Iron is one of those nutrients that rarely makes headlines until something goes wrong. Despite making up a tiny fraction of total body weight, it is the most abundant trace element in the human body — and its absence is felt quickly. From transporting oxygen in the blood to supporting cognitive function and energy metabolism, iron underpins processes that affect how we feel every single day. Understanding what iron does, who needs more of it, and how to address a deficiency is practical knowledge for almost everyone.
What Does Iron Do in the Body?
Iron's most critical role is as the central component of haemoglobin, the protein in red blood cells responsible for binding oxygen in the lungs and delivering it to tissues throughout the body. It is also incorporated into myoglobin, a muscle protein that stores oxygen and supplies it during physical exertion. This intimate relationship with oxygen transport explains why fatigue and breathlessness are among the first signs that something is off with iron status.
Beyond oxygen transport, iron is involved in DNA synthesis, the production of certain neurotransmitters including adrenaline and noradrenaline, and a range of enzymatic metabolic reactions. Research also points to iron's role in cognitive function — concentration, memory, and the capacity for sustained mental effort are all affected when iron levels fall below the optimal range.
Iron Deficiency — Who Is at Risk and What Are the Signs?
Iron deficiency is the most common nutritional deficiency worldwide, affecting an estimated 20% of the global population. The groups most commonly affected include women of reproductive age (due to menstrual blood loss), pregnant and breastfeeding women, infants and adolescents in growth phases, athletes (who lose iron through sweat), older adults, and those following vegetarian or vegan diets.
Early iron deficiency often develops gradually and may initially be asymptomatic. As the body's iron stores deplete and haemoglobin production declines, symptoms become more apparent:
- Persistent fatigue and low energy
- Paleness of skin and mucous membranes
- Shortness of breath during everyday activity
- Difficulty concentrating and reduced motivation
- Brittle nails and disrupted nail and hair growth
- Increased susceptibility to infections
Left unaddressed, iron deficiency leads to iron deficiency anaemia — a condition in which red blood cell production is significantly impaired. It is important to note that anaemia is a symptom, not a diagnosis in itself; identifying the underlying cause of iron loss or poor absorption is essential before beginning supplementation. Possible causes include heavy menstruation, gastrointestinal bleeding, inflammatory bowel conditions such as Crohn's disease, coeliac disease, or hereditary absorption disorders.
[warning:If you suspect iron deficiency, have your levels tested before supplementing. Excess iron is harmful, and supplementation should be based on confirmed deficiency and ideally supervised by a healthcare professional. Iron supplements can interact with certain medications including antibiotics and thyroid medication — always consult your doctor if you take prescription drugs.]Iron in Food — Haem vs Non-Haem Sources
Dietary iron occurs in two distinct forms with very different bioavailability. Haem iron, found in animal products, has a bioavailability of approximately 25% and is efficiently absorbed regardless of the rest of the meal. Non-haem iron, found in plant foods and eggs, is absorbed at only 5–10% under standard conditions — but this can be meaningfully improved with the right dietary approach.
Key food sources by type:
- Haem iron (animal sources): red meat, pork, beef, organ meats (liver in particular), poultry, fish, shellfish, oysters
- Non-haem iron (plant sources): dark leafy greens (spinach, kale), pumpkin seeds, legumes (lentils, chickpeas, kidney beans), asparagus, cashews, almonds, egg yolks
To improve the absorption of non-haem iron, pair plant-based iron sources with vitamin C — either as food (citrus fruit, bell pepper, broccoli) or as a supplement. Other cofactors that support iron absorption include copper, cobalt, and manganese. Conversely, calcium, tannins (found in tea and coffee), and phytates (in whole grains and legumes) can inhibit absorption when consumed at the same meal.
[tip:If you rely primarily on plant-based iron sources, try drinking tea and coffee between meals rather than with them, and pair iron-rich foods with a vitamin C source at the same sitting — for example, lentils with tomatoes or spinach with lemon juice.]Iron Supplementation — Forms and What to Look For
Not all iron supplements are equal. The form of iron used in a supplement significantly affects both absorption efficiency and the likelihood of gastrointestinal side effects, which are the most common complaint with iron supplementation.
Iron fumarate is an organic iron compound with good bioavailability and generally better tolerability than older inorganic forms such as iron sulphate. A standard supplemental dose provides around 100 mg of iron fumarate, yielding approximately 30–35 mg of elemental iron. Iron bisglycinate (also called chelated iron) is widely regarded as the best-tolerated form, with high bioavailability and minimal gastrointestinal irritation — making it a strong choice for sensitive individuals. Liposomal iron offers another well-tolerated delivery option, particularly for those who have struggled with conventional supplements. Liquid iron formulations, including drops, are often preferred for children and those who have difficulty with capsules or tablets.
Explore our full range of iron supplement options in the dedicated iron collection.
[products:doctors-best-high-absorption-iron-with-ferrochel-27-mg-120-tablets, thorne-research-iron-bisglycinate-25-mg-60-capsules, solgar-gentle-iron-25-mg-us-90-vegetable-capsules, dr-jacobs-liposomal-iron-powder-64-g, vitalers-organic-iron-30-mg-60-capsules, now-foods-iron-18-mg-120-veg-capsules]Reference Ranges and When to Test
Blood iron levels are measured in serum and vary by age and sex. Standard reference ranges are:
- Women: 60–180 µg/dl
- Men: 70–200 µg/dl
- Children under 15: 45–185 µg/dl
It is worth noting that serum iron levels can fluctuate throughout the day, which is why a single reading is not always sufficient for a complete picture. Clinicians typically assess iron status alongside ferritin (stored iron), transferrin saturation, and a full blood count. If you belong to a higher-risk group or experience persistent fatigue, it is worth asking for a full iron panel rather than serum iron alone.
For those whose iron levels are borderline but not severely deficient, dietary adjustments combined with a well-tolerated supplement form may be sufficient. Complementary support for energy and red blood cell production is also available through B vitamins — particularly B12 and folate — and through our broader minerals collection.
[products:aliness-iron-microferr-25-mg-100-tablets, pharmovit-organic-iron-iron-fumarate-60-capsules, swanson-iron-fumarate-18-mg-60-capsules, hepatica-endosomal-iron-micronised-100-capsules, aura-herbals-ferradrop-liquid-iron-folic-acid-500-ml, childlife-liquid-iron-natural-berry-flavor-118-ml] [note:All products available at Medpak ship from within the EU — no customs delays or additional import fees for customers across Europe.]
