| Do some searches on here for lantus and depression. Whilst I know of no concrete 100% proof that there is a link, there have certainly been a few folks on here who have said that Lantus did not suit them in terms of mood. In those cases, their mood improved a great deal when they switched to a different insulin. I'm not suggesting you change insulin (especially on reading a few anecdotes on the Internet) but you may find it of interest.
Personally, I am still on Lantus but I was injecting way too much of the stuff. I felt lousy due to constant highs and lows (it was essentially the ratio of Lantus to bolus insulin that I had round the wrong way). I also used to be on 35 units per night. Now I'm on 18 of Lantus. I feel a lot better, though this is to be expected due to the fact that my control is now very good where it was awful. I feel a lot happier, though I have absolutely no idea whether this is due to the better control or to the reduction in Lantus intake.
I did consider swapping to Levemir, but to be honest I'm very happy with my control at present and mentally I feel a million dollars so I'm working on the cliche about broken things and the pointless nature of repairing them.
Is your overall control good? Large swings in BG give lots of people mood swings (me included!). If you haven't done so, testing your basal rates via a fast is a useful excercise IMO; again searching on here can give you details and it will help to show you if the Lantus is causing a bit of a dip which it shouldn't do. Its job is to keep your BG level when no other food or insulin is involved.
Gary  | 
