In a lymphoma patient on metformin 500 mg twice daily and dexamethasone 4 mg twice daily, with a post‑breakfast glucose of 300 mg/dL before starting R‑CHOP chemotherapy in two days, should a correction dose of regular insulin (Actrapid) be administered now?

Immediate Insulin Administration for Steroid-Induced Hyperglycemia

Yes, administer correction insulin (Actrapid/regular insulin) immediately for a post-breakfast glucose of 300 mg/dL in this dexamethasone-treated lymphoma patient, using 4 units of regular insulin subcutaneously, while simultaneously increasing the basal metformin dose and planning for more aggressive scheduled insulin therapy before R-CHOP begins.

Immediate Correction Dose

• For hospitalized patients with blood glucose >250 mg/dL, administer 4 units of rapid-acting or regular insulin immediately as a correction dose 1.
• At 300 mg/dL (16.7 mmol/L), this patient requires urgent correction to prevent further metabolic decompensation and osmotic diuresis 2.
• Regular insulin (Actrapid) given subcutaneously will begin acting within 15-60 minutes, peak at 3-4 hours, and last 6-8 hours 2.

Understanding Dexamethasone-Induced Hyperglycemia

• Dexamethasone causes disproportionate daytime hyperglycemia with peak effects 6-12 hours post-dose, explaining why this patient's post-breakfast glucose is 300 mg/dL 3, 4.
• Glucocorticoid-induced hyperglycemia affects 56-86% of patients and increases mortality, infection risk, and cardiovascular events if untreated 3.
• For patients on high-dose dexamethasone (4 mg twice daily = 8 mg/day total), insulin requirements typically increase by 0.3-0.4 units/kg/day 4.

Immediate Medication Adjustments Required

Optimize Metformin Foundation

• Increase metformin to at least 1000 mg twice daily (2000 mg total) immediately, as the current 500 mg twice daily is subtherapeutic 1.
• Metformin should be continued and maximized (up to 2000-2550 mg/day) when adding insulin, as this combination reduces total insulin requirements and provides superior glycemic control 1.
• Metformin is safe and effective for therapy-induced hyperglycemia in lymphoma patients receiving corticosteroids and chemotherapy 5, 6.

Initiate Scheduled Insulin Therapy

• Do not rely on correction doses alone—sliding-scale insulin as monotherapy is condemned by all major diabetes guidelines and leads to dangerous glucose fluctuations 1.
• For a patient on high-dose dexamethasone with glucose of 300 mg/dL, initiate basal insulin at 0.3-0.4 units/kg/day (approximately 20-26 units for a 65 kg patient) 4.
• Given dexamethasone's daytime hyperglycemic pattern, use NPH insulin in the morning concomitantly with dexamethasone, as NPH peaks at 4-6 hours and matches the steroid's glucose-raising effect 3.
• Alternatively, add 0.1-0.3 units/kg/day of long-acting insulin (glargine) to the usual regimen, with doses determined by steroid dose and oral intake 1.

Specific Insulin Regimen for Dexamethasone

• For patients on steroids requiring higher insulin doses, increase prandial and correction insulin by 40-60% or more in addition to basal insulin 3, 1.
• The recommended distribution for glucocorticoid-induced hyperglycemia is 25% basal and 75% prandial insulin when total daily dose reaches 1.0-1.2 units/kg/day 4.
• Start with basal insulin 10-15 units once daily plus correction doses before meals using the following scale 4:
  • Glucose 180-220 mg/dL: 2 units regular insulin
  • Glucose 221-260 mg/dL: 4 units regular insulin
  • Glucose 261-300 mg/dL: 6 units regular insulin
  • Glucose >300 mg/dL: 8 units regular insulin and notify physician

Monitoring and Titration

• Check blood glucose every 6 hours minimum, or before meals if eating regularly 4.
• Reassess insulin doses daily while on dexamethasone, as requirements can change rapidly 4.
• Target blood glucose 140-180 mg/dL in hospitalized patients 4, 2.
• When dexamethasone is discontinued, reduce insulin doses by 20-30% immediately as requirements decline rapidly 4.

Critical Pitfalls to Avoid

• Never delay insulin initiation when glucose is persistently >250 mg/dL—this prolongs hyperglycemia exposure and increases infection risk, particularly dangerous before chemotherapy 1.
• Never use sliding-scale insulin alone—only 38% of patients achieve adequate control versus 68% with scheduled basal-bolus therapy 1.
• Never discontinue metformin when starting insulin unless contraindicated—this leads to higher insulin requirements and worse outcomes 1.
• Do not give rapid-acting insulin at bedtime as a sole correction dose, as this markedly raises nocturnal hypoglycemia risk 1, 2.

Pre-Chemotherapy Optimization

• With R-CHOP starting in 2 days, achieving glucose control now is critical, as hyperglycemia during chemotherapy is associated with poor outcomes in lymphoma patients 7.
• The combination of metformin plus standard chemotherapy in lymphoma patients has shown improved complete remission rates (92% vs 74%), lower relapse rates (10% vs 36%), and improved overall survival 6.
• Exogenous insulin may be associated with poorer outcomes in lymphoma patients, whereas metformin may be associated with improved outcomes, making metformin optimization particularly important 7.

Practical Implementation

1. Right now: Give 4 units regular insulin (Actrapid) subcutaneously
2. Today: Increase metformin to 1000 mg twice daily
3. Today: Start NPH insulin 15 units in the morning with dexamethasone OR glargine 15 units at bedtime
4. Before each meal: Check glucose and give correction doses per scale above
5. Daily: Titrate insulin doses based on glucose patterns
6. When steroids stop: Reduce insulin by 20-30% immediately

Expected Outcomes

• With appropriate basal-bolus therapy plus metformin, expect glucose to reach target range (140-180 mg/dL) within 24-48 hours 1.
• The combination approach provides superior control compared to insulin alone, with reduced hypoglycemia risk 1.
• Proper glycemic control before chemotherapy reduces infection risk and may improve lymphoma treatment outcomes 6, 7.