From the Guidelines
Vitamin D testing should be ordered selectively for patients with specific risk factors or conditions rather than as routine screening. Testing is appropriate for individuals with:
- Osteoporosis
- Osteomalacia
- Chronic kidney disease
- Malabsorption syndromes (like celiac disease or inflammatory bowel disease)
- Liver disease
- Obesity
- Those taking medications that affect vitamin D metabolism (such as anticonvulsants, glucocorticoids, and antiretrovirals) Other candidates include:
- Older adults with history of falls or fractures
- Patients with hyperparathyroidism
- Pregnant or breastfeeding women at risk for deficiency
- Individuals with limited sun exposure or dark skin The 25-hydroxyvitamin D test is the preferred measurement as it reflects both dietary intake and cutaneous production of vitamin D 1. Testing should be targeted because vitamin D deficiency is common in the general population, making universal screening inefficient and costly. Additionally, many individuals with low levels may be asymptomatic, and the clinical significance of borderline low levels remains debated. Treatment decisions should be based on clinical context rather than laboratory values alone. According to the Institute of Medicine, daily dietary vitamin D intake of 600 IU in adults aged 18 to 70 years and 800 IU in adults older than 70 years should be sufficient to meet the needs of 97.5% of the adult population 1. The USPSTF concludes that the evidence on screening for vitamin D deficiency in asymptomatic adults to improve health outcomes is insufficient and that the potential harms of screening and treatment are small to none 1.
From the Research
Criteria to Order Vitamin D Testing
The following are criteria to consider when ordering vitamin D testing:
- Patients with a history of osteoporosis or osteopenia 2
- Individuals with limited sun exposure, such as those living at higher latitudes or with limited outdoor activity 3, 4
- People with darker skin pigmentation, as they may be at higher risk for vitamin D deficiency 3, 4
- Patients with kidney disease, as they may be at higher risk for vitamin D deficiency 2
- Individuals with malabsorption syndromes, such as Crohn's disease or celiac disease 2
- Older adults, as they may be at higher risk for vitamin D deficiency due to decreased skin synthesis and increased risk of osteoporosis 5, 6
- Patients with a history of falls or fractures, as vitamin D deficiency may contribute to these conditions 2
Laboratory Tests for Vitamin D
Two laboratory tests are available for vitamin D:
- 25-hydroxyvitamin D (25(OH)D), which is the most commonly used test to assess vitamin D status 2
- 1,25-dihydroxyvitamin D, which is not typically used for routine testing due to its shorter half-life and lower concentrations in the blood 2
Interpretation of Test Results
The interpretation of vitamin D test results is as follows: