Vitamin D insuffi ciency remains a costly pandemic in veterans. Treatment requires achievement of desired 25-hydroxyvitamin D [25(OH)D] concentrations. The frequency with which 25(OH)D should be measured following treatment remains speculative. A retrospective analysis of veterans with vitamin D insuffi ciency was conducted. The group was stratifi ed on the basis of initial 25(OH)D and assessed for frequency of follow-up 25(OH)D concentrations. Over 3 years, 278 patients with insuffi cient 25(OH)D concentrations were identifi ed. Of these, 87 (31%) patients had subsequent levels assessed in the year following initial documentation of vitamin D insuffi ciency. The likelihood of follow-up testing was unrelated to the initial vitamin D level. In the patients with follow-up 25(OH)D levels, 90% eventually achieved a serum level of 30 ng/mL or greater. Veterans with vitamin D insuffi ciency have inadequate serial monitoring of 25(OH)D concentrations.