Is drinking more water enough? What to know about starting fluids, choosing a solution, and caring for your cat at home.

When your vet recommends sub-Q fluids, it’s natural to feel uneasy about giving your cat regular injections. Wouldn’t drinking more water be enough?

At Greycoat Research, we believe sub-Q fluids can help cats from mid-stage 2 CKD onward when they need extra hydration. This view is informed by the clinical experience of a veterinarian on our research team.

The Main Goal Is to Replace Lost Fluid

Cats with chronic kidney disease (CKD) can become less able to concentrate their urine. If they lose more water in their urine than they take in, dehydration can develop. This can contribute to poor appetite, low energy, and constipation.

Subcutaneous, or sub-Q, fluids are given through a needle under the skin and absorbed gradually. When dehydration contributes to a cat’s poor appetite or low energy, replacing that fluid may help them feel better.

From Mid-Stage 2, Fluids May Help Cats Who Struggle to Stay Hydrated

At the clinic where a veterinarian on our research team practices, sub-Q fluids are recommended from mid-stage 2, depending on the cat’s condition. The decision takes hydration and test results into account, along with CKD stage.

For cats who need fluids regularly, the clinic recommends daily sub-Q fluids when their vet confirms that schedule is appropriate. The amount is based on hydration, blood test results, and heart health.

Although the procedure may feel unfamiliar at first, most cats tolerate it well. Your veterinary team can teach you how to give fluids at home. A soft bulge may form under the skin, then gradually disappear as the fluid is absorbed over several hours.

What Our Study of 3,006 Cats Found About Potassium

Greycoat Research’s team analyzed blood test records from 3,006 cats. The study was published in Frontiers in Veterinary Science in 2026.

We compared groups with different creatinine levels. Creatinine is measured in a blood test to help assess kidney function. Low potassium was more common in the groups with higher creatinine levels.

Potassium supports muscle function and digestion. Low levels can leave a cat weak and less interested in food, making potassium levels an important consideration when choosing fluids.

Why the Type of Fluid Matters

Fluid solutions differ in their electrolytes and ingredients that help neutralize acid. Here is how the veterinarian on our research team has used them in clinical practice.

Lactated Ringer’s for Cats Who Need Fluids

The clinic generally uses lactated Ringer’s rather than 0.9% saline. Lactated Ringer’s contains potassium and can also be used in cats with low potassium.

Plasma-Lyte A for Stage 3 Cats With Metabolic Acidosis

When the kidneys cannot remove enough acid, it can build up in the blood. This is called metabolic acidosis, and it can contribute to poor appetite.

The veterinarian has used Plasma-Lyte A for cats with stage 3 CKD and metabolic acidosis. It contains acetate, which the body processes to help neutralize excess acid.

Why the Clinic Avoids Saline

0.9% saline contains neither potassium nor buffering ingredients that help neutralize acid. It also contains more chloride than lactated Ringer’s or Plasma-Lyte A.

Fluids that contain a lot of chloride can worsen metabolic acidosis. That is why the clinic does not use saline for routine sub-Q fluids in stage 3 cats with acidosis.

Three Things to Remember at Home

1. Make Water Easy to Reach

Place water bowls in several locations or try wet food. You can also add a little water to your cat’s food if they’ll eat it that way. Even after starting sub-Q fluids, your cat still needs moisture from food and drinking water.

2. Check Potassium Alongside Kidney Values

When your cat has blood tests, check the potassium result as well as creatinine. These results help your vet decide whether the fluid plan or potassium treatment needs adjusting.

3. Take Extra Care if Your Cat Has Heart Disease

Too much fluid can put strain on the heart. If your cat has heart disease, follow the amount and frequency prescribed by their vet.

If your cat repeatedly breathes 30 or more times per minute while asleep, have them checked by a vet. This could be a sign of fluid buildup in the lungs. If breathing is difficult, stop giving fluids and seek emergency veterinary care immediately.

The Right Hydration Support for Your Cat

The goal of sub-Q fluids is to replace lost fluid and help your cat feel more comfortable. Understanding why your cat needs fluids can make getting started feel less daunting.

We aim to build on our analysis of blood tests from 3,006 cats to better understand when to start sub-Q fluids.

If you need help with your cat’s daily CKD care, you’re welcome to request a consultation anytime. Greycoat Research’s experts can share care information and research resources. Veterinarians looking for research materials are welcome to contact us, too.

Request a Consultation

About the Author and Research Team

Alex Shin is a pharmacist with more than 20 years of experience advising on medication use in animals. His work includes counseling owners of cats with kidney disease and advising on nutritional formulations.

Greycoat Research works with veterinarians, pharmacists, and researchers in South Korea and Japan to study feline kidney health and nutrition.

Specializing in Feline Kidney Care
Greycoat Research

Sources

• Dehydration management and ways to encourage water intake in cats with CKD — Taylor S et al. 2026 iCatCare consensus guidelines on the diagnosis and management of chronic kidney disease in cats. Read the guidelines
• Blood-panel findings across creatinine groups in 3,006 cats — Shin H et al. Frontiers in Veterinary Science. 2026;13:1972280. Read the study
• Fluid selection, frequency, and precautions for cats with heart disease — AAHA. 2024 Fluid Therapy Guidelines for Dogs and Cats. Fluid selection · Frequency and precautions
• Electrolytes, buffering ingredients, and acid–base effects of fluids — Rudloff E, Hopper K. Crystalloid and Colloid Compositions and Their Impact. 2021. Read the review
• Evaluating repeated high breathing rates during sleep — Sleeping and resting respiratory rates in healthy adult cats and cats with subclinical heart disease. Read the study

[Educational Disclaimer]

This article is for educational purposes only and is not a substitute for professional veterinary advice, diagnosis, or treatment. It is not intended to diagnose, treat, cure, or prevent any disease.

Please consult your veterinarian before making changes to your cat’s diet, supplements, or care routine.