How do I calculate the morning (two‑thirds) and evening (one‑third) doses of premixed 70/30 insulin from the total daily dose?

Calculating 2/3 and 1/3 Dosing for Premixed 70/30 Insulin

For premixed 70/30 insulin given twice daily, administer 2/3 of the total daily dose before breakfast and 1/3 before dinner.

Standard Dosing Algorithm

• The American Diabetes Association recommends splitting the total daily dose of premixed insulin with 2/3 administered before breakfast and 1/3 administered before dinner 1.
• This 2:1 ratio accounts for greater insulin sensitivity overnight and reduces the risk of nocturnal hypoglycemia 1.

Step-by-Step Calculation

Example: 60 units total daily dose

1. Morning (2/3) dose:

   • 60 units × 0.67 = 40 units before breakfast 1

2. Evening (1/3) dose:

   • 60 units × 0.33 = 20 units before dinner 1

Alternative Calculation Method

• Divide the total daily dose by 3 to get the evening dose 1
• Multiply the evening dose by 2 to get the morning dose 1
• Using the same 60-unit example: 60 ÷ 3 = 20 units (evening), then 20 × 2 = 40 units (morning) 1

Timing of Administration

• Administer the morning dose immediately before breakfast 2
• Administer the evening dose immediately before dinner 2
• Premixed insulin analogues should be given 0–15 minutes before meals for optimal postprandial glucose control 2

Important Considerations for Premixed 70/30 Insulin

• The 70/30 formulation contains 70% intermediate-acting (NPH-like) insulin and 30% rapid-acting insulin 2
• This fixed ratio cannot be adjusted independently for basal versus prandial needs 3
• Premixed 70/30 insulin is contraindicated in hospitalized patients due to a 64% hypoglycemia rate versus 24% with basal-bolus therapy in randomized trials 3

Common Pitfalls to Avoid

• Never use equal morning and evening doses (50:50 split)—this ignores physiological insulin sensitivity patterns and increases nocturnal hypoglycemia risk 1
• Do not administer premixed insulin at bedtime—the rapid-acting component markedly raises nocturnal hypoglycemia risk 3
• Avoid premixed formulations when meal timing or carbohydrate intake varies, as the fixed basal-to-prandial ratio limits flexibility 3

When Converting from Once-Daily to Twice-Daily Dosing

• Reduce the total daily dose to 80% of the current once-daily dose before splitting 1
• Then apply the 2/3:1/3 ratio to this reduced total 1
• Example: If taking 50 units once daily → 50 × 0.8 = 40 units total → 27 units morning, 13 units evening 1

Alternative Regimens for Better Control

• Korean studies suggest that a 55:45 to 60:40 morning-to-evening ratio may be more appropriate than the traditional 2/3:1/3 split, as patients starting with 50:50 ratios required upward adjustment of morning doses over 24 weeks 4
• For patients requiring more flexibility, basal-bolus therapy with separate long-acting and rapid-acting insulins provides superior glycemic control with lower hypoglycemia rates compared to premixed formulations 3