Table 1.

Formulae for Calculating Adherence Rates

Adherence rate since last pill count = # of pills taken since last pill count ÷ # of pills should have taken since last pill count

# of pills taken since last pill count = (# of pills counted at last pill count + # of pills from refills since last pill count) − (# of pills thrown away + # of pills given away/sold + # of pills lost + # of pills broken + # of pills taken, but taken too early/late day of THIS pill count) − (# of pills counted from all locations at this pill count)

# of pills the person should have taken since the last pill count = [(# of full days since last pill count) × (# of pills per day)] + (# of pills that should have been taken later in the day at the last pill count) + (#of pills that should have been taken earlier in the day at THIS pill count)