One of us has an eleven-year-old whose vitamin D dips now and then. Not dramatically, and not every time. Just often enough that we stopped guessing and started checking.
The short answer
- EFSA's reference figure is 15 µg a day from age 1 upwards. That number is useful, and it's less absolute than it looks.
- The tolerable upper limit is 50 µg a day from 1 to 10, and 100 µg from 11.
- The number on the label (%NRV) is based on 5 µg, a different and older figure. That's why a label can say "500%" without anything being wrong.
- If your child already takes vitamin D drops, add the two doses together before adding anything else.
Why the numbers don't line up
There are three different figures in circulation and they're easy to confuse.
The NRV, or nutrient reference value. This is the number used on labels across the EU. For vitamin D it's 5 µg. It's fixed in labelling law and it's not a health recommendation. It's a common ruler so that labels can be compared.
EFSA's adequate intake. The European Food Safety Authority sets 15 µg a day from age 1 through adulthood. An adequate intake is a population figure, not an individual requirement: it's derived assuming minimal sun exposure, and it's set to keep most of a population above a target blood level rather than to describe what any particular person needs.
The tolerable upper level. The safety ceiling for long-term daily intake.
So a label shouting 500% NRV is telling you 25 µg. Against an NRV of 5 µg that looks enormous. Against an adequate intake of 15 µg it's a little over one and a half times. The percentage is more alarming than the microgram.
What is recommended, by age
| Age | Adequate intake (EFSA) | In IU |
|---|---|---|
| 1 to 3 | 15 µg | 600 IU |
| 4 to 10 | 15 µg | 600 IU |
| 11 to 17 | 15 µg | 600 IU |
| Adults | 15 µg | 600 IU |
The figure doesn't change with age, and the reason for that matters more than the number does. It's not adjusted for body weight, which is unusual for a nutrient: a 15 kg five-year-old and a 90 kg adult sit on the same line. How much a given person makes from sunlight varies with latitude, season, skin tone and how much of them is covered, and none of that's in the number either.
Other expert bodies have landed on different figures from the same evidence, which tells you something about how settled this is.
Which is why the number that actually describes a person is a blood test rather than a chart. 25-hydroxyvitamin D is the measurement, a GP can order it, and it's the only way to replace an assumption with a fact.
Infants under 12 months are a separate case and aren't the subject of this article. In Ireland, vitamin D supplementation in the first year is guided by the HSE and your GP or public health nurse, and should not be decided from an article, including this one.
What counts as too much
| Age | Tolerable upper level | In IU |
|---|---|---|
| 1 to 10 | 50 µg | 2000 IU |
| 11 to 17 | 100 µg | 4000 IU |
| Adults | 100 µg | 4000 IU |
These ceilings apply to the daily total from all sources, not to any single product. This is where most mistakes happen, and almost never because of one supplement on its own.
The typical case: a five year old on prescribed vitamin D drops, plus a multivitamin, plus a fortified milk. Each product sits inside the limit. The total may not.
Converting µg to IU
Some labels use micrograms, others use international units. The conversion is fixed:
1 µg = 40 IU
So 15 µg is 600 IU, 25 µg is 1000 IU, and 50 µg is 2000 IU. If a label gives you one unit and your GP gives you the other, multiply or divide by 40.
What to do before you buy
- Read the micrograms, not the percentage. The percentage is measured against 5 µg, a labelling figure.
- Add up everything your child already takes. Drops, multivitamins, fortified foods.
- Compare against the ceiling for their age, not the adult one.
- If there's a medical prescription, it wins. An article doesn't replace the person who knows your child.
D2 or D3, and why there are two
Labels carry two forms.
D3, cholecalciferol. The form your skin makes from sunlight, and the one found in animal-source foods. It's what most supplements use, including ours.
D2, ergocalciferol. Plant-derived, made from fungi exposed to ultraviolet light. It's the usual choice in certified vegan products.
If a label says only "vitamin D" without specifying, the form is in the ingredients list. It's not hidden, it's just rarely highlighted.
What a blood test actually measures
The value on a blood test is called 25-hydroxyvitamin D, sometimes written 25-OH-D. It's the storage form, and it's the one used because it reflects what is held in reserve rather than what was swallowed that morning.
Two things to know before you look at a result.
Reference ranges vary between laboratories and between countries, so the same number can be flagged differently depending on who is reading it. A result is interpreted with the person who ordered it.
It's not a routine test for a healthy child. It's done when there's a clinical reason. If you're thinking of requesting one out of curiosity, that's a conversation to have with your GP first rather than afterwards.
Sun and food: how much you get without a supplement
Sun. Skin makes vitamin D when exposed to UVB, and how much depends on latitude, season, time of day, cloud cover, clothing, sunscreen and skin tone. In Ireland the sun sits at an angle that produces very little UVB for roughly half the year, which is why the question comes up at all, and why Irish guidance on supplementation is more assertive than in southern Europe.
None of that's an argument for more sun exposure. Sun protection advice for children doesn't change because of vitamin D.
Food. There are few dietary sources and the contribution is modest: oily fish such as salmon, sardines and mackerel, egg yolk, and fortified foods including some cereals and plant drinks. A normal diet supplies a fraction of the 15 µg adequate intake.
Vitamin D and K2, which often appear together
Both are fat-soluble and they frequently sit in the same formula. Ours contains both: vitamin D3 and vitamin K2 as MK-7.
Precision matters here, because these two get muddled constantly. They are two nutrients with two different jobs. Vitamin D governs how much calcium is absorbed from food. Vitamin K activates the proteins that direct calcium into bone. Both contribute to the maintenance of normal bones, and they're doing different things when they do it. What advertising often implies, that pairing them multiplies the effect, runs ahead of the evidence: the trials comparing the pair against either alone are few and small.
The honest part about our own product
Pocket Kids Core, for ages 4 to 11, contains 25 µg of vitamin D per daily dose. That's 1000 IU, or 500% NRV.
It's above EFSA's reference figure and half the 50 µg ceiling for that age group. We chose that figure deliberately and it sits inside the safety margin. Two things we want to say out loud anyway.
If your child already takes vitamin D drops, don't simply add ours on top. Add the micrograms first. Two 400 IU drops plus our product comes to 1800 IU, which is still under the ceiling, but it's the kind of sum worth doing rather than assuming.
And if your child eats a varied diet, gets outside regularly and has no medical indication, it's entirely possible they need none of this. You should have that in front of you before you decide, not after.
Sources
- EFSA, dietary reference values
- EFSA, scientific opinion on the tolerable upper intake level for vitamin D, 2023
- Regulation (EU) No 1169/2011, Annex XIII
- HSE guidance on vitamin D for infants and children. Their site is being restructured, so no stable link yet
Written by Lina and Stanislava, founders of MyDailyPocket. This is here to be useful, not to replace your GP or paediatrician.
