I haven't had to split glargine as I get on with it ok, but I did discuss doing so with my DSN, and I know people who have. I think I'd be inclined in your position to follow Dillinger's advice and try levemir, but in the meantime, might it just be as something as simple as raising the dose you take in the morning and lowering the dose you take before bed? You don't say when you are injecting or how much. Could well be that the doses are overlapping (in which case levemir may well be the answer), or it could be that the doses just need to be different at different times (in which case it may be fine to stay on lantus).