What should the Lantus (insulin glargine) dose and carbohydrate ratio be for a patient who received dexamethasone 6 mg 24 hours ago and was previously taking Lantus 24 units with a 1:8 carb ratio?

Lantus Dose and Carbohydrate Ratio Adjustment After Dexamethasone

Increase the Lantus dose to 36 units (150% of the baseline 24 units) for tonight's administration and maintain this for at least 24 hours, while adjusting the carbohydrate ratio from 1:8 to approximately 1:5.5 (about 30% more insulin per carb) for the next 24-48 hours. 1, 2

Rationale for Dose Adjustment

Dexamethasone causes significant hyperglycemia through multiple mechanisms including impaired beta-cell insulin secretion, increased insulin resistance, and enhanced hepatic gluconeogenesis. 1 The hyperglycemic effects typically peak 7-9 hours after administration and persist for at least 24 hours, with characteristic afternoon and evening hyperglycemia that can continue into the next day. 1, 2

Research confirms that 6 mg dexamethasone significantly impairs glucose tolerance by inducing compensatory failure of pancreatic beta-cells and reducing insulin sensitivity by approximately 69%. 3

Specific Lantus Dosing Protocol

Day 1 (Tonight - 24 hours post-dexamethasone):

• Administer 36 units of Lantus (150% of baseline 24 units) 1, 2, 4

Day 2 (48 hours post-dexamethasone):

• Maintain 36 units of Lantus 1, 2, 4

Day 3 and beyond:

• Gradually taper back to baseline 24 units while monitoring blood glucose levels 1, 2, 4
• The taper should be guided by blood glucose readings, reducing by 2-4 units per day as glucose levels normalize 1

Carbohydrate Ratio Adjustment

Current ratio: 1:8 (1 unit per 8 grams of carbohydrate)

Adjusted ratio: 1:5.5 (approximately 30% increase in insulin) 2

• This means giving 1 unit of rapid-acting insulin for every 5.5 grams of carbohydrate instead of every 8 grams 2
• Maintain this adjusted ratio for 24-48 hours after dexamethasone administration 2
• Gradually return to baseline 1:8 ratio as steroid effects diminish 2

Monitoring Requirements

Frequency:

• Check blood glucose every 4-6 hours while affected by dexamethasone 1, 2, 4

Critical timepoints:

• Pay particular attention to afternoon and evening glucose levels, as steroid-induced hyperglycemia is most pronounced during these times 1, 2, 4

Correction doses:

• If blood glucose exceeds target levels despite increased basal insulin, add correction doses of rapid-acting insulin 1, 2, 4

Important Clinical Considerations

Early intervention is essential:

• Aggressive adjustment of insulin dosing is critical to prevent significant hyperglycemia and potential complications 1, 2

Hypoglycemia risk:

• Once steroid effects wear off (typically after 48 hours), the patient is at risk for hypoglycemia if the increased insulin doses are not tapered appropriately 1
• Patients should carry at least 15 grams of carbohydrate for hypoglycemic episodes 5

Injection site:

• The abdomen has the fastest rate of absorption for insulin, which may be preferable during periods of steroid-induced hyperglycemia 5

Individual variability:

• Some patients may require more or less aggressive adjustments based on their glucose response 1
• Clinical studies show that dexamethasone-induced hyperglycemia is often poorly controlled even with insulin adjustments, so close monitoring is essential 6