Anaemia: Types, Causes, Symptoms & Treatment

Quick answer

Anaemia means low haemoglobin and affects nearly a quarter of the world's population. The commonest cause is iron deficiency, but B12 or folate deficiency, chronic disease and blood disorders also cause it. The MCV on your report usually points to the cause — and finding the cause matters more than the number itself.

What anaemia means

Anaemia is a low haemoglobin concentration: the World Health Organization defines it as haemoglobin below 130 g/L in men and below 120 g/L in non-pregnant women.³ The Global Burden of Disease Study found it affected 1.92 billion people worldwide in 2021, close to a quarter of the global population, making it one of the leading causes of disability globally.⁵

It is often detected incidentally on a routine full blood count, because symptoms — fatigue, breathlessness on exertion, poor concentration — accumulate gradually and get attributed to other causes. Iron deficiency accounts for roughly half of all cases; the rest come from B12 or folate deficiency, anaemia of chronic disease, blood loss and inherited or acquired blood disorders.

The practical point our reviewers stress: treat the cause, not the number. Giving iron without finding the source of blood loss can miss bowel cancer, coeliac disease or a peptic ulcer.

How anaemia is usually evaluated

Once low haemoglobin is confirmed, the MCV (mean red cell size) and reticulocyte count together narrow the probable cause. Ferritin is the usual first test for the commonest type, iron deficiency, with a 30 µg/L threshold used in studies — though ferritin rises with infection and inflammation, so a normal ferritin in someone unwell does not rule iron deficiency out.¹

MCV	Type	Common causes	Next tests
Low (<80 fL)	Microcytic	Iron deficiency, thalassaemia, sideroblastic anaemia	Ferritin, iron studies, Hb electrophoresis
Normal (80–100 fL)	Normocytic	Anaemia of chronic disease, acute blood loss, CKD, early combined deficiency	Reticulocyte count, CRP, eGFR
High (>100 fL)	Macrocytic	B12 deficiency, folate deficiency, alcohol, hypothyroidism, certain drugs	B12, folate, thyroid tests, alcohol history

Scroll sideways to see the whole diagram

How mean cell volume and reticulocytes narrow the cause of anaemia.

What the diagram shows. Once anaemia is confirmed, the mean cell volume splits the causes into three groups. Small cells suggest iron deficiency or thalassaemia; normal-sized cells suggest blood loss, chronic disease or kidney disease; large cells suggest B12 or folate deficiency, alcohol or thyroid disease. The reticulocyte count then separates a marrow that is not producing enough cells from one responding normally to bleeding or destruction.

Your next steps after a low haemoglobin result

A low haemoglobin is a finding, not a diagnosis. Work through these steps with your doctor:

Confirm it and look at the MCV. A single borderline reading can be repeated; the MCV on the same report points toward iron, B12/folate, or chronic disease as the likely cause.
Get ferritin checked early. Ferritin falls weeks before haemoglobin does, and a low ferritin with a normal haemoglobin already signals iron deficiency worth investigating.
Investigate the cause, not just the anaemia. Ask what is driving it: blood loss (heavy periods, gut bleeding), poor absorption (coeliac disease), chronic disease, or diet. Treating iron deficiency without finding the source misses serious causes.
Discuss the right replacement with your doctor. Oral iron, B12 or folate each suit different causes — the supplement must match the deficiency, and the underlying cause still needs treatment.
Know when it is urgent. Seek same-day assessment for haemoglobin below about 70 g/L, chest pain, breathlessness at rest, fainting, black stools or vomiting blood.

How anaemia is classified by MCV

Once low haemoglobin is confirmed, the mean cell volume (MCV) on the full blood count decides which direction the work-up takes. This classification is standard worldwide:

MCV pattern	What it is called	Common causes
Low MCV (below 80 fL)	Microcytic anaemia	Iron deficiency, thalassaemia trait, chronic disease
Normal MCV (80–100 fL)	Normocytic anaemia	Chronic kidney disease, acute blood loss, marrow disorders
High MCV (above 100 fL)	Macrocytic anaemia	Vitamin B12 or folate deficiency, excess alcohol, thyroid disease

The reticulocyte count then shows whether the bone marrow is responding: a high count suggests blood loss or haemolysis, while a low count points to underproduction.

These are approximate bands, not quotes: prices vary by city and lab, and bundled anaemia profiles are usually cheaper than ordering each test separately. Where possible, choose a NABL-accredited lab.

ICD-10-CM diagnosis codes

Anaemia is coded by its underlying cause rather than by haemoglobin level alone:

ICD-10-CM code	Description
D50.9	Iron deficiency anemia, unspecified
D50.0	Iron deficiency anemia secondary to chronic blood loss
D50.8	Other iron deficiency anemias
E61.1	Iron deficiency (without anemia)
D52.8	Other folate deficiency anemias
D51.0	Vitamin B12 deficiency anemia due to intrinsic factor deficiency

Codes shown are from the current ICD-10-CM classification (FY2026) and are provided for general reference. Clinical coding is performed by trained coders using the full medical record.

Practical notes

Keeping your old reports is one of the most useful things you can do. File each complete blood count and ferritin report with its date, and glance at haemoglobin, MCV and ferritin side by side across visits — a slow downward drift over two or three reports tells your doctor far more than any single number, and it also stops tests being repeated unnecessarily.

It helps your doctor if you arrive with context: a list of all medicines and supplements (including antacids and painkillers), any history of heavy periods, blood donation, black stools or known gut conditions, and whether you were unwell when the blood was drawn — infection and inflammation can temporarily raise ferritin and muddy the picture.

Doctors often discuss diet alongside treatment: iron from meat is absorbed more easily than iron from plant foods, vitamin C taken with a meal can improve absorption from vegetarian sources, and tea or coffee with meals may reduce it. But supplements and dietary overhauls should follow your doctor’s advice rather than guesswork, because the right replacement depends on the type of anaemia.

Follow-up testing is usually about checking response, not just re-measuring. Your doctor may repeat the blood count and ferritin after some weeks or months to see whether the numbers are moving in the right direction — and, just as importantly, whether the underlying cause has been found and addressed. Ask what interval makes sense for you and what change would prompt a rethink.

In India

In India, a complete blood count typically costs around ₹250–₹500 at private labs and a ferritin test around ₹600–₹1,200, though prices vary by city and lab. Bundled anaemia profiles that include iron studies are often cheaper than ordering each test separately, so it is worth asking the lab for package options.

Where possible, choose a NABL-accredited laboratory, and home sample collection is widely available in most major cities. Whatever the lab’s general reference range, the range printed on your own report is the one that counts, since methods and units differ between labs.

Frequently asked questions

What are the symptoms of anaemia?

Fatigue, pallor (pale inner eyelids, nail beds), shortness of breath on exertion, palpitations, dizziness, headache, poor concentration and cold intolerance. Severe anaemia causes angina and heart failure in those with underlying heart disease.

How quickly can anaemia be corrected?

Iron supplements typically raise haemoglobin by about 10–20 g/L per month. B12 treatment shows a response within 2–4 weeks. Intravenous iron works faster than oral iron, and blood transfusion corrects anaemia within hours. Your doctor chooses the route based on severity and cause.

Can diet alone treat iron deficiency anaemia?

Dietary improvement alone is rarely sufficient to correct established iron deficiency. Supplemental iron is usually required, with dietary optimisation alongside — and the cause of the deficiency still needs addressing. Discuss the right approach with your doctor rather than self-treating.

Does anaemia require blood transfusion?

Most anaemia does not require transfusion. Thresholds vary: most stable patients tolerate haemoglobin above 70–80 g/L, while patients with cardiac disease or acute blood loss may need higher thresholds. Transfusion is reserved for symptomatic severe or refractory anaemia.

Why does the MCV matter when haemoglobin is low?

The MCV (mean red cell size) on the same report often tells you more than the haemoglobin number: a low MCV points toward iron deficiency or thalassaemia, a high MCV toward B12 or folate deficiency. It is also worth checking ferritin early, since ferritin falls weeks before haemoglobin does.

My haemoglobin is only slightly below normal and I feel fine — do I still need to see a doctor?

A borderline result is often simply repeated after some weeks to see whether it persists, and feeling well does not always rule out an early deficiency — ferritin can fall well before haemoglobin does. Rather than ignoring it or treating it yourself, discuss the result with your doctor, who can decide whether further testing is needed.

Can I just start iron tablets on my own?

It is best not to. Iron supplements can mask the underlying cause — such as slow blood loss or poor absorption — and they have side effects of their own. Your doctor needs to confirm the type of anaemia first, because iron only helps when iron deficiency is actually the problem. Discuss it with them before taking anything.

Why is my doctor asking about my stomach and periods when the problem is my blood?

Because anaemia is usually a sign of something else, doctors investigate the cause rather than just the low number. That can include asking about menstrual bleeding, gut symptoms, medicines and diet. These questions are a routine part of working out where the problem lies — bring the details your doctor asks for.

How should I prepare for iron studies blood tests?

Many labs ask for a morning sample, sometimes after an overnight fast, and they may ask you to pause iron supplements beforehand — check the lab’s instructions when you book. Tell the lab about any medicines you take, and keep the report with your other results so trends can be tracked. If anything in the instructions is unclear, ask your doctor.

References

The clinical information on this page is based on peer-reviewed sources indexed in PubMed, the biomedical literature database of the US National Library of Medicine.

Rusch JA, van der Westhuizen DJ, Gill RS, Louw VJ. Diagnosing iron deficiency: controversies and novel metrics. Best Pract Res Clin Anaesthesiol. 2023;37(4):451-467. doi:10.1016/j.bpa.2023.11.001 · PMID 39764832
Ford J. Red blood cell morphology. Int J Lab Hematol. 2013;35(3):351-7. doi:10.1111/ijlh.12082 · PMID 23480230
Anemia. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK499994
Anemia Screening. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK499905
GBD 2021 Anaemia Collaborators. Prevalence, years lived with disability, and trends in anaemia burden by severity and cause, 1990–2021: findings from the Global Burden of Disease Study 2021. Lancet Haematol. 2023;10(9):e713–e734. PMID 37536353 · doi:10.1016/S2352-3026(23)00160-6
Garcia-Casal MN, Pasricha SR, Martinez RX, Lopez-Perez L, Peña-Rosas JP. Serum or plasma ferritin concentration as an index of iron deficiency and overload. Cochrane Database Syst Rev. 2021;5(5):CD011817. PMID 34028001 · doi:10.1002/14651858.CD011817.pub2

Medical Disclaimer: This page is for general education only and does not replace professional medical advice. Always consult a qualified healthcare provider.