Let's explore this situation with critical eyes...
The physician who prescribed 24 units of Humalog with meals didn't simply whip out a crystal ball and conjure up that dose overnight. It probably started as perhaps two, three or even five units with meals. However, once the patient continually failed to achieve good blood glucose control, her physician likely titrated it upward to a dose that finally facilitates good BG control.
I have had badly overweight patients receive 50 units of Humalog with meals in addition to 100+ units of Lantus or Levemir insulin every 12 hours. Insulin resistance is a son of a gun...