Iron Deficiency
Insufficient iron levels affecting hemoglobin production and oxygen transport.
TL;DR
Iron deficiency is a blood-test diagnosis (ferritin first) with two jobs: replace the iron, and find out why it fell. Oral iron works — take it on an empty stomach with vitamin C, away from tea, coffee and dairy; alternate-day dosing absorbs as well as daily with fewer side effects. Constipation and dark stools are normal. In men and postmenopausal women, unexplained iron deficiency always warrants investigation of the gut.
Overview
Iron deficiency is the world's most common nutritional deficiency — a slow drain on the body's iron stores that eventually starves red blood cell production of its essential raw material. Before anaemia develops, falling stores alone cause fatigue, breathlessness on exertion, brain fog, brittle nails and restless legs. In women it is usually menstrual; in men and postmenopausal women it should always prompt the question of where the iron is being lost — because sometimes the answer is bleeding from the gut that matters far more than the deficiency itself.
Common Symptoms
- •Fatigue and low stamina, often before any anaemia
- •Breathlessness on exertion out of proportion to fitness
- •Pale skin, conjunctiva and nail beds
- •Brittle, ridged or spoon-shaped nails; hair shedding
- •Restless legs, especially at night
- •Brain fog, poor concentration and irritability
- •Cravings for ice, clay or starch (pica) — highly specific
- •Headaches and dizziness on standing
- •Cold hands and feet, poor exercise tolerance
Common Causes
- •Menstrual blood loss — the dominant cause in premenopausal women
- •Inadequate dietary intake — restrictive diets, veganism without planning
- •Poor absorption — coeliac disease, gastritis, bariatric surgery, PPIs
- •Gut blood loss — ulcers, gastritis, polyps, inflammatory bowel disease, bowel cancer
- •Pregnancy — demand roughly doubles
- •Frequent blood donation
- •Intense endurance exercise — foot-strike and inflammatory effects
- •Chronic kidney disease and inflammation — functional iron deficiency
Root Causes
The body has no regulated way to excrete iron — stores are controlled entirely at absorption. Deficiency develops when losses or demand outstrip that controlled intake: monthly menstrual loss, the doubled demand of pregnancy, gut bleeding, or an absorption pathway crippled by coeliac disease or acid suppression. Because absorption adapts slowly, replenishment is equally slow — stores take months to rebuild. Hepcidin, the iron-regulatory hormone, rises with inflammation and blocks absorption, which is why inflammatory conditions cause a functional deficiency that oral iron barely touches.
How It's Diagnosed
Diagnostic Markers
- Ferritin — the first test; below ~30 ng/mL indicates depleted stores even with normal haemoglobin
- Full blood count — anaemia is a late sign
- Transferrin saturation — low saturation confirms supply failure
- CRP alongside ferritin — inflammation falsely elevates ferritin
- Coeliac serology in unexplained deficiency
- In men and postmenopausal women: investigation of the GI tract is standard, not optional
When to See a Doctor
{"Confirmed deficiency — to find the cause, not just buy supplements","Fatigue with heavy periods — worth a ferritin test","Any iron deficiency in a man or postmenopausal woman","Deficiency despite oral iron — absorption needs checking (coeliac first)","Breathlessness, palpitations or chest pain on exertion with known deficiency","Pregnancy with symptoms or low ferritin","Restless legs — ferritin should be checked and repleted if under ~75"}
Supplements Studied For This
Diet & Lifestyle
Suggested Pattern
Haem iron from meat absorbs at 15-35%; non-haem plant iron at 2-10% — but plant absorption is highly manipulable. Vitamin C in the same meal multiplies non-haem absorption several-fold; tea, coffee, calcium and phytates in the same meal slash it. The practical rules: pair plant iron with citrus or peppers, keep tea and coffee away from iron-rich meals and iron tablets, and do not take iron with breakfast cereal and milky coffee and expect much of it to arrive.
Eat more
- Red meat, liver and shellfish — the most bioavailable haem iron
- Lentils, beans, tofu, spinach and fortified cereals — plant iron, paired with vitamin C
- Citrus, peppers, kiwi and berries with iron-rich meals
- Pumpkin seeds and dried apricots as iron-rich snacks
- Molasses — a genuinely useful iron-dense sweetener
Avoid
- Tea and coffee within an hour either side of iron-rich meals or tablets
- Calcium supplements and dairy around the iron dose
- Antacids and PPIs near iron intake where avoidable
- High-dose zinc supplements — they compete for absorption
- Phytate-heavy bran with the main iron source of the day
Supporting Research
Alternate day versus consecutive day oral iron supplementation in iron-depleted women: a randomized double-blind placebo-controlled study
Hematologic manifestations of celiac disease
Sleep disturbances in children and adolescents with iron deficiency: Questionnaire-based and actigraphic findings
Ferric Carboxymaltose in Patients with Heart Failure and Iron Deficiency
Lactoferrin or ferrous salts for iron deficiency anemia in pregnancy: A meta-analysis of randomized trials
Frequently Asked Questions
Who It Affects
Iron deficiency affects an estimated 25% of the global population. In developed countries, 10-20% of premenopausal women have depleted stores; it is the commonest deficiency in pregnancy and the leading cause of anaemia worldwide.
Premenopausal women dominate — heavy periods are the usual driver. Also concentrated in pregnant women, young children, frequent blood donors, endurance athletes, people with coeliac or inflammatory bowel disease, bariatric surgery patients and those on long-term acid suppression.
Quick Facts
- •Ferritin is the key test — it falls long before anaemia appears
- •The commonest cause in premenopausal women is menstrual loss
- •In men and postmenopausal women, gut blood loss must be excluded
- •Alternate-day dosing absorbs as well as daily and causes fewer side effects
- •Tea, coffee, calcium and dairy block absorption within 2 hours of a dose
- •Restless legs and ice cravings (pica) are classic non-blood symptoms
Lifestyle Tips
- •Take oral iron on an empty stomach with orange juice or a vitamin C tablet
- •Consider alternate-day dosing — equal absorption, fewer gut side effects
- •Expect dark stools — harmless; report black tarry stools with pain or dizziness instead
- •Re-test ferritin after 8-12 weeks, and continue 3 months beyond normalisation to rebuild stores
- •Investigate heavy periods rather than treating the iron forever
- •If oral iron fails or is intolerable, intravenous iron is fast and effective — ask
Related Topics
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This information is for educational purposes only. Always consult a healthcare professional before starting any supplement regimen.