Vitamin D (25 OH) Blood Test, from our experts to you.
Dr Sam Rodgers MBBS, MRCGP

Chief Medical Officer

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What is
vitamin D?

Vitamin D is a fat-soluble vitamin. It’s also known as the sunshine vitamin because we produce most of what we need through exposure to the sun. We also get some vitamin D from our food, but it’s difficult to get all your requirements from food alone. Sources of vitamin D include oily fish, mushrooms, egg yolks, and vitamin D-fortified foods.

What does
vitamin D do?

Vitamin D controls how your body absorbs calcium and phosphate. It’s vital for keeping your bones, teeth, and muscles healthy, and plays a role in immune function and mental health. Vitamin D is particularly important for pregnant women, breastfed babies, and children under five.

What are the symptoms
of vitamin D deficiency?

Symptoms of vitamin D deficiency can be vague. They include feeling low in energy, having more aches and pains than usual, depression (especially in winter), and frequent illnesses. Even if you don't have symptoms, it’s worth testing your vitamin D level, as a high proportion of adults in the UK are deficient or have insufficient levels.

If your results are outside the normal range, we'll let you know what steps you can take to improve your vitamin D level. For more information, have a look at our guide to vitamin D deficiency.

What's Included?

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Vitamin D Although called a vitamin, vitamin D is actually a hormone which is activated by sunshine on your skin. Vitamin D is essential for bone strength as it helps your intestines absorb calcium. However, it is thought that vitamin D also plays an important role in immune function, as well as in many chronic diseases and mental health. Many people in the UK have low levels of vitamin D with symptoms including muscle weakness, mood swings and fatigue. People who have dark skin, as well as those who don't spend much time outdoors are particularly at risk of low vitamin D. Small amounts of vitamin D can be obtained from food, especially oily fish, eggs and any food which has been fortified with vitamin D. If you are deficient in vitamin D you are unlikely to be able to improve your levels by food alone.

How to prepare
for your test

Special Instructions
Prepare for your Vitamin D (25 OH) Blood Test by following these instructions. You should take this test before you take any medication or vitamin/mineral supplements. Do not take biotin supplements for two days before this test; discuss this with your doctor if it’s prescribed.

Frequently asked questions

How much vitamin D do I need?
To avoid a vitamin D deficiency, the Department of Health and Social Care recommends that adults and children over four should get 10 micrograms of vitamin D a day.
What is the normal range for vitamin D?

The normal range for vitamin D levels in the blood varies between laboratories. But, generally, a level below 50nmol/L is considered insufficient. The following table, based on figures from NICE guidance and other sources, is given as a guide. There is currently no agreement on an ‘optimal’ vitamin D level, which may be as high as 70-80 nmol/L.

Vitamin D level (nmol/L) 
>125Too high
What causes vitamin D deficiency?

Vitamin D deficiency has many causes. You may be more prone to a vitamin D deficiency if you're over 65 or have dark skin, which makes it harder to produce vitamin D through sunlight exposure. Certain medical conditions can affect your body’s ability to absorb vitamin D from your food, such as coeliac and Crohn’s disease. Lifestyle factors including your diet and how long you spend outdoors can also play a part. You can read more about vitamin D deficiency in our Vitamin D Guide.

How can I test my vitamin D level?
The Vitamin D (25 OH) Blood Test is the most accurate way to measure your vitamin D level. You can test your vitamin D level at home with our easy finger-prick blood test kit. Or, you can have your blood sample taken at one of our convenient nationwide partner clinics at a time to suit you.
How can I check my vitamin D level at home?
You can check your vitamin D level at home with our easy finger-prick blood test kit. We’ll send you everything you need, including a pre-paid return envelope. Our at-home vitamin D test includes a full lab analysis of your blood sample. You can access your results on your MyMedichecks dashboard, alongside doctor’s advice to help you take action to improve your health and wellbeing.

How does the weather affect vitamin D levels?


We make most of the vitamin D we need with the help of sunlight. So, it’s not surprising that levels can be affected by the changing seasons. Your risk of a deficiency is greater during autumn and winter, when it’s harder to get adequate amounts of vitamin D from time spent outdoors. And as some areas of the UK are sunnier than others, where you live can also affect your vitamin D level. Read more about how the British weather can affect your vitamin D levels.