What is the lower blood glucose threshold for giving a correction (additional) insulin dose in an adult?

Lower Blood Glucose Threshold for Correction Insulin Dosing in Adults

For hospitalized adults, correction (supplemental) insulin should generally be administered when blood glucose exceeds 150 mg/dL (8.3 mmol/L), with specific thresholds varying by clinical context and patient risk factors. 1, 2

Non-Critically Ill Hospitalized Patients

Standard correction insulin threshold:

• Administer correction insulin for blood glucose >150 mg/dL (8.3 mmol/L) in most hospitalized adults on scheduled insulin regimens 2
• The American Diabetes Association recommends supplemental subcutaneous regular insulin in 5-unit increments for every 50 mg/dL increase above 150 mg/dL, up to 20 units for glucose of 300 mg/dL 2
• For patients eating regular meals, check glucose before meals and administer correction doses as needed to maintain target range of 100-180 mg/dL 2

Higher thresholds for high-risk patients:

• For older adults (>65 years), those with renal failure, or poor oral intake, use more conservative correction thresholds of 250 mg/dL (13.9 mmol/L) before administering supplemental insulin 1, 2
• The simplified algorithm for older adults recommends giving 2 units of rapid-acting insulin only when premeal glucose exceeds 250 mg/dL, and 4 units when glucose exceeds 350 mg/dL (19.4 mmol/L) 1
• These higher thresholds reduce hypoglycemia risk in vulnerable populations while still preventing severe hyperglycemia 1

Critically Ill ICU Patients

Do not use correction-only insulin in ICU settings:

• Critically ill patients requiring insulin should be managed with continuous IV insulin infusion targeting 140-180 mg/dL, not intermittent correction doses 3, 2
• Sliding-scale insulin alone is strongly discouraged in ICU patients as it results in poor glycemic control and increased complications 3, 2
• Initiate IV insulin infusion when blood glucose reaches ≥180 mg/dL on two consecutive measurements 3

Critical Context: Correction vs. Scheduled Insulin

Correction insulin assumes a basal-bolus regimen is already in place:

• The guidelines for correction dosing at 150 mg/dL threshold assume patients are on scheduled basal and/or prandial insulin, not correction insulin alone 2
• Sliding-scale insulin as the sole regimen is strongly discouraged and associated with poor outcomes in all hospitalized patients 3, 2
• For insulin-naive patients with glucose >300 mg/dL, initiate a basal-plus regimen (0.3-0.5 units/kg total daily dose) rather than relying on correction doses 2

Timing Considerations Based on Insulin Type

When using intermediate-acting insulin (NPH):

• Do not administer rapid-acting correction insulin during NPH's peak effect (4-6 hours post-dose), as this creates dangerous "insulin stacking" and significantly increases hypoglycemia risk 2
• If glucose remains >250 mg/dL at 4-6 hours after NPH administration, correction insulin may be considered, but reassess the basal insulin dose rather than repeatedly correcting 2

For patients on basal-bolus regimens:

• Correction insulin can be safely added to scheduled prandial doses when premeal glucose exceeds 150 mg/dL 2
• Use the same insulin type as the prandial insulin (rapid-acting analogs every 4 hours or regular insulin every 6 hours) 2

Common Pitfalls to Avoid

Never use correction insulin as monotherapy:

• Correction doses without scheduled basal insulin lead to unacceptable glycemic variability and poor outcomes 3, 2
• Transition patients to appropriate basal-bolus or basal-plus regimens rather than continuing sliding-scale approaches 2

Avoid overly aggressive correction in high-risk patients:

• Patients with hypoglycemia risk factors (age >65, renal dysfunction, erratic oral intake) should have maximum correction doses reduced and higher glucose thresholds (>250 mg/dL) before dosing 1, 2
• Severe hypoglycemia (<40 mg/dL) dramatically increases mortality risk, especially with repeated episodes 3

Account for insulin duration and overlap:

• Regular insulin has a 6-8 hour duration of action; avoid repeat correction doses within this window to prevent insulin stacking 2
• Rapid-acting analogs have a 4-hour duration; correction doses can be given more frequently but still require caution 2

Immediate correction for severe hyperglycemia:

• Administer correction insulin immediately (without waiting for scheduled dosing times) if glucose exceeds 300-350 mg/dL with symptoms of hyperglycemia or catabolic features 2
• Consider whether diabetic ketoacidosis is present, which requires continuous IV insulin rather than subcutaneous correction doses 2, 4