What Is Hematology? Research Areas, Funding, and Career Paths

Hematology is the branch of medicine and biomedical science that studies blood, the bone marrow and other blood-forming tissues, and the lymphatic and clotting systems that work with them, along with the diseases that affect them. It is both a clinical specialty, diagnosing and managing conditions such as anemia, sickle cell disease, bleeding and clotting disorders and blood cancers, and a research discipline spanning stem cell biology, genetics, immunology, transfusion science and clinical trials. (Many countries, including the UK, spell it haematology; the root is the Greek haima, blood.) This guide explains what hematology covers and how its subfields divide up, then adds the research-administration layer that generic overviews leave out: who funds blood research, the societies and journals that organize the field, how researchers work with blood and marrow samples, and typical training paths. It is educational, not medical advice. A separate CASRAI page covers a different topic that shares part of the name, the veterinary hematology analyzer, which is laboratory equipment rather than a discipline.

What Is Hematology?

Blood is a tissue, not just a fluid. It carries oxygen on red blood cells, defends against infection through white blood cells, stops bleeding through platelets and clotting proteins, and transports nutrients, hormones and waste. All of these cells descend from hematopoietic stem cells in the bone marrow, and the process of making and renewing blood cells, hematopoiesis, is the biological foundation of the field. The discipline is organized around a handful of recurring questions:

• How are blood cells made and regulated? Hematopoiesis, the role of the marrow environment, iron and vitamin metabolism, and the growth signals that control red cell, white cell and platelet production.
• What goes wrong in the cells? Too few cells (anemias, low platelet counts), abnormal cells (inherited hemoglobin disorders such as sickle cell disease and thalassemia), or cells that multiply without control (leukemias, lymphomas and myeloma).
• How does blood clot, and what happens when clotting fails? Hemostasis covers the balance between stopping bleeding and avoiding unwanted clots, from inherited bleeding disorders such as hemophilia to venous thromboembolism.
• How is blood collected, tested, stored and given safely? Transfusion medicine and blood banking cover donor selection, compatibility testing, component preparation and safety monitoring.
• How can blood-forming cells be replaced or modified? Hematopoietic stem cell transplantation and, increasingly, cell and gene-based therapies.

Benign (Non-Malignant) and Malignant Hematology

Hematology has a long-standing internal divide that matters for research funding and training. Benign or non-malignant hematology covers anemias, hemoglobin disorders, bone marrow failure, bleeding and clotting disorders and platelet disorders. Malignant hematology covers cancers of the blood and marrow, such as leukemia, lymphoma and multiple myeloma, which overlap with oncology and are often treated by physicians trained in both. The distinction is visible in the way the US federal government assigns work: the National Heart, Lung, and Blood Institute describes its blood-disease program as focused on non-neoplastic blood diseases, while blood cancers are typically funded through the National Cancer Institute. The two halves share methods, laboratories and many patients, but they have different funders, trial networks and regulatory pathways.

Major Subfields of Hematology

• Red cell disorders — iron deficiency and other anemias, hemolytic anemias, and inherited hemoglobin disorders including sickle cell disease and thalassemia.
• Bone marrow failure and hematopoietic stem cell biology — aplastic anemia, myelodysplastic syndromes, and the basic biology of how stem cells self-renew and differentiate.
• Hemostasis and thrombosis — inherited bleeding disorders such as hemophilia and von Willebrand disease, acquired bleeding, and venous thromboembolism. Day-to-day clinical work includes antithrombotic therapy; see the CASRAI guide on the anticoagulation management program.
• Platelet and white cell disorders — thrombocytopenia, neutropenia and related conditions.
• Malignant hematology — leukemias, lymphomas, myeloproliferative neoplasms and plasma cell disorders, studied with cytogenetic and molecular methods and treated increasingly with targeted agents and cellular immunotherapy.
• Transfusion medicine and blood banking — donor management, blood typing, component therapy and hemovigilance. For related CASRAI coverage see the guides on the massive transfusion protocol, irradiation of blood products and the Specialist in Blood Banking (SBB) certification, plus the blood bank software comparison.
• Hematopoietic cell transplantation and cellular therapy — transplanting blood-forming stem cells from a donor or from the patient, and engineering cells for therapy. The 1990 Nobel Prize in Physiology or Medicine recognized E. Donnall Thomas and Joseph Murray for work on cell and organ transplantation in the treatment of disease.
• Pediatric hematology — inherited and acquired blood disorders in children, often combined with oncology in a single pediatric subspecialty.
• Laboratory hematology — the complete blood count, blood smear review, coagulation testing, flow cytometry and marrow examination that underpin diagnosis, and the quality systems that govern them.

How Hematology Relates to Neighboring Disciplines

Hematology is a clinical and laboratory branch of medicine; see What Is Biology? and the overview of the branches of science for the wider map. Its closest neighbors are immunology (white cells, transplantation, autoimmune cytopenias, transfusion reactions), genomics (inherited hemoglobin and bleeding disorders, tumor profiling), pharmacology (anticoagulants, iron products and targeted drugs), nephrology (the kidney makes the hormone that drives red cell production, so anemia is a common complication of kidney disease) and endocrinology. Research design leans on epidemiology and biostatistics, and the field’s trials often use survival and composite outcomes of the kind described in the dictionary entry on composite endpoints.

How Blood Research Is Funded

In the US, two NIH institutes carry most of the non-malignant hematology portfolio, and a third carries most blood-cancer research:

• National Heart, Lung, and Blood Institute (NHLBI). Its Division of Blood Diseases and Resources describes its mission as research on the causes, prevention and treatment of non-neoplastic blood diseases and on the safety of the blood supply. Its stated focus areas include sickle cell disease and its complications, hemostasis and thrombotic disorders, anemias and bleeding disorders, hematopoietic stem cell transplantation, and blood transfusion safety and benefits, along with cell and gene-based therapies. Programs it lists include the Blood and Marrow Transplant Clinical Trials Network (BMT CTN), the Recipient Epidemiology and Donor Evaluation Study-III (REDS-III) and the Trans-Omics for Precision Medicine (TOPMed) program.
• National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Its hematology program, within the Division of Kidney, Urologic, and Hematologic Diseases, emphasizes the normal and abnormal function of blood cells and the blood-forming system, with interests that include sickle cell disease, thalassemia, aplastic anemia, iron deficiency, hemolytic anemias, thrombocytopenia, iron metabolism and hematopoietic stem cell biology.
• National Cancer Institute (NCI). The usual home for leukemia, lymphoma and myeloma research. Confirm the current institute, program and funding announcement for a specific project with NIH program staff, since assignments depend on the application.

Funding mechanisms vary: investigator-initiated awards, and cooperative agreements such as the U01 that clinical trial networks and consortia often use, where NIH staff take a substantive role. Early-career investigators commonly enter through mentored awards such as the K99/R00. Data and biospecimens from federally funded studies are subject to NIH data-sharing policy (see the NIH Data Management and Sharing Plan guide), and shared biobank resources are common in blood research. Patient organizations, charities and professional societies also fund fellowships and pilot grants, and the American Society of Hematology runs its own research award programs; funding opportunities and priorities change, so always confirm current details with the funder.

Societies, Patient Organizations and Journals

• American Society of Hematology (ASH). Its first official meeting was held in April 1958 in Atlantic City, with more than 300 hematologists attending; it now reports more than 18,000 members from nearly 100 countries. Its stated mission is to foster high-quality, equitable care, transformative research and innovative education to improve the lives of patients with blood and bone marrow disorders. It holds an annual meeting, which it describes as the premier global event in hematology, and publishes the journal Blood, which was established in 1946 by William Dameshek and covers clinical and basic research across hematology.
• International Society on Thrombosis and Haemostasis (ISTH). A global membership organization of specialists in blood coagulation and its disorders. It began in 1954 as the International Committee on Thrombosis and Haemostasis and was reorganized as the ISTH in 1969. It publishes the Journal of Thrombosis and Haemostasis and the open access Research and Practice in Thrombosis and Haemostasis.
• World Federation of Hemophilia (WFH). A non-profit organization, headquartered in Montreal, focused on improving the lives of people with hemophilia and other inherited bleeding disorders; it was established in 1963 by Frank Schnabel and has member organizations in 152 countries.
• Other bodies and journals. National and regional societies, such as the European Hematology Association and the British Society for Haematology, organize European and UK practice, and transfusion-focused organizations such as AABB serve blood banking. Major journals beyond those above include Blood Advances, Haematologica, the British Journal of Haematology, Transfusion and Leukemia.

Common Research Methods and Tools

• Complete blood count and blood smear review — the routine laboratory entry point to most hematologic questions, and a common source of study measurements.
• Bone marrow aspiration and biopsy — the standard way to examine the blood-forming tissue directly, interpreted with morphology, cytogenetics and molecular tests.
• Flow cytometry — identifies and counts cell populations by surface markers, central to leukemia and lymphoma diagnosis and to stem cell research.
• Coagulation assays — clotting-time tests and factor activity measurements for bleeding and clotting disorders.
• Genetic and genomic testing — sequencing for inherited hemoglobin and bleeding disorders and for the mutations that classify blood cancers.
• Registries and cohorts — patient registries for rare diseases such as hemophilia and sickle cell disease, and donor-recipient cohorts in transfusion research.
• Animal and cell models — mouse models, stem cell culture and transplantation experiments, conducted under the same oversight as other vertebrate research (see the animal research ethics guide).
• Randomized and network trials — multicenter trials, including transplant and transfusion networks. For design background see non-inferiority vs. superiority trial design. Because many hematologic diseases are rare, administrators should expect small populations, registry-based designs, long follow-up and extensive biospecimen handling.

Research Administration Considerations

Blood research raises practical administrative questions that sit alongside the science. Human blood and marrow samples require consent that addresses storage and future use, and data from rare-disease populations can be identifying even when names are removed. Transfusion and donor studies involve regulated blood establishments and safety reporting. Gene and cell therapy trials add biosafety review and manufacturing oversight. Multisite networks require data coordinating centers, data safety monitoring and agreed procedures for sharing samples and data. A research administrator reviewing a hematology award should therefore expect budget lines for specimen handling and storage, central laboratories, long-term follow-up and, in transplant trials, registry reporting. Specific obligations depend on the funder, institution and jurisdiction, so confirm them with the relevant compliance offices.

A Brief History

Hematology as an organized specialty grew in the twentieth century alongside advances in blood typing, transfusion, anticoagulation and the study of the marrow. The founding of Blood in 1946, the first ASH meeting in 1958 and the development of dedicated societies for thrombosis and hemophilia mark the formation of a distinct community, while the later growth of stem cell transplantation, molecular diagnostics and targeted and cellular therapies shaped the modern research agenda. Dates for individual discoveries vary by source, so consult the primary literature before citing them.

Career and Training Pathways

The clinical path in the United States runs through medical school, an internal medicine residency (or pediatrics, for pediatric hematology) and a fellowship. The American Board of Internal Medicine states that hematology fellowship training must be accredited by the ACGME (or equivalent Canadian bodies), that candidates need a valid, unrestricted medical license, and that they must pass the Hematology Certification Examination. ABIM also describes a dual certification in hematology and medical oncology that requires three years of accredited combined training; many US programs are organized as combined hematology-oncology fellowships. Check ABIM and the specific program for current requirements, which have changed over time. Laboratory-focused physicians may instead train in pathology with a hematopathology focus, and transfusion medicine has its own fellowship and certification routes.

The research path runs through graduate study in cell and molecular biology, genetics, immunology or epidemiology, typically a PhD followed by postdoctoral training. Many investigators are physician-scientists combining fellowship with research training, often supported by the mentored K awards noted above. Laboratory roles such as medical laboratory scientist and blood bank technologist form a third path.

Frequently Asked Questions

What is hematology in simple terms?

Hematology is the study of blood, bone marrow and the blood-forming system, and of diseases such as anemia, sickle cell disease, bleeding and clotting disorders, and blood cancers.

What is the difference between hematology and oncology?

Hematology covers all blood disorders, both benign and cancerous. Oncology covers cancers of all organs. Blood cancers fall in both, which is why many US physicians train in combined hematology-oncology.

What does a hematologist do?

A hematologist diagnoses and manages blood disorders and often interprets blood and bone marrow tests. Some also run laboratories or research programs. This page is general information, not medical advice.

What is the difference between hematology and haematology?

None in meaning. Hematology is the American spelling and haematology is used in the UK and many other countries.

Who funds blood disorder research?

In the US, NHLBI funds much non-malignant blood disease research, NIDDK has a hematology program, and NCI is the usual home for blood cancer research. Charities, patient organizations and societies such as ASH add fellowships and awards.

What is the role of the American Society of Hematology?

ASH is a professional society whose first official meeting was held in 1958 and that publishes Blood, holds an annual meeting and supports research, education and care for patients with blood and bone marrow disorders.

Is a veterinary hematology analyzer part of this field?

It is laboratory equipment used to count and classify blood cells in animals, a different topic from the discipline described here. See the veterinary hematology analyzer comparison.

Related Guides

This guide is part of a series on scientific disciplines from a research-administration perspective. See the overview of the branches of science, and the companion guides What Is Immunology?, What Is Nephrology?, What Is Endocrinology? and What Is Neurology?.