High morning readings can be associated with something called the dawn phenominon. Hormone levels shift before you wake, to signal to the body that it is time to get up. Many dieticians recommend trying a snack in the evening to help counter this.

12 units of Lantus is extremly unlikely to cause a low during the night.

When I was excercising regularly (before my recent foot problems) I was taking 20 units of Lantus/day - in the evening. My normal fasting BS was between 80 - 90 and would peak to around 120 during post prandial tests. The lowest I ever got on Lantus was 68 and that was after a 2 hour workout.
People frequently eat before taking an insulin shot when they are on fast acting insulin so as to not overcompensate and cause a low before they eat.
For example taking a dose of fast acting insulin before ordering your meal in a crowded restaurant and then waiting for the food to arrive can be problematic. Lantus is a slow acting insulin though.


There are many things that can cause a high reading through. Illness or infection, stress, changes in just about everything can throw your readings off.