In an adult with insulin glargine‑induced hypoglycemia, what should I expect after giving a 50 mL D‑40 (dextrose 40%) IV bolus?

Expected Response After 50 mL D40 (20g Dextrose) IV Bolus in Insulin Glargine-Induced Hypoglycemia

You should expect rapid correction of hypoglycemia within 5-15 minutes, with blood glucose rising by approximately 60-80 mg/dL, but you must recheck glucose at 15 minutes and be prepared for recurrent hypoglycemia requiring additional dextrose or continuous infusion. 1

Immediate Expected Effects (0-15 Minutes)

Blood glucose will typically rise from the hypoglycemic range to 100-170 mg/dL within 5-15 minutes after the 20g dextrose bolus. 1 The pharmacokinetic data shows that IV dextrose produces variable blood glucose increases, with peak levels occurring at 5-15 minutes post-injection, then returning toward baseline by 30 minutes. 1

• The 20g dose (50 mL of D40) is appropriate for moderate to severe hypoglycemia, as guidelines recommend 10-20g of hypertonic dextrose titrated based on initial hypoglycemic severity. 1, 2
• Symptoms of hypoglycemia (altered mental status, diaphoresis, confusion) should resolve as glucose normalizes. 1

Critical 15-Minute Recheck

You MUST recheck blood glucose at 15 minutes post-administration—this is not optional. 1 This timing is critical because:

• Dextrose effect peaks early but can wane rapidly, especially with ongoing insulin activity. 1
• If glucose remains <70 mg/dL (or <100 mg/dL in neurologic injury patients), repeat dextrose administration is required. 1
• Failure to recheck at 15 minutes risks missing recurrent hypoglycemia. 1

Special Considerations for Insulin Glargine

Unlike short-acting insulins, insulin glargine can cause PROLONGED hypoglycemia lasting 24-96+ hours after subcutaneous overdose, requiring extended monitoring and often continuous dextrose infusion. 3, 4

Key Differences Based on Route:

• Subcutaneous glargine overdose: Creates a depot effect with prolonged insulin release, causing recurrent hypoglycemia for days. 3, 4
• Intravenous glargine (if accidentally given IV): Paradoxically causes shorter-duration hypoglycemia (resolving within 3-6 hours) without the depot effect. 5

Since your patient has glargine-induced hypoglycemia, you should anticipate:

• High likelihood of recurrent hypoglycemia after the initial D40 bolus wears off. 3
• Need for continuous dextrose infusion (D10 at 50-100 mL/hour) to prevent repeated hypoglycemic episodes. 3, 4
• Prolonged monitoring for 24-96 hours, preferably in an ICU setting with glucose checks every 1-2 hours. 3, 1

Subsequent Management Algorithm

If glucose >70 mg/dL at 15 minutes:

• Continue monitoring every 1-2 hours. 1
• Start continuous D10 infusion at 50 mL/hour (5g/hour) to prevent recurrent hypoglycemia, especially critical given glargine's long duration. 6, 3
• Do NOT stop basal insulin coverage entirely if this is a type 1 diabetic—they require continuous glucose provision. 6

If glucose remains <70 mg/dL at 15 minutes:

• Administer additional 10-20g dextrose bolus. 1
• Recheck again at 15 minutes. 1
• Strongly consider starting continuous D10 infusion immediately rather than repeated boluses. 3, 4

Common Pitfalls to Avoid

Do not give only a single bolus and assume the problem is solved—glargine's prolonged action means hypoglycemia will likely recur. 3, 4 One case report documented persistent hypoglycemia requiring continuous dextrose for >100 hours after glargine overdose. 4

Avoid overcorrection with repeated large boluses—rapid or repeated D50 boluses have been associated with cardiac arrest, hyperkalemia, and rebound hyperglycemia averaging 169 mg/dL. 1 The 20g dose you gave is appropriate, but resist giving multiple full doses without reassessment.

Do not discharge the patient after a single normal glucose reading—glargine overdoses require admission for 24-96 hours with frequent monitoring, preferably in ICU. 3, 4

Ensure IV patency before and during administration—D40 is hyperosmolar and extravasation can cause severe tissue injury, limb loss, or death. 7 Administer slowly through a large-bore IV in a large vein. 1

Monitoring Requirements

• Blood glucose every 1-2 hours for at least 24 hours, extending to 96 hours if hypoglycemia recurs. 1, 3
• Additional checks at 15 and 60 minutes after each dextrose bolus. 1
• Serum electrolytes (particularly potassium) every 2-4 hours, as dextrose administration can shift potassium intracellularly. 8
• Consider ICU admission for any glargine overdose or persistent hypoglycemia. 3, 4