Iron Deficiency: What It Is, Who Is at Risk, and What to Do About It

What iron actually does

Iron sits at the centre of haemoglobin, the protein in red blood cells that collects oxygen at the lungs and delivers it to every tissue in the body. That single job explains most of what follows. If iron runs low, the body makes less haemoglobin, less oxygen reaches the tissues, and everything that depends on oxygen becomes harder work.

Under GB rules, iron carries a set of authorised claims that describe those roles precisely.

Iron does not work alone. Copper is involved in normal iron transport, riboflavin (vitamin B2) contributes to normal iron metabolism, and vitamin A contributes to normal iron metabolism as well. Vitamin C is the one that matters most in practice, and we come back to it below.

What iron deficiency actually is

It helps to understand that low iron is not a single switch. It happens in stages.

First, stores fall. The body keeps a reserve of iron, mostly in the liver, bone marrow and spleen. If intake does not keep pace with losses, that reserve is drawn down. At this point haemoglobin can still be entirely normal and a standard full blood count can look unremarkable, while ferritin, the blood marker that reflects stored iron, is already falling.

Then, if the shortfall continues, haemoglobin production is affected. Red blood cells become smaller and paler and carry less oxygen. This stage is iron deficiency anaemia, and it is a medical diagnosis rather than a wellness category.

That two stage picture is why the advice below is what it is. Someone can feel genuinely tired with depleted stores and a normal full blood count, which is a common and frustrating experience, and it is also why the specific test matters.

Symptoms people commonly report

The NHS lists tiredness and lack of energy, shortness of breath, noticeable heartbeats, and paler than usual skin as the main symptoms of iron deficiency anaemia. Less common ones include headaches, an altered sense of taste, brittle nails, hair loss, and unusual cravings for non-food items.

Every one of those has other possible explanations, several of them more likely than low iron. Which brings us to the part of this article that matters most.

Test, do not guess 

We make an iron supplement. We would still rather you did not buy it until you know whether you need it.

There are two reasons, and both are worth understanding.

The symptoms are not specific enough to act on

Persistent tiredness has a long list of possible causes, including thyroid function, coeliac disease, sleep disorders, low vitamin B12 or folate, and simply not sleeping enough. Taking iron on the basis of feeling tired means you may spend three months not addressing the actual cause.

Iron you do not need is not harmless

Unlike vitamin C, the body has no efficient route for excreting excess iron. It accumulates. Around one in two hundred people of northern European descent carry two copies of the gene variant associated with haemochromatosis, a condition in which the body absorbs and stores too much iron, and many are unaware of it. Routine iron supplementation is not advisable in that situation. Iron supplements are also a significant cause of accidental poisoning in young children, which is a good reason to keep them well out of reach.

What to ask for

Ask your GP about a ferritin test rather than only a full blood count. Ferritin reflects stored iron and moves first. One caveat worth knowing: ferritin also rises during inflammation or infection, so a normal result taken while you are unwell can be misleading, and your GP may look at it alongside other markers.

Who is most likely to run low

UK reference nutrient intakes are 14.8 mg a day for women aged 19 to 50, and 8.7 mg a day for men and for women after the menopause. That difference is large, and it is the clearest illustration of why iron advice cannot be one size fits all.

How to get more iron from food

Dietary iron comes in two forms, and they behave quite differently.

Haem iron, found in meat, fish and shellfish, is absorbed relatively efficiently and is much less affected by what else is on the plate. Non-haem iron, found in plants, eggs and fortified foods, is absorbed less efficiently and is strongly influenced by the rest of the meal. This is why vegetarians and vegans are generally advised to aim for a higher total intake.

The absorption rules that actually matter

For non-haem iron in particular, how and when you eat it changes how much you absorb. Four practical points cover most of it.

•     Add vitamin C to plant iron. Vitamin C keeps iron in the form the gut absorbs more readily. In practice: peppers in the lentil stew, a squeeze of lemon over the greens, or a piece of fruit with a fortified cereal.

•     Move tea and coffee away from meals. The polyphenols in both bind iron and reduce absorption substantially. Leaving an hour either side of an iron-rich meal is the simplest fix, and for many people it is the single highest impact change on this list.

•     Separate calcium supplements from iron-rich meals. Calcium competes with iron for absorption. Dairy in the diet is fine; it is timing a calcium supplement alongside your main iron source that is worth avoiding.

•     Soak, sprout or ferment where you can. Phytates in wholegrains and pulses reduce iron absorption, and traditional preparation methods reduce phytate content. Sourdough bread is a good everyday example.

If you already take iron: what the absorption research says

This is the part that has genuinely changed, and it is counterintuitive enough to be worth knowing.

Iron absorption is regulated by a hormone called hepcidin. When a dose of iron arrives, hepcidin rises and partially blocks absorption of subsequent doses, and that effect lasts around 24 hours. In 2015, Diego Moretti and colleagues demonstrated this in Blood, showing that daily and twice-daily dosing raised hepcidin and reduced absorption from later doses.

Nicole Stoffel, Michael Zimmermann and colleagues then tested the logical alternative in The Lancet Haematology in 2017. In iron-depleted women, cumulative fractional iron absorption was 21.8 per cent on alternate-day dosing compared with 16.3 per cent on consecutive days. Splitting a dose across the day performed worse than a single morning dose, not better.

The practical conclusion is that taking more iron, more often, does not straightforwardly mean absorbing more of it. Allowing hepcidin to return to baseline between doses makes each one work harder, and alternate-day dosing also tends to be easier on the digestion, which matters because gut side effects are the usual reason people abandon iron.

This has moved from research into practice. The NICE Clinical Knowledge Summary on iron deficiency anaemia and the BNF both now recognise alternate-day regimens as a reasonable option, particularly where daily dosing is poorly tolerated.

One important caveat. That research was conducted at treatment level doses in iron-depleted women. If you have been prescribed iron by a clinician, follow the regimen they have given you and raise any change with them rather than adjusting it yourself.

Our formula

Each capsule of our Iron + Vitamin C contains 15 mg of iron as ferrous bisglycinate (107% NRV) and 400 mg of vitamin C as ascorbic acid (500% NRV). One capsule a day with food.

Two deliberate choices worth explaining. The iron is bisglycinate, a form bound to the amino acid glycine, which is generally better tolerated than ferrous sulphate. The vitamin C is not there as a bonus nutrient. It is there because the evidence on vitamin C and non-haem iron absorption is strong enough that pairing them in a single capsule is the sensible formulation.

Ingredients are ascorbic acid, hydroxypropyl methylcellulose (the capsule) and ferrous bisglycinate. Nothing else. If you want the detail on why that list is so short, our Red List sets out the additives and fillers we choose not to use.

This is a food supplement designed to supplement dietary iron intake.  It is not a treatment for diagnosed iron deficiency anaemia, which is a clinical matter and typically involves considerably higher doses under supervision.

 When to see a GP rather than reach for a supplement

There are situations where topping up is the wrong first move, because low iron is a signal rather than the whole story.

•     Men of any age, and women past the menopause, with low iron. In these groups there is no monthly blood loss to explain it, so the cause should be investigated rather than assumed.

•     Periods heavy enough to affect your daily life. Worth raising in its own right, and treatable.

•     Any change in bowel habit, blood in the stool, unexplained weight loss, or persistent abdominal pain alongside tiredness.

•     Tiredness that persists despite a normal iron result, which points somewhere else.

•     Pregnancy, or planning a pregnancy. Iron needs change substantially and should be managed with your midwife or GP.

For anything on that list, speak to your GP first. If you would like nutritional support alongside clinical care, you can find a practitioner near you through our directory.

Your iron checklist

• •     If you suspect low iron, book a blood test and ask about ferritin as well as a full blood count.

• Check whether you fall into one of the higher risk groups above.

• Put a vitamin C source alongside plant iron at every meal where you can.

• Move tea and coffee an hour away from your main iron-containing meals.

• Build two or three reliable iron sources into meals you already cook rather than overhauling your diet.

• If you have been prescribed iron, follow your clinician's regimen and take any questions back to them.

You can browse our mineral range, or take our online quiz if you would like help working out which form suits you.

Common questions

Can I take an iron supplement without getting tested?

We would advise against it. Iron accumulates rather than being excreted, the symptoms of low iron overlap with several other conditions, and a blood test is quick and usually straightforward to arrange.

What is the difference between iron deficiency and anaemia?

Iron deficiency means stores are depleted. Iron deficiency anaemia is the later stage, where haemoglobin production has been affected. You can have the first without the second, which is why ferritin is a more sensitive early marker than a full blood count alone.

Does spinach really contain a lot of iron?

Less than its reputation suggests, and the iron it does contain is non-haem and accompanied by compounds that limit absorption. It is a perfectly good part of the picture, but pulses, tofu and seeds do more work.

How long does it take to rebuild iron levels?

Longer than most people expect. Stores are rebuilt over months rather than weeks, even once haemoglobin has recovered, which is why clinicians usually continue treatment well beyond the point where someone feels better.

Should I take iron with or without food?

Absorption is somewhat better on an empty stomach, but tolerance is better with food, and the regimen you can actually stick to is the one that works. Our formula is designed to be taken with a meal.

Do vegetarians and vegans need more iron?

Their requirement for total dietary iron is higher, because non-haem iron is absorbed less efficiently. Pairing plant iron with vitamin C at the same meal is the most effective single adjustment.