Vitamin D Testing – Clinical Implementations for Laboratory Practice

Vitamin D is a pre-hormone essential for mineral homeostasis and plays an important role in bone, cardiovascular, and kidney health (1). Epidemiologic studies have associated lower vitamin D levels with increased risk for conditions such as respiratory infections, cardiovascular disease, malignancy, and metabolic disorders (2). However, despite early observational associations, robust randomized controlled trials (RCTs) have not confirmed broad clinical benefits of vitamin D supplementation or widespread testing in the general population (2,3).

Driven by early studies, vitamin D testing—particularly measurement of serum 25-hydroxyvitamin D [25(OH)D]—has become widespread, with over 10 million tests performed annually in the United States (3). Medicare data shows vitamin D testing as the seventh-highest laboratory expenditure, costing nearly $300 million per year (4). One-third of U.S. adults aged 60 years and older also report taking vitamin D supplements (3).

However, evidence from the Vitamin D and Omega-3 Trial (VITAL)—the largest placebo-controlled RCT to date—demonstrated that vitamin D supplementation did not reduce risk of cancer, cardiovascular disease, fractures, or  improve other health outcomes, even among individuals with low baseline 25(OH)D levels (<20 ng/mL) (3). Importantly, these results challenge the clinical value of routine vitamin D testing and supplementation in healthy individuals. Several challenges further limit the utility of routine vitamin D testing, including 1) inter-laboratory variability in vitamin D assay results; 2) seasonal variability within the same individual; and 3) lack of established serum 25(OH)D thresholds that clearly predict improved clinical outcomes (4,5). In addition, unnecessary testing may lead to over-supplementation, which randomized trials have linked to increased risks such as falls in older adults (4).

The 2024 Endocrine Society Clinical Practice Guideline recommends against routine 25(OH)D testing in healthy individuals without specific risk factors (5). Testing should be reserved for patients with clinical indications such as: hypocalcemia, osteoporosis, malabsorption syndromes, chronic kidney disease, and/or symptoms suggestive of osteomalacia. Moreover, experimental vitamin D supplementation without prior testing is supported only for certain high-risk groups, such as pregnant women, adults ≥75 years old, children and adolescents, and individuals with high-risk prediabetes (5).

Given these findings, laboratories should work with clinical teams to implement more targeted vitamin D testing strategies, including 1) restricting orders to patients with clear indications by adherence to testing guidelines; 2) educate providers about the limited utility of routine screening in asymptomatic, healthy individuals; 3) monitor vitamin D test ordering patterns as part of laboratory utilization management programs; and 4) consider decision-support alerts in electronic health records for vitamin D test orders outside guideline recommendations. However, laboratory stewardship alone is not sufficient, as physician resistance to changes in vitamin D testing practices has been reported (6). Therefore, collaboration and active engagement with clinical teams remain essential to ensure sustained implementation and appropriate utilization.

In conclusion, vitamin D plays an important role in health, but widespread 25(OH)D testing in healthy populations is not supported by current evidence. Clinical laboratories have an important role in promoting appropriate vitamin D test utilization by aligning practices with the latest guidelines. However, to ensure success, physicians must be actively involved in these efforts. Their engagement is essential for translating laboratory stewardship into sustained improvements in patient care and reductions in healthcare costs.

References

1. Magagnoli L, Cassia M, Galassi A, Ciceri P, Masso E, Gelpi R, et al. Vitamin D: are all compounds equal? Clin Kidney J. 2025;18(Suppl 1):i61-i96. 
2. Bouillon R, LeBoff MS, Neale RE. Health effects of vitamin D supplementation. J Bone Miner Res. 2023;38(10):1391-1403. doi:10.1002/jbmr.4888. 
3. Cummings SR, Rosen C. VITAL findings — a decisive verdict on vitamin D supplementation. N Engl J Med. 2022;387(4):368–370. doi: 10.1056/NEJMe2205993. 
4. Brett AS, Cummings SR. Podcast 297: Forget about all that vitamin D testing!! [Internet]. Clinical Conversations. Boston (MA): NEJM Journal Watch; 2022 Jul 28 [cited 2025 Apr 26]. Available from: https://podcasts.jwatch.org/index.php/podcast-297-forget-about-all-that-vitamin-d-testing/. 
5. Demay MB, Pittas AG, Bikle DD, Diab DL, Kiely ME, Lazaretti-Castro M, et al. Vitamin D for the prevention of disease: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2024;109(8):1907–1947. doi:10.1210/clinem/dgae290. 
6. College of American Pathologists. EMR order alert significantly decreases vitamin D testing at Kaiser Permanente.CAP.org.https://www.cap.org/member-resources/case-examples/emr-order-alert-significantly-decreases-vitamin-d-testing-at-kaiser-permanente. Published 2022. Accessed June 6, 2025.