Insulin Therapy in Type 2 Diabetes with Severe Hyperglycemia

Indications for Immediate Insulin Initiation

The American Diabetes Association recommends insulin therapy when a patient presents with blood glucose levels ≥300 mg/dL, HbA1c ≥10%, or symptoms of hyperglycemia, such as polyuria and polydipsia 1
Insulin is mandatory when catabolic features, such as unexpected weight loss, or ketonuria are present, as ketonuria reflects profound insulin deficiency 2, 3
Patients with high baseline HbA1c (≥9.0%) have a low probability of achieving near-normal targets with oral monotherapy, justifying direct initiation with insulin 2

The European Association for the Study of Diabetes suggests beginning with basal insulin added to existing pharmacological therapy, while revisiting lifestyle modifications 4
The American Diabetes Association recommends discontinuing sulfonylureas or other medications that can cause hypoglycemia once insulin is started 4
For patients with marked hyperglycemia (blood glucose ≥250 mg/dL, A1C ≥8.5%) who are symptomatic, the American Diabetes Association recommends initiating basal insulin while metformin is started and titrated 5
In patients with ketosis/ketoacidosis, treatment with subcutaneous or intravenous insulin should be initiated to rapidly correct hyperglycemia and metabolic derangement 5

If glycemic targets are not met with basal insulin, progress to multiple daily injections with basal and premeal bolus insulins 5

Once symptoms are relieved and glucose toxicity resolves, it may be possible to taper insulin partially or entirely, transferring to non-insulin antihyperglycemic agents 1, 2
In patients initially treated with insulin and metformin who meet glucose targets based on home blood glucose monitoring, insulin can be tapered over 2–6 weeks by decreasing the insulin dose by 10–30% every few days 5

Proper patient education regarding glucose monitoring, insulin injection technique, insulin storage, recognition/treatment of hypoglycemia, and "sick day" rules is essential 2
When available, certified diabetes educators can be invaluable in guiding patients through insulin initiation 2
In patients with severe hyperglycemia (blood glucose ≥600 mg/dL), consider assessment for hyperglycemic hyperosmolar nonketotic syndrome 5

Glycemic status should be assessed every 3 months to determine if continued insulin therapy is necessary or if de-escalation to oral agents is possible 5