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Complete Guide to Anaemia

Anaemia is not a single diagnosis. It is a symptom with many causes. Identifying the type of anaemia through blood tests is essential before starting any treatment.

Written by Suman Konda, Clinical Pharmacist · Based on peer-reviewed sources · Editorial policy · Not medical advice

Last reviewed and updated: · How we check our content

Quick answer

Anaemia means low haemoglobin for your age and sex, and this guide walks through finding the cause step by step: blood count and cell size first, then iron studies, B12 and folate, and tests for blood loss or breakdown. The takeaway: a normal ferritin does not rule out iron deficiency when inflammation is present, and treatment must match the cause.

Anaemia workup tests at a glance

The tests below are the standard workup this guide walks through. The first two are usually ordered together; the rest follow based on what the red cell size (MCV) suggests.

TestWhat it measuresHow it narrows the causeTypical price band (India)
CBC (full blood count)Haemoglobin, red cell indices including MCV, reticulocytesConfirms anaemia and classifies it by red cell sizeTypically ₹250–₹450
Peripheral blood filmRed cell shape under the microscopeTarget cells, spherocytes, sickle or fragmented cells point to specific causesVaries by lab — check the lab’s own listing
Iron studies (ferritin, serum iron, TIBC, transferrin saturation)Body iron stores and availabilityLow ferritin or transferrin saturation confirms iron deficiencyVaries by lab — check the lab’s own listing
Vitamin B12 and folateB12 and folate levelsLow levels explain a macrocytic (large-cell) patternVaries by lab — check the lab’s own listing
Haemoglobin electrophoresisHaemoglobin variantsIdentifies thalassaemia trait and other inherited causesVaries by lab — check the lab’s own listing
Reticulocyte countYoung red cells in circulationLow points to a production problem; high to bleeding or haemolysisVaries by lab — check the lab’s own listing

Approximate bands compiled from typical online list prices — not quotes. Prices change often and vary by city; home collection can add a small fee, so check the lab’s own listing before booking.

What is anaemia?

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Anaemia is defined as haemoglobin below the normal range for sex and age: below 13.5 g/dL in adult men, below 12.0 g/dL in adult women, and below 11.0 g/dL in pregnant women. It affects approximately 1.6 billion people globally, making it one of the most common medical conditions. The cause determines the treatment, which is why a systematic approach using blood tests is essential.

Anaemia pathway by red cell sizeHow mean cell volume narrows the likely cause of anaemia.Red cell size narrows the cause of anaemiaLow haemoglobinNext: look at MCVMCV < 80 fLMicrocyticIron deficiency,thalassaemia, chronicdiseaseMCV 80–100 fLNormocyticBlood loss, chronicdisease, kidney disease,haemolysisMCV > 100 fLMacrocyticB12 or folate deficiency,alcohol, thyroid, drugsThe reticulocyte count then separates reduced production from increased loss or destruction:low reticulocytes point to a production problem, high to bleeding or haemolysis.
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.

Step 1: CBC + blood film, classifying anaemia by red cell size

MCV (mean cell volume)Red cell appearanceLikely cause
Low MCV (<80 fL)Microcytic (small cells)Iron deficiency (most common), thalassaemia, sideroblastic anaemia
Normal MCV (80–100 fL)Normocytic (normal size)Anaemia of chronic disease, haemolysis, blood loss (acute), kidney disease
High MCV (>100 fL)Macrocytic (large cells)Vitamin B12 deficiency, folate deficiency, alcohol, hypothyroidism, liver disease
Key points
  • Defined by haemoglobin below the age and sex range; MCV classifies the cause by red cell size.
  • Iron deficiency: check ferritin, but inflammation can mask it, so normal ferritin does not always rule it out.
  • B12 and folate deficiency give a megaloblastic pattern and develop slowly; test before supplementing blindly.
  • Blood loss and haemolysis need their own targeted workups.
  • Treatment must match the cause; iron is not the answer to every anaemia.

Step 2: Iron deficiency anaemia workup

TestIron deficiency finding
Ferritin<30 ng/mL (often much lower): most sensitive marker
Serum ironLow
TIBCHigh (body compensates by making more transport protein)
Transferrin saturation<16%
MCVLow (<80 fL)
Blood filmMicrocytic, hypochromic cells; target cells

Why a Normal Ferritin Does Not Rule Out Iron Deficiency

Ferritin is the standard first test for iron stores, and for most people a low result settles the question. The difficulty is what it does when something else is going on, because ferritin is also an acute-phase protein: the body raises it during inflammation, infection, and tissue injury, quite independently of how much iron you actually have.

So inflammation pushes ferritin up while iron deficiency pushes it down, and the two can cancel out. Someone with an inflammatory condition, a chronic infection, kidney disease or obesity can be genuinely iron deficient and still return a ferritin in the normal range. Reviews of iron deficiency in chronic kidney disease make this explicit: inflammation raises ferritin regardless of iron status, and in doing so weakens ferritin’s ability to predict either iron stores or the response to iron treatment.1

The effect is measurable in ordinary populations too. In a study across normal-weight, overweight and obese participants, ferritin rose with body mass index and tracked C-reactive protein closely, while moving in the opposite direction to haemoglobin, serum iron and transferrin saturation, the markers that actually reflect iron availability. Its authors concluded that in these groups ferritin behaves as an inflammation marker rather than an iron marker, and that a full iron profile rather than ferritin alone is needed to identify deficiency.2

What to ask for when ferritin looks normal but you have symptomsA CRP alongside the ferritin, so a raised ferritin can be interpreted rather than taken at face value, and transferrin saturation with total iron binding capacity, which are far less disturbed by inflammation. A low transferrin saturation with a normal ferritin, in someone with a raised CRP, is a recognisable pattern rather than a contradiction.

This matters most in exactly the people most likely to be told their iron is fine: those with inflammatory bowel disease, rheumatoid arthritis, chronic kidney disease, heart failure, or obesity. If you are tired, your ferritin is unremarkable and nobody has looked at your CRP or your transferrin saturation, the question has not been fully answered.3

Step 3: Megaloblastic anaemia workup

TestB12 or folate deficiency finding
Serum B12<200 pg/mL (deficiency); <100 (severe)
Serum folate<3.0 ng/mL
MCV>100 fL (macrocytic)
Blood filmOval macrocytes; hypersegmented neutrophils (5+ lobes)
Peripheral blood smearHypersegmented neutrophils are pathognomonic of megaloblastic anaemia

Step 4: Haemolytic anaemia workup

TestFinding in haemolysis
LDHElevated (released from lysed red cells)
Indirect bilirubinElevated (breakdown product of haemoglobin)
HaptoglobinLow or absent (mops up free haemoglobin; depleted in haemolysis)
Reticulocyte countHigh (bone marrow compensating)
Blood filmSpherocytes (hereditary spherocytosis), sickle cells, fragmented cells (microangiopathy)
Direct Coombs testPositive in autoimmune haemolytic anaemia

Common treatments by anaemia type

Treatment always follows the cause, which is why the classification steps above come first. The table below describes the treatment approach for each type — the specific medicine, formulation and dose are decisions for your doctor, and this guide does not give dosing.

TypeTreatment approach
Iron deficiencyIron replacement (oral iron or, where appropriate, intravenous iron); identify and treat the source of blood loss
Vitamin B12 deficiencyB12 replacement (injections or tablets, as your doctor advises); the underlying cause, such as pernicious anaemia or gut absorption problems, should be identified
Folate deficiencyFolic acid supplementation; address the underlying cause (diet, medication, malabsorption)
Anaemia of chronic diseaseTreat the underlying condition; anaemia linked to kidney disease may involve erythropoietin therapy
Thalassaemia (minor/trait)Usually no treatment needed; genetic counselling is offered where relevant

Never start iron, B12 or folate on the basis of symptoms alone: the wrong supplement wastes time and can delay the real diagnosis. Your doctor will also advise when to recheck your blood tests once treatment has had time to act.

Questions to ask your doctor

  • What type of anaemia do I have based on MCV?
  • Why am I iron deficient: is there internal bleeding?
  • Do I need B12 injections or will tablets work?
  • Should I have a haemoglobin electrophoresis for thalassaemia?
  • Is my anaemia related to a chronic illness?

Anaemia myths vs facts

MYTH Anaemia and iron deficiency are the same thing.

Fact: Iron deficiency is the commonest cause, but anaemia also results from B12 or folate deficiency, blood loss, chronic disease, kidney disease, haemolysis and inherited conditions such as thalassaemia. Iron only helps iron deficiency — the cause has to be identified first.

MYTH A normal ferritin means your iron is fine.

Fact: Ferritin rises with inflammation, infection and tissue injury, independently of iron stores. In someone with a raised CRP — for example with inflammatory bowel disease, rheumatoid arthritis, kidney disease or obesity — a normal ferritin can mask genuine iron deficiency. Transferrin saturation is far less disturbed by inflammation.

MYTH If you feel tired and pale, just start iron tablets.

Fact: Supplementing without a diagnosis wastes months when the cause is B12 deficiency or chronic disease, and can delay finding the real problem — such as slow gastrointestinal blood loss, which needs investigation in its own right. Discuss testing with your doctor before supplementing.

MYTH Anaemia is always obvious — you would know.

Fact: Anaemia that develops gradually is often silent and picked up on a routine CBC long before symptoms appear. Fatigue, breathlessness and pallor tend to surface as it worsens, which is why borderline results still deserve follow-up.

What matters most in anaemia testing

  • Classify before treating: MCV and iron studies first — the treatment follows the cause, not the haemoglobin number.
  • Test, don’t guess: never start iron, B12 or folate on symptoms alone.
  • Look for the source: iron deficiency in an adult means blood is being lost somewhere — finding where matters as much as replacing the iron.
  • Recheck on schedule: your doctor will advise when to repeat blood tests once treatment has had time to act.

Practical notes

Most anaemia tests need no special preparation: a CBC, iron studies, vitamin B12 and folate can usually be drawn at any time of day. Iron studies are sometimes scheduled in the morning because serum iron shifts through the day, so follow whatever timing your lab suggests. Tell your doctor about any iron, B12, folate or multivitamin supplements you take, because recent supplements can distort results.

Bring your previous CBC reports so the doctor can see the trend rather than a single number, plus a complete list of medicines and supplements. Useful questions to ask: what type of anaemia does my red cell size (MCV) point to, which test will confirm the cause, and when should the blood tests be repeated once treatment has started.

Read each result against the reference range printed on your own report, not a range copied from the internet — ranges differ between laboratories, methods, age and sex. A mildly low haemoglobin is a signal to investigate the cause, not a diagnosis in itself. One borderline value matters less than the pattern across your MCV, iron studies and blood film.

Repeat blood tests only when your doctor advises, usually after treatment has had time to act — rechecking too early can be misleading. Never start iron, B12 or folate on symptoms alone, because the wrong supplement wastes time and can delay the real diagnosis. If fatigue worsens, or you notice breathlessness, chest discomfort or fainting, seek medical advice promptly rather than waiting for the next scheduled review.

In India

In India, a CBC typically costs ₹250–₹450 and a full iron studies panel typically ₹800–₹1,500, though prices vary by city and lab and home collection can add a small fee. B12 and folate tests are usually priced separately, so ask the lab for the all-inclusive cost before booking.

Choose an NABL-accredited laboratory, and note that most large labs in major cities offer home sample collection. Whatever lab you use, the reference range printed on your own report is the one that counts — ranges can differ between labs even for the same test.

Frequently Asked Questions

What is anaemia?
Anaemia is defined as haemoglobin below the normal range for sex and age: below 13.5 g/dL in adult men, below 12.0 g/dL in adult women, and below 11.0 g/dL in pregnant women. It affects approximately 1.6 billion people globally, making it one of the most common medical conditions. The cause determines the treatment, which is why a systematic approach using blood tests is essential.
Why a Normal Ferritin Does Not Rule Out Iron Deficiency?
Ferritin is the standard first test for iron stores, and for most people a low result settles the question. The difficulty is what it does when something else is going on, because ferritin is also an acute-phase protein: the body raises it during inflammation, infection, and tissue injury, quite independently of how much iron you actually have.
Do I need iron if my haemoglobin is only slightly low?
Not necessarily. A mildly low haemoglobin still needs a cause: if iron studies show deficiency, iron replacement is appropriate, but if the cause is B12 deficiency or chronic disease, iron will not help. Discuss the full workup with your doctor rather than treating the number alone.
How soon should anaemia blood tests be repeated?
It depends on the cause and the treatment started. Your doctor will advise when to recheck — typically once treatment has had time to act — and will usually repeat the haemoglobin along with the marker that was abnormal (for example ferritin or B12), not just the haemoglobin.
My doctor said my haemoglobin is ‘a bit low’ but didn’t start any treatment — should I be worried?
A mildly low haemoglobin usually triggers investigation first, not immediate treatment, because the cause decides what helps. Your doctor is likely waiting on iron studies, B12 or other results before acting. If no plan was explained, it is reasonable to ask what the next step is and when to recheck.
Do I need to fast before iron studies or a B12 test?
Usually not — CBC, B12 and folate do not require fasting, and iron studies are often simply scheduled in the morning. The safest approach is to follow the instructions your lab gives when you book, and mention any supplements you take.
Can I keep taking my multivitamin before the blood test?
Supplements containing iron, B12, folate or biotin can skew results, so tell your doctor and the lab exactly what you take. They may ask you to note it on the request form or time the test differently — follow their guidance rather than stopping anything on your own.
My MCV is low but my haemoglobin is still normal — what does that mean?
Red cell size can shift before haemoglobin falls, so a low MCV with normal haemoglobin is often an early signal worth discussing with your doctor. It does not diagnose anything on its own — your doctor may suggest iron studies or simply watching it. Don’t start supplements based on MCV alone.

References

The clinical information on this page is drawn from peer-reviewed sources indexed by the US National Library of Medicine. Links go to the source so you can read it yourself.

  1. Ueda N, Takasawa K. Impact of inflammation on ferritin, hepcidin and the management of iron deficiency anemia in chronic kidney disease. Nutrients. 2018;10(9):1173. PMID 30150549 · doi:10.3390/nu10091173
  2. Khan A, Khan WM, Ayub M, Humayun M, Haroon M. Ferritin is a marker of inflammation rather than iron deficiency in overweight and obese people. J Obes. 2016;2016:1937320. PMID 28116148 · doi:10.1155/2016/1937320
  3. Al-Naseem A, Sallam A, Choudhury S, Thachil J. "Iron deficiency without anaemia: a diagnosis that matters." Clin Med (Lond). 2021;21(2):107–113. PMID 33762368 · doi:10.7861/clinmed.2020-0582
Medical Disclaimer: This page is for general educational purposes only and does not constitute medical advice. Always consult a qualified doctor for diagnosis and treatment.
Written and medically reviewed by Suman Konda, Clinical Pharmacist · Sources linked to PubMed · Not medical advice: see our disclaimer