Orthopaedic Nurses Certification Board (ONCB) Metabolic/Inflammatory/Tumors Practice Exam

During which month are vitamin D levels most effectively measured in the blood?

1. June

2. July

3. August

4. September

The correct answer is: September

Measuring vitamin D levels in the blood is most effective in September due to several factors related to sun exposure and vitamin D synthesis. The body produces vitamin D when the skin is exposed to ultraviolet B (UVB) rays from the sun, which tends to peak during the summer months. However, by September, the accumulation of vitamin D in the body from summer sun exposure is still present, while the intensity of sunlight begins to decrease as the seasons change. In June, July, and August, although vitamin D synthesis is at its highest due to increased sun exposure, the body's stores may not reflect the long-term status of vitamin D levels because they are influenced by the recent contributions from sunlight. By September, individuals are more likely to have stable levels of vitamin D that accurately represent the balance of synthesis, dietary intake, and any depletion that may occur during the fall and winter months ahead. Therefore, September serves as a more reliable time for measurement, as it allows for an assessment of how well the body has absorbed and utilized the vitamin D from summer exposure, providing an accurate reflection of vitamin D status.