How should insulin be dosed in a type 2 diabetic patient controlled on oral agents who is now receiving glucocorticoid therapy causing marked hyperglycemia?

Insulin Dosing for Steroid-Induced Hyperglycemia in Type 2 Diabetics

Start NPH insulin at 0.3-0.5 units/kg/day given in the morning simultaneously with the steroid dose, as this matches the pharmacokinetic profile of intermediate-acting glucocorticoids that peak 4-6 hours after administration. 1, 2

Understanding the Glycemic Pattern

Glucocorticoids cause a distinctive hyperglycemic pattern that is critical to recognize:

• Intermediate-acting steroids (prednisone, methylprednisolone) taken in the morning produce disproportionate hyperglycemia during the afternoon and evening (6-9 hours post-dose), with glucose often normalizing overnight even without treatment. 1, 2

• This afternoon/evening peak occurs because prednisone reaches peak plasma levels 4-6 hours after administration, with pharmacologic effects lasting throughout the day. 1

• The magnitude of hyperglycemia directly correlates with steroid dose—higher doses cause more severe elevations. 3, 4

Initial Insulin Selection and Dosing

For patients on once-daily morning intermediate-acting steroids:

• Initiate NPH insulin at 0.3-0.5 units/kg/day given in the morning with the steroid dose. 1, 2, 3 NPH peaks 4-6 hours after administration, perfectly matching the steroid's hyperglycemic effect. 1, 2

• For a 70 kg patient, this translates to 21-35 units of NPH insulin initially. 2

• Continue the patient's oral agents (metformin should be maintained if renal function permits), but sulfonylureas are NOT recommended due to prolonged hypoglycemia risk. 1, 3, 4

For patients on high-dose glucocorticoids (>40 mg prednisone equivalent):

• Increase the total insulin dose by 40-60% or more above baseline, with the additional insulin given as NPH or prandial rapid-acting insulin. 1, 2

• These patients often require "extraordinary amounts" of insulin to achieve glycemic control. 1, 3

For long-acting steroids (dexamethasone) or continuous/multi-dose regimens:

• Use long-acting basal insulin (glargine, detemir, or degludec) as the foundation, starting at 0.1-0.2 units/kg/day, as these steroids affect fasting glucose more significantly. 1, 2

• You may need to combine long-acting basal insulin with NPH to cover both fasting and daytime hyperglycemia. 3, 4

Monitoring Protocol

Check blood glucose 4 times daily: fasting and 2 hours after each meal, with target range 100-180 mg/dL (5.6-10.0 mmol/L). 1, 2, 3

• The most critical reading is 2 hours after lunch (around 2-3 PM), as this captures the peak steroid effect. 2, 3

• Do NOT rely on fasting glucose alone—this will miss the peak hyperglycemic effect and severely underestimate the severity of hyperglycemia. 2, 3, 5

Dose Titration Strategy

Increase NPH by 2 units every 3 days until target glucose is achieved. 2, 3

• If hypoglycemia occurs (particularly overnight), reduce NPH dose by 10-20%. 4

• Daily adjustments based on point-of-care glucose monitoring and anticipated changes in steroid dosing are critical to reducing rates of both hypoglycemia and hyperglycemia. 1, 3, 4

• As steroid doses are tapered or discontinued, insulin requirements decrease rapidly—adjust doses promptly to avoid dangerous hypoglycemia. 1, 3, 4

Special Population Considerations

For elderly patients or those with renal impairment:

• Start at the lower end of the dosing range: 0.2-0.3 units/kg/day. 2, 3, 4

For patients on enteral/parenteral nutrition:

• Give NPH every 8-12 hours to cover continuous feeds, calculating nutritional insulin as 1 unit per 10-15 grams of carbohydrate in the formula. 1, 2, 4

Critical Pitfalls to Avoid

Never use only sliding-scale correction insulin—this approach is associated with poor glycemic control and has been strongly discouraged in guidelines. 2, 3, 4

• Sliding-scale insulin is reactive rather than proactive and fails to prevent hyperglycemia. 2

Failing to anticipate the diurnal pattern leads to inadequate treatment:

• Monitoring only fasting glucose will miss the afternoon/evening peak and result in undertreatment. 2, 3

Not reducing insulin doses when steroids are tapered causes dangerous hypoglycemia:

• Insulin requirements can decline rapidly after steroid discontinuation. 1, 3, 4

Relying solely on oral antidiabetic agents for high-dose steroid therapy is inadequate:

• Oral agents alone cannot overcome the severe insulin resistance induced by high-dose glucocorticoids. 3

When to Escalate Care

Admit for continuous IV insulin infusion if:

• Glucose persistently >360 mg/dL (>20 mmol/L) or meter reads "HI", indicating risk of hyperosmolar hyperglycemic state. 2, 3

• Presence of ketones >2 mmol/L with glucose >270 mg/dL (>15 mmol/L), signaling high risk for diabetic ketoacidosis. 3

Request endocrinology consultation if:

• Persistent capillary glucose >270 mg/dL (>15 mmol/L) despite initial insulin adjustments. 3

• Patient requires very high steroid doses (>80 mg prednisone equivalent), as they may require "extraordinary amounts" of insulin. 3