Iron Intake & Deficiency Risk Calculator

Dietary Iron Guide

What's the difference between Haem and Non-Haem Iron?

Two forms of dietary iron with very different absorption: haem iron (from animal products): well absorbed (15-35%). Sources: red meat, poultry, fish, eggs (limited). Non-haem iron (from plant sources): poorly absorbed (2-20%). Sources: legumes, whole grains, dark leafy greens, fortified foods, nuts and seeds. The same 5mg iron: from beef provides ~1mg absorbed iron. From spinach provides ~0.5mg absorbed. Implications: vegetarians and vegans need approximately 1.8 times more iron from their diet to compensate for the lower absorption rate of non-haem iron sources compared to meat.

What do I need to know about Iron Deficiency Anaemia?

Most common nutritional deficiency in the UK and worldwide. NHS data: 23% of UK women aged 19-64 have iron deficiency. Up to 50% of pregnant women. 3-7% of UK men. Symptoms: fatigue (most common). Pale skin. Shortness of breath. Cold hands and feet. Brittle nails. Restless legs syndrome. Hair loss. Difficult concentration. Risk groups: menstruating women (especially heavy periods). Pregnant women (target 27mg/day). Vegetarians and vegans. Endurance athletes (mechanical haemolysis, sweat losses). Anaemia can only be confirmed with a blood test — in the US, HealthLabs.com offers walk-in iron and ferritin panel testing without needing to book a GP appointment first.

What should I know about Maximising Absorption?

Iron absorption enhancers (take with iron-rich foods): vitamin C — single most important enhancer. 100mg vitamin C (orange, pepper, kiwi, broccoli) can quadruple non-haem iron absorption. Cook in iron pans (cast iron) — small amount of iron transfers to food. Iron absorption inhibitors (separate from iron meals by 1-2 hours): tea and coffee — tannins bind iron, reduce absorption by 50-90%. Calcium supplements and dairy — compete with iron absorption. Phytates (whole grains, legumes) — bind iron.

What do I need to know about Supplementation?

When dietary iron is insufficient: ferrous sulphate (200mg = 65mg elemental iron): standard NHS prescription. Effective but causes GI side effects in 20% (constipation, nausea, dark stools). Ferrous fumarate: similar absorption, often better tolerated. Iron bisglycinate (chelated iron): newer form. Better tolerated, fewer GI effects. Less elemental iron per tablet but better absorbed. Liquid iron supplements, such as Floradix and Spatone, are gentler but lower dose — useful for sensitive stomachs but slower to correct a significant deficiency.

What's the key thing to understand about Heme vs Non-Heme Iron?

Dietary iron comes in two forms that the body absorbs very differently. Heme iron, found only in animal sources (red meat, poultry, fish and offal), is absorbed relatively efficiently — typically 15-35% of what's eaten — because it is bound within haemoglobin and myoglobin molecules that the gut can take up directly through a dedicated transport pathway. Non-heme iron, found in plant sources (leafy greens, beans, lentils, fortified cereals, nuts) and also making up a smaller portion of iron in meat, is absorbed far less efficiently — typically only 2-20% — and its absorption is heavily influenced by what else is eaten in the same meal, unlike heme iron's absorption which is comparatively stable. This is the central reason vegetarians and vegans are advised to consume somewhat more total dietary iron than meat-eaters (UK guidance suggests up to 1.8 times the standard reference intake for a plant-based diet) to compensate for non-heme iron's lower and more variable absorption, rather than because plant foods necessarily contain less iron in absolute terms — some plant sources, like lentils and spinach, are iron-rich on paper, but a meaningfully smaller fraction of that iron actually gets absorbed compared with the same milligram amount from red meat.

What do I need to know about Boosting or Blocking Iron Absorption?

Non-heme iron absorption can be substantially increased or decreased by other foods and drinks consumed in the same meal, which matters most for vegetarians, vegans, and anyone managing lower iron levels. Vitamin C is the best-known booster: consuming a source of vitamin C (citrus fruit, bell peppers, tomatoes, a glass of orange juice) alongside an iron-rich plant meal can increase non-heme iron absorption several-fold, because vitamin C converts iron into a more easily absorbed chemical form and partly counteracts inhibiting compounds in the same meal. Meat, fish and poultry also modestly enhance non-heme iron absorption when eaten in the same meal as plant iron sources. On the inhibiting side, tannins in tea and coffee (particularly black tea) can reduce non-heme iron absorption by up to 50-60% if consumed at the same time as an iron-rich meal, which is why it's generally advised to leave a gap of an hour or so either side of meals if trying to maximise iron intake. Phytates in whole grains, bran and legumes, as well as calcium (from dairy or supplements) and certain plant compounds (oxalates, found in spinach, and polyphenols in some vegetables) also inhibit non-heme iron absorption when eaten simultaneously. None of this applies meaningfully to heme iron from meat, which absorbs via a separate pathway largely unaffected by these dietary factors.

What should I know about Iron Overload Risk?

Unlike many vitamins and minerals, where excess is simply excreted, the body has only limited ability to actively remove excess iron once absorbed, which makes iron one of the nutrients where 'more is better' doesn't apply and unsupervised high-dose supplementation carries real risk. Haemochromatosis, a genetic condition causing the body to absorb too much iron from food, affects a meaningful number of people (particularly those of Northern European ancestry) often without symptoms for years, during which excess iron gradually accumulates in organs including the liver, heart and pancreas, eventually causing serious damage if undiagnosed. For people without this condition, iron supplements taken without a diagnosed deficiency can still cause gastrointestinal side effects (constipation, nausea, stomach pain) and, over sustained high intake, contribute to iron overload. A distinct and very serious risk is accidental iron overdose in young children, for whom iron supplement tablets are a recognised cause of poisoning, since a dose that's safe for an adult can be dangerous for a small child — iron supplements should always be stored safely out of children's reach. The general guidance is to supplement iron only when a blood test has confirmed deficiency, under medical advice, rather than taking it as a general precaution.

Worked Example: Reaching the Daily Iron Target From Food

UK government guidance (NHS) sets reference daily iron intakes at 8.7mg for adult men and women over 50, and 14.8mg for women aged 19–50 due to menstrual losses. A day's meals containing 100g of lean beef (around 2.1mg iron), a bowl of fortified breakfast cereal, and a handful of dried apricots (around 1mg per 30g) could realistically reach or exceed the target for most adults, especially when fortified cereal is included, since many UK breakfast cereals are fortified specifically to help meet iron intake targets.

What should I know about Tea, Coffee and Iron Absorption?

Tannins in tea and polyphenols in coffee can meaningfully reduce the absorption of non-haem iron from a meal when drunk at the same time, which is why common dietary advice is to leave a gap of around an hour either side of a meal before having tea or coffee if non-haem iron intake is a specific concern, such as for someone with iron deficiency anaemia. This effect is specific to non-haem iron from plant foods and fortified cereals; haem iron from meat, fish and poultry is absorbed through a different pathway and is much less affected by tannins and polyphenols in the same meal.

Iron Content of Common Foods

Hitting a daily iron target is easier with a sense of which everyday foods actually contribute meaningfully, since the amount varies enormously between food groups.

Notice that plant sources can appear to deliver as much or more iron by weight than meat, but because non-haem iron absorbs at only roughly 2-20% efficiency compared to haem iron's 15-35%, a vegetarian diet typically needs a notably higher total intake to deliver the same amount of iron actually absorbed into the body.