A blood cancer diagnosis is rarely made from one test. Blood tests such as a complete blood count (CBC) or blood smear may show that something needs further investigation, but they cannot diagnose every type of blood cancer.
The next step depends on what doctors are trying to confirm. A bone marrow test, tissue biopsy, specialised blood tests or imaging may be needed before the diagnosis and exact subtype are clear. Being sent for further tests does not mean that cancer has already been confirmed.
Key takeaways • A blood test may be the first sign that further investigation is needed, but it cannot diagnose every type of blood cancer. • Different blood cancers need different tests. Leukaemia may be investigated through blood and sometimes bone marrow, while lymphoma usually needs a tissue biopsy. • Not everyone being investigated for blood cancer needs a bone marrow biopsy. • Some tests help confirm the diagnosis, while others identify the subtype or provide information that may later guide treatment. • Results may become available at different times because samples can go through several separate laboratory tests. |
Blood tests are often the first step in investigating blood cancer
A complete blood count (CBC) is often one of the first tests ordered when doctors are investigating a possible blood cancer. It measures red blood cells, white blood cells and platelets. A differential breaks the white cells down by type.
A peripheral blood smear may also be examined under a microscope. This lets a specialist look at the size, shape and maturity of the blood cells and see whether unusual cells are present.
An abnormal result does not automatically mean cancer. Infections, nutritional deficiencies, inflammatory conditions, medicines and non-cancerous blood disorders can also change blood counts. A normal routine CBC does not universally rule out blood cancer either, particularly when the disease is mainly in lymph nodes or other tissues.
A CBC is only one part of the assessment. Symptoms, examination findings and the pattern of the blood results are read together, which is why understanding the early signs and symptoms of blood cancer can also help put the test into context.
What can blood tests tell doctors?
Different blood tests can show different kinds of changes:
Test | What it may show |
CBC | Whether red cells, white cells or platelets are unusually high or low. |
Differential | Changes in the balance of different white blood cell types. |
Blood smear | Whether blood cells look unusual or unusually immature. |
Other selected blood tests | Organ function, abnormal proteins or other findings relevant to the condition being investigated. |
What happens if the first tests suggest more investigation is needed?
An abnormal blood test does not point to one diagnosis. Doctors read it alongside symptoms and examination findings before deciding whether anything else needs to be checked.
Your doctor may repeat the blood tests, examine you again or arrange specialist assessment. The next test is chosen to answer a specific question. For example, doctors may need to know whether abnormal cells are present in the bone marrow, whether an enlarged lymph node should be sampled or whether an abnormal protein needs further assessment.
Because leukaemia, lymphoma and multiple myeloma begin in different cells and tissues, understanding the differences between them also helps explain why the diagnostic tests are not the same.
Further tests are chosen for the condition being investigated
There is no standard set of tests for everyone. A bone marrow test, tissue biopsy, specialised testing, protein testing or imaging may be used according to what the earlier results suggest. Some people need only one of these; others need several.
Bone marrow testing
Bone marrow is the soft tissue inside certain bones where blood cells are made. Examining a sample can sometimes show abnormalities that cannot be fully assessed from a blood sample alone. Bone marrow testing is particularly useful in some leukaemias and plasma-cell disorders such as multiple myeloma, but it is not required for everyone being investigated for blood cancer.
A bone marrow sample is usually taken from the back of the pelvic bone using local anaesthetic. You may feel pressure or a brief sharper sensation during the procedure, and some soreness or bruising afterwards is common. Pain-relief options can vary between centres. If you take blood-thinning medicines or have a bleeding disorder, tell the clinical team beforehand.
Lymph-node or tissue biopsy
If lymphoma is suspected, doctors usually need tissue from an affected lymph node or another involved area. Looking at the tissue allows a pathologist to examine the abnormal cells and the way they are arranged, which helps confirm and classify lymphoma.
Doctors may remove all or part of an accessible lymph node or use a core needle biopsy to collect tissue. Sometimes the first sample is too small or does not contain enough useful tissue. In that situation, another biopsy may be recommended simply to obtain a reliable answer.
Specialised tests on blood, marrow or tissue
Once blood, bone marrow or tissue has been collected, the laboratory may run specialised tests on the same sample.
Flow cytometry looks at markers on the cells. This can help identify which type of blood cell is abnormal and distinguish between certain blood cancers.
Chromosome and molecular tests look for changes inside the abnormal cells. These results can help confirm the subtype and, in some blood cancers, may influence treatment decisions.
Changes found in cancer cells are often acquired during a person’s lifetime rather than inherited. Inherited genetic testing is different and is only considered when there is a clinical reason for it.
Blood and urine protein tests
If multiple myeloma is suspected, blood and urine tests may be used to look for abnormal proteins made by plasma cells.
Finding one of these proteins does not always mean active multiple myeloma. Similar findings can occur in conditions such as monoclonal gammopathy of undetermined significance (MGUS), so doctors interpret the result alongside other blood tests, bone marrow findings and scans.
Scans
CT, PET/CT or MRI scans may be used to see where disease is present, assess bone involvement or help choose an area for biopsy.
The type of scan needed depends on the blood cancer being investigated. A scan can add useful information, but it usually cannot confirm a blood cancer on its own.
How do tests differ between leukaemia, lymphoma and multiple myeloma?
The tests that matter most are not the same for every blood cancer:
If doctors are investigating | Tests that may be particularly relevant |
Leukaemia | Blood tests, blood smear, flow cytometry and sometimes bone marrow evaluation |
Lymphoma | Tissue biopsy, with blood tests and imaging supporting the wider assessment |
Multiple myeloma | Blood and urine protein tests, bone marrow evaluation and imaging |
These are common patterns, not a fixed sequence. The exact tests depend on the suspected subtype and what earlier results have shown.
Why might some results take longer than others?
Not every result comes from the same laboratory process. Microscopy, flow cytometry, tissue processing, chromosome testing and molecular testing are carried out separately, so the reports may arrive at different times.
An initial diagnosis may be available before the full subtype or molecular information is complete. Turnaround times vary between hospitals and laboratories, so there is no single timeline that applies to everyone.
The time a result takes to come back does not tell you whether it will be good or bad news. If you are unsure what is still pending, ask the treating team which reports are complete and which are still awaited.
What happens once the diagnosis is confirmed?
Once the diagnosis is confirmed, the next discussion is based on more than the name of the cancer. Doctors first establish the exact type or subtype. They may also consider the extent of disease where relevant, important biological features, blood counts, organ function and the person's overall health.
Not every blood cancer is staged in the same way. Some use formal stages, while others are described using disease-specific classifications, phases or risk groups. These systems help clinicians organise medical information, but they do not predict exactly what will happen to an individual person.
The same information also shapes how blood cancer treatment is decided, including whether treatment is needed now and which options may be suitable.
Questions you may want to ask at your next appointment
You do not need to ask everything at once. A few questions can help you understand where you are in the diagnostic process:
• What has been confirmed so far, and what is still being investigated?
• Do we know the exact type or subtype yet?
• Why do I need this particular test, biopsy or scan?
• Are any results still pending?
• Which results are likely to matter when the next step is decided?
Writing down the answers, or bringing someone who can take notes, can make a complicated appointment easier to follow.
By the time a diagnosis is confirmed, you may have several reports rather than one definitive test result. The important part is understanding what has already been confirmed and what is still being investigated.
If tests are still pending, ask your treating team what each remaining test is meant to clarify and when the results are likely to be reviewed.
If you already have a diagnosis
If you have been diagnosed with blood cancer and want to discuss supportive care alongside your oncology treatment, you can schedule a consultation with Dr Tarang Krishna. This does not replace care from your haematology or oncology team.
Read more from the blood cancer series
• What Is Blood Cancer? Early Signs, Symptoms and When to Get Checked
• Leukaemia, Lymphoma and Multiple Myeloma: What Is the Difference?
• How Is Blood Cancer Treatment Decided? Type, Stage, Age, Overall Health and Other Factors
References
American Cancer Society (2025) ‘Tests for Multiple Myeloma’. Last revised 28 February 2025.
American Cancer Society (2026) ‘Bone Marrow Biopsy and Aspiration’. Last revised 26 March 2026.
Döhner, H. et al. (2022) ‘Diagnosis and management of AML in adults: 2022 recommendations from an international expert panel on behalf of the ELN’, Blood, 140(12), pp. 1345–1377.
Eyre, T.A. et al. (2025) ‘Lymphomas: ESMO Clinical Practice Guideline for diagnosis, treatment and follow-up’, Annals of Oncology, 36(11), pp. 1263–1284.
NHS (2026) ‘Tests and next steps for non-Hodgkin lymphoma’. Page last reviewed 10 March 2026.
