Testing Blood Glucose
Glucose can be measured in blood or interstitial fluid. Glucose in interstitial fluid is similar to blood glucose and can be measured using a continuous glucose monitor (a small monitor implanted under the skin for a few days to a week or more).
Glucose can also be measured in blood using a handheld glucometer or glucose test strips, which only need a drop of blood, several times a day.
How to Collect a Blood Sample
There are a few different options. Your veterinarian may collect a blood sample from a vein. The glucose concentrations are then measured in the laboratory. If you are using a blood glucose test strip or a handheld glucometer to measure blood glucose only a drop of capillary blood is needed. Your veterinarian will show you the most suitable place and proper method to collect a drop of blood from your cat. The most common sites are the ear (pinna), the inner lip or elbow callus. Alternate sites, including tail and foot pads can be considered depending on you and your veterinarian’s preference and your cat’s comfort level.
Make sure that your cat’s ear is warm. If not, hold it between your hands for about 1 minute. This makes collecting a drop of blood easier.
Quickly prick a clean, hairless part of the ear with a sterile lancet or hypodermic needle.
A small drop of blood will appear. Collect the drop onto the glucose test strip as per instructions provided.
Gently but firmly press some clean cotton or gauze onto your cat’s ear until bleeding stops.
Read the test strip or insert the sample into the glucometer as instructed.
Your veterinarian may want to make a blood glucose curve for your diabetic cat. When creating a glucose curve, remember that general health, feeding, exercise, insulin dose, and stress can affect the results and the glucose curve is only one of the tools that can be used to help manage cats with diabetes. As stress plays a role in glucose and insulin metabolism, your veterinarian might request that you measure glucose in capillary blood samples taken from your cat at home over a certain period.
What is a glucose curve used for?
A blood glucose curve can help determine
- If and when the insulin given to your cat starts working
- How responsive your cat is to the insulin dose it has been given
- How low your cat’s blood glucose falls and when this occurs
- How long the insulin works in your cat
This information is used to monitor the response to an insulin dose – especially at the start of treatment or after a change in insulin dose. It is also used to investigate cats that appear not to be responding to insulin treatment – sometimes after a period of stability.
When to take blood samples
- Just prior to giving insulin and food
- Then, every 60 to 120 minutes (with the shorter intervals particularly useful when blood glucose falls to 9 mmol/l or 162 mg/dl or lower)
- For as long as possible e.g. for 8 to 12 hours or longer
Your veterinarian will interpret the glucose curve based on your cat’s progress (e.g. water intake, appetite, attitude, body weight).