If you're posting in Main Health, the suggestion is not to shoot under 200.
On the Lantus/Lev group, For new members that have a preshot number under 150, we suggest that you post and ask for guidance on how to proceed.
An experienced Lantus user would look at your spreadsheet to see what all is going on and help you figure out if it's safe to shoot. You'd be asked if you are able to monitor after the shot in case the cat goes into lower numbers, if you have high carb cat food, karo, honey, or maple syrup and plenty of test strips if you need them.
And the tradition here is that if a person suggests you shoot a lower number, they will also stay with you to teach you how to deal with low numbers if you get them.
The interesting thing about Lantus is that it works very well at lower numbers, and you'll see by people's subject lines that with a preshot that's in normal numbers, say under 100 or so, the hours after the shot might just be a flat "surf." When a cat spends time in normal numbers (50-120), the opportunity exists for the cat's pancreas to heal, if that is at all possible, and for the cat to become diet-controlled. We don't know what cats will be able to do that, but some can.
Sienne corrected my math error - 0.25u x 4.5 = 1.125, which would suggest starting at 1.0u if you were following Tight Reg, or the 0.5u if you want to follow SLGS.
As far as the dose for tomorrow morning goes, it's pretty important not to start too high for a couple of reasons. One is that it's less nerve-wracking to not see low numbers immediately! Another reason is that too much insulin can cause the cat's body to have high numbers. If the cat's body perceives that it's going into low numbers - the body will release sugars and hormones to send the blood sugar high. That's called a bounce. There's a more descriptive post
here - the second one in the thread - if it would be helpful.
Increases are done slowly and in small increments, with those decisions made by the tests you get, so that the cat doesn't become overdosed and miss the right dose.