How the problems work
Pick topics and a number of problems. Every set has a code, and a class link carries the code, topics and rules, so the whole group gets the same numbers. Weights are in kg, volumes in ml, and costs (if you tick them) in pounds with VAT at 20%.
Answers follow the Harper Adams OSCE booklet: round to the nearest whole number (5 and above rounds up), and injection volumes to one decimal place. Each question says how to round, and the answer is worked at full precision and rounded once, at the end.
A worked example from Bristol
Bristol's clinical skills sheet has a 6.8 kg puppy, 6% dehydrated, on a 20 drops/ml giving set. Maintenance at 3 ml/kg/hr is 3 × 24 × 6.8 = 489.6 ml and the deficit is 6.8 × 6 × 10 = 408 ml, so 897.6 ml over 24 hours is 37.4 ml/hr. That is 37.4 ÷ 60 × 20 = about 12.47 drops a minute (Bristol writes 12.5), which rounds to 12. At 4 ml/kg/hr it is 15 drops, about one every 4 seconds. Try ten fluid and drip problems.
Rules and where they come from
| Rule | Default | Source |
|---|---|---|
| Adult maintenance | 50 ml/kg/day | Bristol CSL_A10: 2 ml/kg/hr or 50 ml/kg/24 h. By size, 60 small dogs, 50 cats and medium dogs, 40 large dogs: Aqupharm poster; Melbourne Polytechnic gives 40 to 60. The cut-offs used here (10 and 25 kg) are this page's choice. |
| Puppies and kittens | 3 ml/kg/hr | Bristol CSL_A10: 3 to 4 ml/kg/hr. |
| Deficit | % × kg × 10 ml | Aqupharm poster; Bristol CSL_A10 (kg × % as a decimal, 1 kg = 1 litre). |
| Drip rate | ml/hr ÷ 60 × drops/ml | Bristol CSL_A10 and Melbourne Polytechnic; sets of 20 and 60 drops/ml. |
| Urine output | 1 to 2 ml/kg/hr | Harper Adams OSCE booklet 2026-27; The Veterinary Nurse (2019). |
| RER | 70 × kg^0.75 | Carlson, Today's Veterinary Nurse (2023), which gives 30 × kg + 70 for 2 to 45 kg. Melbourne Polytechnic: 30 × kg + 70 for dogs over 5 kg, 60 × kg for cats and smaller dogs. |
| Energy | kcal | kJ option for Australian courses: Melbourne Polytechnic multiplies kcal by 4.2. |
| Rounding | whole numbers | Harper Adams OSCE booklet 2026-27; injection volumes to one decimal place. |
Sources checked 24 October 2026.
Questions
How do you calculate maintenance fluids for a dog or cat?
Bristol's clinical skills sheet uses 2 ml/kg/hr or 50 ml/kg per 24 hours for an adult, so a 35 kg dog needs 70 ml/hr or 1,750 ml a day. Puppies and kittens get 3 to 4 ml/kg/hr. Some colleges use 60, 50 or 40 ml/kg/day by size: pick yours under "Rules this sheet uses".
How do you work out drops per minute?
Divide the ml per hour by 60 to get ml per minute, then multiply by the drops per ml printed on the giving set. 116 ml/hr is 1.93 ml a minute, and on a 20 drops/ml set that is 38.7 drops, so 39 to the nearest whole number (Bristol's sheet writes 38). Check it by counting 10 drops in 15 seconds.
How do you calculate a fluid deficit?
Multiply the % dehydration by the weight in kg and by 10 to get ml. A 35 kg dog that is 8% dehydrated has lost 2.8 kg of fluid, which is 2,800 ml. If it is replaced over 24 hours, add it to the day's maintenance and divide by 24.
What is normal urine output?
1 to 2 ml/kg per hour. The Harper Adams OSCE booklet asks for it as a range over the hours given, for example 40 to 80 ml over 4 hours, which fits a 10 kg patient.
How do you calculate RER?
RER = 70 × weight (kg)^0.75 kcal a day, so a 20 kg dog needs about 662 kcal. Some courses use 30 × kg + 70 (670 kcal for 20 kg), meant for 2 to 45 kg, and Melbourne Polytechnic uses 60 × kg for cats and dogs under 5 kg. Pick yours under "Rules this sheet uses".
Does the RCVS give a formula sheet for the OSCE?
We could not find one. Colleges teach their own figures, which is why this page names its sources and lets you switch. Harper Adams asks for answers to the nearest whole number with units, and injection volumes to one decimal place.
How do I give my class the same problems?
Set the topics, number of problems and rules, then tap Share with class and send the link. It always opens the same set. Print the answer key for yourself.
Practice arithmetic only. The patients, drugs and doses are made up so the numbers work; they are not dosing advice. Always follow the veterinary surgeon's instructions and your practice's protocols.
Sources: University of Bristol, IV Fluid Therapy Calculations, CSL_A10, August 2024 (PDF); University of Bristol, IV Fluid Therapy Set Up, CSL_A09 (PDF); Harper Adams University, Student Veterinary Nurse OSCE Task Booklet 2026-27 (PDF); Aqupharm fluid therapy poster (PDF); Melbourne Polytechnic, Veterinary Nursing Mathematics: fluid therapy and dietary requirements; The Veterinary Nurse, fluid therapy (2019, PDF); Carlson, Nutrition Math 101, Today's Veterinary Nurse (2023); GOV.UK, VAT rates.