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Vitamins

What your vitamin D levels mean

Your vitamin D level tells you how much vitamin D your body has in store, and that number depends heavily on the month your blood was drawn. September is your yearly high, late March your yearly low, with nothing about your health having changed in between. From October to March the sun sits too low over the Netherlands for skin production, so you live off what you built up in summer. One result on its own therefore says less than you would think, and two results say something only if you know both months.

Doctor's Assessment Included

When is this value abnormal?

See the value that applies to you:

Choose male or female — this range differs by sex.

Enter your age — this range changes with age.

This range also depends on context such as cycle phase or sample material; the highlighted rows apply to your group.

up to 69 years Your group

Decision limits per result, in nmol/l
Result Value (nmol/l)
Deficiency < 30
Sufficient ≥ 30

70 years and older Your group

Decision limits per result, in nmol/l
Result Value (nmol/l)
Severe deficiency < 35
Deficiency 35–50
Sufficient ≥ 50

Dutch guidelines disagree on this limit. The Dutch National Health Care Institute (Zorginstituut) concluded in 2022 that there is no single agreed limit for vitamin D deficiency. We follow the Health Council of the Netherlands (Gezondheidsraad), the NHG and the Farmacotherapeutisch Kompas. The NVKC uses 50 nmol/l for everyone; the osteoporosis guideline uses 50 nmol/l when fracture risk is raised.

Source: Gezondheidsraad Reference population: Dutch population (Health Council of the Netherlands 2012)

Source: Zorginstituut Nederland Reference population: Dutch population (Health Council of the Netherlands 2012)

Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.

Vitamin D (25-OH): what this test measures

What you are measuring is 25-hydroxyvitamin D, 25-OH-D for short, reported in nmol/l. Think of it as the level in your storage tank rather than what you took in yesterday: its half-life is two to three weeks, so the result covers roughly the past few months and lags behind your summer and behind your winter.

There is also an active form, 1,25-dihydroxyvitamin D, and it is deliberately not measured here. It clears from your blood within hours and parathyroid hormone, the hormone from your parathyroid glands that regulates your calcium, keeps it tightly regulated. Your body steps up the conversion when the tank is nearly empty, so a normal or even raised active value does not rule out a shortage. That is why it is the wrong test when a shortage is suspected.

Your report should give total 25-OH-D, meaning D2 and D3 together. If you use a plant-based D2 supplement, say so, because not every immunoassay picks up D2 fully.

The lab prints a reference range of 50 to 150 nmol/l next to your result. The Dutch Health Council uses a different yardstick: no range, but a floor you must meet all year round, 30 nmol/l until you turn seventy and 50 nmol/l after that. If you sit between 30 and 50, the lab therefore flags you as low while the Health Council calls you sufficient under seventy. What that means for you is a conversation with your GP.

Vitamin D (25-OH): why this value matters

What vitamin D does explains the rest: it lets you absorb calcium and phosphate from your food. Once your stores run down, you take up less calcium, parathyroid hormone rises and your body pulls calcium out of your bones to cover the shortfall in your blood. So the reading is judged against your skeleton rather than against how you feel.

The Dutch Health Council works with a floor rather than a single normal value. Until you turn seventy that floor is 30 nmol/l, all year round: below it is a deficiency, above it is sufficient. From seventy that line moves up to 50 nmol/l, and the Farmacotherapeutisch Kompas calls anything below 35 nmol/l at that age a severe deficiency. The Health Council names no target above that floor, so higher is not something to aim for here.

The lab also prints its own range of 50 to 150 nmol/l, so between 30 and 50 the two yardsticks diverge. Always read both limits next to your result, and never read the number on its own: calcium, phosphate and PTH finish the picture. If PTH is raised while your 25-OH-D is low, that is called secondary hyperparathyroidism, and it outweighs the vitamin D figure alone.

Vitamin D (25-OH): how the blood test works

Referral
No GP referral needed. After the order we arrange the referral through ZorgDomein, within one business day; orders after 17:00 or at the weekend start on the next business day. ZorgDomein emails a barcode, and that barcode is what the draw site needs.
The draw
A blood draw from a vein in the arm, at a partner laboratory's draw site. No home kit, no finger prick.
Which test
on its own €35,- Vitamin D Test · €70,- · InsideTracker Inflammation · €139,- · Basic Health Checkup · €104,- · Vegetarian · €161,-
Where
650+ draw sites run by independent laboratories across the Netherlands. Draw sites

Vitamin D (25-OH): when is testing worthwhile?

Test when you have complaints that fit a deficiency, such as heavy thighs, difficulty standing up, or bone pain. Test too if you get outdoors little, have darker skin, or wear covering clothing, because the odds of a low value are higher then.

Above all, watch the month. In September you sit at your highest point of the year and in February and March at your lowest, so if you want to put two results side by side, pick the same month. Otherwise you are comparing seasons. You do not need to fast and the time of day does not matter; the result is back within about 72 hours.

Vitamin D (25-OH): symptoms of a high or low value

Low Levels

The awkward part is that low stores usually do not feel like anything. When you do notice something, it is rarely recognisable: strength draining out of your thighs and hips, a struggle to get up from a low chair, stairs that start to feel heavier, nagging bone and muscle pain and a slightly unsteady walk. If a deep shortage lasts, new bone tissue mineralises poorly; in adults that is called osteomalacia, in children rickets, and both bring bone pain and deformity.

In older people a low value often goes with weak muscles and more falls, which raises the chance of a fracture. All of these fit dozens of other explanations, and that is why the number starts the conversation rather than the feeling.

High Levels

The sun will not give you a high value, because your skin stops making vitamin D once it has enough. If your result is high, it almost always comes out of a supplement. Real toxicity with calcium climbing too high is seen in the literature only around 250 nmol/l, and then after months of taking far too much; the lab prints 150 nmol/l as its upper limit.

A second route matters more. In some lymphomas and in granulomatous conditions such as sarcoidosis and tuberculosis, macrophages make the active form themselves, and the normal brake does not apply there. Your calcium can then run high while your 25-OH-D looks perfectly ordinary. If calcium and vitamin D are both on the high side, call your doctor before you change anything about your supplements.

Vitamin D (25-OH): what to do about an abnormal value

Male

If Low

Low vitamin D may cause fatigue, muscle weakness, and bone pain. Consider 2000-5000 IU daily supplementation and increase sun exposure.

If High

High vitamin D may indicate excessive supplementation. Reduce supplement dose and retest in 3 months.

Female

If Low

Low vitamin D may cause fatigue, muscle weakness, and bone pain. Consider 2000-5000 IU daily supplementation and increase sun exposure.

If High

High vitamin D may indicate excessive supplementation. Reduce supplement dose and retest in 3 months.

Vitamin D (25-OH): lifestyle and this value

The Netherlands sits at about 52 degrees north. Between early October and late March too little UVB of 290 to 315 nanometres gets through and your skin cannot get to work, so you live off what you built up between June and August: your level peaks around September and bottoms out in March.

Only compare two results if you know both months. Going from 78 nmol/l in September to 44 nmol/l in March is the ordinary annual swing and no decline, while the same 44 nmol/l in August stands out, because August is when you should be at your peak.

You run lower with darker skin, because melanin soaks up UVB and you need more time outdoors. A lower result also fits with covering clothing, indoor work or night shifts, with obesity, because vitamin D stays behind in fat tissue and less remains in your blood, with older age, because your skin holds less of the precursor, with fat malabsorption and with enzyme-inducing drugs such as anticonvulsants and rifampicin, or glucocorticoids, which speed up breakdown.

The Dutch Health Council advises several groups to supplement: pregnant women, people with darker skin, those rarely outdoors and everyone over seventy. How much is a question for your doctor or the Voedingscentrum. If you take high-dose biotin, say so when your blood is drawn, because it can falsely raise some 25-OH-D assays.

Vitamin D (25-OH): frequently asked questions

What is a good vitamin D level?

The Dutch Health Council names a floor: until you turn seventy at least 30 nmol/l, all year round, and from seventy at least 50 nmol/l. It names no target above that, so higher is not a goal. The lab also prints 50 to 150 nmol/l as its own range; if you sit between 30 and 50, discuss with your GP which yardstick counts for you.

How low is too low for vitamin D?

Below 30 nmol/l is a deficiency until you turn seventy. If you are seventy or over, that line sits at 50 nmol/l, and anything below 35 nmol/l then counts as a severe deficiency. Falls and fractures weigh more heavily at that age. So the same number means something different at forty-five than at seventy-five.

What are the symptoms of vitamin D deficiency?

Often you notice nothing. If you do feel it, it sits in your thighs and hips: standing up or stairs takes effort. Bone and muscle pain occur too. Those complaints fit all sorts of things, so your result starts the conversation.

What is a normal vitamin D level in blood?

Your result is in nmol/l and covers 25-OH-D, the storage form. The lab prints 50 to 150 nmol/l as its reference range; the Dutch Health Council keeps 30 nmol/l as the floor until you turn seventy and 50 nmol/l after that. Also look at the month of your draw: if it was March a lower number is normal, and in September you are at your peak.

Vitamin D (25-OH): sources

  1. Gezondheidsraad. Evaluatie van de voedingsnormen voor vitamine D. Den Haag: Gezondheidsraad, 2012; publicatienr. 2012/15. Overgenomen in NHG LESA Laboratoriumdiagnostiek Vitamine D-deficiëntie (2018). (retrieved 2026) gezondheidsraad.nl
  2. Zorginstituut Nederland. Farmacotherapeutisch Kompas: vitamine D-deficiëntie bij ouderen. Geraadpleegd 14 juli 2026. (retrieved 2026) farmacotherapeutischkompas.nl

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Vitamin D (25-OH)

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