg per kg (0.91 mg per lb), with every 8-24 hours (based on severity) recorded as the reference frequency. Use the calculator to see the arithmetic for your cat's weight, then confirm the indication, product, and actual dose with a veterinarian.

Onset
30-60 minutes (oral), 5 minutes (injectable)
Duration
6-8 hours
Class
Loop diuretic

Weight-based calculator estimate from the references listed on this page. This page has not been independently DVM-reviewed — see our methodology .

This information is for educational purposes only. Always consult your veterinarian before giving medication to your pet. Do not use this calculator for emergencies, overdoses, pregnancy, very young animals, very old animals, pets with liver/kidney disease, or pets taking multiple medications.

Each medication page lists the references recorded for its data. The calculator math and editorial presentation are maintained by PetDosageChart; a page is independently DVM-reviewed only when a named reviewer byline appears. See our methodology and limitations.

Furosemide (often known by brand names such as Lasix and Salix) is a loop diuretic commonly used in veterinary medicine for congestive heart failure, pleural effusion, pulmonary edema, fluid retention, and ascites. Understanding the correct dosage, administration, and potential side effects of Furosemide is critical for your cat’s safety and well-being.

A typical Furosemide dose for cats is around 2 mg/kg every 8-24 hours (based on severity), within a usual range of 1-4 mg/kg. Available forms include tablet, injectable, and liquid.

Calculator Warning: Use this only as an educational estimate. Your veterinarian may prescribe a different dose based on your pet’s condition, age, weight, other medications, and medical history.

Furosemide Dosage Calculator for Cats

Enter your cat’s weight below to estimate the Furosemide dose from the 2 mg/kg guideline. Your veterinarian may adjust it for your cat’s age, condition, and other medications, so treat the result as an educational starting point, not a prescription.

Dosage Calculator · 01

Enter your cat's weight

Quick Dosage Chart

Typical Furosemide amounts for common cat weights, for quick reference:

Dosage Chart · 02

Lasix weight-based reference chart for cats

Scroll sideways to see full table

Weight Lower Reference Standard Reference Upper Reference Frequency
3 lbs (1.4 kg) 1.4 mg 2.8 mg 5.6 mg every 8-24 hours (based on severity)
4 lbs (1.8 kg) 1.8 mg 3.6 mg 7.2 mg every 8-24 hours (based on severity)
5 lbs (2.3 kg) 2.3 mg 4.6 mg 9.2 mg every 8-24 hours (based on severity)
6 lbs (2.7 kg) 2.7 mg 5.4 mg 10.8 mg (12.5mg tablet) every 8-24 hours (based on severity)
7 lbs (3.2 kg) 3.2 mg 6.4 mg 12.8 mg (12.5mg tablet) every 8-24 hours (based on severity)
8 lbs (3.6 kg) 3.6 mg 7.2 mg 14.4 mg (12.5mg tablet) every 8-24 hours (based on severity)
9 lbs (4.1 kg) 4.1 mg 8.2 mg 16.4 mg every 8-24 hours (based on severity)
10 lbs (4.5 kg) 4.5 mg 9.0 mg 18.0 mg every 8-24 hours (based on severity)
12 lbs (5.4 kg) 5.4 mg 10.8 mg (12.5mg tablet) 21.6 mg every 8-24 hours (based on severity)
14 lbs (6.3 kg) 6.3 mg 12.6 mg (12.5mg tablet) 25.2 mg (2 × 12.5mg) every 8-24 hours (based on severity)
16 lbs (7.3 kg) 7.3 mg 14.6 mg (12.5mg tablet) 29.2 mg every 8-24 hours (based on severity)
18 lbs (8.2 kg) 8.2 mg 16.4 mg 32.8 mg every 8-24 hours (based on severity)
20 lbs (9.1 kg) 9.1 mg 18.2 mg 36.4 mg (3 × 12.5mg) every 8-24 hours (based on severity)
25 lbs (11.3 kg) 11.3 mg (12.5mg tablet) 22.6 mg (2 × 12.5mg) 45.2 mg every 8-24 hours (based on severity)

Parenthetical tablet amounts are arithmetic comparisons only. They do not account for scoring, release type, concentration, product labeling, or whether this medication is appropriate for an individual animal.

By Weight

Lasix reference by cat weight

Choose a common weight to open its optional reference page. Use the main medication calculator for a different exact weight.

Common-weight pages are convenience views of the same educational reference, not separate medical recommendations.

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How to Give Furosemide to Your Cat

Give furosemide with food to reduce stomach upset. Ensure fresh water is always available, as this drug causes significant fluid loss through urination. Your cat will urinate much more frequently — this is expected and means the drug is working. Monitor litter box usage closely. Keep the litter box extra clean, as the increased volume can be unpleasant for cats. Your vet will need to check kidney values and electrolytes regularly.

It is generally recommended to give Furosemide with food to help reduce stomach upset. It may interact with ACE inhibitors (enhanced hypotension), aminoglycoside antibiotics (increased ototoxicity), digoxin (toxicity risk with low potassium), and NSAIDs (reduced diuretic effect).

Side Effects and Safety

Common side effects include increased urination, increased thirst, dehydration, and electrolyte imbalances (low potassium). More serious side effects can occur, such as severe dehydration, kidney failure (prerenal azotemia), dangerous electrolyte depletion, and hearing loss (ototoxicity, especially with aminoglycosides).

Cautions · 12

When Lasix should be used with caution or avoided

Some cats should not take Lasix, or need a different dose and closer monitoring. Tell your veterinarian about your pet's full health history and every other medication or supplement they take before giving Lasix.

  • severe dehydration
  • anuria (no urine production)
  • severe electrolyte imbalances
  • pregnancy

Interactions · 13

Lasix drug interactions

Lasix can interact with other drugs. This list is not complete — always give your veterinarian a full list of your cat's medications and supplements.

ACE inhibitors (enhanced hypotension)
aminoglycoside antibiotics (increased ototoxicity)
digoxin (toxicity risk with low potassium)
NSAIDs (reduced diuretic effect)

Calculator Limits · 14

When not to use this calculator

This calculator gives a general educational estimate for a healthy adult cat at a known weight. Do not rely on it in these situations — talk to your veterinarian instead:

  • In an emergency, or after accidental ingestion or a suspected overdose
  • For pregnant or nursing pets
  • For very young or very old cats
  • For pets with liver disease, kidney disease, or another chronic illness
  • For pets taking several medications at once
  • When you are not sure of your cat's current, accurate weight
  • For combination products that contain additional active ingredients

Overdose · 15

Suspected overdose: what to do

If you think your cat had too much Lasix, or swallowed any medication by accident, act right away. Do not wait for symptoms to appear.

  • Call your veterinarian or the nearest emergency animal hospital.
  • ASPCA Animal Poison Control Center: (888) 426-4435
  • Pet Poison Helpline: (855) 764-7661

A consultation fee may apply to the poison hotlines. Have the medication packaging ready, and note how much your pet may have taken and when. Do not try to make your pet vomit unless a veterinarian tells you to.

When to Call the Vet

If your cat experiences any of the following, contact your veterinarian or an emergency clinic immediately:

Frequently Asked Questions

Frequently Asked · 07

Questions about this medication

How does furosemide help cats with heart failure?
Furosemide removes excess fluid from the body by causing the kidneys to excrete more sodium and water. In cats with congestive heart failure, fluid accumulates in the lungs (pulmonary edema) or chest cavity (pleural effusion), making it difficult to breathe. Furosemide is the cornerstone emergency treatment to relieve this fluid buildup and improve breathing.
Will my cat pee a lot on furosemide?
Yes, significantly increased urination is the expected and desired effect. Your cat may need to use the litter box much more frequently. Keep the litter box accessible and clean, and always provide unlimited fresh water to prevent dehydration. This is a sign the medication is working correctly.
Can furosemide damage my cat's kidneys?
Yes, furosemide can worsen kidney function, especially in cats with pre-existing chronic kidney disease (common in senior cats). It causes fluid loss that reduces blood flow to the kidneys. Your vet will balance the need for fluid removal (to help the heart) against the impact on the kidneys through careful dose adjustments and regular blood work.
How long can a cat live on furosemide?
Many cats with heart failure live months to years on furosemide combined with other cardiac medications. Survival depends on the underlying heart condition, response to treatment, and any concurrent diseases like kidney disease. Regular veterinary monitoring every 1-3 months is essential for long-term management.
What happens if I give too much furosemide to my cat?
Overdose can cause severe dehydration, electrolyte depletion (especially dangerously low potassium), kidney failure, and collapse. Signs include extreme lethargy, weakness, loss of appetite, and reduced or no urination. This is a medical emergency — contact your vet immediately if you suspect an overdose.

Use This Guide Safely · 08

What weight alone cannot tell you

The calculator performs one narrow job: it multiplies your cat's weight by the lower, standard, and upper mg/kg values recorded for Lasix. It cannot decide whether this drug, indication, formulation, or schedule is appropriate for an individual animal.

Context in this medication record

Commonly listed uses
congestive heart failure, pleural effusion, pulmonary edema, fluid retention, ascites
Recorded forms
tablet, injectable, liquid
Reference timing
every 8-24 hours (based on severity); onset 30-60 minutes (oral), 5 minutes (injectable); duration 6-8 hours

Individual checks a calculator cannot perform

  • Confirm the diagnosis and the reason this medication is being considered.
  • Match the exact product, concentration, route, and whether a tablet may be split.
  • Account for age, pregnancy, organ function, genetics, allergies, and prior reactions.
  • Review every prescription, over-the-counter product, and supplement your pet takes.

Recorded cautions

severe dehydration; anuria (no urine production); severe electrolyte imbalances; pregnancy.

Recorded interactions

ACE inhibitors (enhanced hypotension); aminoglycoside antibiotics (increased ototoxicity); digoxin (toxicity risk with low potassium); NSAIDs (reduced diuretic effect).

These lists reproduce the structured record used by this page and may not be exhaustive. Show your veterinarian the product label and your cat's complete medication list before acting on a number.

For Dogs

Looking for Lasix dosage for dogs?

View the Lasix dosage chart and calculator for dogs.

Related · 08

Related medications for cats

Sources · 09

Sources & references

The structured medication record behind this page names the references below. The links open the publisher or official resource; they do not turn this page into a prescription for an individual animal.

Source names are shown at the record level; passage-level page and label citations are still being added. Read our methodology and limitations.

Transparency · 11

How this page was made

This page's structured medication record includes Plumb's Veterinary Drug Handbook among its source names. PetDosageChart applies the record's mg/kg values to the entered weight and presents the arithmetic result. A source record is not the same as an individualized prescription or an independent clinical review.

Sources cited
  • Plumb's Veterinary Drug Handbook
  • Merck Veterinary Manual
Calculator formula
Doses scale linearly from a standard basis of 2 mg per kg (0.91 mg per lb) of body weight, given every 8-24 hours (based on severity). The calculator multiplies that basis by your cat's weight and shows an arithmetic comparison with recorded tablet sizes. That comparison does not determine whether a tablet is scored, splittable, or appropriate for your pet.
Editorial owner
Prepared and maintained by the PetDosageChart editorial team, a software-led publisher and not a veterinary practice.
DVM review status
Not independently DVM-reviewed. A named reviewer and review date appear here only after a confirmed review.

More on our methodology and editorial process — how we source, calculate, and review cats dosage data.

Safety · 10

More resources