Patient concerns about low vitamin D levels ebb and flow based on media coverage, clinicians say, but endocrinologists now generally encourage screening and supplementation, particularly for people older than age 50 with a chronic condition.
Based on clinical experience as well as guideline recommendations from The Endocrine Society, Duke endocrinologist Richard Lee, MD, says a vitamin D level of approximately 30 ng/mL or greater is considered satisfactory. Conflicting studies have generated controversy about optimal levels, Lee says, but he and fellow practitioners in the bone clinic within Duke’s Division of Endocrinology, Metabolism and Nutrition suggest that patients maintain this target.
“We believe that 28 to 30 ng/mL is generally an adequate level,” Lee says. “A patient at 20 ng/mL or below is considered to have insufficient levels.”
Healthy adults do not need vitamin D tests, but Lee encourages regular monitoring for patients with risk factors such as obesity, liver or kidney disease, diabetes, or osteoporosis. In some young adults with endocrine disorders, vitamin D testing is recommended. For patients older than 50 years and with chronic conditions, Lee strongly urges supplementation.
The test recommended by Lee and the Duke clinic is measurement of the serum 25-hydroxyvitamin D level (not 1,25-dihydroxyvitamin D). More complex tests are required only for patients presenting with specific conditions.
“Among the general population of patients in our clinic, low vitamin D levels are fairly common, and we think supplementation is generally a good practice,” he says. “It’s a low-risk, preventive step.”
In recent years, several clinical research articles have warned of global vitamin D deficiencies, including among North Americans. The reports triggered media articles highlighting risk factors associated with deficiencies, but a New England Journal of Medicine editorial suggested in November 2016 that most of the conclusions were based on misinterpretation and misapplication of the Institute of Medicine reference values for vitamin D.
Long-term consequences of vitamin D deficiency have been linked to heart disease, diabetes, cancer, autoimmune diseases such as lupus, and even allergic conditions. Although clinical research has not yet identified definitive results, Lee is among many endocrinologists who suggest that observational evidence points to connections between low levels of vitamin D and high-risk diseases.