Home › Biomarkers › Vitamin D (25-OH)
People over 70 need 20 micrograms of vitamin D a day, while a recommended daily amount of 10 micrograms applies to everyone. In your blood, vitamin D is measured as 25-hydroxyvitamin D.[1]
On this page you can read what Vitamin D (25-OH) is, what the guidelines say about a level that is too low or too high, what affects your level and which values are best read alongside it.
Also known as: 25-hydroxyvitamin D. At the lab: VD3.
Vitamin D is a fat-soluble vitamin. It is one of the few vitamins your body can make itself: your skin forms vitamin D under the influence of sunlight. You also get vitamin D from your food.[1]
In the liver, vitamin D is converted into 25-hydroxyvitamin D, or 25-OH for short. This form is not active in the body itself, but it is what a blood test uses to determine whether there is a vitamin D deficiency. In the kidneys, 25-hydroxyvitamin D is then converted into 1,25-dihydroxyvitamin D, the active form.[1]
In our food, vitamin D comes in two forms: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Vitamin D2 is formed in certain mushrooms and fungi, vitamin D3 in the skin of humans and animals. Both forms are active, although vitamin D3 has a slightly stronger effect.[1]
Vitamin D makes sure the calcium and phosphorus from your food are well absorbed and laid down in your bones and teeth during growth. That is how vitamin D gives you strong bones and teeth.[1]
Vitamin D is needed to keep the loss of calcium from your bones as low as possible, and so to reduce the risk of a bone condition later in life. Vitamin D also plays an important role in maintaining good muscle function and matters for the normal working of your immune system.[1]
Not everything has been proven. There is not yet enough evidence that a vitamin D supplement lowers the risk of common respiratory conditions.[1]
Guidelines on vitamin D are changing. In 2024, the Journal of Clinical Endocrinology and Metabolism published a correction to the Endocrine Society's clinical guideline on vitamin D deficiency.[3]
Labplusarts, the laboratory BioProfile works with, uses a reference value of 50 to 150 nmol/l for Vitamin D (25-OH). The lab calls a value between those limits normal.[4]
| Value | What the lab says about it | Who it is for |
|---|---|---|
| 50 to 150 nmol/l[4] | The lab calls a value between these limits normal | Everyone for whom Labplusarts measures this value |
Reference value of Labplusarts, the laboratory BioProfile works with, for Vitamin D (25-OH) (VD3). List of 24 September 2026.[4]
A low value can point to a vitamin D deficiency, because 25-hydroxyvitamin D is exactly what a blood test uses to determine that. Sunlight is the main source, and in the winter months the sun in the Netherlands is too low for your body to make vitamin D. For young children, older people, pregnant people, people with dark skin and people who rarely go outside, the advice is to take a vitamin D supplement.[1]
There is a limit at the top end too. Products that have vitamin D added in the Netherlands are capped at 4.5 micrograms per 100 kilocalories, so that intake does not get too high. For a supplement, the Voedingscentrum keeps to the recommended daily amount of 10 micrograms a day.[1]
BioProfile is working on its own zones for each value, from risk to optimal. A doctor reviews those zones before they appear in your result.
You make most of your vitamin D yourself, in your skin, under the influence of sunlight. The advice is to spend a quarter of an hour to half an hour outside every day from March to October inclusive, between 11:00 and 15:00, with your face and hands uncovered. In the winter months the sun in the Netherlands is too low to make vitamin D, and you draw on the store you have built up.[1]
Vitamin D occurs naturally in oily fish, such as herring and salmon. Meat and eggs also contain vitamin D, but less than oily fish. In the Netherlands, vitamin D is added to low-fat spread, margarine and baking and frying products, but not to oil. A 100 gram piece of trout provides 9.4 micrograms and a 50 gram boiled egg 0.9 micrograms.[1]
Your gut absorbs vitamin D best when fat or oil is present too. Average absorption of vitamin D from food is estimated at 80%. Your body can store vitamin D in fat tissue and in organs such as the liver.[1]
The more skin you leave uncovered, the faster you make vitamin D, and the longer you stay outside, the more your skin makes. For young children, older people, pregnant people, people with dark skin and people who rarely go outside, the advice is to take a vitamin D supplement.[1]
Vitamin D (25-OH) is in all five packages, from BioProfile 31 to BioProfile 150.[5]
The BioProfile editorial team wrote this page on 1 October 2026 from the sources below, which we read on 1 October 2026. Every number on this page appears in one of those sources, with that source's number next to it. An expert is still to review this page; after that review, the expert's name and the date of the review will appear at the top. This page offers explanation, not a diagnosis. Discuss an abnormal value with your GP.
