What the test measures
The test measures 25-hydroxy vitamin D, the form your body stores and the standard marker of vitamin D status. In the UK, results are commonly read like this: below 25 nmol/L is deficient, 25 to 50 nmol/L is insufficient for some people, and above 50 nmol/L is generally adequate.
Who is most likely to be low
People who spend little time outdoors, people with darker skin, people who cover most of their skin, older adults, people living with obesity, and anyone with a condition that affects absorption, such as coeliac disease. In the UK, sunlight from October to March is not strong enough for the skin to make vitamin D, so levels usually reach their lowest from late winter into early spring.
Symptoms of low vitamin D
Often none. When there are symptoms they tend to be vague: tiredness, low mood, muscle aches, bone pain and frequent infections. Long-standing deficiency can weaken bones.
Do I need a test if I already take a supplement?
The UK government advises everyone to consider a daily 10 microgram (400 IU) supplement in autumn and winter. A test is still useful if you have symptoms, are in a higher-risk group, or have been taking a higher dose and want to check the level is where it should be. A recheck about three months after starting a supplement shows whether it is working.
Preparation
No fasting is needed and the test can be taken at any time of day. Tell us if you take a supplement and at what dose.
At Omnia
Our vitamin D blood test in Chiswick costs £61, analysed by Randox and reviewed with you. Vitamin D is also included in the Standard Screen (£127), Tired All The Time (£165) and the Randox Everyman and Randox Everywoman. See every test and price.