Nutrients
Vitamin D (25-OH)
Also known as: 25-hydroxyvitamin D, 25(OH)D
What it is
25-hydroxyvitamin D is the circulating form used to gauge vitamin D status. Levels reflect sunlight exposure, diet and supplementation, and tend to fall in winter at higher latitudes such as the UK.
Why it matters
Vitamin D supports bone health and plays a role in immune function. Low levels are common in the UK, particularly in winter, which is why it is a frequently checked and modifiable marker.
What “optimal” looks like
There is a healthy sufficiency range; very high levels are not better and can be harmful. This is general information, not a recommendation to supplement - dosing decisions belong with your clinician.
This is general information, not medical advice or a diagnosis. Always discuss your results with a qualified clinician.
Related
See your own Vitamin D (25-OH)
bettr.now measures this and dozens of other markers, scores them against optimal, and reads them as one plain-English story.