Subcutaneous fluids are not always appropriate and should not be administered without veterinary approval. If your cat has a heart condition, discuss that with your vet as it relates to your specific fluid therapy plan.
From the 2016 ISFM guidelines: 75-150 mL every 1 to 3 days. Most common in advanced stage cats (stages 3 and 4), but should be considered on a case-by-case basis.
From iCatCare 2024 article: Generally, around 10-20 mL/kg of body weight can be given at a single SQ injection site (around 60-100 mL for an average-sized cat).
More recommendations for amounts from veterinary organizations:
How to give fluids:
How to give subcutaneous fluids to your cat
From the 2016 ISFM guidelines: 75-150 mL every 1 to 3 days. Most common in advanced stage cats (stages 3 and 4), but should be considered on a case-by-case basis.
From iCatCare 2024 article: Generally, around 10-20 mL/kg of body weight can be given at a single SQ injection site (around 60-100 mL for an average-sized cat).
More recommendations for amounts from veterinary organizations:
How to give fluids:
How to give subcutaneous fluids to your cat