Should I round down 22.5 units of insulin to the nearest whole number the night before a procedure?

Insulin Dosing: Rounding 22.5 Units

You should round 22.5 units of insulin to either 22 or 23 units rather than administering a fractional dose, with the specific direction depending on your recent glucose patterns and hypoglycemia risk.

Practical Approach to Rounding Insulin Doses

Standard Rounding Guidelines

• Most standard insulin pens and syringes deliver only whole-unit doses, making fractional dosing impractical with conventional delivery devices 1
• Round down to 22 units if you have experienced any recent hypoglycemia or if your glucose levels have been running lower than target 2
• Round up to 23 units if your glucose levels have been consistently elevated and you have had no hypoglycemia 2

When Precise Half-Unit Dosing Matters

• Half-unit insulin pens are specifically designed for insulin-sensitive patients who require greater dosing precision, particularly younger children, geriatric patients, and those prone to hypoglycemia 1
• If you are using a half-unit pen, you can administer 22.5 units precisely - these devices have demonstrated accurate delivery of half-unit doses 1
• Half-unit pens are ideal for patients requiring flexible dosing adjustments in small increments to achieve stringent glycemic control 1

Perioperative Context (Night Before Procedure)

Specific Preoperative Insulin Adjustment

• The American Diabetes Association recommends reducing your usual insulin dose by approximately 25% the evening before surgery to decrease hypoglycemia risk while maintaining reasonable glucose control 2
• If 22.5 units represents your reduced dose (75% of your usual 30 units), round to 22 units to err on the side of caution given NPO status and procedure-related stress 2
• Monitor blood glucose every 4-6 hours while NPO and use short-acting insulin for correction as needed rather than increasing basal insulin 2

Key Safety Considerations

• Rounding down is generally safer in the perioperative setting due to increased hypoglycemia risk when patients are NPO 2
• A 1-unit difference (22 vs 23 units) represents only a 4.5% variation in dose, which is clinically insignificant for most patients 3
• Frequent glucose monitoring (every 4-6 hours) is more important than precise dosing when making adjustments around procedures 2

Common Pitfalls to Avoid

• Do not skip your basal insulin entirely the night before a procedure - this can lead to dangerous hyperglycemia and ketosis, particularly in type 1 diabetes 2
• Do not round up if you have any concerns about hypoglycemia risk - the consequences of severe hypoglycemia while NPO are more dangerous than transient mild hyperglycemia 2
• Ensure you have a plan for correction insulin available if glucose rises above 180 mg/dL while NPO 2