© 2021 Gülsen Yılmaz et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution 4.0 International License.Objectives: The aim of this study is to identify the possible effects of the Ministry of Health regulation on Vitamin D testing and vitamin D deficiency detection and to investigate the effect of the reflex test algorithm implementation. Materials and methods: A total of requested 78,919 25(OH)D and 5,653 1,25(OH)2D test results were examined. Test requests were classified in 3 groups according to the Regulation; Group 1: Requests from inpatients and intensive care units, Group 2: Requests from outpatients of non-restricted departments, Group 3: Requests from outpatients of restricted departments. In addition, the reflex test algorithm was simulated and the name of the 1,25-dihydroxyvitamin D test request was changed to 1,25-dihydroxycholecalciferol. Results: Changing the test name as 1,25 dihydroxycholecalciferol reduced the number of monthly test requests (−71.7%). The hypovitaminous detection rate was similar in Group 1, 2, and 3 in the 25(OH)D requests and was higher in the reflex test algorithm. In 1,25(OH)2D requests, the rate of hypovitaminous detection was higher in Group 1 than in Group 2 and 3. Discussion: With simple acts like using structured test ordering forms, reflex test algorithms applied in the clinic-laboratory-interface involving Medical Biochemistry Specialists, bigger impact with less underdiagnosis might be possible in test demand management.