Vitamin D Blood Test
25-OH vitamin D is the standard measurement of your vitamin D status.
A vitamin D blood test measures 25-hydroxyvitamin D — known as 25-OH D — which is the form clinicians use to assess vitamin D status. In the UK, deficiency is common between October and March when sunlight exposure is limited.
What it measures
25-OH Vitamin D
Why it matters
- Vitamin D supports bone health, immune function and muscle function.
- Public Health England advises considering a 10 µg daily supplement during autumn and winter for most UK adults.
- Both deficiency and excess are possible — testing avoids guessing your dose.
How testing works
- Order a finger-prick home kit or a clinic venous draw from an accredited UK provider.
- Collect the sample and return by post; most kits include pre-paid return packaging.
- Results are typically returned in 2–5 working days.
Compare Vitamin D Blood Test prices in the UK
Side-by-side comparison of CQC-regulated providers and UKAS-accredited laboratories. Transparent pricing, typical turnaround times and sample methods.
Frequently asked questions
What is a healthy vitamin D level?
UK NICE guidance defines deficiency as below 25 nmol/L, insufficiency as 25–50 nmol/L and sufficiency as 50 nmol/L or above. Many clinicians target 75–100 nmol/L for optimal health.
How often should I test vitamin D?
Once or twice a year is usually enough for most adults — typically late winter (to catch deficiency) and late summer (to confirm replenishment).
Related guides
This guide is for general information only and does not constitute medical advice. Always discuss test results with a qualified clinician.