Vitamin D (25-OH vitamin D)

Your body’s vitamin D status — mostly made in your skin from sunlight, and important for bones and immunity.

What it measures

The blood level of 25-hydroxyvitamin D, the best marker of your overall vitamin D stores.

Why it matters

Genuine deficiency harms bone health and is common in low-sun regions and winters. Correcting a real deficiency matters — but more is not better, and mega-doses don’t buy extra benefit.

Healthy target

75–125 nmol/L

How to read your value

Aim for repletion, not excess — pushing levels far above the range brings no proven benefit and very high intakes can cause harm. Units differ between countries (nmol/L vs ng/mL); make sure you’re comparing the same scale.

What can affect it

• Sun exposure and latitude/season
• Skin tone and age
• Supplementation
• Body weight (higher weight dilutes levels)

Does the target differ by age or sex?

Same target level for everyone. Needs (intake) are higher in pregnancy and older age, but the healthy blood level is the same.

When to talk to a clinician

Persistent deficiency, or very high levels from supplements, should be managed with a clinician.