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Correction factor: an introduction to the concept

Conceptual only. No specific factors. Always defer to your prescribing clinician.

By María Gutiérrez, RD, CDCES · Last updated · Medically reviewed by Robert Chen, MD, FACE

The clinical concept

The correction factor (CF), sometimes called the insulin sensitivity factor (ISF), describes how much one unit of insulin is expected to lower the user’s blood glucose. It is conventionally expressed as “1 unit of insulin lowers blood glucose by X mg/dL” (or X mmol/L).

The correction factor is used together with the insulin-to-carbohydrate ratio in a bolus calculator. Where the user’s pre-meal glucose is above the target range, the calculator recommends an additional unit-fraction of insulin, computed from (current glucose minus target) / correction factor. The correction component is added to the meal-coverage component (carbohydrates / insulin-to-carbohydrate ratio) to produce the recommended bolus.

The editorial team will not specify any CF in this article, in any other article, or in response to any inquiry. The CF is individualized; it depends on the user’s body weight, total daily insulin requirement, residual endogenous insulin secretion, insulin sensitivity, time of day, recent activity, illness state, and many other variables. Determining the appropriate CF for a particular user is the prescribing clinician’s responsibility.

How clinicians determine CF

The clinical workflow for CF determination is parallel to that for the insulin-to-carbohydrate ratio:

  1. Initial estimation. The prescribing clinician proposes an initial CF, typically derived from heuristic rules involving total daily insulin requirement and the user’s typical glucose excursions.
  2. Trial period. The user doses per the initial CF for documented out-of-range glucose values, while logging the dose and the subsequent glucose response.
  3. Iterative adjustment. The clinician reviews the post-correction CGM curves and adjusts the CF.
  4. Time-of-day variation. As with ICR, CF often varies by time of day.
  5. Periodic re-evaluation. CF drifts over time and changes with weight changes, illness, pregnancy, and many other variables. Re-evaluation is part of the standard endocrinology and CDCES workflow.

Insulin-on-board

The correction-bolus calculation interacts with the insulin-on-board (IOB) value: insulin from a previous bolus is still acting, and a new correction should account for the residual effect of the previous dose. Most bolus calculators handle IOB automatically given a configured insulin-action duration; the user should confirm with the prescribing clinician that the configured IOB duration is appropriate for the user’s specific insulin (rapid-acting analogs, ultra-rapid analogs, regular).

Stacking corrections without accounting for IOB is a documented cause of severe hypoglycemia. The editorial team’s position is conservative: when in doubt, defer the correction.

What the carbohydrate-tracking application is, and is not, for

The carbohydrate-tracking application is for the carbohydrate count. It is not, in general, for the correction calculation. Bolus calculators (mySugr, the pump’s calculator, AID systems) handle the correction component using the user’s clinician-set CF.

Users should not infer a CF from any consumer application’s defaults. Users should not adjust their CF based on a single correction’s CGM response. CF adjustments are a clinical decision made together with the prescribing clinician.

Limits

This article is conceptual. It does not specify any correction factor. Specific factors are individualized and must come from the prescribing clinician.

References

Reviewed by Robert Chen, MD, FACE on . Reviews every clinical guidance article before publication.
Medical disclaimer Content on Carb Counting Hub is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Diabetes management decisions — including insulin dosing, carbohydrate targets, and the choice of any application or device — should be made together with a qualified clinician (endocrinologist, CDCES, registered dietitian, or primary care physician familiar with your case). Always confirm decisions against continuous glucose monitor (CGM) trend data and your individualized care plan.