We have tried giving 0.5 units a few days (8 cycles) but his PSs were upped to 300s. That were astonishing when the time we read the meter.
You've done great to get the test data already in the spreadsheet.
Some of those higher numbers could be what we call 'bouncing' - if a cat's BG goes too low (or even lower than its body has been used to recently) the body's self-protective mechanisms will trigger the cat's liver to start releasing glucose into the bloodstream and this can produce much higher numbers. Depending on the cat, it can take several days for a bounce to clear, during which time the trick is to 'ride out' the bounce and wait for the cat's body to settle down again before considering whether an increase is justified. It may very well be that a dose of, say, 0.25 IU (for example) may be too low for your cat but it really does look like the 1.0 IU may be too high. You end up with very, very low preshot numbers and where you have given insulin on those occasions it has taken Jai Jai very low - dangerously low, to be truthful - hence my recommendation above to agree a 'no shoot' preshot BG value. (Any time a BG value is lower than the 'no shoot' value, you either stall for a little while and retest to see if you get a safe number, or else you skip the dose and wait for the next preshot test.)
If you look at your spreadsheet, you will see that you are getting preshot numbers in the greens and then you've given 1.0 iu which has taken Jai Jai way too low and then his BG soars when the cat's body's safety mechanisms kick in to put extra sugar into his blood. If you can get to the right dose for Jai Jai, you should end up with two preshot numbers a day that are at a level safe enough to give insulin, and the nadir should be above the hypo threshold, not dangerously below it.
Another thing to mention: since Jai has experienced a number of asymptomatic hypos,
there is a strong possibility that his body may have become much more sensitive to insulin as a result. That is another factor that could point to the 1.0 IU dose of Lantus being too high - Jai's insulin needs may have decreased.
@BJM is going to have a look at your spreadsheet later (thank you, BJ!) and will provide you with further feedback.
In the meantime, I wonder whether you could answer the following questions for us:
1. Dehydration / Fluid Therapy - Does Jai Jai have any underlying health conditions that are causing the dehydration? Could you let us know more about this, please? (Are they sub-q fluids?)
2. What type of food does Jai Jai eat? Does he drink any water himself.
3. VERY IMPORTANT - How confident are you about the diabetes management advice and instructions for giving insulin that you have received from your vet? For the record, you are not testing Jai Jai too frequently. Your testing has provided us with data that will help us to help you keep him safe on insulin.
MOST IMPORTANT OF ALL -
I recommend that for the next several days you ask for help here with Jai Jai's dosing: it could help a lot to bring all those wild swings under control. Take the preshot test and then post asking for help with Lantus dosing (include the preshot number in the thread title). You can post on this board at first, and hopefully one of the Lantus & Levemir Insulin Support Group members will be able to guide you toward posting in their group. (It's very busy, hence my suggestion to post for advice on Feline Health first - less overwhelming when getting started!

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