Vitamin D Guidelines: Test Selectively and Favor Targeted Supplementation
Vitamin D functions as a system-wide hormone important for bone, immunity, and cardiometabolic health, best viewed through three domains: secure substrate (sun, diet, supplements), proper activation (hepatic/renal hydroxylation and FGF23-PTH regulation), and tissue responsiveness. The 2024 Endocrine Society guideline advises against routine 25(OH)D screening in healthy people and limits testing to specific medical indications. It supports empiric supplementation for adults aged 75+ due to potential mortality benefits but does not endorse universal supplementation above dietary references for younger adults to prevent chronic disease, and finds no strong extraskeletal prevention evidence. For those over 50 with an indication, daily low-dose vitamin D is preferred over high-dose boluses, which can be ineffective or harmful. The USPSTF similarly finds no meaningful reduction in fractures or falls in generally healthy older adults. There is modest evidence that vitamin D may reduce progression to diabetes in high-risk prediabetes when added to lifestyle changes, but not as a general preventive measure in euglycemic individuals. The guideline underlines treating documented deficiency and preventing nutritional rickets in children.
