Normal vitamin D levels:
what the number on your 25(OH)D test means
Normal vitamin D levels: if you have your lab report in front of you and a number underlined in red, let's start with the part that confuses everyone. The reference range printed there isn't a law of nature. It's a convention, and laboratories in Romania usually use a stricter one than the threshold on which European intake recommendations are based.
Why your report says low
at 28 ng/ml
Laboratories in Romania usually report a reference range of 30 to 100 ng/ml for 25(OH)D, with severe deficiency below 10, deficiency below 20 and relative insufficiency between 20 and 29. So at 28 you get the asterisk. Below the threshold. Red.
Except that the threshold of 30 doesn't come from the authority that sets intakes in the European Union. It comes from a professional society's position statement, widely adopted by laboratories because it was the most cautious option available at the time.
EFSA, in its 2016 opinion on dietary reference values for vitamin D, says something else in black and white: a serum 25(OH)D concentration of 50 nmol/l is a suitable target value for all population groups. 50 nmol/l means 20 ng/ml. Not 30.
And in 2024, the very professional society the threshold of 30 came from took a step back. Its guideline that year states that, given insufficient evidence, the panel could not establish specific 25(OH)D thresholds, either for adequacy or as targets for disease prevention.
So, to be precise: at 28 ng/ml you don't have a disease. You have a number that falls between two conventions, one of which has since been withdrawn by the very people who proposed it.
A reference range tells you where you stand relative to the convention that laboratory has chosen, not how healthy you are. When you compare two test results, look first at the threshold printed on each report, not just at the colour of the number.
ng/ml or nmol/l,
the same value in two outfits
Half the confusion on the internet comes from here. Lab reports in Romania usually use nanograms per millilitre, ng/ml. European literature and many foreign articles use nanomoles per litre, nmol/l.
The conversion is a single multiplication: 1 ng/ml equals 2.5 nmol/l. To go the other way, divide by 2.5.
- 12 ng/ml is 30 nmol/l
- 20 ng/ml is 50 nmol/l, exactly the EFSA threshold
- 30 ng/ml is 75 nmol/l
- 40 ng/ml is 100 nmol/l
That's why you panic for nothing when you read a foreign guideline talking about values below 50 while your report says 24. The two numbers can't be compared directly.
The thresholds, side by side,
and who set them
There's no single number everyone agrees on. There are different sources, with different reasoning, and your report uses just one of them without telling you which.
| Source | What it considers sufficient | What else it says |
|---|---|---|
| EFSA, 2016 opinion | 50 nmol/l which is 20 ng/ml | Target value for all population groups. Adequate intake of 15 µg a day for children over one year and for adults, including during pregnancy and breastfeeding, and 10 µg for infants aged 7 to 11 months. |
| Laboratories in Romania, typically | 30 ng/ml which is 75 nmol/l | Reference range often printed: 30 to 100 ng/ml. Below 10 severe deficiency, below 20 deficiency, between 20 and 29 relative insufficiency. |
| The Romanian guideline for assessing vitamin D status in adults | above 20 ng/ml | Does not recommend screening for deficiency in the general population of asymptomatic adults. For adults without increased risk, it discusses an intake of 600 to 1,000 IU during the cold season, without measuring serum levels. |
| The 2024 professional society guideline | does not set one | Suggests against routine 25(OH)D testing and states that the evidence did not allow an adequacy threshold to be set. |
What emerges if you read all four: there is reasonable consensus around 20 ng/ml. Above 20, the discussion becomes about preferences, not evidence.
Enter your value
and see what each threshold says
Move the slider to the number on your lab report. It isn't a diagnosis and it doesn't replace your doctor; it's just a translation of the same value into the two languages in circulation.
Who actually has a reason
to get this test
This is where it will seem as if we're arguing against our own interest, and that's more or less the case. The vitamin D test is among the most requested in Romania, and the guidelines say fairly clearly that it isn't worthwhile for everyone.
The Romanian guideline for assessing vitamin D status in adults is explicit: screening for deficiency is not recommended in the general population of asymptomatic adults. The 2024 professional society guideline goes further and suggests against routine testing, because no benefits linked to a particular value could be identified.
So what's left? The test makes sense when there's a concrete medical reason, and that reason is established by your doctor, not by a blog post. The 2024 guideline separately discusses a higher than standard intake for four groups: children and adolescents, adults over 75, pregnant women and people with prediabetes. These are medical situations, not shelf recommendations.
If you're a healthy adult, between 25 and 40, who simply wants to get through the cold season more easily, you have a simpler option than the test: a reasonable intake, within the range the guidelines discuss for the cold season anyway, without turning it into a project.
What to do next,
in three scenarios
Five things people say
about this test
Low values are common at our latitude, especially in the cold months, when the angle of the sun greatly reduces synthesis in the skin. But the round percentages circulating in adverts, like 90 per cent, are usually quoted without a source. What's verifiable is the mechanism, not the percentage.
Reserves fall over the cold season, and the rate varies a lot from person to person. That's why a test in February and one in August, in the same person, can look completely different. When you compare two results, first look at which month the samples were taken in.
EFSA set a tolerable upper intake level of 100 µg a day, which is 4,000 IU, for adults and adolescents, and reconfirmed it in 2023. Above that limit, no extra benefit follows; you enter a zone where the risk rises without you gaining anything.
25(OH)D moves slowly. The Romanian guideline talks about reassessment after 3 to 4 months in severe deficiency, then annually if risk factors persist, and says that retesting is not normally needed in a person who is asymptomatic and consistent with treatment. Not every two weeks.
It means you're below the threshold chosen by that laboratory. As you saw in the table, two laboratories can print different thresholds for exactly the same sample. What the number means for you, with your history and context, is for your doctor to say.
When to retest,
and why not in two weeks
Vitamin D isn't blood glucose. 25(OH)D is the storage form; it changes over weeks and months, not from one day to the next. A retest after two weeks mostly shows you the noise of the laboratory method, not the effect of what you're doing.
The Romanian guideline for adults is fairly practical here: in severe deficiency, reassessment after 3 to 4 months, then annually if risk factors remain. In a person who is asymptomatic and consistent with treatment, retesting is not normally needed.
A detail that often gets lost: if you want to compare two values, have the samples taken at the same time of year and, as far as possible, at the same laboratory. Otherwise you're comparing two conventions and two seasons, not two states.
Before you increase the dose. The tolerable upper intake level set by EFSA for adults and adolescents is 100 µg a day, which is 4,000 IU, from all sources combined. Don't exceed it on your own. High doses, loading regimens and supplementation during pregnancy, breastfeeding or in children are decided by a doctor. If you have kidney problems, high calcium levels or are on long-term treatment, ask your doctor before starting any vitamin D supplement.
What a D3 gummy does
and doesn't do
Because we sell vitamin D3 gummies, it's only fair to say exactly where things stop, especially after a whole article about thresholds and conventions.
What any manufacturer in the European Union can legally say about vitamin D3, because these are authorised claims: it contributes to the normal function of the immune system, to the maintenance of normal muscle function and to normal absorption/utilisation of calcium and phosphorus. That's it. No “strengthens”, no “prevents”, no stories about 200 genes.
What a gummy doesn't do: it doesn't tell you what your value is. It doesn't replace the test, it doesn't replace your doctor and it doesn't make up for a real medical reason why a value stays low.
Something to know before you buy anything. Our gummies contain 4,000 IU per serving of two gummies, which is 100 µg. That is exactly the tolerable upper intake level set by EFSA, not a maintenance dose for everyone. The adequate intake for an adult, again according to EFSA, is 15 µg a day, which is 600 IU. If you don't have a reason, a documented low value or your doctor's recommendation, the high dose gives you nothing extra compared with a modest one. We'd rather you knew this before you buy, not after.
Frequently asked questions
Comments (0)
There are no comments for this article. Be the first one to leave a message!