When caring for an unstable client in the ICU with a dangerously high serum blood glucose, through which route should the nurse prepare to administer regular insulin?

When managing a client in the ICU with a dangerously high serum blood glucose, administering regular insulin intravenously is the most effective approach. This route allows for rapid and precise control of blood glucose levels, which is crucial in unstable patients.

Intravenous administration of regular insulin provides immediate availability in the bloodstream, enabling healthcare providers to quickly adjust dosages as needed based on the client's blood glucose readings. This precision is particularly important in critical care settings where fluctuations in glucose levels can occur rapidly.

In contrast, subcutaneous administration is slower, delaying the insulin's action and not suitable for urgent situations like severe hyperglycemia. The oral route is not practical for insulin, as it would be ineffective due to degradation in the gastrointestinal tract. Intramuscular administration is also not typically used for insulin because it can lead to unpredictable absorption rates. Therefore, the intravenous route is the preferred method in this clinical scenario.