Testing Your Cat's Blood Sugar: A Step-By-Step Guide (2025)

Testing a cat's blood sugar is important for monitoring and controlling diabetes. While a veterinarian can perform this test, cat owners can also check their cat's blood sugar at home using a blood glucose monitor or glucose test strips. The ear is the most common site for blood collection, but blood can also be drawn from the toe pad, lip, callous, or foot pad. It is important to monitor a cat's behaviour and weight, as well as their food and water intake, as these can be indicators of uncontrolled blood sugar.

Testing your cat's urine

Step 1: Purchase Glucose Test Strips

Buy glucose test strips from a drug store. The same urine test strips used for humans will work for testing your cat's glucose levels. These strips are easy to use, less invasive than blood tests, and detect the amount of glucose in the urine when dipped into it.

Step 2: Prepare the Litter Box

Fill your cat's litter box with a non-absorbing litter. This is important because the urine needs to stay in liquid form for accurate results. Remove the absorbent litter and replace it with a non-absorbent alternative, such as commercial non-absorbing cat litter or styrofoam packing peanuts. This will ensure that the urine doesn't get soaked up and remains accessible for testing.

Step 3: Collect the Urine Sample

After your cat has urinated in the box, take a fresh test strip and dip it into the pooled urine. You may need to tilt the box slightly to collect enough urine for the test. If your cat hasn't urinated yet and you need to test their glucose levels urgently, you can mix a clump of litter with 8 fl oz (240 mL) of water and dip the strip into it. However, testing with pure urine will provide more accurate results.

Step 4: Read the Results

If the test strip shows that glucose is present in the urine, it is generally safe to administer your cat's normal dose of insulin. Remember that urine testing is not a reliable way to determine the exact amount of insulin required. It only indicates whether it is safe to give your cat its standard dose.

Step 5: Replace the Litter

After you have completed the test, throw away the non-absorbing litter and put your cat's regular, absorbent litter back into the box. Ensure that you use fresh, clean litter and do not reuse old litter.

By following these steps, you can conveniently test your cat's urine to monitor their blood sugar levels and make informed decisions about insulin administration.

Using a blood glucose monitor

If you want to test your cat's blood sugar at home, consult your veterinarian first. They can recommend a monitor and instruct you on how to use the device on your cat. You can purchase a special blood glucose monitor designed for cats, which are easy to use and relatively inexpensive.

Your veterinarian will advise you on how often to check your cat's blood glucose and how to go about it. A single test may not provide helpful information unless your cat's blood sugar is too low, so you may need to perform a 12- or 24-hour curve test to show how effective your cat's current insulin dose is and whether it needs to be adjusted. This type of test requires a blood sample every 1 to 2 hours.

When you need to administer the test will depend on what your vet is checking for. You may need to test before your cat has eaten if your vet is concerned about high blood sugar, or 6 hours after your cat has eaten if your vet suspects low blood sugar. Eating raises your cat's blood glucose levels, so it is important to wait until your cat has processed its food before testing.

Both your cat's ear or toe pad are acceptable locations for drawing blood for a blood glucose test. Only a small drop of blood is required. Press the device against your cat's ear or toe pad and press the button to extend the lance and draw the blood. It is important to keep your cat calm while you take the test, so choose the location that seems less bothersome to your cat.

The device should provide a readout of the blood glucose level within a couple of minutes. The normal range is between 75 and 120 mg. If your cat's blood sugar levels are within this range, then it is normal. If the number is above or below this range, then it is abnormal, and you should call your veterinarian to set up an appointment.

If you have concerns about your cat's behaviour or if you get an abnormal reading on one of the tests, your cat may need to stay at the veterinarian's office all day or overnight for a blood glucose curve test. This test requires a blood sample every 1 to 2 hours over an 8, 12, or 24-hour period to provide your veterinarian with more data to help them make a diagnosis.

Signs of uncontrolled blood sugar

Uncontrolled blood sugar in cats can be a sign of diabetes. The clinical signs of diabetes mellitus are related to elevated concentrations of blood glucose and the inability of the body to use glucose as an energy source.

The four main symptoms of diabetes mellitus are:

• Increased thirst
• Increased urination
• Weight loss
• Increased appetite

These signs may go unnoticed, especially in the early stages of the disease, or if a cat spends a lot of time outdoors.

Cats with uncontrolled blood sugar are also prone to rapid weight changes. If your cat suddenly loses or gains a pound, then it is best to take it to the vet.

Other signs of uncontrolled blood sugar include a difference in gait (walking) and hind-leg weakness. In rare cases of uncontrolled diabetes, cats may experience damage to the nerves in the hind limbs, resulting in a “plantigrade” stance of the hind limbs (walking or standing with their hocks on or close to the ground).

If you suspect your cat's blood sugar is uncontrolled, you can test its blood sugar at home or take it to the veterinarian for a blood glucose test.

Choosing a blood collection site

When choosing a blood collection site, it is important to consider the size, temperament, and physical characteristics of the cat. The best site is one that the cat will tolerate and that will consistently yield an adequate sample. The method should be safe and require minimal restraint.

The lateral ear margin is the most common collection site for cats and is generally well tolerated. Cats have small veins that run around the outside of their ears, which can be easily accessed from the dorsal surface. Blood can be sampled on both the cranial and caudal border of each ear, providing a total of four sites. Shaving the hair directly over the vein with a scalpel blade allows for better visualisation and, with very slow hair regrowth, will last for several weeks.

The inside of the ear flap can also be used, especially in "floppy-eared" cats such as spaniels. It is important not to try to hit the vein of the lateral ear margin with the skin prick; simply get close to it. Hitting the vein may result in excessive bleeding or bruising.

Another option is the pisiform (wrist) paw pad, which yields excellent blood samples. However, collecting from the primary pads can be painful and may not be well tolerated by the cat. Using a non-weight-bearing pad can alleviate this issue and is generally well-tolerated in cats who do not mind having their paws handled.

Selecting insulin dose

Insulin injections are typically given to cats twice a day, roughly 12 hours apart, at the same times each day. The injections are usually administered under the skin of the cat's back using either a syringe and very fine needle or a purpose-designed insulin pen.

Insulin is typically started at a low dose, which will often need to be gradually increased based on the cat's response. The low dose is used because overdosing on insulin is much more dangerous than underdosing. It can take some weeks to reach the optimal dosage by incremental increase.

The insulin dose should be based on the cat's ideal body weight and blood glucose levels. The recommended starting dose is 0.5 U/kg q 12 hr if BG > 360 mg/dL or 0.25 U/kg q 12 hr if BG < 360 mg/dL. This equates to 1 U q 12 hr in the average cat. Even in a very large cat, the starting dose of insulin should not exceed 2 U per cat q 12 hr. Most cats are well regulated on insulin at an average dose of 0.5 U/kg q 12 hr, with a range of 0.2–0.8 U/kg.

In cats, Caninsulin dosing is calculated on a per-animal basis (initial dosing for cats is based on blood glucose results). The initial recommended dose of Caninsulin (porcine insulin zinc suspension) is 1 to 2 IU per injection, given twice daily.

In cats, the goal of insulin therapy is to maintain blood glucose concentrations below the renal threshold (which is <12-16 mmol/L) for a substantial part of the day to alleviate most of the cat's clinical signs.

Frequently asked questions