Measurement of blood glucose concentration (BG) is usually the best method of determining the correct insulin dose for diabetic cats. Stress hyperglycaemia occurs commonly when cats visit a veterinary surgery and can result in the wrong dose of insulin being selected. Thus, the stress-free environment at home is the best place to measure a cats BG.
Most human glucometers are very accurate at measuring cat blood. We prefer the Accu-Chek brand which can be purchased from any chemist for approximately $60.
The easiest and safest place for owners to sample blood from is the ear veins. Cats have small veins that run around the outside of their ears and these veins can be easily accessed from the dorsal surface. Blood can be sampled on both the cranial and caudal border of each ear giving a total of 4 sites to sample. Shaving the hair directly over the vein with a scalpel blade allows much better visualisation and with very slow hair regrow, will last for many weeks.
1. Turn the glucometer on or insert test strip so the digital display is requesting blood.
2. Hold the edge of the ear between index-middle finger and thumb-fourth finger and firmly pull taut.
3. Quickly prick the vein with an insulin needle so a small drop of blood is produced on the skin surface. Pre-used insulin syringes are fine to use for this.
4. Bring glucometer down to the skin and place the end of the test strip into the blood until it beeps.
5. Read the number on the display and record it.
6. Wipe any excess blood away with a moist tissue.
Cats rarely react to their ears being pricked but topical anaesthetic creams such as EMLA can be applied prior to sampling if required. The most common complaint from owners is spraying of blood around the house if they shake their heads while blood is pooled on the skin. This can be minimised by not releasing the initial grip on the ear until blood has been transferred (with one hand) to the glucometer and a tissue applied to the ear. Blood glucose samples are best collected just before an insulin dose is due so dose adjustments can be made immediately if required rather than waiting until the next injection.
Selecting insulin dose
For newly diagnosed diabetic cats (less than 2 months):
If BG is above 12mmol/L then increase insulin dose 0.5 units (half a unit)
If BG is between 6 and 11mmol/L then keep insulin dose the same
If BG is between 3 and 6mmol/L then reduce dose by 0.5 units
If BG is less than 3mmol/L then don’t give insulin and call the clinic to discuss
For longer-term diabetic cats (more than 2 months of insulin therapy):
If BG is above 25mmol/L then increase insulin dose 1 units
If BG is between 14 and 25mmol/L then increase insulin dose 0.5 units
If BG is between 6 and 13mmol/L then keep insulin dose the same
If BG is between 4 and 6mmol/L then reduce dose by 0.5 units
If BG is less than 4mmol/L then don’t give insulin and either check for remission or call the clinic to discuss.
How often to sample
Ideally, diabetic cats should have BG sampled several times daily (just like humans do) but for many reasons this is not practical. We recommend that newly diagnosed cats should have their BG checked every 2-3 days for the first few weeks and longer-term diabetic cats be sampled every 1-2 weeks. If insulin dose is changed, then a repeat BG should be done 2-3 days afterwards to check the right decision was made, whereas if the insulin dose is kept the same then a repeat BG is probably not required for 1-2 weeks.
A table should be kept which contains the date, current insulin dose, the BG reading and the new insulin dose selected. Initially, this table should be reviewed by a veterinarian in consultation every few weeks. Your veterinarian will assess the BG readings and the decisions you have made and comment as necessary. Most owners rapidly become competent at sampling blood and selecting the correct insulin dose making it unnecessary to consult us for long periods.