Iron deficiency: symptoms, causes & how to fix it

Imagine waking up every morning already exhausted. You drag yourself through the day, struggling to focus, feeling dizzy when you stand, and wondering why your hair seems to be thinning. You assume it is stress — work, family, the relentless pace of modern life. But for millions of people across Southeast Asia and South Asia, the real cause is something far more treatable: iron deficiency.

Iron deficiency is the world's most common nutritional deficiency. According to the World Health Organization, it affects an estimated 30% of the global population, with women and children in South and Southeast Asia among the most impacted. Yet it remains dramatically underdiagnosed, largely because its symptoms are easy to dismiss or attribute to other causes.

This guide explains what iron deficiency is, who is most at risk, how to recognise it, and — most importantly — how to address it through diet, lifestyle, and where necessary, medical care.

What is iron deficiency?

Iron is an essential mineral that your body cannot produce on its own — it must come from food. Its primary role is to help produce haemoglobin, the protein in red blood cells that carries oxygen from your lungs to every cell in your body. Iron is also crucial for producing myoglobin (which supplies oxygen to muscles), supporting immune function, and generating energy at the cellular level.

Iron deficiency occurs when your body's iron stores fall too low to meet its needs. Left untreated, it progresses to iron deficiency anaemia — a condition in which you have too few healthy red blood cells to carry sufficient oxygen around your body. The key marker doctors look at is serum ferritin, a protein that stores iron. A ferritin level below 30 ng/mL is generally considered low, though reference ranges vary by laboratory and country.

Key distinction: You can have depleted iron stores (low ferritin) and experience symptoms long before your blood count becomes abnormal. This is called iron deficiency without anaemia — and it is far more common than most people realise.

Who is most at risk?

Iron deficiency does not affect everyone equally. Certain groups face significantly higher risk, and many of these groups are disproportionately represented in South and Southeast Asia.

Women of reproductive age

Menstruation is the leading cause of iron deficiency worldwide. Women who experience heavy periods lose significant amounts of iron each month. In India, data from the National Family Health Survey (NFHS-5, 2019–21) found that approximately 57% of women aged 15–49 were anaemic — one of the highest rates in the world.

Vegetarians and vegans

Plant-based diets are deeply embedded across India, Indonesia, and parts of the Philippines and Malaysia. While many plant foods contain iron, they contain non-haem iron, which the body absorbs far less efficiently than haem iron from animal sources. A vegetarian eating lentils absorbs roughly 2–5% of the iron in that meal; someone eating red meat absorbs 15–35%.

Pregnant and breastfeeding women

During pregnancy, iron demand nearly doubles to support the growing foetus and the increased volume of maternal blood. Iron deficiency in pregnancy is strongly linked to low birth weight, premature delivery, and poor infant development — all significant concerns across rural South and Southeast Asia.

Frequent tea and coffee drinkers

Culturally important note: Tannins in black tea — consumed daily by hundreds of millions across India, Sri Lanka, Malaysia, and Indonesia — significantly inhibit iron absorption when consumed with or shortly after meals. Switching to drinking tea between meals rather than with food can meaningfully improve iron absorption.

Children and adolescents

Rapid growth during childhood and adolescence increases the body's demand for iron. Insufficient dietary iron during these stages can impair cognitive development and school performance.

Recognising the symptoms

Iron deficiency develops gradually, and its early symptoms are easy to overlook. The following are the most common signs — though experiencing one or two does not confirm a deficiency; only a blood test can do that.

Symptom and What it means

Persistent fatigue & low energy: The most common symptom. Without enough iron, cells receive less oxygen and produce less energy.

Pale skin and pale inner eyelids: One of the easiest self-checks: pull down your lower eyelid — it should be deep pink or red. Paleness suggests low haemoglobin.

Shortness of breath on exertion: Climbing stairs or walking briskly causes breathlessness disproportionate to the effort.

Brain fog & poor concentration: Oxygen-deprived brain cells affect memory, focus, and mood — often dismissed as stress or overwork.

Cold hands and feet: Poor circulation from low haemoglobin reduces blood flow to the extremities.

Hair loss and brittle nails: Iron is essential for hair follicle health.

Restless leg syndrome: An uncomfortable urge to move the legs at night — a less-known but established link to low iron.

Pica (craving non-food items): Craving ice, chalk, clay, or raw rice is a distinctive sign of severe deficiency — more common than many doctors expect.

How is iron deficiency diagnosed?

The only way to confirm iron deficiency is through a blood test. Self-diagnosis based on symptoms alone is unreliable — fatigue and brain fog, for instance, have many possible causes. If you suspect low iron, visit a doctor or licensed clinic and ask for the following tests:

Test and What it measures

Full blood count (FBC): Checks haemoglobin, haematocrit, and red blood cell size. Abnormal results indicate anaemia but may be normal in early iron deficiency.

Serum ferritin: The most sensitive early marker. Measures iron stores before anaemia develops. Below 30 ng/mL is generally low.

Transferrin saturation: Measures how much iron is being carried in the blood. Low levels indicate the body is iron-starved.

Iron-rich foods for SE Asian diets

The most effective long-term strategy for preventing and correcting iron deficiency is diet. The good news: many of the richest iron sources are everyday staples across South and Southeast Asia.

Animal-based sources (haem iron — highly absorbable)

Plant-based sources (non-haem iron)

Absorption tip: Pair plant-based iron sources with vitamin C to dramatically increase absorption. Squeeze calamansi over kangkung, add guava to a lentil meal, or eat papaya for dessert. These fruits are abundant, affordable, and widely available across the region.

Absorption blocker: Avoid drinking tea or coffee with iron-rich meals. Tannins can reduce non-haem iron absorption by up to 60%. Calcium-rich foods (dairy, calcium-fortified soy milk) also inhibit absorption when eaten at the same time. Leave a gap of at least one hour.

Supplements — when food is not enough

If a blood test confirms iron deficiency, your doctor may recommend iron supplements. It is important to take supplements only under medical guidance — excess iron is toxic and can cause serious harm.

Common types of iron supplements

• Ferrous sulphate — the most widely prescribed form; effective but can cause constipation and nausea
• Ferrous gluconate — gentler on the digestive system; may suit people who experience side effects from ferrous sulphate
• Ferric iron (ferric ammonium citrate) — less well absorbed but sometimes prescribed for those with gastrointestinal sensitivity

Taking supplements for best results

• Take on an empty stomach or with a small amount of vitamin C-rich food for maximum absorption
• Avoid taking with tea, coffee, dairy, or calcium supplements — these significantly reduce absorption
• Dark or greenish stools are a normal and harmless side effect
• If constipation is a problem, ask your doctor about a lower dose or alternative formulation
• Continue taking supplements for the full prescribed period — ferritin levels take weeks to months to recover

Important caution: Never supplement iron without a confirmed blood test. Too much iron causes oxidative stress, damages organs, and — in children — can be fatal in overdose. More iron is not always better.

Key takeaways

• Iron deficiency is the world's most common nutritional deficiency and is especially prevalent across South and Southeast Asia
• Women of reproductive age, vegetarians, and pregnant women are at highest risk
• Symptoms include fatigue, pale skin, brain fog, hair loss, and cold extremities — but only a blood test can confirm the cause
• Locally available foods — tempeh, moringa, lentils, kangkung, calamansi, clams — are among the most effective dietary remedies
• Drinking tea or coffee with meals significantly reduces iron absorption — a critical lifestyle adjustment
• Supplements should only be taken when clinically indicated and under medical supervision

When to see a doctor?

Seek medical advice if you experience persistent, unexplained fatigue lasting more than two to three weeks, especially alongside any of the following:

• Breathlessness during light activity
• Visible paleness of skin or inner eyelids
• Heavy menstrual periods
• Pregnancy or planning to conceive
• Symptoms in a child, particularly affecting school performance or energy

Medical disclaimer: This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.