Vitamin D normative values by age, sex, and supplement use

Problem considered: Vitamin D levels vary by age, sex, lifestyle, and supplement use. Establishing normative values for Vitamin D within these populations is crucial to advancing global health and reducing the disease burden. This study aimed to establish age-, sex-, and supplementation-specific normative values for serum 25-hydroxyvitamin D2 [25(OH)D2], 25-hydroxyvitamin D3 [25(OH)D3], and total Vitamin D using nationally representative United States data from the NHANES 2017–2018 cycle. Methods: A cross-sectional analysis was conducted using data from 3668 NHANES participants aged 1 year and older. Serum 25(OH)D2, 25(OH)D3, and total Vitamin D levels were measured. Participants were stratified by age, sex, and supplement use. Percentile distributions were calculated to provide reference values for subgroups. Results: 25(OH)D3 was the primary contributor to total Vitamin D levels across all demographics. Adults 51 years and older displayed higher upper percentiles for 25(OH)D3 and total Vitamin D. Males exhibited higher levels than females, especially in younger age groups. Among non-supplement users, Vitamin D levels at the 5th percentile were above 20 nmol/L across all ages, suggesting adequate levels from natural sources, such as sunlight and diet. Conclusion: This study established normative values for Vitamin D across demographic groups, emphasizing the importance of age- and sex-specific values in clinical evaluations. These findings highlight that many individuals obtain Vitamin D naturally, reinforcing the global relevance of environmental and nutritional health strategies. These normative values can inform clinical and public health assessments and help to refine Vitamin D guidelines and support worldwide efforts toward optimal population health.