Transitioning from IV to Subcutaneous Insulin in HHS
For a 70 kg insulin-naive male with T2DM transitioning from IV insulin after overnight HHS treatment, administer subcutaneous basal insulin at 50% of the total 24-hour IV insulin dose, given as a single evening dose of long-acting insulin (e.g., glargine), with the remaining 50% divided equally as rapid-acting insulin before each meal. 1
Calculating the Transition Dose
Step 1: Determine Total 24-Hour IV Insulin Requirement
- Calculate the total units of IV insulin infused over the previous 24 hours when glucose levels have been stable (ideally <180 mg/dL or 10 mmol/L) 1
- For example, if the patient received 2 units/hour × 24 hours = 48 units total
Step 2: Calculate Basal Insulin Dose
Give 50% of the 24-hour IV insulin total as once-daily long-acting (basal) insulin 1
- Using the example above: 48 units × 0.5 = 24 units of insulin glargine
- Administer this dose subcutaneously in the evening (ideally around 20:00 hours) 1
- Critical timing: Give the basal insulin immediately after stopping the IV infusion to prevent rebound hyperglycemia 1, 2
Step 3: Calculate Prandial (Mealtime) Insulin Doses
The remaining 50% of the 24-hour IV insulin total should be divided by 3 for rapid-acting insulin before each meal 1
- Using the example: 48 units × 0.5 = 24 units ÷ 3 = 8 units of rapid-acting insulin analog before each meal
- If the patient has insufficient oral intake, give only half of the calculated prandial dose 1
Practical Example for Your 70 kg Patient
If your patient received 2 units/hour IV insulin overnight (48 units total in 24 hours):
- Basal insulin (glargine): 24 units subcutaneously once in the evening
- Rapid-acting insulin (lispro/aspart/glulisine): 8 units before each meal (breakfast, lunch, dinner)
- Total daily dose: 48 units (24 basal + 24 prandial)
Critical Timing Considerations
The IV insulin infusion must overlap with subcutaneous insulin administration 1, 2:
- Administer basal insulin 2-4 hours before discontinuing IV insulin 1, 2
- Alternatively, continue IV insulin for 1-2 hours after giving subcutaneous insulin 2
- This overlap prevents rebound hyperglycemia and recurrence of hyperglycemic crisis 2, 3
Alternative Approach for Insulin-Naive Patients
If IV insulin was used for less than 24 hours or dosing is uncertain, start with weight-based dosing 1:
- Total daily dose: 0.5-1 unit/kg body weight
- For your 70 kg patient: 35-70 units total daily
- Divide as 50% basal (17.5-35 units glargine) and 50% prandial (split among 3 meals)
- Use the lower end (0.5 units/kg) for insulin-naive patients to minimize hypoglycemia risk 1, 4
Monitoring Requirements
Intensive glucose monitoring is mandatory during transition 1:
- Check capillary blood glucose every 2-4 hours initially 1, 5
- Monitor serum potassium closely as insulin drives potassium intracellularly 1, 5
- Ensure adequate renal function (urine output >0.5 mL/kg/h) before full insulin dosing 1
Common Pitfalls to Avoid
Do not abruptly stop IV insulin without overlapping subcutaneous coverage 2, 3:
- This is the most common error and leads to rebound hyperglycemia in >90% of patients 3
- One study showed that giving glargine 0.25 units/kg during IV insulin infusion reduced rebound hyperglycemia from 93.5% to 33.3% 3
Do not use sliding-scale insulin alone 4:
- Sliding-scale regular insulin as monotherapy is inferior to basal-bolus regimens 4
- Only 38% of patients achieve glucose <140 mg/dL with sliding scale versus 66% with basal-bolus 4
Adjust doses if hourly IV insulin rate was >5 units/hour 1:
- This indicates significant insulin resistance
- Consider leaving IV insulin in place and consulting endocrinology 1
Special Considerations for HHS
HHS resolution criteria must be met before transition 1:
- Calculated serum osmolality <315 mOsm/kg 1
- Patient alert and able to tolerate oral intake 1, 2
- Glucose target 200-250 mg/dL during HHS treatment (higher than DKA) 1
For insulin-naive T2DM patients, this basal-bolus regimen may be temporary 1: