Role and sources
Vitamin D supports calcium absorption, bone health and other physiological functions. Sun exposure, diet and supplements contribute, but production and intake vary with season, skin pigmentation, clothing, latitude and other factors.
Testing and deficiency
Testing is useful in selected clinical situations rather than as a universal measure of wellness. A result should be interpreted with the laboratory method, units, symptoms and clinical context.
Excess can harm
Very high supplemental intake can cause excessive calcium levels and kidney or other complications. Multiple products may contain vitamin D, making accidental duplication possible.
Useful information to track
- Daily or intermittent product and strength
- Other supplements containing vitamin D or calcium
- Test date, result, unit and laboratory range
- Clinician-directed treatment and repeat-test date
Sources
Reviewed against the following official guidance and primary evidence. Product information and clinical guidance can change.