Vitamin D Testing and Optimal Levels

Optimal Vitamin D Levels

The Endocrine Society defines vitamin D deficiency as total serum 25-(OH)D levels less than 20 ng/mL and vitamin D insufficiency as 21-29 ng/mL 4, 5
Most experts consider levels above 30 ng/mL as optimal for overall health benefits 6
The Institute of Medicine concluded that serum 25-(OH)D levels of 20 ng/mL or greater meet the needs of nearly all of the population 2, 3
An expert panel consensus recommended maintaining 25-(OH)D levels between 30-100 ng/mL for optimal health benefits in patients with or at risk for musculoskeletal problems, cardiovascular disease, autoimmune disease, and cancer 6

Population-wide screening for vitamin D deficiency is not recommended by any major national organization 1, 4, 2
The USPSTF concluded that there is insufficient evidence to assess the balance of benefits and harms of screening for vitamin D deficiency in asymptomatic adults 7
Testing is recommended for individuals at high risk for vitamin D deficiency, including persons with low vitamin D intake or decreased absorption 9, those with limited sun exposure 8, individuals with darker skin pigmentation 6, obese individuals 3, elderly and institutionalized persons 6, patients with osteoporosis or at risk for falls and fractures 5, 3, patients with malabsorptive conditions or inflammatory bowel disease 9, and patients who have undergone gastric bypass surgery 9

Choose an assay that measures both 25(OH)D₂ and 25(OH)D₃ for accurate assessment 10, 6
For individuals at high risk without testing, supplementation with 800 IU/day is reasonable 6
The recommended dietary allowance (RDA) for vitamin D is 600 IU/day for adults aged 19-70 years and 800 IU/day for adults older than 70 years 3

There is considerable variation in vitamin D measurement methods between laboratories, complicating interpretation 1, 7
Vitamin D status assessment is complicated by factors such as obesity, race/ethnicity, and calcium metabolism 8, 9
African Americans have lower reported 25-(OH)D levels but paradoxically lower rates of fractures than white persons, suggesting that racial differences in vitamin D metabolism may exist 8, 9