Can oral prednisone (40–60 mg daily for 5–10 days) used for an acute asthma exacerbation cause morning hyperglycemia in a previously healthy adult?

Corticosteroids and Morning Hyperglycemia

Yes, oral prednisone 40–60 mg daily for acute asthma exacerbations commonly causes hyperglycemia, but the peak glucose elevation occurs in the afternoon (approximately 8 hours post-dose), not in the morning. When prednisone is taken as a single morning dose, glucose levels typically return to baseline by the following morning. 1, 2

Timing and Pattern of Steroid-Induced Hyperglycemia

Expected Glucose Pattern with Morning Prednisone

• Prednisone administered as a once-daily morning dose causes peak hyperglycemia approximately 8 hours after administration, corresponding to late morning and afternoon elevations rather than morning hyperglycemia. 1
• Glucose levels typically return to baseline by the next morning when prednisone is given as a single morning dose, meaning fasting morning glucose is often normal despite significant afternoon hyperglycemia. 2
• In a prospective hospital audit of patients on high-dose steroids (≥25 mg prednisone daily), hyperglycemia developed within 48 hours in 94% of patients, with 86% having at least one glucose ≥8 mmol/L (144 mg/dL) and 70% having at least one glucose ≥10 mmol/L (180 mg/dL). 2

Mechanism and Onset

• Corticosteroids cause hyperglycemia through multiple mechanisms: impaired beta-cell insulin secretion, increased total-body insulin resistance, and increased hepatic gluconeogenesis. 1
• The pharmacokinetic profile of prednisone leads to peak insulin resistance and hyperglycemia around 8 hours post-dose, which explains the afternoon pattern rather than morning elevation. 1

Clinical Implications for a 5–10 Day Prednisone Course

Incidence in Previously Healthy Adults

• Steroid-induced hyperglycemia is extremely common even in non-diabetic patients: in one study of hospitalized patients with asthma or COPD exacerbations receiving standard-dose corticosteroids, 82% developed hyperglycemia, and 79% of those without prior diabetes showed hyperglycemia. 3
• The degree of hyperglycemia correlates with the corticosteroid dose, and 40–60 mg prednisone daily falls within the range that commonly triggers hyperglycemia. 1

Monitoring Recommendations

• If monitoring is performed, check glucose in the afternoon (4–8 hours post-dose) rather than fasting morning glucose, as this captures the peak hyperglycemic effect of prednisone. 1, 2
• For short courses (5–10 days) in previously healthy adults without diabetes risk factors, routine glucose monitoring is not mandated by guidelines, but should be considered if the patient has metabolic risk factors (obesity, family history of diabetes, elevated baseline HbA1c). 1, 2

Treatment Considerations

• For short courses lasting 5–10 days, hyperglycemia typically resolves spontaneously after corticosteroid discontinuation and does not require treatment in most previously healthy adults unless glucose levels are severely elevated (>15–20 mmol/L or 270–360 mg/dL). 1, 4
• If treatment is needed, intermediate-acting insulin (isophane/NPH) given in the morning is more effective than long-acting basal insulin (glargine) for prednisone-induced hyperglycemia, because it better matches the afternoon peak glucose pattern. 4

Important Caveats

Beta-Agonist Contribution

• Salbutamol (albuterol) and other beta-agonists used concurrently for asthma exacerbations also cause acute hyperglycemia, which may be more pronounced than the corticosteroid effect in the first 24 hours of treatment. 5
• The combined effect of prednisone plus frequent albuterol use amplifies hyperglycemia risk, particularly in the afternoon and evening. 5, 3

Risk Factors for Severe Hyperglycemia

• High baseline HbA1c, elevated C-reactive protein, and current smoking are the strongest predictors of steroid-induced hyperglycemia in patients without known diabetes. 3
• Patients with these risk factors warrant closer glucose monitoring during the prednisone course. 3

Comparison to Other Corticosteroids

• Dexamethasone and methylprednisolone cause greater hyperglycemia than prednisone or hydrocortisone at equivalent anti-inflammatory doses, with dexamethasone producing peak glucose elevation 7–9 hours post-dose. 1, 6
• If hyperglycemia is a major concern, prednisone or prednisolone are preferred over dexamethasone or methylprednisolone for outpatient asthma management. 6