It seems to peter out sort of slowly sometime in that time frame, leaving very little
Lantus working to help with his dinner-time quick-
acting insulin. So it may take more
insulin in the evenings than at other mealtimes to cover the same amount of carbs.
Some of us prefer to split the Lantus dose, taking some in the morning and some in the evening to equal the complete dose. That way, only half is petering out after 20 hours, and the sugar levels stay more even throughout the day.