How to initiate insulin therapy in patients with diabetes (Diabetes Mellitus) who are currently on steroid treatment?

How to Initiate Insulin in Patients on Steroids

For patients on glucocorticoids, start NPH insulin at 0.3-0.5 units/kg/day given in the morning simultaneously with intermediate-acting steroids (prednisone, methylprednisolone), as NPH peaks 4-6 hours after administration, matching the steroid's peak hyperglycemic effect. 1, 2

Understanding the Glycemic Pattern

The timing and type of steroid dictates your insulin strategy:

• Intermediate-acting steroids (prednisone, methylprednisolone) taken in the morning cause disproportionate hyperglycemia during the afternoon and evening, with glucose often normalizing overnight even without treatment 1, 2
• Peak hyperglycemia occurs 6-9 hours after steroid administration, making afternoon glucose monitoring critical 2
• Long-acting steroids (dexamethasone) or continuous/multi-dose regimens cause sustained hyperglycemia throughout 24 hours, requiring a different approach 1, 3

Insulin Selection Algorithm

For Once-Daily Morning Intermediate-Acting Steroids (Prednisone, Methylprednisolone):

Use NPH insulin as the primary agent 1, 2:

• Start at 0.3-0.5 units/kg/day given in the morning with the steroid dose 2, 4
• NPH is administered in addition to existing basal-bolus insulin or oral agents (do not stop baseline therapy abruptly) 1
• For insulin-naive patients with pre-existing diabetes on oral agents, add NPH at 0.1-0.2 units/kg/day 4

For Long-Acting Steroids (Dexamethasone) or Continuous Use:

Use long-acting basal insulin (glargine, detemir) as the foundation 1, 3:

• Start basal insulin at 0.1-0.2 units/kg/day 1, 5
• Often requires both long-acting basal insulin AND NPH to cover fasting and daytime hyperglycemia 2, 3
• For dexamethasone specifically, consider combination therapy from the start 3

For Nighttime Steroid Dosing:

Switch to long-acting basal insulin given at bedtime 2:

• The hyperglycemic pattern shifts to overnight and following day
• NPH is inappropriate here as it would peak during sleep
• Use glargine or detemir at 0.3-0.5 units/kg/day with the nighttime steroid dose 2

Dose Escalation for High-Dose Steroids

For patients on high-dose glucocorticoids (>40 mg prednisone equivalent or 80 mg total), increase prandial and correctional insulin by 40-60% or more above baseline 1, 2, 4:

• These patients often require "extraordinary amounts" of insulin 1
• Total daily insulin requirements may reach 0.5 units/kg/day or higher 1
• Consider early endocrinology consultation for very high doses 2

Monitoring Protocol

Check blood glucose 4 times daily: fasting and 2 hours after each meal 2:

• The most important reading is 2 hours after lunch to capture peak steroid effect 2
• Target range: 100-180 mg/dL (5.6-10.0 mmol/L) 1, 2, 3
• Do NOT rely on fasting glucose alone—this misses the peak hyperglycemic effect and leads to undertreatment 2

Titration Strategy

Increase NPH by 2 units every 3 days until target glucose achieved 1, 3, 4:

• For persistent hyperglycemia despite NPH, add or increase prandial rapid-acting insulin before meals 1
• If hypoglycemia occurs, reduce insulin dose by 10-20% 1, 4
• Adjust insulin doses daily based on glucose patterns and anticipated steroid dose changes 1

Critical Pitfalls to Avoid

1. Relying on Sliding Scale Insulin Alone

Using only correctional insulin without scheduled basal or NPH coverage is associated with poor glycemic control and is strongly discouraged 2, 3

2. Monitoring Only Fasting Glucose

This completely misses the peak hyperglycemic effect of steroids and leads to delayed intervention 2

3. Failing to Reduce Insulin When Steroids are Tapered

Insulin requirements decrease rapidly after steroid discontinuation—failure to adjust causes severe hypoglycemia 2, 4

4. Stopping Baseline Diabetes Medications Abruptly

Continue metformin and other oral agents unless contraindicated; stopping causes rebound hyperglycemia 6

5. Using Sulfonylureas for Steroid-Induced Hyperglycemia

These agents carry excessive hypoglycemia risk and are not recommended 4

Special Populations

Patients on Enteral/Parenteral Nutrition:

Give NPH every 8-12 hours to cover continuous feeds 1, 3, 4:

• Calculate nutritional insulin as 1 unit per 10-15 grams of carbohydrate in the formula 1
• Add correctional insulin subcutaneously every 6 hours with regular human insulin 1
• If enteral nutrition is interrupted, start dextrose infusion immediately to prevent hypoglycemia 1

Elderly or Renally Impaired Patients:

Start at the lower end of dosing range: 0.2-0.3 units/kg/day 2

Perioperative Patients on Steroids:

Give 50% of NPH dose or 75-80% of long-acting insulin dose on day of surgery 1:

• Hold oral glucose-lowering agents the morning of surgery 1
• Monitor glucose every 2-4 hours while NPO 1
• Target 100-180 mg/dL perioperatively 1

When to Escalate Care

Admit for continuous IV insulin if glucose persistently >360 mg/dL (>20 mmol/L) or meter reads "HI" 2:

• This indicates risk of hyperosmolar hyperglycemic state, which increases mortality 1, 2
• Steroid-induced hyperglycemia increases infection risk and cardiovascular events if untreated 1

Patient Education Points

• Warn that glucose levels will be highest in the afternoon/evening with morning steroids 2
• Emphasize that insulin doses will need frequent adjustment as steroid doses change 1, 2
• Instruct to seek immediate care if glucose >360 mg/dL or meter shows "HI" 2
• Explain that overnight hypoglycemia is possible even with daytime hyperglycemia 2