Buying iron: price per day, not price per mg
Futures Nutrition Editorial Team · 12 August 2026
Buying iron: price per day, not price per mg
The short answer: with iron, the price per milligram rewards exactly the wrong thing. Anyone who holds two tins side by side and works out how many milligrams a euro buys inevitably ends up with the high-dose pack — and overlooks the fact that the body takes proportionally far less out of one large single dose than out of a small one. The figure that carries a purchase decision is the price per day at the intake stated on the pack.
Before that, however, comes a question no label answers: whether to supplement at all. Iron is the mineral the body cannot get rid of in a targeted way — which is why the German Nutrition Society (DGE) advises deliberate iron supplementation only after a medically diagnosed deficiency.
First the finding, then the basket
Iron deficiency is not a self-diagnosis. Tiredness, pallor and hair loss have many causes, and ferritin, the storage value, can be read in the blood but not in the mirror. Ferritin also rises during inflammation, so without an inflammatory marker such as CRP beside it a normal value says little. That is a question for a blood test, not for the shelf.
The second part of that preliminary question concerns the amount. The DGE reference value is 11 mg a day for men and 16 mg for menstruating women; next to it, the label carries the nutrient reference value of 14 mg, to which the percentage figure is tied (Regulation (EU) No 1169/2011, Annex XIII). Anyone who has settled these two points is comparing packs — before that, they are comparing numbers without a reference.
Why the price per milligram leads you astray
Iron absorption is limited, and not in a linear way. A paper in the journal Blood tested single doses from 40 to 240 mg of iron in 2015: six times the amount produced three times the absorbed quantity of iron in the end — 6.7 against 18.1 mg (PubMed 26289639). From 60 mg upwards, hepcidin also remained elevated for 24 hours and throttled absorption from the next dose. More milligrams on the tablet therefore mean less absorbed iron per milligram — the price per mg measures the amount printed on the label, not the amount that arrives.
In practice that means packs are comparable through the number of days they cover.
Price per day = pack price ÷ tablets per pack × tablets per day
Price per month = price per day × 30
Three invented but market-typical packs show how far the two figures diverge:
| Pack | Price | Tablets | Iron per day | Price per 100 mg of iron | Lasts | Price per month |
|---|---|---|---|---|---|---|
| A — “high dose” | €14.90 | 100 | 65 mg (1 tbl.) | €0.23 | 100 days | €4.47 |
| B — standard | €16.90 | 180 | 30 mg (1 tbl.) | €0.31 | 180 days | €2.82 |
| C — combination with vitamin C | €19.90 | 120 | 28 mg (2 tbl.) | €1.18 | 60 days | €9.95 |
On price per milligram, A beats B by around a quarter. On price per month, A costs a good half more than B — and delivers a single dose above the 60 mg threshold from the Blood study, the range that regularly produces the most gastrointestinal complaints in tolerability trials. Pack C fails for a third reason: “120 tablets” on the front is 60 days here, because two a day are intended.
Food supplement or medicine — two shelves, two legal frameworks
Iron tablets exist in both categories, and comparing prices across that border leads nowhere. A food supplement is legally a food: the manufacturer notifies the competent national authority — in Germany the Federal Office of Consumer Protection and Food Safety (BVL) — no examination of the ingredients or of their efficacy takes place before sale, and harmonised EU maximum levels for minerals in food supplements do not exist to this day.
A medicinal product goes through an authorisation procedure under Directive 2001/83/EC in which efficacy, safety and dosage are demonstrated and fixed; iron(II) preparations of this category carry an indication and are usually sold in pharmacies only — they are meant for a diagnosed deficiency, not for prevention. The 100 mg tablet from the pharmacy is therefore not a particularly good-value version of the 30 mg product from the shelf, but something else.
To place the amounts: the German Federal Institute for Risk Assessment (BfR) proposes 6 mg per daily portion of a food supplement to the legislator, EFSA names 40 mg per day as the safe level of intake from all sources together (EFSA Journal 2024;22(6):8819). The entire market moves between those two figures.
What counts on the label: mg of iron, not mg of compound
The nutrition table states “iron” with the milligram figure and the percentage of the reference value. Which compound sits behind it is revealed only by the list of ingredients — and there, the number on the front is sometimes that of the compound rather than of the element: 100 mg of ferrous gluconate is around 12 mg of iron. The difference between the forms and their iron shares is set out in Iron forms compared.
Two things deserve a second look here. First: only the iron sources from Annex II of Directive 2002/46/EC are admissible in the EU — nineteen of them in the consolidated version of 17 July 2024. Iron picolinate is not among them, although it is sold in non-EU shops. If it appears in the list of ingredients, the goods are not intended for this market. Second: “chelate” and “amino acid chelate” are advertising terms without defined content; what is capable of authorisation is the specific designation, ferrous bisglycinate for instance.
Additives: what changes something and what only lengthens the list
Vitamin C is the only additive with an authorised claim: Vitamin C increases iron absorption (Regulation (EU) No 432/2012). The effect is well documented in single-meal experiments — it just hardly pays off as a surcharge on the tablet. In a randomised trial with 440 adults with iron deficiency anaemia, haemoglobin rose by 2.00 g/dl after two weeks on iron plus 200 mg of vitamin C and by 1.84 g/dl on iron alone; the difference of 0.16 g/dl was not statistically confirmed (Li et al., JAMA Network Open 2020;3(11):e2023644). What vitamin C does achieve alongside a meal is set out in Iron absorption: vitamin C, coffee and tea — 40 g of raw pepper costs less than any combination surcharge.
Inulin appears in several preparations and is advertised with better absorption via the large intestine. The human trials that showed anything at all worked with 15 to 40 g of inulin or of a comparable prebiotic per day — amounts from the kitchen scale, not from a tablet, which carries milligrams of it.
Calcium and zinc in the same tablet are the additive that actively interferes: both inhibit iron absorption, which is why they belong in another half of the day and not in the same serving — as set out in Taking iron: fasting, in the morning, every other day. A multivitamin with 5 mg of iron next to calcium is therefore not an iron supplement but a multivitamin.
Folic acid and vitamin B12 make sense in combination when both are needed — but they are the most common reason for buying twice. Anyone who already has Folic acid 1000 µg or a B12 preparation in the cupboard covers the same gap a second time with a combination product.
Dosage form: “depot” is no advantage with iron
Iron is absorbed predominantly in the upper small intestine, in the duodenum and the adjoining jejunum. That is exactly where enteric-coated and sustained- release forms fail: they release the iron only once this section has been passed. This was measured in women with low iron stores who received the same amount once as an enteric-coated and once as an uncoated tablet — absorption was 3.5 against 12 per cent (Thankachan et al., Indian Journal of Medical Research 2020;151(4):371–374). A review in Haematologica summarises the evidence on this and advises against such preparations (Pantopoulos, 2024;109(9):2790–2801).
The selling point is understandable in itself: delaying release reduces stomach pressure. It is paid for in absorption. Anyone who tolerates a tablet badly gets further with a smaller amount or with the timing than with a coating.
The ten-second check at the shelf
What has to appear on the pack is set out in Articles 6 and 8 of Directive 2002/46/EC, transposed into national law in every Member State (in Germany by § 4 of the Food Supplements Regulation, NemV). If any of it is missing, that is not a detail:
- the name “food supplement”
- the portion recommended for daily consumption — the days covered follow from it
- the amount of iron per daily portion and the percentage of the reference value (14 mg)
- the warning not to exceed the stated recommended daily dose
- the statement that the product is not a substitute for a varied diet
- the statement that it should be stored out of the reach of young children
The last point is no formality with iron but the reason to prefer a resealable tin to an open pouch: for small children, iron is the most critical substance in the medicine cabinet. And the annual tin is cheaper only if the days it covers do not run past the best-before date.
What we carry
Our Iron 30 mg + inulin contains 30 mg of iron from ferrous fumarate per tablet, which is 214 % of the nutrient reference value of 14 mg. One tablet daily with a glass of water 15 to 30 minutes before a meal is intended — so 180 tablets cover 180 days, which reduces the “price per month” calculation to one division. Further strengths and combinations stand side by side in the Iron category.
Among the claims authorised for iron are these (Regulation (EU) No 432/2012): 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. Iron contributes to the normal function of the immune system. Food supplements are not a substitute for a balanced and varied diet and a healthy lifestyle.
Frequently asked questions
Is the large tin always the cheaper one? Only if it is actually used up. Two figures decide: the days it covers and the best-before date. If the coverage runs past that date, the low price per month is never realised. With a preparation intended for a few months after a diagnosed deficiency, the annual tin is rarely the right size anyway.
Is the surcharge for bisglycinate worth it? An advantage in tolerability is documented for pregnant women, though at very low certainty of the evidence; in children the same review found no difference. Anyone paying the surcharge buys a possibility, not a measured superiority — the figures are in Iron forms compared.
Does vitamin C have to be in the preparation? No. The additive is permitted and the claim for it authorised, but in the comparative trial in adults with iron deficiency anaemia it made no confirmed difference to haemoglobin. A squeeze of lemon or some pepper with the same meal serves the same purpose without a surcharge.
How do I recognise goods not intended for this market? At three points: missing mandatory particulars, or particulars only in a language not spoken here — Regulation (EU) No 1169/2011 requires them in a language easily understood in the country of sale; an iron source that is not in Annex II of Directive 2002/46/EC, iron picolinate being the most common case; and amounts without the percentage of the nutrient reference value. A certificate of analysis on request is a good sign the other way round, a purity claim without evidence is not.
Sources: DGE, selected questions and answers on iron · Regulation (EU) No 1169/2011, Annex XIII · Directive 2002/46/EC, Articles 6 and 8 and Annex II (consolidated version of 17/07/2024) · Directive 2001/83/EC · § 4 of the German Food Supplements Regulation (NemV) · BfR, maximum level proposals for iron in foods including food supplements · EFSA, Scientific opinion on the tolerable upper intake level for iron, EFSA Journal 2024;22(6):8819 · Moretti D et al., Oral iron supplements increase hepcidin and decrease iron absorption from daily or twice-daily doses in iron-depleted young women, Blood 2015;126(17):1981–1989 (PubMed 26289639) · Li N et al., The efficacy and safety of vitamin C for iron supplementation in adult patients with iron deficiency anemia, JAMA Network Open 2020;3(11):e2023644 (PubMed 33136134) · Thankachan P et al., Fractional iron absorption from enteric-coated ferrous sulphate tablet, Indian Journal of Medical Research 2020;151(4):371–374 (PubMed 32461401) · Pantopoulos K, Oral iron supplementation: new formulations, old questions, Haematologica 2024;109(9):2790–2801 · Regulation (EU) No 432/2012.
