What is 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 from October to March 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.
Which blood values show vitamin D deficiency?
Every value below has its own page with the reference ranges of four Dutch labs.
| 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 |
| 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 |
What are the symptoms of vitamin D deficiency?
These complaints are described for vitamin D deficiency in guidelines and research. None of them is exclusive to it: the same complaints fit many other explanations, and an abnormal value can exist without any of them.
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.
- Muscle weakness or muscle pain, mostly in the upper legsin the guideline
Only with a severe, long-standing deficiency; in older people it comes with a higher risk of falls.
Also described at underactive thyroid, low testosterone.
- Bone pain or tender bonesin the guideline
Equally a complaint of a severe, long-standing deficiency (osteomalacia), not of a mild dip.
Often named, not confirmed
You will run into these links everywhere. We list them deliberately, with what the research does show.
- Tirednessnot confirmed
Attributed to vitamin D everywhere, but supplementation trials show no consistent effect on fatigue. For GPs, tiredness is accordingly no reason to test vitamin D.
- Low mood in the winter monthsnot confirmed
In the Dutch D-Vitaal trial, a year of supplementation had no effect on depressive complaints. For winter blues, light therapy is what has the evidence.
A complaint points in more than one direction, and a measurement explains no complaint: blood testing shows where your values stand, the reading and the diagnosis belong with your GP. The complaint list follows the Dutch Health Council and the Netherlands Nutrition Centre; the unconfirmed links follow trial reviews in the Dutch GP journal Huisarts & Wetenschap.
What causes vitamin D deficiency?
Too little sunlight
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
What is vitamin D deficiency confused with?
Each with the one value that tells the two apart.
Iron deficiency
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.
Distinguishing value: Ferritin
Underactive thyroid
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.
Distinguishing value: TSH
Anaemia
Tiredness with paleness fits a low haemoglobin sooner than a low vitamin D. The blood count decides.
Distinguishing value: Hemoglobin
What you do about vitamin D deficiency
Go outside: a quarter to half an hour of daylight on face and arms between April and September is enough to build up the store, without burning. Eat oily fish twice a week, herring, mackerel, salmon or sardines, and use low-fat spread or margarine, to which vitamin D is added in the Netherlands. Anyone with belly fat sees the value rise on losing weight, because the store is then released from the fat tissue. From October to March the skin makes nothing in the Netherlands, and then a small daily supplement is the simplest way not to fall: 10 micrograms a day for anyone who rarely goes outside, has a dark skin or wears covering clothing, and 20 micrograms from 70 years; pregnant women and young children fall under that all year round. With a measured deficiency a higher dose for a few months is the way, after which the ordinary dose keeps it up. More is not better: above 250 nmol/L calcium can start to deposit, and you only get there with high doses for years. Measure again after three to four months, in the same season if you want to compare, because the storage form moves slowly. A value that does not rise despite taking it means the dose is too low or the gut is not absorbing it.
From which vitamin D does a lab call it low?
This is what the four largest Dutch labs publish themselves, side by side.
50 – 130nmol/L
Between 30 and 50 and between 130 and 250 it depends on the lab, because each sets its limits on its own method and population. Above 250 every lab calls it abnormal.
every lab calls 50 – 130 nmol/L normal. Between 30 and 50 and between 130 and 250 it depends on the lab.
Every age group per lab
| Lab | Group | Reference range |
|---|---|---|
| Unilabs(Saltro, Medlon, SHO, Atalmedial)2026 | All ages | 30–130 nmol/L |
| Star-shl2026 | All ages | 50–150 nmol/L |
| Certe2026 | All ages | 50–250 nmol/L |
| Clinical Diagnostics2026 | All ages | 50–250 nmol/L |
How to get vitamin D deficiency measured
- Fasting
- No fasting needed. Time of day makes no difference to 25-OH vitamin D.
- Material
- Venous blood, drawn at one of our collection points.
- Results
- Results within 24 hours of analysis, in the app.
- Referral
- No referral from a GP required.
- Which test
- The comprehensive test (€229, single test) measures the values on this page.
- Where to draw
- You can draw at 250+ locations near you, no referral needed. See the locations
Frequently asked questions
From which vitamin D value is there a deficiency?
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, and around 75 is often held as optimal.
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 three to four 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.
Sources
- 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
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.
Read about our scientific approach