Split your Lantus and test frequently.
I usually take my Lantus at 22.30, forgot it one day (so I woke up with >22 (400s)). I did half the dose (instead of 18, 9) at 08.30 and increased my humalog during lunch & dinner.
At night I did smaller dose of Lantus (14 I think), had an alarm at 04.00 to...