Diagnosis and tests

Diagnosis step by step

When leukemia is suspected, people often do not know what will happen next: which doctor to see, which tests there will be, when they will hear the result. This topic describes the path from the first blood test to a treatment plan, step by step and in practical terms, so that you know what to expect at each stage.

Last updated: 7 October 2026~5 min read

Five glowing translucent stepping stones in a row over calm water on a dark navy background; each stone is a little brighter than the last, with warm golden light at the end of the path. — **Figure 1.**Concept: diagnosis is a path you walk one step at a time.

01Short answer

The diagnostic path usually looks like this: 1) a family doctor or GP listens to your symptoms, examines you and orders a complete blood count; 2) if it shows serious changes, you are referred urgently to a hematologist — with a suspected acute leukemia this is often the same day or within one or two days, sometimes straight into hospital; 3) the hematologist orders a repeat blood count, a blood smear, blood chemistry and clotting tests; 4) a bone marrow test is done and the sample is sent for microscopy, flow cytometry, cytogenetics and molecular tests; 5) if needed, further tests follow (lumbar puncture, heart tests, infection tests, imaging); 6) the results are put together, often discussed in a multidisciplinary team meeting, and the doctor explains the diagnosis and the treatment plan to you. With chronic leukemias this path can move at a calmer pace, over several weeks.

02Simple explanation

It often starts with an ordinary blood test. When your doctor sees unusual changes, you are referred to a specialist in blood disorders — a hematologist.

If acute leukemia is suspected, things happen quickly: sometimes you are admitted to hospital the same day. This does not mean the situation is hopeless; it means time matters.

The hematologist orders several tests and usually does a bone marrow test. This is a short procedure under local anaesthetic.

Then comes a waiting period: some results are ready within a day or two, genetic results later.

Finally your doctor sits down with you, explains the diagnosis and the plan, answers your questions and asks for your agreement (informed consent).

03Scientific explanation

Urgent referral. UK NICE guidance says that adults with signs that could suggest leukemia (pallor, persistent tiredness, unexplained fever, repeated infections, bruising, petechiae, an enlarged liver or spleen) should have a very urgent blood count, within 48 hours, and that children with unexplained petechiae or an enlarged liver and spleen should be referred for immediate specialist assessment. The NHS notes that blood test results may come within a few days, while other test results can take a few weeks. With chronic leukemias (CML, CLL), referral is often routine.

First hematology tests. These include a repeat blood count with differential, a blood smear, blood chemistry (kidney and liver function, LDH, uric acid, potassium, phosphate), clotting tests (especially if APL is suspected), blood group and infection screening (hepatitis B and C, HIV). According to the ACS, these tests help both with the diagnosis and with preparing for treatment.

Bone marrow and the laboratory. The aspirate and biopsy are sent for microscopy, flow cytometry, cytogenetics (karyotype, FISH) and molecular tests. In ALL and some other situations, a lumbar puncture is done to check the central nervous system, usually at the start of treatment.

Decision and consent. In many centres, results are discussed in a multidisciplinary team meeting (hematologists, pathologists, laboratory specialists, nurses). According to the ACS, before treatment the aims, risks and alternatives must be explained and informed consent obtained.

04What happens in the body?

Step 1: the first doctor and the first test

When you see a doctor about tiredness, paleness, frequent infections, bruising, bleeding gums or bone pain, they examine you and order a blood count. Sometimes the changes are found with no symptoms at all, on a routine test.

Step 2: referral to a hematologist

If the result shows serious changes, you are referred to a hematologist. If acute leukemia is suspected, this happens the same day or within one or two days; sometimes you are admitted straight away so that tests and any support you need happen in one place.

A translucent glowing envelope with a tiny drop of blood inside flying along a gentle line of light towards a bright doorway marked with a blood-cell symbol, on a dark navy background. — **Figure 2.**Referral: a fast track from the first doctor to the hematologist.

Step 3: more blood tests and the bone marrow

The hematologist orders repeat blood tests, chemistry and clotting tests, then does a bone marrow test. The procedure usually takes 20–30 minutes; a local anaesthetic, and sometimes a mild sedative, is used to reduce discomfort.

Step 4: waiting and further tests

While the results are awaited, you may have heart tests (ECG, echocardiogram), infection tests, a chest X-ray or CT scan and, if needed, a lumbar puncture. Transfusions and protection against infection may already start during this time.

Step 5: discussing the results and the plan

Once all the results are in, your doctor meets you to explain the type of leukemia, the risk group and the aim and plan of treatment. Write your questions down beforehand and note the answers. This is also a good time to ask for a second opinion.

Four glowing result cards — a cell, coloured dots, a chromosome and DNA — floating above a round translucent table on a dark navy background and merging into one glowing sphere in the centre; no faces. — **Figure 3.**Once the results are in, the team discusses the plan together.

05From the first test to the plan

The four main transitions on the way.

1First testThe family doctor spots a concern.

2HematologistUrgent referral and further tests.

3Bone marrowThe sample is shared between laboratories.

4ConversationDiagnosis and plan explained, consent.

A clear timelineKnowing what happens when.

Prepared questionsGetting the most from each visit.

Starting with consentThe plan is agreed with you.

06Pace of diagnosis in acute and chronic leukemia (general example)

Stage	Suspected acute leukemia	Suspected chronic leukemia
Referral to a hematologist	Same day to 2 days	A few days to a few weeks
Hospital admission	Often needed	Usually not needed
Bone marrow test	In the first days	Usually in CML; not always in CLL
First results	1–3 days	A few days
Genetic results	A few days to 3 weeks (urgent ones sooner)	1–3 weeks
Start of treatment	Often within a few days	Sometimes not straight away; “watch and wait” is possible in CLL

* This is only a general example. Actual timings depend on the country, the hospital and your condition — ask your own team.

07Key terms

Referral: When one doctor sends a patient to another specialist.
Hematologist: A doctor specialising in disorders of the blood and bone marrow.
Blood chemistry: Blood tests for kidney, liver and salt levels.
Clotting tests: Tests of the blood’s ability to clot (PT, APTT, fibrinogen).
Lumbar puncture: Taking a sample of spinal fluid with a thin needle.
Multidisciplinary team: A meeting where specialists from different fields decide together.
Informed consent: Agreement given after the aims and risks of treatment are explained.
Screening: A check-up test to detect hidden problems.

08Key points

Diagnosis usually begins with a complete blood count.
With a suspected acute leukemia, things happen within days.
With chronic leukemia, the pace can be calmer.
A bone marrow test is the key step in most cases.
Supportive treatment may start while you wait.
The diagnosis and plan must be explained to you and your consent obtained.
Write down your questions and bring someone close with you.

09Frequently asked questions

Why was I admitted to hospital so quickly?

In acute leukemia, blood counts can change fast and the risk of infection and bleeding is high. In hospital, tests are done quickly in one place, and support such as transfusions and antibiotics can start straight away.

Waiting for results is very hard. What can I do?

Ask which results are awaited and roughly when they will be ready. Write your questions down, talk to people close to you and ask about psychological support. Waiting does not mean treatment is being delayed.

Who should I bring to the diagnosis conversation?

Someone close whom you trust. They can take notes and help you remember what was said afterwards. If you would like to record the conversation, ask your doctor first.

Do I have time to think before agreeing to treatment?

Usually yes, but with acute leukemia time may be limited. Ask your doctor how long it is safe to wait. If you would like a second opinion, say so openly.

Will my family doctor be told about the diagnosis?

In many countries the hematologist sends a letter to the family doctor. This helps with care at home later on. Ask how this works at your hospital.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

Why was I admitted to hospital so quickly?
Waiting for results is very hard. What can I do?
Who should I bring to the diagnosis conversation?
Do I have time to think before agreeing to treatment?
Will my family doctor be told about the diagnosis?

My questions

12Sources

National Institute for Health and Care Excellence (NICE). Suspected cancer: recognition and referral (NG12)
NHS. Acute myeloid leukaemia — Tests and next steps
NHS. Acute lymphoblastic leukaemia — Tests and next steps
NHS. Chronic myeloid leukaemia — Tests and next steps
Cancer Research UK. Tests for acute myeloid leukaemia (AML)
Cancer Research UK. Tests for chronic lymphocytic leukaemia (CLL)
American Cancer Society. Tests for Acute Myeloid Leukemia (AML)
American Cancer Society. Tests for Childhood Leukemia
American Cancer Society. Informed Consent
National Cancer Institute (NCI). Questions to Ask Your Doctor about Your Diagnosis
National Cancer Institute (NCI). Adult Acute Lymphoblastic Leukemia Treatment (PDQ®) — Patient Version
MedlinePlus (U.S. National Library of Medicine). How to Understand Your Lab Results
Blood Cancer United (formerly The Leukemia & Lymphoma Society). Acute lymphoblastic leukemia (ALL) diagnosis

Medical disclaimerThis information is for educational purposes only and does not replace medical advice.

Last updated: 7 October 2026← Back to the list

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