Overview
25-OH vitamin D is the most reliable marker of vitamin D status. Vitamin D is essential for calcium absorption and bone strength.
Why it's done
It is ordered for bone pain, muscle weakness, frequent fatigue or a risk of osteoporosis.
How to prepare
No special preparation is needed.
What to expect
A venous blood draw.
Understanding the results
A low level indicates vitamin D deficiency and is often corrected with supplements. The optimal range and supplement dose should be set by a doctor.