Steroid-Induced Diabetes (Glucocorticoid-Induced Diabetes Mellitus)

Definition

Epidemiology

• Among patients with no prior diabetes prescribed steroids for ≥1 month, the incidence of steroid-induced hyperglycemia is approximately 32% (meta-analysis, Nature Reviews Endocrinology)
• Incidence rises significantly with dose, duration, and pre-existing metabolic risk factors

Pathophysiology

• Dose-dependent (higher dose → worse hyperglycemia)
• Timing-dependent — most pronounced postprandially, especially with once-daily morning steroids causing a peak glucose rise in the afternoon/evening
• Type-dependent — dexamethasone causes more sustained hyperglycemia; intermediate-acting (e.g., methylprednisolone) causes predominantly daytime rises
• Usually reversible upon steroid discontinuation

Risk Factors

• Pre-existing impaired glucose tolerance or prediabetes
• Obesity / metabolic syndrome
• Family history of type 2 diabetes
• Older age
• Higher cumulative steroid dose
• Type 2 diabetes polygenic risk score (recent genetic evidence: PMID 37353344)

Clinical Pattern

• Fasting glucose often normal or near-normal early on
• Postprandial hyperglycemia predominates, especially mid-afternoon to evening with morning steroid dosing
• This means A1c and fasting glucose alone can miss early SID — 2-hour post-lunch glucose monitoring is preferred for screening

Diagnosis

• Screening: Check random blood glucose, A1c, and eGFR before initiating steroids (especially in at-risk patients)
• Monitor: 2-hour post-prandial glucose 2x/week during therapy (ideally after the largest meal of the day)
• Diagnostic threshold: Consistent blood glucose ≥11.1 mmol/L (200 mg/dL) post-prandially, or fasting ≥7.0 mmol/L (126 mg/dL)

Management

Glucose Targets

• Generally 6–10 mmol/L (108–180 mg/dL) during treatment
• Avoid hypoglycemia (particularly nocturnal/early morning, as glucose drops when steroids wear off)

Treatment Selection — Based on FPG Level

• Oral agents may be sufficient: sulfonylureas, metformin, DPP-4 inhibitors, pioglitazone
• Sulfonylureas/meglitinides are particularly useful for postprandial hyperglycemia
• SGLT-2 inhibitors: use with caution (risk of euglycemic DKA, especially if fasting or unwell)

• Oral agents usually insufficient → insulin therapy required

Insulin Strategy

• "Sliding scale" alone is inadequate — basal or scheduled insulin is essential
• Hypoglycemia risk is real overnight/early morning as steroid effect wanes — reduce insulin doses accordingly
• Oral agents (especially sulfonylureas, SGLT-2 inhibitors, metformin) should generally be stopped on hospital admission given risks (hypoglycemia, euglycemic DKA, lactic acidosis)

Steroid Tapering

• Reduce insulin by ~50% of the proportional GC reduction (e.g., if steroid reduced by 50%, reduce added insulin by 25%)
• Continue monitoring glucose ≥3 days after stopping steroids — if persistent hyperglycemia, re-evaluate for underlying diabetes

Complications & Special Situations

• Transplant recipients: Particularly high risk; glucocorticoid-induced diabetes frequently co-occurs with tacrolimus-induced beta-cell toxicity
• Cancer patients on dexamethasone: Dexamethasone has prolonged activity; careful NPH or long-acting insulin dosing is needed
• COVID-19: Dexamethasone (RECOVERY trial dose) causes significant hyperglycemia; dedicated management algorithms exist
• Mucormycosis risk: SID (especially unrecognized) dramatically increases risk of invasive fungal infections — Harrison's notes mucormycosis cases presenting simultaneously with first recognition of glucocorticoid-induced hyperglycemia

Reversibility

1. Screened for pre-existing underlying T2DM (especially if hyperglycemia persists post-taper)
2. Counseled about increased long-term diabetes risk
3. Followed up with fasting glucose / A1c 6–12 weeks post-steroid cessation

Key References

• Harrison's Principles of Internal Medicine 22E (2025), Chapter on Diabetes (Glucocorticoids section)
• JBDS Guidelines: Management of Hyperglycaemia and Steroid Therapy (2023)
• Cho JH & Suh S: Glucocorticoid-Induced Hyperglycemia: A Neglected Problem (Endocrinol Metab, 2024) [PMID 38532282]
• Deutsch AJ et al.: Type 2 Diabetes Polygenic Score Predicts Glucocorticoid-Induced Hyperglycemia (Diabetes Care, 2023) [PMID 37353344]