What is the effect of steroid treatment on blood sugar levels in a patient with diabetes?

Effect of Steroids on Blood Glucose in Patients with Diabetes

Steroids cause significant hyperglycemia in patients with diabetes through multiple mechanisms, with peak effects occurring 4-9 hours after administration, requiring aggressive insulin dose adjustments—often 40-60% increases in prandial insulin plus addition of NPH insulin at 0.3-0.5 units/kg/day given with morning steroid doses. 1

Mechanisms and Patterns of Steroid-Induced Hyperglycemia

Glucocorticoids induce hyperglycemia through three primary mechanisms: 1

• Impaired beta cell insulin secretion
• Increased insulin resistance in muscle, liver, and adipose tissue
• Enhanced hepatic gluconeogenesis

The hyperglycemic pattern is distinctly diurnal—blood glucose rises dramatically in the afternoon and evening (6-9 hours post-dose) but often normalizes overnight even without treatment. 1 This unique pattern is critical because relying solely on fasting glucose measurements will completely miss the peak hyperglycemic effect and lead to inadequate treatment. 1

The prevalence of steroid-induced hyperglycemia in hospitalized patients approaches 56-86%, affecting both those with and without pre-existing diabetes. 1

Monitoring Requirements

Monitor blood glucose four times daily: fasting and 2 hours after each meal, with particular attention to afternoon readings (2-3 PM) when steroid effects peak. 1

Target blood glucose range: 100-180 mg/dL (5.6-10.0 mmol/L) during steroid therapy. 1 The FDA label for prednisone confirms that corticosteroids increase blood glucose concentrations, requiring dosage adjustments of antidiabetic agents. 2

Treatment Algorithm for Patients with Pre-existing Diabetes

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

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

Increase prandial (mealtime) rapid-acting insulin by 40-60% or more above baseline doses. 1 For higher steroid doses (e.g., 80 mg prednisone), extraordinary amounts of prandial and correctional insulin are often needed in addition to basal insulin. 3, 1

For Long-Acting Steroids (Dexamethasone) or Multiple Daily Doses:

Long-acting basal insulin (glargine or detemir) is required to control fasting blood glucose, as the hyperglycemic effect persists throughout the 24-hour period. 3, 1

For Nighttime Steroid Dosing:

Switch from NPH to long-acting basal insulin (glargine or detemir) given at bedtime, as the hyperglycemic pattern shifts to overnight and the following day. 1

Dose Titration Protocol

• Monitor glucose every 2-4 hours initially 1
• If target not achieved, increase NPH by 2 units every 3 days 1
• Adjust prandial insulin based on carbohydrate intake and correction needs 1

As steroid doses are tapered, insulin doses must be proportionally decreased to prevent hypoglycemia—this is a critical pitfall that causes significant morbidity. 1

Special Populations

Type 1 Diabetes Patients:

Never stop basal insulin—this is non-negotiable and prevents diabetic ketoacidosis. 4 Continue baseline basal insulin and add NPH plus increase prandial insulin as described above. 4

Elderly or Renally Impaired Patients:

Start with lower insulin doses (0.2-0.3 units/kg/day) to reduce hypoglycemia risk. 1

Patients Receiving Enteral/Parenteral Nutrition:

Calculate nutritional insulin as 1 unit per 10-15 grams of carbohydrate in the formula, with NPH given every 8-12 hours to cover continuous feeds. 3, 4

Critical Pitfalls to Avoid

Failing to monitor afternoon/evening glucose levels and relying only on fasting values will result in missed hyperglycemia and inadequate treatment. 1 The Joint British Diabetes Societies guideline emphasizes that steroid-induced hyperglycemia is associated with harm and increased hospital lengths of stay. 5

Not reducing insulin doses when steroids are tapered leads to severe hypoglycemia. 1 Adjustments must be made frequently based on anticipated changes in glucocorticoid dosing. 3

Using only sliding-scale correction insulin without scheduled insulin is associated with poor glycemic control and has been discouraged in guidelines. 1

Waiting for fasting hyperglycemia before treating leads to delayed intervention, as fasting glucose may remain normal while postprandial values are dangerously elevated. 1

Intra-articular and Topical Steroid Considerations

Even intra-articular steroid injections cause hyperglycemia in diabetic patients, with peak values reaching as high as 500 mg/dL, typically occurring 24-72 hours post-injection. 6 Patients should monitor blood glucose for up to one week after injection. 6

For potent topical steroids applied over large surface areas, monitor glucose 2-4 hours after application when systemic absorption and hyperglycemic effects are maximal. 7 Consider temporary insulin therapy with NPH 0.1-0.2 units/kg/day if significant hyperglycemia develops. 7

Life-Threatening Complications

Monitor for hyperosmolar hyperglycemic state, a life-threatening complication of severe steroid-induced hyperglycemia requiring immediate intervention. 1 The FDA label warns that corticosteroids suppress the immune system and increase infection risk, which combined with hyperglycemia significantly increases morbidity. 2