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Your blood contains red blood cells (RBC), white blood cells (WBC), and platelets. Blood count tests measure the number and types of cells in your blood. This helps doctors check on your overall health. The tests can also help to diagnose diseases and conditions such as anemia, infections, clotting problems, blood cancers, and immune system disorders.

Specific types include tests for:

• RBC - the numbers, size, and types of RBC in the blood
• WBC - the numbers and types of WBC in the blood
• Platelets - the numbers and size of the platelets
• Hemoglobin - an iron-rich protein in red blood cells that carries oxygen
• Hematocrit - how much space red blood cells take up in your blood
• Reticulocyte count - how many young red blood cells are in your blood
• Mean corpuscular volume (MCV) - the average size of your red blood cells

The complete blood count (CBC) includes most or all of these. The CBC is one of the most common blood tests.

NIH: National Heart, Lung, and Blood Institute

Bone marrow is the spongy tissue inside some of your bones, such as your hip and thigh bones. It contains stem cells. The stem cells can develop into the red blood cells that carry oxygen through your body, the white blood cells that fight infections, and the platelets that help with blood clotting.

With bone marrow disease, there are problems with the stem cells or how they develop:

• In leukemia, a cancer of the blood, the bone marrow makes abnormal white blood cells
• In aplastic anemia, the bone marrow doesn't make red blood cells
• In myeloproliferative disorders, the bone marrow makes too many white blood cells
• Other diseases, such as lymphoma, can spread into the bone marrow and affect the production of blood cells

Causes of bone marrow diseases include genetics and environmental factors. Tests for bone marrow diseases include blood and bone marrow tests. Treatments depend on the disorder and how severe it is. They might involve medicines, blood transfusions or a bone marrow transplant.

If you have anemia, your blood does not carry enough oxygen to the rest of your body. The most common cause of anemia is not having enough iron. Your body needs iron to make hemoglobin. Hemoglobin is an iron-rich protein that gives the red color to blood. It carries oxygen from the lungs to the rest of the body.

Anemia has three main causes: blood loss, lack of red blood cell production, and high rates of red blood cell destruction.

Conditions that may lead to anemia include:

• Heavy periods
• Pregnancy
• Ulcers
• Colon polyps or colon cancer
• Inherited disorders
• A diet that does not have enough iron, folic acid or vitamin B12
• Blood disorders such as sickle cell anemia and thalassemia, or cancer
• Aplastic anemia, a condition that can be inherited or acquired
• G6PD deficiency, a metabolic disorder

Anemia can make you feel tired, cold, dizzy, and irritable. You may be short of breath or have a headache.

Your doctor will diagnose anemia with a physical exam and blood tests. Treatment depends on the kind of anemia you have.

NIH: National Heart, Lung, and Blood Institute

Aplastic anemia is a rare but serious blood disorder. If you have it, your bone marrow doesn't make enough new blood cells. It happens when there is damage to stem cells inside your bone marrow. There are different types of aplastic anemia, including Fanconi anemia.

The causes of aplastic anemia can include:

• Autoimmune disorders, which are the most common cause
• Certain inherited gene changes, such as the one that can cause Fanconi anemia
• Toxic substances, such as pesticides, arsenic, and benzene
• Radiation therapy and chemotherapy for cancer
• Certain medicines
• Viral infections such as hepatitis, Epstein-Barr virus, or HIV
• Pregnancy

In many people, the cause is unknown. This is called idiopathic aplastic anemia.

Aplastic anemia can develop suddenly or slowly. It can be mild or severe. The symptoms of aplastic anemia can include:

• Fatigue
• Weakness
• Dizziness
• Shortness of breath
• Easy bruising or bleeding

Aplastic anemia can cause other problems, including frequent infections and bleeding. It raises your risk of developing a serious blood disorder.

If not treated, aplastic anemia can also lead to heart problems such as an arrhythmia (a problem with the rate or rhythm of your heartbeat), an enlarged heart, or heart failure.

To find out if you have aplastic anemia, your doctor will:

• Take your medical and your family medical histories
• Do a physical exam
• Order tests, such as tests to check if you have low numbers of cells in your bone marrow and blood

If you have aplastic anemia, your doctor will create a treatment plan for you. The plan will be based on how severe the anemia is and what is causing it. Treatments can include:

• Blood transfusions
• Blood and marrow stem cell transplants
• Medicines to suppress your immune system

Because of the risk of blood disorders, your doctor will monitor your condition and screen you for blood disorders regularly.

NIH: National Heart, Lung, and Blood Institute