Why does my age count in the limit?

Because the need rises while production falls. An older skin makes less vitamin D on the same sunlight, and bones and muscles need more precisely to stay ahead of fractures and falls. That is why the lower limit from 70 years is at 50 nmol/L instead of at the general limit of 30, and why the advice from that age is to take 20 micrograms a day all year round.

When is the best time to measure vitamin D?

The time of day does not matter, the season does. The store is at its lowest at the end of winter and at its highest after summer. If you want to follow yourself over time, measure in the same season; a winter measurement just below the limit is not worth a summer surprise. Anyone who wants to know whether the supplement is enough measures after a few months of taking it.

Does a supplement make the measurement pointless?

No. What is measured is the storage form 25-hydroxyvitamin D, and that moves slowly: a tablet on the day itself changes nothing. If you have been taking it for months, you measure your status with supplementation, and that too is a real answer: it shows whether the dose you take is enough for your body. If the value stays low despite taking it, the dose is too low or the gut is not absorbing it.

What about vitamin D in pregnancy?

The need is higher and the advice is to take 10 micrograms daily all year round, regardless of the result, because the child builds its bones from the mother's store. The measurement changes little about that; it mainly shows where you start and whether the dose is enough. The bands on this page apply outside pregnancy; in that period your midwife reads the result with you.

Vitamin D deficiency

A vitamin D deficiency means your body has too little vitamin D for strong bones and well-working muscles. Usually you notice nothing. One value in your blood shows where you stand: vitamin D. At the end of winter it is at its lowest for many people.

Medically reviewed by

Aäron Spapens

Lifestyle physician at Optimize

What are the symptoms of a vitamin D deficiency?

ComplaintEvidence
Muscle weakness
Only with a severe, prolonged deficiency.
strong
Bone pain
With a severe deficiency that softens your bones.
fair

How strong is the evidence?

strong: In the Dutch guideline, or confirmed in several controlled trials.
fair: From one controlled trial, an international guideline or a review of research.
limited: The research does not point one way.

Evidence as of October 2026. New research can shift this.

These complaints are also described with an underactive thyroid, low testosterone.

A mild or moderate vitamin D deficiency usually gives no complaints at all: you only notice it with a severe, long-standing deficiency, and then mainly in muscles and bones.

None of these complaints belongs to a vitamin D deficiency alone, and a measurement explains no complaint: the reading and the diagnosis belong with your GP. The complaint list follows the Netherlands Nutrition Centre, Thuisarts.nl and research on severe deficiency.

Often named, not confirmed

You will run into these links everywhere. We list them deliberately, with what the research does show.

Tiredness
Thuisarts: tiredness is not caused by a deficiency. That extra vitamin D helps has not been shown.
not confirmed
Low mood in the winter months
Thuisarts: depression is not caused by a deficiency. A year of extra vitamin D did not help.
not confirmed

See what your vitamin D means

When is your vitamin D too low?

Normal:

50 to 130 nmol/L

Your value

Enter your value as it appears on your results. Range for adults.

50130

No value yet? How to get it measured

How do you replenish a vitamin D deficiency?

Go outside every day

From March to October. A quarter to half an hour in the middle of the day, with your face and hands uncovered. That builds a store for the winter.

Oily fish, margarine and eggs

With your food. Food covers only part, but it counts.

Where vitamin D is

Oily fish
- Herring
- Salmon
Margarine and fats
- Spread
- Margarine
- Cooking fat
EggsLess than oily fish.

10 micrograms a day

In a risk group. If you have dark skin, rarely go outside or cover your face, as a woman aged 50 to 69 and when pregnant.

20 micrograms a day

From 70. Everyone this age, all year round.

Replenishing, in consultation

With a measured deficiency. Which dose and for how long is something you can discuss with your GP. Then measure again, in the same season.

The advice follows the Netherlands Nutrition Centre.

What causes a vitamin D deficiency?

Too little sunlight

Most common

The skin makes vitamin D on sunlight, and that is by far the largest source.

Working mostly indoors or rarely getting outside
Darker skin, which makes less at this latitude
Covering clothing

Reduced production and uptake

The sunlight is there, but the body does less with it.

From about 70 years the skin structurally makes less
Excess weight, which keeps vitamin D stored in fat tissue
Bowel conditions that slow fat absorption

Higher demand

Production is normal, but more is temporarily needed.

Pregnancy and breastfeeding

How to get a vitamin D deficiency measured

Every value below has its own page: what is normal, and what your value means.

Which blood values show a vitamin D deficiency?
Value	What it shows	Points here when
Vitamin Ddefining	The storage form 25-OH vitamin D. The gauge the age-based limit reads from.	low

And 2 values that complete the picture

Which blood values show a vitamin D deficiency?
Value	What it shows	Points here when
Calcium	The calcium economy vitamin D steers. Usually only abnormal in a long-standing deficiency.	abnormal
Corrected Calcium	The same calcium, corrected for the protein that carries it. The more honest of the two.	abnormal

The comprehensive test (€229, single test) measures the values on this page.
Every draw is fasted: nothing to eat or drink from midnight, only water. Appointments are therefore in the morning, until 12:00.
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Results within 24 hours of analysis, in the app.

What is a vitamin D deficiency?

Vitamin D is a hormone rather than a vitamin: the skin makes it itself, on sunlight, and the body converts it into a storage form that can be measured in the blood as 25-hydroxyvitamin D. That store regulates how much calcium the gut absorbs and how firm bone and muscle stay. Anyone who rarely goes outside, has a dark skin or wears covering clothing makes structurally less; above seventy the skin takes it easier anyway, and with excess weight part of the store disappears into the fat tissue. The diet covers the difference only in small part: oily fish, eggs and the margarine and low-fat spread to which it is added in the Netherlands. Above the fiftieth parallel, and all of the Netherlands lies there, the sun stands too low in the winter months for the skin to make anything, so the store you build up in summer has to last the winter. Reading the result asks two things most tables do not tell. First age: below 30 nmol/L it is a deficiency for everyone, but from 70 years below 50 already counts as a deficiency, because bones and muscles then need more. Second the season: the store is at its lowest at the end of winter and at its highest at the end of summer, so the same value means something different in March than in September.

What is a vitamin D deficiency confused with?

Each with the one value that tells the two apart.

Iron deficiency

Distinguishing value: Ferritin

The same tiredness, a different store. Ferritin points down the iron route; the 25-OH value down the vitamin D route. They do not exclude each other and are often measured together.

Underactive thyroid

Distinguishing value: TSH

Tiredness, muscle complaints and low mood here too. TSH keeps the two apart: it belongs to the thyroid and does not move with vitamin D.

Anaemia

Distinguishing value: Hemoglobin

Tiredness with paleness fits a low haemoglobin sooner than a low vitamin D. The blood count decides.

Frequently asked questions

Below 30 nmol/L it is a deficiency for everyone, and from 70 years the bar shifts and below 50 already counts as a deficiency, because bones and muscles then need more. In between the store is called insufficient: no alarm, but the range in which a daily supplement makes sense. Above 50 everyone is fine.

Sources 6

1.Gezondheidsraad, Evaluation of dietary reference values for vitamin D. 2012. gezondheidsraad.nl
2.Voedingscentrum, Vitamin D. 2026. voedingscentrum.nl
3.Huisarts & Wetenschap, Insufficient evidence that vitamin D helps with fatigue. 2019. henw.org
4.Huisarts & Wetenschap, Vitamin D supplementation in older adults has no effect on depression. 2019. henw.org
5.Thuisarts.nl (NHG), Do I need extra vitamin D?. 2026. thuisarts.nl
6.Bhan et al., osteomalacia as a result of vitamin D deficiency, Endocrinology and Metabolism Clinics of North America. 2010. pubmed.ncbi.nlm.nih.gov

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This page explains what a result means. It is not a diagnosis and not treatment advice. Discuss complaints or an abnormal value with your doctor.

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