Vitamin B12 daily requirement: 2.5 µg NRV, 4 µg reference
Futures Nutrition Editorial Team · 12 August 2026
Vitamin B12 daily requirement: 2.5 µg NRV, 4 µg reference
The short answer: the reference value for adults is 4.0 µg a day. The 2.5 µg printed on every pack are something else — a labelling figure, not a requirement. And the 1,000 µg in a high-dose tablet are something else again: a calculation based on absorption in the gut, not a statement about how much the body needs.
Three numbers, three meanings, and all three appear on the same tin. That is why the percentage on the back looks so puzzling: 1,000 µg correspond to 40,000 % of the nutrient reference value. Anyone who reads that as an overdose is misreading the figure — and so is anyone who reads it as a 400-fold effect.
Three numbers that do not mean the same thing
| Value | Amount per day | What it states | Source |
|---|---|---|---|
| Nutrient reference value (NRV) | 2.5 µg | the arithmetic basis for the percentage on the label | Regulation (EU) No 1169/2011, Annex XIII |
| Estimated value for an adequate intake | 4.0 µg | the reference value for adults in Germany | D-A-CH / German Nutrition Society (DGE), 2018 |
| Adequate Intake (AI) | 4.0 µg | the same value at European level | EFSA (2015) |
| Proposed maximum amount per daily portion | 25 µg | a recommendation to the legislator for food supplements | German Federal Institute for Risk Assessment (BfR), 2021 |
| Tolerable Upper Intake Level (UL) | not derived | there was no threshold from which one could be derived | Scientific Committee on Food (SCF), 2000 |
The most important point in this table: between the first and the second row there is no contradiction, only a difference in purpose. The 2.5 µg are a labelling figure for the whole of Europe; the 4.0 µg are the value that dietary advice in Germany is oriented towards.
Why the pack says 2.5 µg
The nutrient reference value is an arithmetic quantity defined by the food information regulation. It exists so that 1.25 µg of vitamin B12 on a pack can be expressed as 50 % NRV — uniformly across Europe, so that declarations stay comparable. It is deliberately set low and comes from an older derivation; national reference values have risen since.
The value has a second, practical function as well. A nutrient may only be advertised on a food at all if a certain amount of it is present: at least 15 % of the NRV in solid foods, 7.5 % in beverages. For vitamin B12 that means 0.38 µg per portion and 0.19 µg respectively — the BfR sets this out explicitly in its opinion on maximum amounts. Below that threshold a manufacturer may not advertise the vitamin, even if traces are present.
The reference value by stage of life
The German Nutrition Society revised its vitamin B12 chapter completely in 2018 and raised the value for adults from 3.0 to 4.0 µg. It is an estimated value for an adequate intake — not a recommended intake in the narrower sense. The difference is not hair-splitting: for a recommendation you would need to know the average requirement, and even EFSA could not determine it from the available data. Both bodies therefore took the detour via blood markers: at 4 µg a day, cobalamin, holotranscobalamin, methylmalonic acid and homocysteine lie within the expected range in adults.
| Age group | Estimated value (DGE) | Adequate Intake (EFSA) |
|---|---|---|
| 4 to under 7 years | 2.0 µg | 1.5 µg |
| 7 to under 10 years | 2.5 µg | 2.5 µg |
| 10 to under 13 years | 3.5 µg | 3.5 µg |
| 13 to under 15 years | 4.0 µg | 3.5 µg |
| from 15 years, adults | 4.0 µg | 4.0 µg |
| pregnant women | 4.5 µg | 4.5 µg |
| breastfeeding women | 5.5 µg | 5.0 µg |
The small deviations between the columns are not a disagreement about the requirement but a consequence of different calculation routes for children: EFSA scales down from the adult value to metabolically active body mass and adds a growth factor on top.
What the diet actually delivers
Here lies the second common misconception: that 4 µg would be a hard amount to reach. For everyone who eats animal foods, it is not. The German National Nutrition Survey II measured a mean intake in people aged 14 and over of between 5.5 and 6.0 µg a day in men and between 3.7 and 4.0 µg in women; at the upper end (95th percentile) it was 7.7 to 13.5 µg depending on age and sex. EFSA reports average values of between 4.2 and 8.6 µg a day for adults in several EU countries. How such daily totals add up out of single portions — an egg, a slice of cheese, a piece of fish — is worked through with example days in vitamin B12 foods.
The BfR draws a clear conclusion from this: the reference values are reached in Germany in all age groups and in part clearly exceeded; supply in the healthy general population is secured. Supplementation is therefore not a rule but an answer to a particular situation — and the most common one of those is doing without animal foods. Anyone eating a vegan diet takes in hardly any vitamin B12 from conventional food; the BfR expressly lists this group as a vulnerable population group.
Why the tablet holds 1,000 µg
The jump from 4 µg to 1,000 µg looks absurd until you know how absorption works. Vitamin B12 is not simply let through the wall of the small intestine but ferried across by a carrier: intrinsic factor, a protein from the gastric mucosa. This route has a fixed capacity. The Scientific Committee on Food describes it like this: the receptors in the ileum are saturated at roughly 1.5 to 2.5 µg of vitamin B12 per meal. Anything above that the active route can no longer transport.
What remains is passive diffusion — plain migration through the intestinal wall, without a carrier. It works at any dose, but very poorly: around 1 % of the amount supplied. That turns the arithmetic around. The percentage share falls as the dose rises; the absolute amount rises all the same.
| Amount supplied | Share that is absorbed | gives roughly |
|---|---|---|
| 1 µg | around 50 % | 0.5 µg |
| 25 µg | around 5 % | 1.25 µg |
| 1,000 µg | around 1 % (calculated) | 10 µg via passive diffusion |
The first two rows come straight from the SCF opinion. The third is an extrapolation using the one-percent figure and not a measurement — on top of it come the roughly 1.5 µg contributed by the saturated active route. Roughly calculated, then, some 11 to 12 µg out of a 1,000 µg tablet end up in the body. That is the answer to the 40,000 %: the figure describes the content of the tablet, not what arrives.
That is exactly what a high-dose tablet is designed for — a small percentage of a large number. One tablet a day, 1,000 µg as methylcobalamin: vitamin B12 1000 µg, 180 tablets.
The chemical form changes nothing about this calculation: the passive route does not distinguish between cyano-, methyl-, hydroxo- and adenosylcobalamin. Where they actually do differ — shelf life, light sensitivity, the residue on the cobalt atom — is set out in vitamin B12 forms compared.
The store that lasts for years
Vitamin B12 is water-soluble but does not behave that way. The body holds a reserve of 2 to 3 mg, mostly in the liver — a thousand times a daily amount. And it gives up only 0.1 to 0.2 % of that per day, regardless of how large the reserve currently is. From these two figures follows perhaps the most important practical consequence: a full store carries over years, and a change of diet correspondingly shows up in blood values late.
But the opposite follows too: an intake that is too low over months does not stand out, because nothing hurts. The store is a buffer zone, not an all-clear signal. Conversely, an emptied reserve takes a correspondingly long time to fill again.
EFSA once calculated backwards from these losses as well: 2 to 3 mg of stores, 0.1 to 0.2 % loss per day, an assumed absorption rate of 40 % — that would give a requirement of between 5 and 15 µg a day. It expressly rejected this route because the range is too wide. It nevertheless shows how blurred the question of how much do I need actually is scientifically.
Who lies above the reference value
The reference value applies to healthy adults with intact absorption. Several groups lie systematically above it — not because their requirement at the cell is different, but because less arrives along the way:
- People living vegan. Without animal foods practically no source remains in conventional food. Fortified foods or a preparation are the rule here, not the exception.
- Older people. Gastric acid production declines with age, and without it B12 is released less well from the protein of food. The SCF refers to studies according to which availability from food falls while that from synthetic B12 remains unchanged — which is precisely why high-dose preparations are widespread in this group.
- People with impaired absorption in the gastrointestinal tract. If intrinsic factor is missing or the small intestine is affected, the active route no longer helps; whether and how supplementation happens is then decided by a doctor, not by the shelf.
- Pregnant and breastfeeding women. Here the reference value itself is higher, because foetal tissue is being built and breast milk formed.
For an overview of strengths and forms, everything stands side by side in the vitamin B12 category. And because vitamin B12 and folate work in the same metabolic step, folic acid preparations almost always stand alongside in consultations.
The same percentage, a different nutrient: iron
Once you have kept the three numbers for vitamin B12 apart, you quickly carry that reading over to the whole pack — and iron is exactly where the comparison pays off. Because the first half of the story repeats exactly, while the second half is reversed.
The first half: with iron too, the label figure lies below the reference value. The nutrient reference value is 14 mg (Regulation (EU) No 1169/2011, Annex XIII), while the DGE revised its reference values for iron in 2024 and gives 16 mg a day for menstruating women, 14 mg for postmenopausal women, 11 mg for men from 19 years, 27 mg during pregnancy and 16 mg after birth. As with B12, label figure and requirement are two different things.
The second half runs differently. For vitamin B12 the SCF found no threshold for adverse effects — for iron there is one. The US Institute of Medicine set a LOAEL of 60 mg a day for adverse gastrointestinal effects and derived from it a Tolerable Upper Intake Level of 45 mg for adolescents from 14 years and adults. EFSA itself derived no UL in 2004, though for a different reason than with B12: not because nothing was to be found, but because no dose-response relationship could be derived for the long-term risks of high iron stores under discussion.
| Vitamin B12 | Iron | |
|---|---|---|
| Nutrient reference value (label) | 2.5 µg | 14 mg |
| Reference value adults (DGE) | 4.0 µg | 11 mg (m) / 16 mg (f, menstruating) |
| Tolerable Upper Intake Level | not derived (SCF 2000) | 45 mg (IoM); EFSA 2004 none |
| BfR proposal per daily portion | 25 µg | 6 mg |
The BfR uses the same calculation route as with B12, only with different figures: from the IoM's UL (45 mg) the institute subtracts the 95th intake percentile of women from the German National Nutrition Survey II (20 mg), allocates half of the remainder to food supplements (12.5 mg) and applies an uncertainty factor of 2 — which makes 6 mg per recommended daily intake. In addition the BfR recommends a warning notice on iron-containing preparations: men, postmenopausal women and pregnant women should take iron only after consulting a doctor, because in them the risk of adverse effects from high iron stores is increased. For vitamin B12 there is no comparable recommendation — and that is the real difference behind the two percentages.
This becomes practical for the same group already discussed above. Alongside pregnant and menstruating women, the DGE expressly names vegetarians and people living vegan as those who should pay attention to a sufficient iron intake: iron from plant foods is trivalent and utilised less well than the divalent iron from animal foods; phytates from wholegrain and pulses as well as polyphenols from coffee and black tea inhibit absorption further, while vitamin C improves it. Anyone thinking about B12 for that reason almost inevitably ends up at the second question too.
Our iron 30 mg + inulin contains iron fumarate — a water-soluble compound that is markedly better available than the largely inert elemental iron in fortified breakfast cereals — plus inulin from chicory root, 180 tablets at one a day. The 30 mg correspond to 214 % of the nutrient reference value and thus lie clearly above the BfR proposal of 6 mg; who that matters for is set out in the paragraph above. Further strengths and combinations are listed in the iron category.
Among the claims authorised for iron are these: Iron contributes to normal formation of red blood cells and haemoglobin. Iron contributes to normal oxygen transport in the body. Iron contributes to the reduction of tiredness and fatigue. (Regulation (EU) No 432/2012). The third claim exists for vitamin B12 as well — but it says nothing about which of the two substances is lacking in an individual case.
How much is too much
For vitamin B12 no Tolerable Upper Intake Level has been derived. The reason is sober: in 2000 the SCF found no clearly defined adverse effects from which a threshold could have been derived — neither from foods nor from preparations in amounts far above the requirement.
There is a figure all the same, and how it was arrived at is instructive. The BfR proposes 25 µg per recommended daily intake of a food supplement. The starting point is consumption data according to which 100 µg a day were taken from supplements without known adverse effects. The BfR allocates half of these 100 µg to food supplements and half to fortified foods and, because of possible multiple intake from different products, applies an uncertainty factor of 2 — 100 → 50 → 25.
Two things belong with that. First, this is a proposal to the legislator, not a maximum amount in force; binding upper limits for vitamins in food supplements do not so far exist in Germany. Second, the factor of 2 is not a safety margin against a known hazard but against the absence of data and against the possibility of taking several preparations at once. Anyone who knows this can place a 1,000 µg tablet correctly: it lies far above the proposal and below any observed effect threshold.
Among the claims authorised for vitamin B12 are these: Vitamin B12 contributes to normal energy-yielding metabolism. Vitamin B12 contributes to normal functioning of the nervous system. Vitamin B12 contributes to normal red blood cell formation. Vitamin B12 contributes to the reduction of tiredness and fatigue. (Regulation (EU) No 432/2012). Food supplements are not a substitute for a balanced and varied diet and a healthy lifestyle.
Frequently asked questions
How much vitamin B12 do I need a day? For adults from 15 years, the DGE and EFSA agree on 4.0 µg a day, for pregnant women 4.5 µg, for breastfeeding women 5.0 to 5.5 µg. The 2.5 µg on the label are not the requirement but the basis for the percentage.
Are 1,000 µg in one tablet an overdose? By amount supplied: yes, far above the BfR proposal of 25 µg per daily portion. By effect: in 2000 the SCF could not determine a threshold for adverse effects and therefore derived no Tolerable Upper Intake Level. The high figure follows from absorption: from about 1.5 to 2.5 µg per meal the active route is saturated, above which only around 1 % passes passively through the intestinal wall.
Why does the pack say 40,000 %? Because 1,000 µg divided by the reference value of 2.5 µg gives exactly that. The declaration is prescribed and arithmetically correct — it simply says nothing about how much of it arrives in the body.
Is a balanced diet enough? For people who eat animal foods, as a rule yes: measured intake in Germany averages 3.7 to 6.0 µg a day. Without animal foods it lies close to zero — and then the way leads via fortified foods or a preparation.
Does the logic of a high percentage yet still harmless apply to other nutrients too? No, and iron is the nearest counter-example. For vitamin B12 the SCF could not determine a threshold for adverse effects; for iron there are two concrete figures, the Tolerable Upper Intake Level of 45 mg (IoM) and the BfR proposal of 6 mg per daily portion, plus the recommendation of a warning notice for men, postmenopausal women and pregnant women. The percentage on the label says nothing about either — it merely divides by the reference value.
How quickly do you notice an intake that is too low? Usually not at all for years. The body holds 2 to 3 mg in reserve and gives up only 0.1 to 0.2 % of it per day. That is why a change of diet only shows up in blood values late — and why prevention here is not a matter of weeks.
