College of Veterinary Medicine

Pet Health Topics

Giving Subcutaneous Fluids to a Cat  

This information is not meant to be a substitute for veterinary care. Always follow the instructions provided by your veterinarian.
tabby cat
In the photographs below, unless otherwise noted, the cat is facing to your right.


Variations on these instructions exist.

Supplies used in giving subcutaneous fluids will vary by manufacturer and may differ from those pictured here.

Fluid given under the skin, subcutaneously (SQ), is absorbed into the blood stream and can be used to correct or prevent dehydration. The most frequent disease for which fluids are given is chronic kidney failure. Cats with chronic kidney failure pass large amounts of urine and may not feel well enough to drink enough to prevent dehydration. The cat owner may give subcutaneous fluids a few times a week to supplement the water the cat is drinking in order to prevent dehydration and help flush waste products through the kidneys. 

Your veterinarian will prescribe a certain type of fluids and a volume and frequency for administration to your cat. The most common fluid type given to cats with chronic kidney failure is Lactated Ringers Solution (LRS).

There are 3 general techniques used to give SQ fluids:

  • with a syringe and needle 
  • with a syringe, needle and flexible tubing called an extension set 
  • from a vinyl bag using a solution drip set

Most cats  tolerate being given subcutaneous fluids. You can give about 10-20 ml per kg of body weight (5 -10 ml per pound) in one spot (e.g. 50 ml for a 10 pound cat) before you move to another location.  It usually takes 6 to 8 hours for all the fluids to be absorbed. Check to see if the previously administered fluids have been absorbed before giving more fluids. Even though the fluids are given on the back, gravity will cause the fluids to accumulate on the belly, so check for residual fluids on the belly before you give more. Check with your veterinarian if the fluids are not being fully absorbed.

Usually the skin is not cleansed before inserting the needle. If the cat has a normal immune system, the few bacteria that are pushed under the skin with the needle will be killed by the cat's immune system.

You can use alcohol on a cotton ball to make the hair lay flat so it is easier to see where the hair ends and the skin starts. Alcohol takes about 30 minutes before bacteria are killed, so just swiping the hair with alcohol is not effective in killing bacteria.

If your cat may have an abnormal immune system, for example is on anti cancer drugs, then several patches of hair may be shaved and the injection sites scrubbed with an antiseptic solution such as Novalsan or Betadine before placing the needle, to prevent pushing bacteria under the skin.  

parts of a hypodermic needle The thickness of a needle is measured by gauge (g), the smaller the number, the thicker the needle. An 18 gauge needle is thicker than a 20 gauge needle. Needles may also be different lengths, one-inch and one and one-half-inch are most commonly used.  
 The plastic hub is the wide part of the needle that attaches to the syringe. The hub of the needle is color coded by size, although these colors may vary by manufacturer. 18g needles have a pink hub, 20g needles have a yellow hub. 20g needles are most commonly used to give SQ fluids although larger needles (18g) may be used to draw fluid from the container of fluids. Smaller needles (22g) may be recommended for cats.
packaging of hypodermic needles Needles are packaged in a rigid plastic cover and wrapped in paper or plastic to keep them sterile. Keep the needles in the original package until use. Do not dispose of needles or syringes in the trash. Keep used needles and syringes in a puncture-proof container and return them to your veterinarian for disposal.

Don't use the same needle that was placed under the skin to draw more fluids from the container of fluids or bacteria will be introduced into the container of sterile fluids.

If you use an 18g (pink) needle to draw from the solution container and a 20g (yellow) needle to give the fluids, it will be easier to keep track of which needle to use. Keep the white plastic cap to place over the sharp needle when it is not in use.

syringe in case Usually a large (60 ml) syringe is used for fluid delivery. The syringe is often packaged in a plastic case. If the syringe is to be used more than once, you may want to keep the container. The plastic container is also useful for placing used needles for disposal.
60 ml syringe  
parts of a syringe The syringe has 2 parts, a barrel and a plunger.
markings on a syringe The syringe is marked in milliliters (ml) and ounces. The syringe is marked at 5 ml increments (5 ml, 10 ml, 15 ml, etc.). Each line between the numbers is 1 ml. 

The plunger has a domed end. The top edge of the plunger is used to read the amount of fluid in the syringe. This syringe contains 26 ml of fluid.

There is a small air bubble in this syringe. It is not necessary to remove tiny air bubbles such as this one when you are giving fluids SQ.

plastic needle cap Remove the needle from the paper/plastic wrap but leave the plastic cover on the needle. Place the hub of the needle firmly over the tip of the syringe. Some needles and syringes have threads that screw together (luer-lock). Remove the plastic needle cap just before use.
vinyl bag of fluids Fluids are in plastic bags or glass bottles. Bags of fluids come packaged in a plastic wrapper. Remove the wrapper from the plastic bag just before using. The fluid type that is most often given SQ is Lactated Ringers Solution (LRS). 


Fluids do not contain a preservative, so ideally they should only be used only once and then any remainder should be discarded. Most veterinarians stock fluids in 1,000 ml bags. This volume is larger than is given to a cat at one time. You may be given instructions to draw fluids from the same bag for a few days. See the instructions below for suggestions on how to prevent contamination of the bag of fluids.

injection port of bag of fluids The neck of the bag of fluids has 2 ports; the injection port that is covered with a rubber stopper and a port covered by plastic (blue) in which the spike of a solution set is inserted (discussed below).



clean injection port with antiseptic

Follow your veterinarian’s instructions for handling the fluids sterilely so the container of fluids is not contaminated, and you may be able to use the same container of fluids for a few days, if recommended by your veterinarian. 

Clean the rubber stopper of the injection port with an antiseptic solution such as Novalsan (chlorhexadine) or Betadine (povidone iodine) before inserting the needle, if more than one puncture will be made through the stopper.

Alcohol takes about 30 minutes of contact before bacteria are killed, so it is not a good solution to use for this purpose.

Always use a sterile needle to draw fluids from the sterile container. Do not use the same needle to give the fluids to the cat, and then place that needle back into the fluid container as it will become contaminated with bacteria from the skin. 

If you use an 18g (pink) needle to draw from the solution container and a 20g (yellow) needle to give the fluids, it will be less confusing. 

Never use a bag of fluids if it appears cloudy.

inserting needle into injection port

Remove the plastic cap from the needle and place the tip of the needle in the injection port.


inserting needle into injection port The needle must be inserted into the center of the rubber stopper. The injection port itself is held so the needle is inserted straight into the injection port.

needle aligned with injection port


This needle is properly aligned.


 incorrect needle placement This needle is placed off-center and is puncturing the injection port.


draw fluids into the syringe
do not overfill syringe
Draw back on the syringe plunger while holding the syringe barrel steady so the needle does not pull out of the fluid bag. Fill the syringe to the volume prescribed by your veterinarian. 

Do not fill a 60 ml syringe past 50 ml as the plunger may accidentally be pulled out of the barrel of the syringe, spilling the fluid.


If you used an 18g needle to draw from the bag, replace the plastic cap, remove from the syringe, and set aside this needle. 


needle cap

Replace the 18 g needle with a 20g needle. When you have given the first syringeful of fluids, change back to the 18g needle to draw another syringeful. Then change back to the 20g needle to inject the cat. Keep the plastic caps on the needles as you exchange them. Use one new 18 g and one new 20g needle each time you give fluids to your pet; alternating needles between syringefuls of fluids. 


pick up skin fold Pinch up a fold of skin anywhere along the neck or back using your left hand if you are right-handed.


insert needle under the skin Use your right hand to place the needle into the skin fold along the long axis of the fold.


needle inserted across a fold of skin If you place the needle in the opposite direction, across the skin fold, it is more likely that the needle will go through one fold of skin and out the other fold of skin. The needle in this picture is yellow and is attached to a flexible piece of tubing (technique described below).

Before injecting the fluid, pull back on the plunger of the syringe. If air bubbles appear in the syringe, the needle has gone through both folds of skin and you are sucking room air into the syringe. Remove the needle from the skin and try again. 

If you get blood, the tip of the needle is in a blood vessel. Remove the needle and try again.


extension set If the needle is not directly attached to the syringe, but is attached to a flexible piece of tubing (an extension set) first, the cat can move around a bit while the fluids are being injected.

The extension set will be packaged in a plastic/paper wrapper. Remove from wrapper, remove the white plastic cap from one end and firmly place on the tip of the syringe. Remove the cap on the other end and place into the hub of the needle.

The two ends are different, the female end fits over the tip of the syringe. The male end fits into the hub of the needle.

draw fluid from fluid bag

The needle attached to the extension set is inserted into the injection port as described above for a needle directly attached to a syringe. Draw the prescribed amount of fluids into the syringe. Replace the 18g needle with a 20g needle and recap the 18g needle with the plastic needle cap.

Push some of the fluid through the tubing to evacuate air from the tube, a procedure called priming.


place needle under skin

The syringe containing the fluids is laid on the table. The needle is placed under the skin. Pull back on the plunger of the syringe. If air bubbles appear in the syringe, the needle has gone through both folds of skin and you are sucking room air into the syringe. Remove the needle from the skin and try again.

If you get blood, the tip of the needle is in a blood vessel. Remove the needle and try again.


inject fluids under the skin Once you have checked that the needle is correctly placed, push the plunger to inject the fluids. The plunger can be pushed using one hand by holding the syringe between the index finger and middle finger and pushing the plunger with the thumb of the same hand.  If this is difficult, hold the syringe in one hand and push the plunger with the other. 


comfort the cat

If you handle the syringe with one hand, your other hand is free to comfort or restrain the cat.


syringe, needle and extension set

When you are finished giving fluids, if you are instructed to use the same syringe and extension set for more fluids later, place a clean needle covered by its plastic cover on the end of the extension set.


fluid delivery tubing

The third method to give SQ fluids is to attach a solution drip set to a bag of fluids.

Remove the solution set from the plastic/paper wrapper. Both ends are covered with plastic caps. After removing the cap, the male end fits into the hub of the needle. The white spike is punctured into the spike port of the bag of fluids after removing the plastic tube that covers the spike.


spike port on bag covered with plastic

The spike port on the bag of fluids is covered by a blue plastic cover. This cover is pulled off. The cover is tightly covering the spike port and you have to pull firmly to remove it.


insert spike into bag The white spike on the solution set is pushed into the spike port. Hold the spike port in your left hand to guide the spike straight into the port. If you push the spike in at an angle, it may puncture the bag of fluids.



fluid delivery system, labeled


Attach a needle to the other end of the solution set.


fluid administration set, labeled The plastic tubing has 2 clamps that must be opened to allow fluid to flow. 
  • The dark blue pinch clamp has a tapered slot, the tubing is pushed to the widest part of the slot to open and pushed to the narrowest part of the slot to stop fluid flow
  • The light blue clamp is a roller clamp. Use your thumb to roll the white disk up, toward the solution chamber to open and in the opposite direction to close. 

The fastest flow of fluids occurs with both clamps fully open.

Before placing the needle in the SQ, open the clamps and let fluid flow until the air is evacuated from the tubing (priming).


You will see drops of fluid drop in the drip chamber when the clamps are open. If the drip chamber fills with fluid so that you cannot see the drops forming, turn the drip chamber upside down and squeeze some of the fluids back into the bag. 

giving fluids using an administration set The skin is tented and the needle inserted along the long axis of the fold. You cannot suck back to check for air so watch the site at which the fluids are entering the skin fold to make sure the hair isn't getting wet suggesting the needle is incorrectly placed.

roller clamps on tubing


There are 2 clamps on the solution drip set that must be opened to allow fluids to flow.


fluids dripped into sc space


The fluids can be dripped into the SQ space as fast as the drip will go. The higher you hang the bag, the faster the fluids will flow.


squeeze bag to increase fluid rate You can also roll up the bag and squeeze the fluids out of the bag.

If you are instructed to use the same fluids and solution set for more fluids later, place a clean needle covered by its plastic cover on the end of the solution set. 


Complications of SQ fluid administration can include:

  • development of an abscess which will be a hard, painful lump that is warm to the touch
  • edema if too much fluid is given
  • if the cat is severely dehydrated, the fluids will not be absorbed

photographs by Henry Moore

Washington State University assumes no liability for injury to you or your pet incurred by following these descriptions or procedures.

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Last Edited: Jan 08, 2016 11:04 AM   

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