🩸 Nutrition
Iron Deficiency Symptoms — Signs, Causes & Treatment (2026)
Iron deficiency is the most common nutritional deficiency worldwide. Learn to recognise the signs, understand causes, and discover the best food sources. Updated January 2026.
Key Takeaways
- Iron deficiency affects approximately 1 in 3 women of childbearing age in Western countries
- Fatigue is the hallmark symptom — but breathlessness, pale skin, and brittle nails are also common
- Haem iron (from animal sources) is 2–3× more bioavailable than non-haem iron (plant sources)
- Vitamin C taken with plant iron sources increases absorption by up to 67%
- Never self-supplement high-dose iron without a blood test — excess iron is toxic
In This Article
What Is Iron Deficiency?
Iron is essential for producing haemoglobin — the protein in red blood cells that carries oxygen from the lungs to every cell in the body. When iron stores are depleted, the body cannot produce enough healthy red blood cells, resulting in iron deficiency anaemia.
Iron deficiency is the most common nutritional deficiency worldwide, affecting an estimated 2 billion people — and it is far more prevalent in developed countries than commonly appreciated.
2B
People worldwide affected by iron deficiency (WHO)
1 in 3
Women of reproductive age in UK/USA have low iron stores
3–6 mo
Time to fully restore iron stores with supplementation
Recognising the Symptoms
Early Iron Depletion (Low Ferritin, Normal Haemoglobin)
- Unexplained fatigue not relieved by sleep
- Reduced exercise tolerance
- Difficulty concentrating, brain fog
- Increased susceptibility to infections
- Restless legs syndrome (strong association with low ferritin)
Iron Deficiency Anaemia (Low Haemoglobin)
- Pale skin, inside of eyelids, and nail beds
- Breathlessness on minimal exertion
- Heart palpitations — heart working harder to compensate
- Headaches and dizziness
- Cold hands and feet
- Brittle, spoon-shaped nails (koilonychia)
- Hair loss — iron is essential for hair follicle function
- Pica — unusual cravings for non-food items (ice, clay, chalk)
- Swollen or sore tongue (glossitis)
Who Is Most at Risk?
- Women of reproductive age: Menstrual blood loss is the primary cause in premenopausal women
- Pregnant women: Iron requirements nearly double during pregnancy
- Vegetarians and vegans: Non-haem plant iron is poorly absorbed; no haem iron intake
- Frequent blood donors: Each donation removes significant iron
- Endurance athletes: Foot-strike haemolysis and high losses in sweat and urine
- People with coeliac disease or IBD: Impaired absorption in the small intestine
- Older adults: Reduced dietary intake and possible bleeding from gastrointestinal conditions
Iron-Rich Foods
| Food | Iron per 100g | Type | Bioavailability |
|---|---|---|---|
| Chicken liver | 12mg | Haem | High (25–30%) |
| Oysters | 7mg | Haem | High |
| Lean beef (fillet) | 3.5mg | Haem | High |
| Sardines (canned) | 3mg | Haem | High |
| Lentils (cooked) | 3.3mg | Non-haem | Low (5–12%) |
| Pumpkin seeds | 8.8mg | Non-haem | Low |
| Spinach (cooked) | 3.6mg | Non-haem | Low |
| Tofu (firm) | 2.7mg | Non-haem | Low |
✅ How to Boost Non-Haem Iron Absorption
Add vitamin C to every plant-iron meal — a squeeze of lemon juice on lentils, orange slices with spinach salad, or kiwi after a bean-based meal can increase iron absorption by up to 67%. Avoid tea, coffee, and calcium-rich foods (dairy) within 1 hour of iron-rich meals — tannins and calcium both inhibit iron absorption.⚠️ Always Test Before Supplementing Iron
Unlike vitamin D or magnesium, high-dose iron supplementation without confirmed deficiency can be harmful. Iron overload (haemochromatosis) causes organ damage. Always get a full blood count and serum ferritin test before starting iron supplements above 18mg/day.🔢 Free Tool
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Frequently Asked Questions
What does iron deficiency feel like?▼
The most noticeable symptom is persistent, unexplained fatigue that does not improve with rest — often described as a heavy tiredness affecting every task. Breathlessness during activities that previously posed no difficulty, heart palpitations on minimal exertion, difficulty concentrating ("brain fog"), and increased susceptibility to infections are also common. Many people are surprised to discover severely low iron on routine blood tests having dismissed their fatigue as normal life.
How quickly can iron levels be restored?▼
With oral iron supplements (typically ferrous sulphate 200mg, 1–3 times daily), haemoglobin levels begin to rise after 2–4 weeks. Full restoration of iron stores typically takes 3–6 months of supplementation even after haemoglobin normalises. IV iron infusion (used in severe cases or those who cannot tolerate oral supplements) restores iron stores within weeks.
Can you have iron deficiency without anaemia?▼
Yes — iron depletion occurs in stages. Early deficiency depletes iron stores (low ferritin) before haemoglobin is affected. This "latent iron deficiency" causes fatigue, reduced cognitive function, and impaired exercise tolerance even with a normal haemoglobin level. Many women with normal full blood counts but low ferritin (below 30 μg/L) report significant symptom improvement with supplementation.
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⚕️ Medical Disclaimer: For informational and educational purposes only. Not a substitute for professional medical advice. Always consult a qualified healthcare professional before making health decisions.
SM
Dr. Sarah Mitchell, MD
WellCalc Medical Contributor
All WellCalc articles are written and reviewed by qualified healthcare professionals following NHS, AHA, WHO, and current clinical guidelines.