Hi Looby,
I'm going to start by giving you the link to the FDMB Hypo document.
(The very scarily titled)...
How to treat HYPOS - THEY CAN KILL! Print this Out!!
In the first section you'll see a list of common symptoms of hypoglycemia.
In the next part there is detailed general info on what to do depending on the cat's blood glucose level (so this info is to be used in conjunction with hometesting).
Do have a
read through of the document and then print it out and keep it somewhere handy in case you need it in an emergency.
I can say from experience that hypo is
very much easier to deal with if you have at least some basic idea of what you'll need to be doing; which mostly entails getting carbohydrate into the cat.
When we treat cats with insulin our aim is to try to get their blood glucose levels low enough so that they can feel better, and so that their bodies have the chance to heal. But we don't want their blood glucose levels to drop
so low that it becomes dangerous for them. It's 'a balancing act'.
So, if the blood glucose drops too low, or is in
danger of dropping too low, we take action to raise the blood glucose level so that the cat is safe from hypoglycemia.
A cat in very low numbers, or showing symptoms of hypoglycemia, should be given glucose/honey immediately. These 'simple sugar's raise the blood glucose very fast. The cat may also need to be given gravy from high carb food. The reason for this is that glucose/honey works fast but wears off relatively quickly; while gravy from high carb food usually takes a tad longer to raise the BG, but should stay in the system for longer.
In some situations where the blood glucose is dropping
too fast, or is in
danger of dropping too low, it may be possible - through the judicious use of food - to just 'steer' the cat safely through the insulin cycle and completely avoid numbers that are too low.
The situation also depends, somewhat, on the insulin type and the insulin dose.
There is a general 'rule of thumb' on FDMB that we should aim to keep cats' blood glucose above 2.7 mmol (50 mg/dL).
But my own feeling is that with certain insulins, such as Caninsulin, we should aim - at least initially - to not let the blood glucose drop below 5 mmol (50 mg/dL). '5' is a perfectly safe number, but Caninsulin can drop the blood glucose much
faster than the longer-lasting insulins, so trying to not let the BG drop below 5 gives some buffer of safety.
And it's not just what the number is, but also where you see it during the insulin cycle.
For example, if you saw a 5 at the peak of the insulin cycle (lowest number of the cycle) that might be a very nice thing to see, and shouldn't need any action other than you maybe do another test a bit later to check that it's not dropping lower.
But if you see a 5 just a couple of hours into the insulin cycle, when there is still some time to go until the peak of the cycle, it would be wise to take some action to stop it dropping much lower. It may be that a little low carb food is all that is needed to keep the numbers from dropping. Or is may be that medium carb food, or higher carb food becomes necessary. It all depends on the situation, your ability to hometest, and your confidence in dealing with the situation.
FDMB is an international forum and there is almost always someone here who can help you.
Or you can call your vet for advice.
If you're not testing but you see actual hypo symptoms then give honey/glucose before taking any further action.
I know it all might sound a bit scary at first. We've all 'been there', Looby, so we do understand.

I think you'll feel a whole lot more comfortable and confident once you've got the hang of how the glucose meter works.
Eliz