Iron Deficiency and Anaemia: Symptoms, Causes, Ferritin Levels, Treatment and Prevention - The Complete Doctor's Guide

The world’s number one nutritional deficiency, and what every woman, man, and parent needs to know

✍️ Written and reviewed by: Dr. Qazi Taqweemulhaq, FCPS Medicine — Professor of Medicine, Women Medical and Dental College, Abbottabad, Pakistan. Consultant Physician, 32 Years Clinical Experience
📅 Last Updated: May 2026 | References: WHO, NIH ODS, NCBI StatPearls, AGA 2024, AAFP 2025, HemaSphere 2024, Merck Manual

⚡ Quick Answer: Iron deficiency is the world’s most common nutritional deficiency, affecting 1.27 billion people globally. It causes fatigue, pallor, shortness of breath, brain fog, hair loss, brittle nails, and pica. Diagnosis is by serum ferritin. Deficiency is < 45 ng/mL per AGA 2024 guidelines (the old cutoff of 12 ng/mL misses most cases). Treatment is oral ferrous sulphate with Vitamin C; IV iron for malabsorption or non-response. In men and post-menopausal women, iron deficiency demands GI investigation to exclude colorectal cancer.

✅ KEY TAKEAWAYS — Iron Deficiency

• Iron deficiency is the world’s most common nutritional deficiency, affecting 1.27 billion people globally

• Iron deficiency WITHOUT anaemia (depleted stores, normal Hb) is common, symptomatic, and frequently missed — ferritin must be checked

• Iron deficiency anaemia in a man or post-menopausal woman demands GI investigation, colorectal cancer must be excluded

• A ferritin of 15 ng/mL is NOT normal . The AGA 2024 cutoff for deficiency is < 45 ng/mL, not the outdated lab reference range

• Treat to ferritin > 100 ng/mL, not just to a normal haemoglobin. Stopping at Hb normalisation guarantees relapse

• Vitamin C taken with iron tablets doubles or triples non-haem iron absorption; a free, evidence-based intervention

She Had Seen Four Doctors. Taken Three Antidepressants. Nobody Had Checked Her Ferritin.

In thirty-two years of medicine, the diagnosis I have been most frustrated to inherit from other doctors is iron deficiency. Not because it is rare. Not because it is complicated. But because the answer was sitting in a ferritin level that nobody had bothered to order.

A 29-year-old primary school teacher came to me looking hollowed out:

Two years of exhaustion
hair falling out in handfuls in the shower
a heart that raced when she climbed a single flight of stairs
on her third antidepressant but no improvement

Her haemoglobin was 9.2 g/dL. Her ferritin was 4 ng/mL, barely detectable. She had heavy periods and ate almost no red meat. Three months of iron supplementation changed her life. She told me she felt ‘like a human being again’ for the first time in two years.

Her story is not unusual. Iron deficiency affects an estimated 1.27 billion people worldwide, making it the world’s most prevalent nutritional deficiency. Two thirds of all anaemia globally is caused by iron deficiency.

Are any of the following true for you?

You are a woman in your twenties, thirties, or forties who feels constantly tired
You have been told your blood count is ‘a bit low’ and left with no further action
You are pregnant, or planning to be
You follow a vegetarian or vegan diet
You are a man with unexplained fatigue or breathlessness that is getting gradually worse

Then this article is written for you.

🏥 From My Clinic: The teacher I described is one of dozens of similar cases I see every year. What they share is a gap between a symptom and the test that would explain it. Fatigue is treated with reassurance. Breathlessness is attributed to being unfit. Hair loss is told to wait and see. Get the test. A ferritin level costs almost nothing and can transform a life.

What Is Iron and Why Is It So Critical to Human Life?

Iron is an essential trace mineral at the centre of virtually every oxygen-related process in the human body. It is the key component of haemoglobin, the protein inside red blood cells that binds oxygen in the lungs and delivers it to every cell.

Iron’s role extends far beyond haemoglobin. It is also:

The core of myoglobin, oxygen storage in muscle
A cofactor for enzymes involved in energy metabolism, DNA synthesis, and immune function
Required for neurotransmitter production, dopamine and serotonin synthesis both depend on iron

This explains why iron deficiency impairs brain function, immune defence, exercise capacity, and mood. This is not attributed to anaemia, but because iron itself is needed for these functions at the cellular level.

The Iron Economy – How the Body Manages Supply

Total body iron in an adult: 3,500–4,000 mg (men); 2,300–2,800 mg (women)
Haemoglobin iron: ~65–70%, the largest pool, inside red blood cells
Storage iron: ~25% stored as ferritin and haemosiderin in liver, bone marrow, and spleen
Only 1–2 mg per day needs to be absorbed from diet. Losses from menstruation or GI bleeding can far exceed this.

The body recycles iron with remarkable efficiency. 95% of daily iron needs are met by recycling iron from old red blood cells. Only dietary absorption compensates for losses.

Hepcidin – The Master Regulator of Iron

Hepcidin is the hormone that controls iron absorption and distribution. Made in the liver, it responds to:

High iron stores → high hepcidin → blocks iron absorption and release from stores
Low iron stores / anaemia → low hepcidin → opens iron absorption and releases stored iron
Inflammation → high hepcidin → blocks iron despite low stores (functional iron deficiency)

💡 Clinical Insight: Patients with chronic inflammatory conditions like Crohn’s disease, cancer, heart failure, CKD develop iron deficiency that does not respond to oral iron. The elevated hepcidin blocks gut absorption. These patients need intravenous iron that bypasses the hepcidin block entirely.

The Three Stages of Iron Deficiency – Why ‘Normal Blood Count’ Does Not Mean ‘Normal Iron’

Iron deficiency progresses through three sequential stages before reaching the clinical picture of anaemia. Understanding this progression is vital because Stages 1 and 2 are fully correctable, symptomatic, and frequently missed.

Stage 1 Iron depletion: Ferritin is reduced but serum iron, transferrin saturation, and haemoglobin remain normal. No anaemia but stores are running low. Symptoms may be subtle. Ferritin is the only abnormal test. Most patients at this stage are told ‘everything is normal.’
Stage 2 Iron-deficient erythropoiesis: Ferritin is very low. Serum iron falls. TIBC rises. Transferrin saturation drops below 20%. The bone marrow is now making iron-deficient red cells. Haemoglobin may still be normal or borderline. Symptoms worsen; fatigue, brain fog, reduced exercise tolerance, hair loss.
Stage 3 Iron deficiency anaemia (IDA): Haemoglobin falls below WHO threshold. Red cells become small (microcytic) and pale (hypochromic). All symptoms are now established. This is the stage at which most patients finally present to a doctor, often after months or years at Stages 1 and 2.

💡 Clinical Insight: Treating only Stage 3 (anaemia) is insufficient. The goal is to restore iron stores, ferritin to > 100 ng/mL and not merely normalise haemoglobin. A patient whose Hb reaches 12 g/dL but whose ferritin remains 8 ng/mL will relapse within months. Always treat to ferritin, not just Hb.

Iron Deficiency Symptoms: From Early Warning Signs to Full Anaemia

System	Mild–Moderate Iron Deficiency	Severe / Iron Deficiency Anaemia
General	Fatigue, reduced exercise tolerance, weakness	Profound exhaustion, inability to perform daily tasks, syncope
Cardiovascular	Palpitations on exertion	Resting tachycardia, dyspnoea at rest, cardiac flow murmur
Skin, Hair & Nails	Pale skin, brittle nails, hair thinning	Koilonychia (spoon-shaped nails), significant hair loss, pallor of conjunctivae and palmar creases
Mouth & Tongue	Mouth ulcers, mild glossitis	Angular stomatitis, atrophic glossitis smooth, sore tongue
Neurological / Cognitive	Brain fog, poor concentration, irritability	Cognitive impairment, headache, tinnitus; impaired child development
Specific Signs	Restless legs syndrome (RLS), reduced cold tolerance	Pica (craving non-food items; ice, clay, chalk, Plummer-Vinson syndrome
Pregnancy	Increased maternal fatigue	Preterm birth, low birth weight, postpartum haemorrhage risk, neonatal iron deficiency
Children	Irritability, reduced play activity	Growth retardation, impaired cognitive development may be irreversible

Table 1. Iron deficiency and IDA symptoms by severity. Sources: NCBI StatPearls; Cleveland Clinic; Merck Manual.

The Symptoms in Clinical Detail

1. Fatigue, The Universal Symptom

Every patient with iron deficiency is tired. But the nature of this tiredness is distinctive:

It does not resolve with sleep or rest
It is cellular fatigue. Muscles and organs cannot get the oxygen they need
Even mild iron deficiency without anaemia causes measurable reductions in exercise capacity and cognitive performance

2. Pica, The Symptom Nobody Expects

Pica is the compulsive craving and consumption of non-food substances. In iron deficiency:

Pagophagia (ice eating), the most common form; patients may consume bags of ice daily
They may eat clay, chalk, dirt, paper, and raw starch other documented forms
Pica is a recognised marker of severe iron deficiency and resolves with iron replacement

💡 Clinical Insight: I have had multiple patients, mostly young women who sheepishly admitted to eating ice or chalk every day, too embarrassed to mention it to previous doctors. Always ask about pica directly. It is a simple question that leads directly to a diagnosis.

3. Koilonychia, Spoon-Shaped Nails

A pathognomonic sign of longstanding, severe iron deficiency:

Nails become concave, thin, and brittle, literally spoon-shaped, capable of holding a drop of water
Develops because iron is required for normal keratin production
Rarely seen in mild deficiency but unmistakable in advanced cases

4. Restless Legs Syndrome

Iron deficiency is one of the most important and treatable causes of restless legs syndrome (RLS), the overwhelming urge to move the legs at night, accompanied by uncomfortable crawling sensations.

Iron is required for dopamine synthesis in the brain; dopaminergic dysfunction underlies RLS
Checking iron studies is mandatory in any patient presenting with RLS
Iron replacement significantly reduces RLS severity in deficient patients

5. Cognitive Impairment in Children, A Particularly Serious Consequence

Iron deficiency in children, even without overt anaemia, causes measurable impairment of:

Cognitive development and IQ
Attention, concentration, and learning capacity
Language acquisition

During the first two years of life, when brain development is most rapid, iron deficiency can cause irreversible reductions in cognitive performance. This is a public health priority of the highest order.

What Causes Iron Deficiency? Every Cause Explained

Iron deficiency always has a cause. Finding that cause is not optional; it is the most important part of management. Treating iron without finding the source is like refilling a leaking bucket without patching the hole.

Mechanism	Specific Cause	Key Clinical Detail
Blood loss, gynaecological	Heavy menstrual bleeding (HMB)	Most common cause in pre-menopausal women. Losing > 80 mL blood per cycle constitutes HMB
Blood loss, GI	Colorectal cancer	IDA in a man or post-menopausal woman = colorectal cancer until proven otherwise. Bidirectional endoscopy mandatory (AGA 2024).
Blood loss, GI	Peptic ulcer disease	Chronic NSAID use causes gastric erosions and occult GI bleeding, progressively depleting iron
Blood loss, GI	NSAIDs / aspirin use	High risk of irreversible neurological damage. Urgent treatment, IM injections preferred
Dietary	Vegetarian / vegan diet	Plant-based diets contain only non-haem iron, absorbed at 2–20% efficiency vs 15–35% for haem iron
Malabsorption	Coeliac disease	The duodenum — primary iron absorption site — is destroyed by gluten-triggered inflammation. IDA is often the presenting feature of undiagnosed coeliac disease
Malabsorption	H. pylori infection	It increases gastric pH, reduces ascorbic acid secretion, competes for dietary iron. Eradication improves absorption
Malabsorption	Bariatric surgery	Bypasses duodenum, primary iron absorption site. Affects up to 50% of post-bypass patients
Increased demand	Pregnancy	Iron requirement doubles. Blood volume expands 50%; foetal and placental demands are prioritised over maternal stores
Functional deficiency	Chronic inflammation / CKD / cancer	Elevated hepcidin blocks iron absorption and release from stores. Iron is trapped even when stores are adequate. Oral iron fails, IV iron bypasses the hepcidin block

Table 2. Complete causes of iron deficiency. Sources: NIH ODS; NCBI StatPearls; AGA 2024; AAFP 2025.

The Colorectal Cancer Rule – Non-Negotiable

Iron deficiency anemia in a man of any age, or in a post-menopausal woman, is colorectal cancer until proven otherwise.

The AGA 2024 Clinical Practice Update recommends bidirectional endoscopy (both colonoscopy and upper GI endoscopy) in men and post-menopausal women presenting with IDA. This is not optional. Colorectal cancer is curable when caught early and fatal when caught late.

⚠️ Warning: Never attribute iron deficiency anemia in a man or post-menopausal woman solely to diet without GI investigation. Occult GI bleeding from cancer, ulcer, or polyp is the most dangerous missed diagnosis in iron deficiency management.

The Coeliac Connection -Always Screen

The duodenum, where iron is preferentially absorbed is the most severely affected segment in coeliac disease
IDA is often the presenting feature of undiagnosed coeliac disease
Screen with anti-tissue transglutaminase IgA antibodies in any patient with unexplained iron deficiency, recommended by AAFP 2025 and British Society of Gastroenterology

How Is Iron Deficiency Diagnosed? Blood Tests and What They Mean

The single most important lesson: normal hemoglobin does NOT exclude iron deficiency. Ferritin must be checked especially in patients with symptoms consistent with Stage 1 or 2 deficiency.

Test	Normal Range	Iron Deficiency	Clinical Note
Serum Ferritin	20–300 ng/mL	< 45 ng/mL (AGA 2024)	Best single test for iron stores. AGA 2024 cutoff of 45 ng/mL: 85% sensitivity, 92% specificity. Old cutoff of 12 ng/mL is dangerously insensitive
Serum Iron	60–170 µg/dL	Low	Varies widely with recent intake. Less reliable alone
Transferrin Saturation (TSAT)	20–50%	< 20%	TSAT = serum iron ÷ TIBC × 100. Useful when ferritin is elevated due to inflammation (functional iron deficiency).
TIBC	250–370 µg/dL	Elevated (> 370)	Rises in iron deficiency as transferrin increases to scavenge more iron. Low in anemia of chronic disease.
Haemoglobin (Hb)	≥12 g/dL (F); ≥13 g/dL (M)	Below threshold = anaemia	Anemia is a LATE sign. Iron deficiency without anaemia (Stage 1–2) requires ferritin to detect
MCV	80–100 fL	< 80 fL (microcytosis)	Microcytosis appears only in established deficiency. Normal MCV does NOT exclude early iron deficiency

Table 3. Iron studies interpretation. Sources: AGA 2024; AAFP 2025; NIH ODS.

Population Group	Anaemia (Hb below)	Severe Anaemia
Children 6 months–5 years	11.0 g/dL	< 7.0 g/dL
Non-pregnant women ≥15 years	12.0 g/dL	< 8.0 g/dL
Pregnant women	11.0 g/dL	< 7.0 g/dL
Men ≥15 years	13.0 g/dL	< 8.0 g/dL

Table 4. WHO hemoglobin thresholds for anemia by population group. Source: WHO 2011.

The Ferritin Threshold Debate, What the Latest Guidelines Say

AGA 2024: ferritin < 45 ng/mL, 85% sensitivity, 92% specificity for IDA. This is the threshold I use.
ASH Draft 2025: ferritin ≤ 20 ng/mL, a stricter threshold under consultation
When inflammation is present (elevated CRP/ESR): ferritin can be normal or elevated despite deficiency. Use TSAT (< 20%) as an alternative marker.

💡 Clinical Insight: A ferritin of 15 ng/mL in a tired, menstruating woman is iron deficiency, even if the laboratory marks it as ‘normal.’ Treat the patient, not the reference range. The outdated cutoff of 12 ng/mL misses the vast majority of symptomatic iron-deficient women.

Iron Deficiency Treatment: Oral Iron, IV Iron, and When to Transfuse

Treatment has three pillars: replace the iron, restore the stores, and correct the cause. The first without the third guarantees relapse.

Clinical Scenario	First-Line Treatment	Monitoring & Duration
Mild–moderate deficiency (no anaemia)	Oral ferrous sulphate 200 mg (65 mg elemental) once or twice daily	Recheck ferritin at 3 months; continue until ferritin > 100 µg/L
Iron deficiency anaemia (mild)	Oral ferrous sulphate 200 mg twice daily with Vitamin C (orange juice)	Hb should rise ≥1 g/dL within 2 weeks (AGA 2024). Continue 3 months after Hb normalises to replenish stores
IDA, oral intolerance / non-response	IV iron: ferric carboxymaltose, iron sucrose, or ferric derisomaltose. Single infusion often sufficient	Reassess at 3 months. Faster Hb rise than oral; preferred in IBD, post-bariatric, CKD
IDA in pregnancy	Oral iron first line. IV iron if Hb < 10 g/dL after 28 weeks or oral not tolerated	Monitor Hb every 4 weeks. Continue 3 months postpartum
Severe anaemia (Hb < 7 g/dL) or haemodynamic compromise	Blood transfusion. 1–2 units packed red cells. IV iron to follow for store replenishment	Transfuse to symptomatic threshold, not to a number. Identify underlying cause urgently.
Functional iron deficiency (CKD, chronic disease)	IV iron preferred. Oral iron fails because hepcidin blocks absorption	Monitor TSAT and ferritin. Target TSAT > 20%, ferritin > 100 µg/L.

Table 5. Iron deficiency treatment protocol. Sources: AGA 2024; HemaSphere 2024; AAFP 2025.

Recovery Timeline

What Improves	Timeline After Starting Treatment
Fatigue and brain fog	2–4 weeks. Often the earliest improvement
Haemoglobin rises ≥1 g/dL	2 weeks (if not, switch to IV iron)
Haemoglobin fully normalises	6–8 weeks
Iron stores (ferritin > 100 ng/mL)	3 months of continued supplementation after Hb normalises
Hair loss improves	3–6 months

Table 6. Iron deficiency recovery timeline. Source: AGA 2024; clinical experience.

Practical Tips for Maximum Oral Iron Absorption

Take on an empty stomach: iron absorption is significantly better without food
Take with Vitamin C: a glass of orange juice doubles or triples non-haem iron absorption
Alternate-day dosing: emerging evidence suggests every-other-day dosing may result in better total absorption. Daily iron triggers a hepcidin spike that temporarily reduces the next day’s absorption
GI side effects: if constipation or nausea occurs, switch from ferrous sulphate to ferrous gluconate; gentler, equally effective

When to Use IV Iron

IV iron should not be regarded as a last resort. It is often the right first choice:

Oral iron not tolerated (GI intolerance)
Oral iron not absorbed (IBD, coeliac, post-bariatric, functional iron deficiency)
Rapid correction needed (third-trimester pregnancy, pre-operative optimisation)
Hb has not risen ≥1 g/dL within 2 weeks of correct oral iron; switch to IV (AGA 2024)

Blood Transfusion – When and When Not

Transfuse when: Hb < 7 g/dL with haemodynamic compromise; active bleeding with cardiovascular instability
Never transfuse to a number alone: transfuse to relieve symptoms
Transfusion does not treat iron deficiency: the iron in transfused cells is recycled, not retained. IV iron must follow to prevent relapse

Best Food Sources of Iron: Haem vs Non-Haem

Not all dietary iron is equal. Understanding the difference between haem and non-haem iron is essential, especially for vegetarians and vegans.

Feature	Haem Iron	Non-Haem Iron
Source	Meat, poultry, fish, shellfish	Plants, fortified foods, dairy, eggs
Absorption rate	15–35% stable regardless of body stores	2–20%, highly variable; depends on enhancers and inhibitors
Affected by diet?	Minimally	Strongly. Vitamin C enhances; tea, coffee, calcium inhibit
Best food sources	Liver, beef, oysters, dark poultry meat	Lentils, white beans, tofu, spinach, fortified cereal

Table 7. Haem vs non-haem iron — key differences for dietary planning.

Food Source	Serving	Iron (mg)	Type & Notes
Chicken liver (cooked)	85 g	11.0 mg	Haem, highly bioavailable
Oysters (cooked)	85 g	8.0 mg	Haem, excellent source
Beef (ground, cooked)	85 g	2.2 mg	Haem, well absorbed
Fortified breakfast cereal	1 serving	Up to 18 mg	Non-haem, check label; often 100% RDA
White beans (cooked)	½ cup	3.9 mg	Non-haem, take with Vitamin C
Lentils (cooked)	½ cup	3.3 mg	Non-haem, excellent plant source
Tofu (firm)	½ cup (126 g)	3.4 mg	Non-haem
Spinach (boiled)	½ cup	3.2 mg	Non-haem, pair with Vitamin C
Pumpkin seeds	28 g (1 oz)	2.5 mg	Non-haem

Table 8. Top dietary sources of iron. Source: NIH ODS / USDA FoodData Central. Adult women RDA = 18 mg/day; men = 8 mg/day.

Iron Absorption Enhancers and Inhibitors

Substance	Effect on Iron Absorption	Practical Guidance
Vitamin C (ascorbic acid)	ENHANCES doubles or triples non-haem absorption	Take iron tablet with glass of orange juice
Tea and coffee (tannins)	Reduces absorption significantly	Leave 1 hour gap before and after iron-rich meals
Calcium supplements / dairy	Competes with iron at intestinal absorptive site	Separate calcium and iron supplements by at least 2 hours
PPIs and antacids	Reduce gastric acid, impairs conversion of Fe³⁺ to absorbable Fe²⁺	If on long-term PPI, consider IV iron instead of oral
Phytates (whole grains, legumes)	Bind iron and reduce absorption	Soak, sprout, or ferment to reduce phytate content

Table 9. Substances that enhance or inhibit iron absorption — practical guidance.

💡 Clinical Insight: In South Asia and the Middle East, the habit of drinking tea with meals is a major but overlooked contributor to iron deficiency, particularly in women. Tannins in tea powerfully inhibit non-haem iron absorption. Leaving even a 1-hour gap between tea and iron-rich meals makes a measurable clinical difference.

How to Prevent Iron Deficiency

For the General Population

Eat iron-rich foods regularly. Red meat 2–3 times per week (if not vegetarian), lentils, beans, fortified cereals, dark leafy vegetables
Pair plant-based iron sources with Vitamin C at every meal
Avoid tea and coffee with meals. Leave a gap of at least 1 hour
Do not take calcium supplements at the same time as iron supplements or iron-rich meals

For Women of Reproductive Age

Have your ferritin checked annually, not just haemoglobin.
If you have heavy periods, discuss treatment with your gynaecologist. Tranexamic acid and hormonal options can significantly reduce monthly iron losses.
Increase dietary iron during and after menstruation when losses are highest.

During Pregnancy

All pregnant women: recommended 27 mg elemental iron per day from the second trimester
Check Hb and ferritin at booking, 28 weeks, and 36 weeks
If Hb < 10 g/dL at or after 28 weeks: consider IV iron for rapid correction before delivery.
Continue iron supplementation 3 months postpartum.

For Vegetarians and Vegans

Plan iron intake deliberately and systematically.
Annual iron studies (ferritin + Hb) as routine monitoring.
If ferritin falls below 30 ng/mL, discuss supplementation with your doctor.

Iron vs Vitamin B12 vs Vitamin D Deficiency — How to Tell Them Apart

Feature	Iron Deficiency	Vitamin B12 Deficiency	Vitamin D Deficiency
Global burden	1.27 billion people	Hundreds of millions	~1 billion people
Anaemia type	Microcytic, hypochromic	Megaloblastic (macrocytic)	Not a direct cause
Key early symptom	Fatigue, pallor, pica	Tingling, numbness	Bone pain, body ache
Neurological damage?	No	Yes. Irreversible if delayed	Proximal myopathy only
Key diagnostic test	Serum ferritin	Serum B12 + MMA	Serum 25(OH)D
Critical rule	In men / post-menopausal women: GI investigation mandatory	Always exclude B12 before treating folate	Order 25(OH)D NOT 1,25(OH)2D.

Table 10. Comparative guide — Iron vs B12 vs Vitamin D deficiency. Source: Clinical experience + NCBI StatPearls; NIH ODS.

Frequently Asked Questions About Iron Deficiency and Anaemia

Persistent fatigue and reduced exercise tolerance; the most consistent early signs, even before anaemia develops.
Brain fog, difficulty concentrating, and mild irritability, Stage 1 and 2 symptoms.
Hair thinning and brittle nails, may appear before Hb falls below normal

Laboratory reference ranges typically label ferritin as normal above 12–15 ng/mL. This is clinically outdated and inadequate. The AGA 2024 guideline recommends < 45 ng/mL as the threshold for iron deficiency diagnosis. For optimal iron stores, ferritin should ideally be above 50–100 ng/mL. A ferritin of 15 ng/mL in a symptomatic patient is iron deficiency.

Yes. Iron is required for dopamine and serotonin synthesis. Deficiency reduces the availability of these neurotransmitters, contributing to low mood, anxiety, and emotional dysregulation. Iron replacement frequently improves psychological symptoms particularly in women.

2–4 weeks: fatigue and brain fog begin improving
6–8 weeks: haemoglobin fully normalises.
3 months: iron stores (ferritin) replenished. Supplementation must continue after Hb normalises

Underlying cause not corrected, ongoing blood loss.
Poor absorption, taking iron with tea, coffee, or calcium.
Malabsorption condition; coeliac, IBD, post-bariatric surgery.
Elevated hepcidin (functional iron deficiency in chronic disease).
Hb has not risen ≥1 g/dL within 2 weeks → switch to IV iron and investigate further.

Yes, and when they do, it almost always means GI blood loss. Unlike women, men have no physiological iron losses from menstruation. Iron deficiency in a man demands urgent GI investigation. Colonoscopy and upper endoscopy to exclude peptic ulcers, colorectal cancer, and other sources of occult bleeding.

Yes, iron deficiency is one of the most common and most overlooked causes of diffuse hair thinning in women. Studies show ferritin below 30–40 ng/mL correlates with diffuse hair shedding. Hair loss typically improves with iron replacement over 3–6 months.

Functional iron deficiency occurs when iron stores are present but cannot be mobilised due to elevated hepcidin from chronic inflammation (CKD, cancer, heart failure, IBD). Ferritin is often normal or elevated, but TSAT is low. Oral iron fails because hepcidin blocks absorption. IV iron bypasses the hepcidin block and is the treatment of choice.

Yes, safe, recommended, and important. Iron deficiency anaemia in pregnancy is associated with preterm birth, low birth weight, and increased maternal mortality risk. Standard dose: 30–60 mg elemental iron per day. Take with Vitamin C and away from calcium supplements and tea.