From the Guidelines
To calculate an insulin dose using Insulin Sensitivity Factor (ISF), first determine how many units of insulin you need to lower your blood glucose by dividing the difference between your current blood glucose and target blood glucose by your ISF, as recommended by the most recent guidelines 1. When calculating the insulin dose, consider the following steps:
- Determine your current blood glucose level and your target blood glucose level.
- Calculate the difference between your current and target blood glucose levels.
- Divide this difference by your ISF to determine the units of insulin needed, for example, if your current blood glucose is 250 mg/dL, your target is 100 mg/dL, and your ISF is 50 mg/dL per unit, you would calculate: (250-100) ÷ 50 = 3 units of insulin needed.
- Your ISF is typically determined by your healthcare provider, but a common starting point is 1800 divided by your total daily insulin dose for rapid-acting insulin, as suggested by previous studies 1. Some key points to consider when using ISF to calculate insulin doses include:
- Accounting for any carbohydrates you're consuming by using your insulin-to-carb ratio separately.
- Considering active insulin (insulin on board) from previous doses to avoid stacking and potential hypoglycemia.
- Regular blood glucose monitoring is essential when using this method to calculate insulin doses, as your ISF may vary throughout the day and can be affected by factors like illness, stress, exercise, and hormonal changes 1. It's also important to note that ISF may need to be adjusted based on factors such as fasting or daytime glucose outside of target, and that AID systems may require adjustments to carbohydrate ratio, insulin on board, targets, and/or ISF depending on the activity of URAA/RAA bolus 1.
From the Research
Calculating Insulin Dose with ISF
To calculate the insulin dose with the Insulin Sensitivity Factor (ISF), the following steps can be taken:
- Determine the patient's current blood glucose level and the target blood glucose level.
- Calculate the difference between the current and target blood glucose levels.
- Use the ISF to determine how much insulin is needed to lower the blood glucose level by 1 unit (e.g., 1 mmol/L or 1 mg/dL).
- Multiply the difference between the current and target blood glucose levels by the ISF to determine the total amount of insulin needed.
Factors Affecting Insulin Dose Calculation
Several factors can affect the calculation of insulin dose, including:
- Type of insulin used (e.g., rapid-acting, short-acting, intermediate-acting, long-acting) 2, 3, 4
- Patient's insulin sensitivity and resistance 4
- Presence of other health conditions, such as kidney or liver disease 4
- Patient's diet and physical activity level 3, 5
Clinical Considerations
When calculating insulin dose with ISF, it is essential to consider the patient's individual needs and circumstances, including: