Diabetes Mellitus: Inpatient Insulin Therapy

 Non-critically ill patient

Hyperglycemia if blood glucose > 140 mg/dl

Treatment recommended if glucose levels persistently >=180 mg/dl

HbA1c needed for all admitted patients with diabetes or hyperglycemia ( blood glucose >= 140 mg/dl ) if not performed in the prior 3 months. 

Oral anti-diabetic agents typically discontinued during acute illness

Sliding Scale insulin alone is not appropriate to treat sustained hyperglycemia

Basal Bolus regimen- a. Basal insulin ( long acting )   

                                    b. Mealtime prandial bolus insulin ( short acting) 

                                    c. Correction insulin

Initial Dosing:

- 1st step is to estimate patient's total daily dose ( TDD)  

- For patients on insulin before admission, best indicator of insulin requirement is TDD before admission. If A1C value is elevated then increase TDD. If glycemia too tightly controlled or admitted for hypoglycemia, then reduce.

- For insulin naive patients, initial TDD is 0.3-0.6 units/kg body weight. ( Lean patients and renal sufficiency - lower dose and higher dose for obese patients and those under corticosteroid use )

- 50% of TDD- Basal insulin

- 50% of TDD - meal time bolus insulin

Withheld mealtime bolus insulin if patients are not eating or if their pre-meal glucose level is < 70 mg/dl

Correction insulin is used when glucose levels exceeds 140-150 mg/dl

    - Low scale: 1 units insulin for every 40-50 mg/dl increase above 140-150 mg/dl ( If TDD 20-42 units)

    - Moderate scale: 2 units every 40-50 mg/dl increase above 140-150 mg/dl ( If TDD 43-84 units)

    - High scale: 3 units for increase ( If TDD 85-126 units ) 

Example: Basal/Bolus insulin dose calculation for a patient weighing 80 kg with BMI 28 kg/m2 and normal renal function:

Step 1: TDD= 0.5 units/kg body weight X 80= 40 units

Step 2: Basal insulin= 50% of TDD= 50% of 40 units= 20 units of glargine

Step 3: Bolus insulin dose calculation= (50% of TDD)/3= 20/3= 6 units of rapid acting insulin before each meal

Step 4: Correction scale estimation: low scale correctional scale should be ordered

Monitor Blood Glucose at Fasting, Pre-Lunch, Pre-dinner and Bed time. Measure glucose every 4-6 hrs in NPO patients.

 

Critically Ill Patients 

 Recommended glucose range in acute critical illness= 140-180 mg/dl

Continuous IV insulin is preferred and it is initiated when blood sugar > 180 mg/dl

Transition from IV insulin to SC basal bolus preferred as patient starts feeding reliably

IV insulin should be continued for atleast 4 hours after the glargine insulin dose is administered during transition.