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Insulin Sensitivity Factor Calculator

Work out insulin sensitivity factor instantly with clear inputs, formula shown and shareable results.

About Insulin Sensitivity Factor Calculator

Applies the 1800, 1500 or 2000 rule to a total daily insulin dose to estimate how far one unit of insulin lowers blood glucose.

Formula

Sensitivity rules

ISF (mg/dL per unit) = constant / total daily dose, with constant 1800 for rapid analogues and 1500 for regular insulin

Worked example

With the default values below, Insulin Sensitivity Factor Calculator returns Insulin sensitivity factor of 36.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Total daily insulin doseaccepts 5–300 units
50 units
Rule constantone of 1800 rule (rapid-acting analogue), 1500 rule (regular insulin), 2000 rule (very sensitive)
1800 rule (rapid-acting analogue)

Results

Insulin sensitivity factor
36.0 mg/dL per unit
Sensitivity factor
2.00 mmol/L per unit
Rule constant
1,800

Step by step

  1. 1Values used
  2. 2Sensitivity rules
  3. 3Insulin sensitivity factor= 36.0 mg/dL per unit
  4. 4Sensitivity factor= 2.00 mmol/L per unit
  5. 5Rule constant= 1,800

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

Which constant should be used?

1800 is usual for rapid-acting analogues and 1500 for regular human insulin; the choice belongs with the prescribing team.

Is the factor fixed all day?

No. Sensitivity commonly varies between morning, afternoon and overnight periods.

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