Feline Fluid Therapy Calculator
Fluid therapy is one of the most common and important treatments in feline veterinary medicine, used for dehydration, kidney disease, post-surgical care, and many other conditions. The total fluid requirement combines two components: the daily maintenance volume the cat needs to sustain normal hydration, and the deficit volume needed to correct existing dehydration. The maintenance rate used here is 60 mL/kg/day, a widely accepted standard. The deficit is calculated from the estimated percentage of body weight lost to dehydration. The combined total is divided over the replacement period to give an hourly infusion rate. Always have your veterinarian review fluid plans before administration.
Feline fluid therapy formula
Maintenance (mL/day) = 60 x Weight (kg)
Deficit (mL) = Weight (kg) x Dehydration (%) / 100 x 1000
Total (mL) = Maintenance + Deficit
Rate (mL/hr) = Total / Replacement hours
The 60 mL/kg/day maintenance rate is a standard veterinary reference value. Your veterinarian may use a different rate based on the individual cat's condition, body condition score, and concurrent disease.
Clinical considerations for feline fluid therapy
- Subcutaneous fluids are commonly used for mild dehydration in stable cats; intravenous fluids are required for moderate to severe cases.
- Cats with heart disease (particularly hypertrophic cardiomyopathy) are at risk of fluid overload; fluid rates must be reduced under cardiac monitoring.
- Isotonic crystalloids (such as Lactated Ringer's or normal saline) are the most common choices for feline fluid therapy.
- Urine output, body weight changes, and mucous membrane status are used to monitor response to treatment.
- Ongoing losses from vomiting or diarrhea must be estimated and added to the calculated total.
Feline fluid therapy calculator: frequently asked questions
What is maintenance fluid rate for cats?
The standard maintenance fluid rate for cats is approximately 60 mL/kg/day, or about 2-3 mL/kg/hour. Some references cite 50-60 mL/kg/day. Your veterinarian may adjust this based on the cat's condition, urine output, and ongoing losses.
How is the dehydration deficit calculated?
Deficit (mL) = body weight (kg) x dehydration percentage (as a decimal) x 1000. For example, a 4 kg cat that is 5% dehydrated needs 4 x 0.05 x 1000 = 200 mL to replace the deficit. This is added to the maintenance requirement.
How do I estimate dehydration percentage in a cat?
Dehydration is assessed clinically. Skin turgor (tent test), mucous membrane moisture, capillary refill time, and eye position are used. Less than 5% is not detectable; 5-6% shows mild skin tent; 6-8% shows obvious tent and dry mucous membranes; over 8% shows severe signs.
Over what period should the deficit be replaced?
The deficit is typically replaced over 12 to 24 hours in addition to maintenance fluids, depending on the severity of dehydration and underlying cause. Rapid replacement may be indicated for shock; slower replacement for chronic dehydration. Your vet determines the schedule.
Does the calculator account for ongoing losses?
No. Ongoing losses from vomiting, diarrhea, or fever must be estimated and added on top of the total shown. This calculator covers only the standard maintenance plus initial deficit components.
Official sources
- American Animal Hospital Association (AAHA): AAHA Homepage.
- FDA Center for Veterinary Medicine: Animal and Veterinary.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.