How much do you inject; where do you inject it; how do you inject it...syringe or pen. What needle size? What I'm leaning towards here is that you may be injecting into a muscle sometimes. That will definitely drop your BG as Lantus is a 24-hour insulin. It releases its insulin into your body by converting the liquid injection into crystals that slowly release their insulin into the body. Another explanation could be your Lantus dosage is too high. What's the history on you and Lantus?
This happens in some cases. Just curious...how do you know exactly when the Lantus wears out? That's a very specific time. As an option you can choose to split your dose of Lantus to twice a day and see how that works for you. If Lantus doesn't seem to be what works for you...you can try double dosing Levimir.