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Medication Adherence Rate Calculator

Work out medication adherence rate instantly with clear inputs, formula shown and shareable results.

About Medication Adherence Rate Calculator

Divides days of medication supplied by days in the period to give the proportion of days covered, the standard adherence measure in pharmacy claims data.

Formula

Proportion of days covered

PDC (%) = days supplied / days in the measurement period x 100, capped at 100%

Worked example

With the default values below, Medication Adherence Rate Calculator returns Proportion of days covered of 82.19%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Days of medication suppliedaccepts 0–1,000
300
Days in the measurement periodaccepts 1–1,000
365

Results

Proportion of days covered
82.19%
Days without medication
65 days
Threshold check
Adherent by the 80% threshold
Days covered
300 days

Step by step

  1. 1Values used
  2. 2Proportion of days covered
  3. 3Proportion of days covered= 82.19
  4. 4Days without medication= 65 days
  5. 5Threshold check= Adherent by the 80% threshold
  6. 6Days covered= 300 days

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 or fees or charges 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.

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

Why is 80% the threshold?

It is the level above which clinical benefit is generally maintained in cardiovascular and diabetes outcome studies.

How does PDC differ from MPR?

The medication possession ratio can exceed 100% with early refills; PDC is capped and counts covered days only.

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