The aim of our study was to determine whether the SLEDAI-2K calculated using a timeframe of 30 days prior to a visit for clinical and laboratory variables was equivalent to the prescribed 10-day period. One hundred forty nine consecutive lupus patients seen over 9 weeks at the University of Toronto Lupus Clinic enrolled. The SLEDAI-2K score was completed twice, for a 10- and 30-day window. Forty patients had a classic SLEDAI-2K activity score of 0 and 109 patients had varying levels of disease activity ranging from 1 to 31. In all but one patient, there was agreement between the SLEDAI-2K 10 and 30 days. Thus SLEDAI-2K 30 days is similar to SLEDAI-2K 10 days, both in patients in remission and with a spectrum of disease activity levels. SLEDAI-2K 30 days may now be used to describe disease activity over the previous 30 days.