Iron: Food, Blood Tests and Performance — A Pillars Guide

The 60-second answer

• Iron matters, particularly for red blood cells, oxygen transport and energy metabolism.
• Low iron stores can exist before anaemia develops. A normal haemoglobin result does not always tell the whole story.
• Symptoms are not a diagnosis. Fatigue, breathlessness or reduced performance can have many causes.
• Food intake helps us assess risk, not iron status. Blood testing and clinical context are needed when deficiency is suspected.
• More is not automatically better. Iron supplements can cause side effects, interact with medicines and be harmful when they are not needed.
• The Pillars approach is food first and investigate first: understand the pattern, identify relevant risks, seek appropriate testing when indicated and support treatment only when the evidence supports it.

What iron does

Iron is an essential part of haemoglobin, the protein in red blood cells that transports oxygen around the body. It also contributes to:

• myoglobin, which helps muscles use oxygen;
• cellular energy production;
• normal red-blood-cell formation;
• neurological and cognitive function;
• the ability to train, recover and adapt when iron status is adequate.

Iron deficiency develops in stages. Iron stores can begin to fall before haemoglobin drops far enough to meet an anaemia threshold. This is why iron deficiency without anaemia and iron-deficiency anaemia are related but different.

How much do I need?

Current UK adult reference intakes are:

• Men aged 19 and over: 8.7 mg per day
• Women aged 19–49: 14.8 mg per day
• Women aged 50 and over: 8.7 mg per day

Women who continue to have periods after 50 may still require the higher reference amount. These are healthy-population reference intakes. They are not treatment doses and they cannot tell us whether a particular person is iron deficient. Source: NHS — Iron

Where can I get iron from food?

Haem iron

Haem iron is generally absorbed more readily and is found in:

• red meat;
• poultry;
• fish;
• shellfish.

Red meat is not the only answer. The NHS advises limiting red and processed meat, and liver should be avoided during pregnancy because of its vitamin A content.

Non-haem iron

Non-haem iron is found in:

• beans, lentils and chickpeas;
• tofu, edamame and other soya foods;
• iron-fortified breakfast cereals and breads;
• nuts and seeds;
• leafy green vegetables;
• dried fruit.

You do not need to eat meat to obtain iron, but a plant-based eating pattern usually benefits from deliberate variety because non-haem iron is absorbed less readily.

Helping your body absorb it

A few practical choices can help:

• Pair a plant-based iron source with a vitamin-C-rich food such as peppers, broccoli, berries, kiwi or citrus fruit.
• Tea and coffee can reduce iron absorption when consumed with an iron-rich meal or supplement.
• Calcium and phytates can also reduce absorption within that eating occasion.
• Do not create unnecessary food rules if there is no concern about iron status. A varied, iron-containing diet matters more than trying to make every meal chemically perfect.

Where low status has been identified, meal and supplement timing can be refined with the clinician or dietitian managing the plan.

Who may be at greater risk?

A stronger reason to review iron exists when one or more of the following apply:

• heavy or prolonged menstrual bleeding;
• endurance training or a large training volume;
• low energy availability, aggressive dieting or consistently inadequate intake;
• vegetarian or vegan eating without enough iron-rich variety;
• previous iron deficiency or iron-deficiency anaemia;
• frequent blood donation;
• planned altitude training;
• gastrointestinal symptoms, coeliac disease, inflammatory bowel disease or suspected malabsorption;
• pregnancy;
• visible blood loss or another possible source of blood loss.

Risk does not equal diagnosis. It tells us when asking better questions or seeking testing may be appropriate.

Signs worth investigating

Possible signs can include:

• persistent tiredness or weakness;
• reduced training capacity or an unexplained decline in performance;
• breathlessness that is unusual for you;
• dizziness, headaches or looking unusually pale;
• difficulty recovering despite appropriate food, sleep and training management;
• restless legs;
• recurrent illness or injury alongside other risk factors.

These signs are non-specific. Sleep disruption, low energy availability, stress, illness, training overload, folate or vitamin B12 status, thyroid conditions and many other factors can produce similar experiences.

What blood tests can — and cannot — tell us

A clinician assessing possible low iron may consider:

• full blood count or haemoglobin, which helps identify anaemia;
• serum ferritin, which provides information about stored iron;
• transferrin saturation, which helps assess iron available for use;
• C-reactive protein or another inflammation marker, when inflammation could affect ferritin interpretation.

Other tests may be appropriate depending on menstrual history, diet, symptoms, medicines, gastrointestinal health and previous results. A normal haemoglobin result does not completely exclude iron deficiency. Equally, low haemoglobin does not prove that iron is the cause. Ferritin can also appear normal or high during inflammation, so individual markers should not be interpreted in isolation.

For runners: making a blood test easier to compare

When a clinician or sports practitioner is assessing an athlete, the Australian Institute of Sport suggests improving test consistency by testing in the morning, in a normally hydrated state, without hard training in the previous 24 hours, without recent muscle-damaging exercise and when there is no current illness or infection. This reduces avoidable noise. It does not replace clinical interpretation.

Iron and runners

Runners can face several overlapping risks: menstrual blood loss, high training volume, low energy availability, plant-based eating, blood donation, gastrointestinal loss, exercise-related red-blood-cell breakdown, inflammation and altitude exposure. The Australian Institute of Sport uses haemoglobin, ferritin and transferrin saturation together in its minimum athlete screening framework. Some athlete frameworks use ferritin below approximately 35 micrograms/L as a reason for closer assessment.

That number is not a universal diagnosis, an automatic instruction to supplement or proof that performance will improve by pushing ferritin higher. Source: Australian Institute of Sport — Iron

What does the current research tell us?

The clearest conclusion is that baseline iron status matters.

• A 2024 meta-analysis of 13 studies involving 449 athletes found that oral iron increased ferritin, especially in athletes beginning with very low stores. The overall improvement in aerobic performance was not conclusive.
• A 2025 systematic review focused on iron-deficient, high-level female athletes found that treating deficiency could improve performance in that specific population.
• A 2026 systematic review and meta-analysis of 42 studies in active females found that oral iron improved haemoglobin and ferritin, with the largest responses in those starting with lower stores. Performance outcomes remained inconsistent.

These findings are not contradictory. They show why correcting a genuine deficiency is different from taking iron in the hope of creating a performance advantage when iron status is already adequate.

What about supplements?

There is no generic Pillars iron product, dose or ferritin target. When a clinician or appropriately qualified sports dietitian has established an indication:

• the amount of elemental iron matters, not just the name or total weight of the compound;
• the form, dose, frequency and duration should match the reason for treatment and the person’s tolerance;
• gastrointestinal effects such as nausea, abdominal discomfort, constipation or diarrhoea are common;
• interactions with medicines and other supplements must be checked;
• follow-up blood testing is used to confirm response and avoid blind long-term use.

Iron can be dangerous in overdose, particularly for children, and supplements must be stored securely. Haemochromatosis and other iron-loading conditions make unsupervised supplementation especially inappropriate.

What Pillars will do

Pillars can help you:

1. Review your habitual food intake across multiple days rather than judge one meal or one Cronometer entry.
2. Identify practical haem or non-haem food sources that suit your preferences.
3. Consider relevant context such as menstruation, training load, energy availability, dietary restriction, blood donation and previous results.
4. Prepare useful questions for your GP or another appropriate professional.
5. Support the food, routine and adherence parts of an established clinical plan.
6. Monitor how your energy, recovery and training experience change without claiming that iron is the cause.

Pillars does not diagnose iron deficiency, prescribe treatment or independently interpret a blood result as an instruction to supplement.

Your practical next step

• No current concern: include a regular variety of iron-containing foods.
• Plant-based eating: combine different non-haem sources and pair them with vitamin-C-rich foods when practical.
• Low intake across several days: improve the food pattern and discuss the wider context with your Pillars coach.
• Persistent symptoms or higher-risk history: speak with your GP or an appropriate qualified professional about whether assessment is indicated.
• Confirmed low status: follow the agreed treatment and monitoring plan; Pillars can support the nutrition around it.

Evidence and further reading

UK and athlete guidance

• NHS — Iron
• NHS — Iron-deficiency anaemia
• Australian Institute of Sport — Iron

Research

• Šmid et al. 2024 — oral iron supplementation in athletes
• Pengelly et al. 2025 — iron deficiency, supplementation and performance in female athletes
• McCarthy et al. 2026 — diet and supplements for iron status in active females

Expert coaching perspective reviewed

David and Megan Roche’s Iron Tutorial for Athletes helped inform the runner-specific questions and the emphasis on looking beyond haemoglobin alone. Its individual product, dose and ferritin-target preferences have not been adopted as generic Pillars recommendations.

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Evidence base reviewed: 2 August 2026 This resource provides general education and coaching support. It does not diagnose, prescribe treatment or replace advice from your GP, pharmacist, registered dietitian or another appropriately qualified healthcare professional.

Help putting this into practice

Want help making sense of your everyday food choices? Explore personal nutrition coaching in Oswestry and across Shropshire, or book a free conversation with Tim. For concerns about iron deficiency or treatment, speak with your healthcare professional. You can also browse our free learning guides.