Hi and Welcome to the L B & L forum. And I am glad that you have started to home test. It is so important to keep Sammy safe. But, it is always important to get a test before you shoot. When you say you can't get a blood sample to test , are you saying that you can't get him to bleed? If so, you can gently rub each ear for a few seconds to help with circulation or you can get a small sock and put some rice in it and tie a knot in the sock and heat it up for about 30 seconds. You just want it to be warm not hot. Put that on Sammy's ear for a 1/2 minute or so and that will also help to get him to bleed faster. After a while the kitties eats learn to bleed faster.
As far as the vet recommending 1 unit once a day, Lantus needs to be dosed twice a day, 12 hours apart. And you can do the curve yourself at home which would be better for Sammy. When our kitties are at the vets they are so stressed out and that stress causes higher numbers which then will result in the vet recommending a higher dose that might not be necessary. To do a curve, you would start with the AM pre shoot test and then test every 2 hours for 12 hours up to the PM pre shot.
Can we get you to set up a spread sheet like the rest of us are using? It will help you to keep track of his numbers and to spot patterns and trends with the dose he is getting. It also helps us help you with dosing questions. The instructions are
Here and if you have any trouble setting it up just yell and someone with help you get it set up. Then you would attach it to your signature.