Hematologist
CION Cancer Clinics
Which tests find the cause of anaemia? | CION Cancer Clinics
The cause of anaemia is usually found in two rounds. First, a full blood count, a blood smear, iron studies, vitamin B12 and folate, often with kidney, liver and thyroid tests. Then, guided by the size of your red cells, the doctor looks for the source: hidden bleeding, an inherited trait, the kidneys, or the bone marrow. This page explains that order, and what the tests cannot tell you. At CION Cancer Clinics, our haematologist cares for anaemia, bleeding, clotting and inherited blood disorders, with ArogyaSri, CGHS and cashless insurance accepted.
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Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
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On this page
- Which tests are done first to find the cause?
- In what order are the tests usually done?
- Which follow-up tests match which pattern?
- What do the test names on the form mean?
- What do families often get wrong about these tests?
- What can these tests not tell you, and how do you prepare?
- Common questions about tests for anaemia
The short answer
Which tests are done first to find the cause?
The cause of anaemia, a low haemoglobin, is usually found in two rounds of tests. First come simple blood tests: a full blood count, a look at the blood under a microscope, iron levels, vitamin B12 and folate. Then, depending on what those show, the doctor looks for where the problem starts: blood loss, the kidneys, the bone marrow or red cells breaking down too early.
Why a low haemoglobin is not the answer on its own
A low haemoglobin tells you there are too few healthy red cells. It does not tell you why. The same number can come from heavy periods, a slow bleed in the stomach, a diet short in B12, a kidney problem, an inherited trait or, less often, a blood cancer. Each of those needs a different plan. That is why a good doctor tests before treating.
The single most useful clue
The size of your red cells is on your first report, as the MCV. Small cells point towards low iron or an inherited trait such as thalassaemia. Large cells point towards low B12 or folate, the liver, the thyroid or alcohol. Normal-sized cells send the search towards the kidneys, long illnesses, bleeding that has just started, or the bone marrow.
Reference ranges differ between laboratories. A single result is always read alongside your symptoms and a repeat test.The pathway
In what order are the tests usually done?
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The history and examination
The doctor asks about diet, periods, pregnancy, stool colour, piles, pain-killer use, weight loss and family history. They also examine you.
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First blood tests
A full blood count with red cell size, a peripheral smear, iron studies with ferritin, vitamin B12 and folate. Kidney, liver and thyroid tests are often added at the same visit, from the same sample.
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Sorting by pattern
The results are grouped by cell size and by whether the white cells and platelets are also affected. A low haemoglobin alone is a very different picture from all three counts being low together.
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Looking for the source
If iron is low, the next question is where it is being lost. This may mean a stool test for hidden blood, a gynaecology review, or a camera test of the stomach and bowel.
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Specialist blood tests
Tests for inherited haemoglobin conditions, red cells breaking down early, or a problem with the immune system, chosen only when the first round points that way.
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Bone marrow test, if needed
Only when the blood tests cannot explain the picture, or other counts are also abnormal. Most people with anaemia never need one.
Not sure whether this applies to you?
Ask an oncologistReading your first report
Which follow-up tests match which pattern?
Your doctor picks the next tests from what the first round showed. These are the usual groupings, not a checklist to order yourself.
Small red cells
Usually low iron. If iron stores are normal, an inherited trait such as thalassaemia is checked next, which matters before marriage and pregnancy.
Tests often added
- Ferritin and transferrin saturation
- HPLC for haemoglobin types
- Stool test for hidden blood
Large red cells
Often low B12 or folate, which is common in vegetarian diets. Thyroid, liver and alcohol are also looked at.
Tests often added
- Vitamin B12 and folate
- Thyroid and liver tests
- Antibodies linked to poor B12 absorption
Normal-sized cells
Common with kidney disease, long-standing infection or inflammation, and in older adults. It can also be the early stage of a bleed.
Tests often added
- Kidney function and CRP
- Reticulocyte count
- LDH, bilirubin and a Coombs test
Other counts low too
When white cells or platelets are also abnormal, or the smear shows unusual cells, a haematologist needs to see the report without delay.
This pattern does not mean cancer, but it is the one pattern that should not wait.
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When testing cannot wait for an appointment
If you have black or tarry stools, are vomiting blood, feel breathless at rest, have chest pain, or have fainted, do not wait for the test results. Go to the nearest emergency department today, or call 108. Tell them you have been told your haemoglobin is low, and take your latest report with you.
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On your report
What do the test names on the form mean?
- Ferritin
- A measure of your stored iron. A low result points clearly to low iron. A normal result can hide low iron if you have an infection or inflammation.
- Transferrin saturation
- How much of the iron-carrying protein in the blood is loaded with iron. It helps when ferritin is hard to read.
- Reticulocyte count
- The number of young red cells. It shows whether the bone marrow is trying to keep up or is not making enough.
- Peripheral smear
- A trained eye looking at a drop of your blood under a microscope, to see the shape and size of the cells.
- HPLC
- A test that separates the types of haemoglobin. It picks up thalassaemia trait and sickle cell trait.
- Coombs test (DAT)
- Checks whether your own immune system is attacking your red cells.
Commonly believed
What do families often get wrong about these tests?
"It is only anaemia. Iron tablets will fix it, no need to test."
Iron helps only when iron is the problem, and it does nothing to find where the iron went. If the cause is low B12, a kidney problem or an inherited trait, tablets delay the real answer. Tell your doctor if you have already started iron, because it changes the results.
"My ferritin is normal, so iron cannot be the cause."
Ferritin rises during infection, inflammation and liver problems. A normal number can sit alongside genuinely low iron. Your doctor reads it together with transferrin saturation and the size of your red cells.
"He has no stomach pain, so a camera test is a waste."
Slow bleeding from the stomach or bowel often causes no pain at all. Low iron with no clear reason, especially in men and in women after menopause, is exactly when a camera test is usually advised.
"If they want a bone marrow test, it must be cancer."
A marrow test is asked for when the blood tests leave a question open. It also finds non-cancer causes, such as marrow that has simply slowed down. It is a way of getting an answer, not a sign of which answer it will be.
Being straight with you
What can these tests not tell you, and how do you prepare?
No single test gives the cause on its own. Each one rules some causes in and some out, and more than one cause is common. An older adult can have low iron and a kidney problem at the same time. A young woman can have heavy periods and thalassaemia trait together.
Why the order matters
Tests are best done before any treatment changes the picture. Iron tablets, vitamin injections and a blood transfusion can all make the first results harder to read. Do not stop or skip anything you have been prescribed. Simply tell the doctor what you are already taking, and since when.
What to bring
Bring every old blood report, even ones from years ago, because a slow fall over time tells a different story from a sudden drop. Bring a list of your medicines, including pain-killers and blood thinners. A man or a woman past menopause with low iron and no clear reason usually needs the stomach and bowel looked at.
This page cannot tell you which test you need. Your report and your history decide that.Questions we are asked
Common questions about tests for anaemia
Do I need to fast before these blood tests?
Most anaemia tests do not need fasting. Some laboratories prefer a morning sample for iron studies, because iron levels change through the day. If a sugar or cholesterol test is being done from the same sample, fasting may be asked for. Check with the laboratory when you book, and follow what they tell you.
Can one blood test tell me the cause of my anaemia?
Rarely. The full blood count shows that anaemia is there and gives the first clue from the size of the red cells. The cause usually needs two or three more tests chosen from that clue. Sometimes it takes a camera test or a specialist opinion before the picture is complete.
Why does the doctor want to test my stool?
Low iron in an adult who is not losing blood through periods often means a small, hidden bleed from the stomach or bowel. A stool test can pick up blood you cannot see. A negative result does not fully rule a bleed out, so a camera test may still be advised.
Is an endoscopy or colonoscopy really necessary?
Not for everyone. It is usually advised when iron is low with no clear reason, especially in men, women past menopause and anyone with weight loss or a change in bowel habit. It can find ulcers, polyps, piles higher up, and sometimes an early cancer that is easier to treat when found early.
Should my family be tested for thalassaemia too?
If your HPLC test shows thalassaemia trait, your doctor may suggest testing your spouse, and your brothers and sisters. This matters most when planning a pregnancy, because two parents with the trait can have a child with a serious form. Carrying the trait alone does not usually need treatment.
When is a bone marrow test done for anaemia?
When the blood tests do not explain the anaemia, when white cells or platelets are also abnormal, or when the smear shows cells that should not be in the blood. It is done with a needle from the back of the hip bone under local numbing. Most people with anaemia never need it.
My tests came back normal but I am still anaemic. Now what?
This is the point to see a haematologist, a blood specialist. Less common causes include kidney hormone shortage, long illnesses, early marrow problems and red cells breaking down too quickly. Bring every report you have, because a haematologist reads the pattern across them, not just the latest one.
Can CION arrange all of these tests?
CION's haematology team reviews your reports, advises which tests are needed and in what order, and helps you access them with qualified laboratories and centres where required. Call the helpline with your latest report and we will tell you the next step.
Your Haematologist
Meet CION's haematologist. One specialist for your blood report and your plan.
Dr. Basudev Pokhrel reviews blood counts, transfusion needs and blood disorders, and works with the CION tumour board on blood cancers.
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Where to find us
Our centres in and around Hyderabad
Addressed by landmark, because that is how this city navigates. A haematology consultation can be booked at any of these centres through one helpline, and your team will tell you where each test or treatment takes place.
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Sources
- NHS — Iron deficiency anaemia
- NHS — Vitamin B12 or folate deficiency anaemia
- NHLBI — Anemia: Diagnosis
- NICE Clinical Knowledge Summaries — Anaemia - iron deficiency
- American Society of Hematology — Anemia
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
MCV, MCH and RDW: Reading Your Anaemia PanelWhat the red cell size numbers on your first report meanAnaemia That Does Not Improve With IronWhen iron tablets are not the answerWhen Anaemia Needs a HaematologistThe patterns that should go to a blood specialistAnaemia: Recognising and Classifying ItThe full guide to low haemoglobin
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Holding a report with a low haemoglobin?
Share it with us or call the helpline. CION's haematology team will tell you which tests make sense next, and in what order. One helpline serves every CION centre.