Vitamin d (25 oh)

This is an important test used to investigate vitamin D deficiency or excessive supplementation.

Finger-prick blood
1 tests included
2 days turnaround



About Vitamin d (25 oh)

What is vitamin D?

Vitamin D is a fat-soluble vitamin with an important role in aiding the absorption of calcium, magnesium and phosphates. It also contributes to bone and musculoskeletal health. Vitamin D in the blood can be measured in two different forms; 1,25-dihydroxy vitamin D (1,25-OH) and 25-hydroxy vitamin D (25-OH). 25-OH vitamin D is generally inactive, circulating in the blood until it is converted to the active 1,25-OH vitamin D when required.

25-OH vitamin D is typically the preferred measure of vitamin D in the blood as it is present for longer and in higher concentrations than 1,25-OH vitamin D. Measuring 1,25-OH vitamin D is useful for monitoring conversion between 25-OH vitamin D and 1,25-OH vitamin D by the kidneys. In the UK, the sun is only powerful enough to stimulate vitamin D production in the skin between around April and September.

Due to the fact that this is the primary source of vitamin D in the body, it is common for vitamin D deficiency to occur in many parts of the UK during the winter months without supplements. Vitamin D deficiency can result in weakness in bones and muscles and has been associated with asthma in children and cognitive impairment in adults. Excess vitamin D through supplementation can lead to hypercalcemia.

Why take the test?

This test measures the levels of 25-OH vitamin D in the blood. It is typically used to investigate vitamin D deficiency or excessive supplementation. Vitamin D deficiency can be the result of insufficient intake and production or problems absorbing the vitamin.


What's tested


How it works



Purchase your Kit

Just order a test online and get your kit delivered right to your door unless you are ordering a COVID-19 Fit to Fly test where you will be given appointment options to attend our clinics across the United Kingdom for a nose and throat swab PCR test at the checkout stage.



Take your test and post

Follow our simple instructions to take your sample and post back the enclosed prepaid envelope to our accredited lab for processing. We also offer home or workplace visits by a qualified nurse. For COVID-19 Fit to Fly tests you must attend one of our partner clinics for our trained collection officers to take your sample. You will then have the results emailed to you.



Get results directly to your dashboard

You will receive an email notification from our medical team when your results are available on your secure personalised health dashboard.