Nutritional

Vitamin D

25-Hydroxy Vitamin D. Measured in clinic at The Wellness in Marylebone, read by a doctor.

What It Is

Vitamin D is made in the skin in response to sunlight and taken in through some foods, then converted in the body to its storage form, which is what this blood test measures. It functions more like a hormone than a typical vitamin, with receptors throughout the body.

Why It Matters

Vitamin D is central to calcium absorption and bone health, and it plays a role in muscle and immune function. Low levels are common in the UK, particularly through winter, which is why the marker appears in most general health panels.

What Results Can Suggest

A low vitamin D level can suggest limited sun exposure, low dietary intake or reduced absorption, and over time it is associated with weaker bones. Very high levels, usually from heavy supplementation, can also cause problems. Discuss your result with a doctor before changing what you take.

This page is general information, not medical advice and not a substitute for a consultation. Reference ranges vary between laboratories, and results should always be interpreted by a doctor who knows your history.