How do I diagnose steroid‑induced diabetes in a patient receiving systemic glucocorticoids (e.g., prednisone, prednisolone, methylprednisolone, dexamethasone) at a dose of ≥10 mg prednisolone‑equivalent per day, especially if they have risk factors such as obesity, family history of diabetes, prior impaired glucose tolerance, or metabolic syndrome?

Diagnosis of Steroid-Induced Diabetes

Steroid-induced diabetes is diagnosed when a patient on corticosteroids has either two separate random glucose readings ≥11.1 mmol/L (≥200 mg/dL) or a new HbA1c ≥6.5% without prior diabetes history; persistent hyperglycemia coinciding with glucocorticoid use is considered diagnostic. 1

Key Diagnostic Principles

Timing of Glucose Monitoring is Critical

• Monitor glucose 2 hours after lunch (approximately 2-3 PM), not just fasting glucose, as this captures the peak steroid effect occurring 6-9 hours after morning administration. 1, 2
• Fasting glucose measurements will systematically miss the peak hyperglycemic effect and severely underestimate the severity of steroid-induced hyperglycemia. 1, 3
• All 13 patients identified with steroid-induced diabetes in one study had glucose ≥200 mg/dL specifically at the 2-hour post-lunch measurement, while fasting values may have been normal. 2

Recommended Monitoring Schedule

• Perform capillary glucose checks four times daily: fasting and 2 hours after each meal, with the post-lunch reading being the most diagnostically important. 1
• For patients at moderate risk (newly starting corticosteroids), check serum glucose 2 hours postprandial or 8 hours after prednisone dosing at clinic visits. 3
• For high-risk patients with pre-existing diabetes, provide a glucometer for daily self-monitoring. 3

Diagnostic Criteria

Formal Diagnosis

• Two abnormal glucose measurements (random glucose ≥11.1 mmol/L [≥200 mg/dL] on separate occasions) OR
• A new HbA1c ≥6.5% in the setting of corticosteroid therapy 1

The diagnosis does not differ from generally accepted diabetes criteria, but the temporal relationship with glucocorticoid use is key. 4

Understanding the Hyperglycemic Pattern

Pharmacokinetic Considerations

• Morning-administered prednisone produces peak hyperglycemia approximately 8 hours after dosing, causing the greatest glucose elevations in late morning and afternoon. 1, 3
• Glucose levels often normalize overnight even without treatment, creating a characteristic diurnal pattern. 1, 5
• The magnitude of hyperglycemia rises proportionally with steroid dose—higher prednisone doses generate more pronounced glucose elevations. 1, 3

Incidence and Risk Factors

• Steroid-induced hyperglycemia occurs in 56-86% of hospitalized patients with and without pre-existing diabetes. 1
• Advanced age and elevated cholesterol after prednisolone treatment are significantly associated with steroid-induced diabetes development. 2
• The majority of hyperglycemia cases (68-76%) in patients on steroids are directly attributable to corticosteroid administration. 6

Common Diagnostic Pitfalls to Avoid

Critical Errors in Detection

• Relying solely on fasting glucose is the most common diagnostic error—this approach misses the afternoon/evening peak and leads to systematic underdiagnosis. 1, 3
• Failure to monitor within the first 48 hours of high-dose glucocorticoid therapy, when the majority of hyperglycemia cases occur. 4
• Not recognizing that patients may have completely normal fasting glucose yet experience significant afternoon/evening hyperglycemia requiring treatment. 1

Monitoring Frequency Adjustments

• For low-dose steroids (e.g., 5 mg prednisone daily), monitor postprandial glucose (2 hours after lunch) rather than fasting glucose to capture the true hyperglycemic effect. 3
• Close monitoring of glucose profile should be performed within the first 48 hours after starting glucocorticoid therapy, as this is when most cases manifest. 4

Risk Stratification for Screening Intensity

Low Risk (Newly Commencing Steroids)

• Serum glucose (fasting preferred) with treatment cycles and 3-monthly HbA1c. 6

Moderate Risk (Commencing Corticosteroids)

• Serum glucose 2 hours postprandial or 8 hours after steroid dosing at clinic visits. 3

High Risk (Pre-existing Diabetes)

• Daily self-monitoring with glucometer, four times daily (fasting and 2 hours after each meal). 1, 3

When to Escalate Care

• Persistent capillary glucose >15 mmol/L (≈270 mg/dL) warrants referral to an endocrinology specialist. 1
• Continuous glucose >20 mmol/L or a meter "HI" reading mandates immediate hospital presentation to evaluate for hyperosmolar hyperglycemic state. 1, 5
• Presence of ketones >2 mmol/L together with glucose >15 mmol/L signals high risk for diabetic ketoacidosis and requires urgent hospital assessment. 1