A hematologist is a doctor who specializes in researching, diagnosing, treating, and preventing blood disorders and disorders of the lymphatic system (lymph nodes and vessels).

If your primary care physician has recommended that you see a hematologist, it may be because you are at risk for a condition involving your red or white blood cells, platelets, blood vessels, bone marrow, lymph nodes, or spleen. Some of these conditions are:

  • hemophilia, a disease that prevents your blood from clotting
  • sepsis, an infection in the blood
  • leukemia, a cancer that affects blood cells
  • lymphoma,a cancer that affects the lymph nodes and vessels
  • sickle cell anemia, a disease that prevents red blood cells from flowing freely through your circulatory system
  • thalassemia, a condition in which your body doesn’t make enough hemoglobin
  • anemia, a condition in which there aren’t enough red blood cells in your body
  • deep vein thrombosis, a condition in which blood clots form inside your veins

If you want to learn more about these disorders and other blood conditions, you can find out more through webinars created by the Centers for Disease Control and Prevention (CDC).

The American Society of Hematology can also connect you with support groups, resources, and in-depth information about specific blood disorders.

To diagnose or monitor blood disorders, hematologists often use these tests:

Complete blood count (CBC)

A CBC counts your red and white blood cells, hemoglobin (a blood protein), platelets (tiny cells that clump together to make a blood clot), and hematocrit (the ratio of blood cells to liquid plasma in your blood).

Prothrombin time (PT)

This test measures how long it takes your blood to clot. Your liver produces a protein called prothrombin which helps to form clots. If you’re taking a blood thinner or your doctor suspects that you may have a liver problem, a PT test may help monitor or diagnose your condition.

Partial thromboplastin time (PTT)

Like a prothrombin test, the PTT measures how long your blood takes to clot. If you’re having problematic bleeding anywhere in your body — nosebleeds, heavy periods, pink urine — or if you’re bruising too easily, your doctor can use a PTT to find out whether a blood disorder is causing the problem.

International normalized ratio (INR)

If you take a blood thinner like warfarin, your doctor may compare the results of your blood clotting tests with results from other labs to be sure the medication is working properly and to be sure your liver is healthy. This calculation is known as an international normalized ratio (INR).

Some newer at-home devices allow patients to conduct their own INR testing at home, which has been shown to improve quality of life for patients who need to have their blood-clotting speed measured regularly.

Bone marrow biopsy

If your doctor thinks you are not making enough blood cells, you may need a bone marrow biopsy. A specialist will use a small needle to take a bit of bone marrow (a soft substance inside your bones) to be analyzed under a microscope.

Your doctor may use a local anesthetic to numb the area before the bone marrow biopsy. You’ll be awake during this procedure because it’s relatively quick.

Hematologists are involved in many of the therapies, treatments, and procedures related to blood and bone marrow. Hematologists do:

  • ablation therapy (procedures in which abnormal tissue can be eliminated using heat, cold, lasers, or chemicals)
  • blood transfusions
  • bone marrow transplants and stem cell donations
  • cancer treatments, including chemotherapy and biological therapies
  • growth factor treatments
  • immunotherapy

Because blood disorders can affect almost any area of the body, hematologists usually collaborate with other medical specialists, especially internists, pathologists, radiologists, and oncologists.

Hematologists treat both adults and children. They may work in hospitals, in clinics, or in laboratory settings.

The first step to becoming a hematologist is to complete four years of medical school, followed by a two-year residency to train in a specialty area like internal medicine.

After the residency, doctors who want to become hematologists complete a two- to four-year fellowship, in which they study a subspecialty like pediatric hematology.

To earn a board certification in hematology from the American Board of Internal Medicine, doctors must first become board certified in internal medicine. Then they must pass the 10-hour Hematology Certification Exam.

Hematologists are doctors who specialize in blood, blood-making organs, and blood disorders.

If you’ve been referred to a hematologist, you will probably need blood tests to find out if a blood disorder is causing the symptoms you’re experiencing. The most common tests count your blood cells, measure enzymes and proteins in your blood, and check whether your blood is clotting the way it should.

If you donate or receive a bone marrow or stem cells during a transplant, a hematologist will probably be part of your medical team. If you have chemotherapy or immunotherapy during cancer treatment, you may also work with a hematologist.

Hematologists have extra training in internal medicine and the study of blood disorders. Board-certified hematologists have also passed extra examinations to ensure their expertise.