Tell me I want to give glargine and regular insulin to a pt with weight 70 kg how to devide the dose and how to divide dose if I want to use mixtard (70/30)
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Insulin Dosing for a 70 kg Patient
Step 1 — Calculate the Total Daily Dose (TDD)
The standard starting TDD = weight (kg) × 0.5 for insulin-naïve patients (conservative start), or × 0.7 for those who clearly need full replacement.
| Approach | Formula | Result for 70 kg |
|---|---|---|
| Conservative (new to insulin) | 70 × 0.5 | 35 units/day |
| Standard | 70 × 0.7 | 49 units/day |
Most guidelines recommend starting at 0.5 units/kg/day (~35 units) and titrating up to avoid hypoglycemia.
Regimen 1: Glargine (Basal) + Regular Insulin (Bolus) — Basal-Bolus
This mimics physiological insulin secretion. Split the TDD 50/50.
Using TDD = 35 units (conservative start):
| Component | Dose | Timing |
|---|---|---|
| Glargine (basal) | 50% of TDD = 17–18 units | Once daily (same time each day, usually bedtime or morning) |
| Regular insulin (bolus) | 50% of TDD = 17–18 units | Divided equally across 3 meals = ~6 units per meal |
Using TDD = 49 units (standard):
| Component | Dose | Timing |
|---|---|---|
| Glargine | 50% = ~25 units | Once daily |
| Regular insulin | 50% = ~24 units | ~8 units per meal (3 meals) |
Key rules for Regular insulin:
- Inject 30 minutes before a meal (unlike rapid-acting analogs which are 15 min before)
- Adjust prandial dose for meal size:
- Very large meal with dessert → +3 units
- Large meal without dessert → +1–2 units
- Smaller meal → −1–2 units
Titration:
- Glargine: Increase by 1 unit/day until fasting BG < 100 mg/dL
- Regular: If 2-hr postprandial glucose is consistently >50 mg/dL above premeal, increase that meal's dose by 1–2 units
Correction dose (insulin sensitivity factor):
1800 ÷ TDD = expected BG drop per 1 unit
- Example: 1800 ÷ 49 = ~37 mg/dL per unit
- Correct only if premeal BG > 180 mg/dL, targeting 150 mg/dL
Regimen 2: Mixtard 70/30 (Premixed Insulin)
Mixtard 70/30 contains:
- 70% NPH (intermediate-acting, covers basal needs)
- 30% Regular (short-acting, covers meal)
Dose division:
| Injection | Dose | Timing |
|---|---|---|
| Morning (breakfast) | 2/3 of TDD | 30 min before breakfast |
| Evening (dinner) | 1/3 of TDD | 30 min before dinner |
For 70 kg patient (TDD = 35 units):
| Injection | Calculation | Dose |
|---|---|---|
| Morning | 2/3 × 35 | ~23 units |
| Evening | 1/3 × 35 | ~12 units |
For TDD = 49 units:
| Injection | Calculation | Dose |
|---|---|---|
| Morning | 2/3 × 49 | ~33 units |
| Evening | 1/3 × 49 | ~16 units |
Important considerations for Mixtard:
- The patient must eat on a fixed schedule — the NPH component will peak whether or not they eat
- A mid-morning snack may be needed (between breakfast and lunch) to prevent hypoglycemia from the morning NPH peak
- Less flexible than basal-bolus — cannot easily adjust for variable meal sizes
- If control is inadequate with twice-daily Mixtard, consider switching to basal-bolus
Quick Summary Comparison
| Feature | Glargine + Regular | Mixtard 70/30 |
|---|---|---|
| Injections/day | 4 (1 basal + 3 prandial) | 2 |
| Flexibility | High | Low |
| Meal timing | Flexible | Fixed |
| Hypoglycemia risk | Lower with good titration | Higher (fixed NPH peak) |
| Patient compliance | More complex | Simpler |
| Best for | Type 1 DM, motivated T2DM | T2DM needing simple regimen |
Source: Textbook of Family Medicine 9e, pp. 988–989 (Unger, 2007 protocol)
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