The insulin given is NPH insulin which is long acting and peaks in effect in 8-12 hrs. Thus, to get a maximal effect on awakening in the morning, we give the insulin in the evening or at bedtime. In theory, the more insulin we give at bedtime, the lower the Fasting glucose (FBS) will be. We are trying to achieve a FBS below 7.0 mmol/L (125 mg/dl).
Alternatively we can use an extended long acting insulin such as Glargine (Lantus) or Detemir (Levemir), these insulins give an essentially constant insulin level for 24 hours so they can be given at any time of the day (except that the timing should be consistent from one day to the next).
We will start by taking 10u NPH insulin in the evening. If FBS remains high (above 7.0 mmol/L) consistently for 3 days in a row, increase evening insulin by 2 units at a time. Keep measuring glucose levels in the morning and if the morning glucose (before breakfast) continues to be above 7.0 mmol/L (125 mg/dl) then increase again the bedtime insulin dose. We keep on doing this until we achieve a morning (before breakfast) glucose level that is consistently between 4.0 & 7.0 mmol/L (70-125 mg/dl).
We need to be cautious about nighttime low glucose (see hypoglycemia) and if this occurs, decrease the insulin dose by 2u until you see the doctor.
Usual starting bedtime dose is 10u NPH insulin at bedtime.
If using Lantus or Levemir, the insulin can be taken at any time of the day at your convenience but the dosing times should be constant from day to day.