Calculating Total Daily Dose (TDD) and Distribution for Apidra and Lantus
Initial TDD Calculation Based on Patient Weight and Clinical Context
For a 70-80 kg patient with type 2 diabetes requiring insulin initiation, start with 10 units of Lantus once daily OR use 0.1-0.2 units/kg/day (7-16 units for this weight range), continuing metformin unless contraindicated. 1
For patients with severe hyperglycemia (HbA1c ≥9%, blood glucose ≥300-350 mg/dL), use higher starting doses of 0.3-0.5 units/kg/day as total daily insulin, requiring immediate basal-bolus therapy rather than basal insulin alone. 1
TDD Distribution Formula: The 50/50 Split for Basal-Bolus Therapy
When initiating basal-bolus insulin therapy, divide the total daily dose as 50% basal insulin (Lantus) given once daily and 50% prandial insulin (Apidra) divided among three meals. 1
Practical Example for 70 kg Patient:
Type 1 diabetes: Start with 0.5 units/kg/day = 35 units TDD 1
- Lantus: 17.5 units once daily (50% of TDD)
- Apidra: 17.5 units total, divided as approximately 6 units before each meal
Type 2 diabetes (mild-moderate hyperglycemia): Start with 10 units Lantus once daily, add Apidra only if needed after basal optimization 1
Type 2 diabetes (severe hyperglycemia, HbA1c >10%): Start with 0.3-0.5 units/kg/day = 21-35 units TDD 1
- Lantus: 10.5-17.5 units once daily (50% of TDD)
- Apidra: 10.5-17.5 units total, divided among meals
Critical Threshold: When to Add Prandial Insulin
When basal insulin (Lantus) exceeds 0.5 units/kg/day (35 units for a 70 kg patient) and approaches 1.0 units/kg/day without achieving glycemic targets, add prandial insulin (Apidra) rather than continuing to escalate basal insulin alone. 1
Start Apidra with 4 units before the largest meal OR use 10% of the current basal dose, then titrate by 1-2 units every 3 days based on 2-hour postprandial glucose readings. 1
Basal Insulin (Lantus) Titration Algorithm
Increase Lantus by 2 units every 3 days if fasting glucose is 140-179 mg/dL, or by 4 units every 3 days if fasting glucose is ≥180 mg/dL, until fasting plasma glucose reaches 80-130 mg/dL. 1
If hypoglycemia occurs without clear cause, reduce the dose by 10-20% immediately. 1
Prandial Insulin (Apidra) Dosing Calculations
Carbohydrate-to-Insulin Ratio (CIR):
Use the formula CIR = 300/TDD for breakfast, or CIR = 400/TDD for lunch and dinner. 2
For example, with TDD of 40 units:
- Breakfast: 1 unit per 7.5 grams carbohydrate (300/40)
- Lunch/Dinner: 1 unit per 10 grams carbohydrate (400/40)
Correction Factor (Insulin Sensitivity Factor):
Calculate as 1500 ÷ TDD to determine how many mg/dL one unit of Apidra will lower blood glucose. 1
For TDD of 40 units: 1500/40 = 37.5 mg/dL reduction per unit of Apidra
Special Populations Requiring Dose Adjustments
Chronic Kidney Disease Stage 5:
Lower TDD by 50% for type 2 diabetes patients with CKD stage 5, and by 35-40% for type 1 diabetes patients with CKD stage 5. 3
Hospitalized Patients:
For patients on high-dose home insulin (≥0.6 units/kg/day), reduce TDD by 20% upon hospitalization to prevent hypoglycemia. 1
For high-risk patients (elderly >65 years, renal failure, poor oral intake), use lower doses of 0.1-0.25 units/kg/day. 1
Common Pitfalls to Avoid
Never continue escalating Lantus beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia with Apidra, as this leads to "overbasalization" with increased hypoglycemia risk and suboptimal control. 1
Clinical signals of overbasalization include: basal dose >0.5 units/kg/day, bedtime-to-morning glucose differential ≥50 mg/dL, hypoglycemia episodes, and high glucose variability. 1
Always continue metformin (unless contraindicated) when adding or intensifying insulin therapy, as this reduces total insulin requirements and provides complementary glucose-lowering effects. 1
Monitoring Requirements
Daily fasting blood glucose monitoring is essential during titration, with HbA1c checked every 3 months during intensive titration. 1
Assess adequacy of insulin dose at every clinical visit, looking specifically for signs of overbasalization. 1