What it measures
- 25-hydroxy vitamin D
Who it’s for
- Tiredness, aches, muscle weakness or bone pain
- Spending little time outdoors, or covering your skin
- Darker skin, which makes less vitamin D from sunlight
- Pregnancy, breastfeeding or planning a pregnancy
- Checking whether a supplement is working
Why so many people in the UK are low
Your skin makes most of your vitamin D from sunlight. In the UK the sun is too weak to make any from about October to early March, so levels drop through the winter. Darker skin, covering up, working indoors and being over 65 all make a low level more likely. The NHS advises everyone to consider a daily 10 microgram (400 IU) supplement in autumn and winter.
Getting the dose right
If you’re low, your GP may suggest a higher-dose course followed by a maintenance dose. Testing again after about three months shows whether it’s working. Very high doses taken for a long time can be harmful, which is another good reason to test rather than guess.
| 25-hydroxy vitamin D (nmol/L) | What it means |
|---|---|
| Below 25 | Deficient |
| 25 to 50 | May be too low for some people |
| Above 50 | Enough for almost everyone |
How to prepare
- Drink a couple of glasses of water beforehand: it makes the sample quicker and easier to take.
- No fasting needed. Eat and drink as normal.
How it works at our Croydon clinic
Book online
Choose your test and a time that suits you. No GP referral needed.
A 15-minute visit
A trained clinician takes a small blood sample at 169 Shirley Road, Croydon. Tell us if you’re nervous.
Results in 1–3 days
A clear report showing each result against its reference range.
Next steps
Share your report with your GP, who can arrange NHS follow-up if anything needs it.
Questions
How long after starting supplements should I retest?
About three months, which gives your level time to settle.
Do I need to fast?
No. You can eat and drink normally.
Vitamin D test or Bone Health test?
They cost the same. The Bone Health test includes vitamin D plus calcium, phosphate, PTH and ALP, so it’s better value if you’re thinking about your bones.
How much is a Vitamin D Test in Croydon?
£70 at our clinic at 169 Shirley Road, Croydon, including taking your blood sample and your report.
How quickly will I get my results?
Usually within 1 to 3 days, in a clear report showing each result against its reference range.
Pregnant? See our pregnancy blood tests, including NIPT from £295 and the early gender blood test from 6 weeks.