Definition
Subcutaneous fluids (also written sub-Q fluids or SC fluids) are sterile electrolyte solutions administered beneath a cat's skin — into the subcutaneous tissue — using a needle and giving set. The fluid is absorbed gradually into the bloodstream, supplementing the cat's hydration over several hours.
The procedure is distinct from intravenous (IV) fluids, which deliver fluid directly into the bloodstream and require hospitalisation. Subcutaneous fluids can be administered at home by owners after training from a vet or vet nurse.
When subcutaneous fluids are used
The most common reason vets prescribe home subcutaneous fluids for cats is chronic kidney disease (CKD). In CKD, the kidneys lose the ability to concentrate urine efficiently, causing the cat to produce larger volumes of dilute urine and become chronically dehydrated despite drinking more. Cats are also not naturally high drinkers — they evolved to obtain most hydration from prey — making it difficult for them to compensate orally.
Other conditions for which subcutaneous fluids may be prescribed include:
- Hyperthyroidism (increased fluid demand)
- Diabetes mellitus
- Liver disease
- Recovery from acute illness or surgery
For cats over 10, regular monitoring of kidney function is recommended. Our signs it is time to call the vet guide describes the early signs of kidney disease that are worth acting on before the condition becomes advanced.
How the procedure works
The fluid is administered using a giving set (tubing) connected to a bag of prescribed sterile solution. The needle is inserted into the scruff of the neck or the side of the body. A typical administration volume for a cat is 100–200 ml — delivered over 5–15 minutes. The fluid forms a temporary visible lump under the skin, which disperses as it is absorbed.
Your vet team will demonstrate the technique and have you practice before sending the supplies home. Most owners become comfortable with the procedure within a few sessions. The Cornell Feline Health Center provides written guidance on the home administration technique.
What fluids are used
The most commonly prescribed solutions for subcutaneous use are:
- Lactated Ringer's solution (Hartmann's): balanced electrolyte solution; the most widely used
- 0.9% sodium chloride (normal saline): alternative if potassium supplementation is not needed
Potassium supplementation may be added to the fluid bag for cats with hypokalaemia, which is common in CKD. The specific fluid and dose will be on the prescription — never change the type or volume without checking with your vet.