As an example this morning around 4am I was at 6.1. by 9am it was 8.6, then 11am it had shot to 14.4, despite not having eaten anything.
As
@grovesy suggests, that sounds like Dawn Phenomenon and maybe a Waking Rise too. The first is caused by your blood sugar rising as your body gets ready to wake up for the day, and the second is basically the ‘stress’ of getting up. I get both of those. My blood sugar rises from about 4am and, if I don’t eat breakfast and bolus, it will go up to around 9 without insulin.
I have a pump so I set it to give me extra insulin to stop the Dawn Phenomenon. To stop the Waking Rise, I try to eat and bolus soon after getting up. If I can’t do that, i’ll small bolus without food to keep my blood sugar down.
I get what you’re saying about not wanting to split your Lantus but it might be worth a trial to see if it helps. What time do you inject it?