Archives January 2023

What is a Complete Blood Count?

A complete blood count, or CBC, is a blood test that measures many different parts and features of your blood, including:

Red blood cells, which carry oxygen from your lungs to the rest of your body.

White blood cells, which fight infections and other diseases. There are five major types of white blood cells. A CBC test measures the total number of white cells in your blood. A different test called a CBC with differential measures the number of each type of these white blood cells.

Platelets, which stop bleeding by helping your blood to clot.

Hemoglobin, a protein in red blood cells that carries oxygen from your lungs to the rest of your body.

Hematocrit, a measurement of how much of your blood is made up of red blood cells.

Mean corpuscular volume (MCV), a measure of the average size of your red blood cells.

Other names for a complete blood count: CBC, full blood count, blood cell count

What is it used for?

A complete blood count is a common blood test that is often part of a routine checkup. Complete blood counts can help detect a variety of disorders including infections, anemia, diseases of the immune system, and blood cancers.

Why do I need a complete blood count?

Your health care provider may have ordered a complete blood count as part of your checkup or to monitor your overall health. The test may also be used to:

Help diagnose blood diseases, infection, immune system disorders, or other medical conditions

Check for changes in an existing blood disorder

What happens during a complete blood count?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

Usually there is no special preparation necessary for a complete blood count. But if your provider ordered other tests on your blood sample, you may need to fast (not eat or drink) for several hours before the test. Your provider will let you know if there are any special instructions to follow.

Are there any risks to the test?

There is very little risk to having a blood test. You may experience slight pain or bruising at the spot where the needle went in, but most symptoms go away quickly.

What do the results mean?

A CBC counts the cells in your blood. There are many reasons your levels may not be in the normal range. For example:

Abnormal levels of red blood cells, hemoglobin, or hematocrit may be a sign of anemia, heart disease, or too little iron in your body.

Low white cell count may be a sign of an autoimmune disorder, bone marrow disorder, or cancer.

High white cell count may be a sign of an infection or a reaction to medicine.

If any of your levels are abnormal, it doesn’t always mean you have a medical condition that needs treatment. Diet, activity level, medicines, a menstrual period, not drinking enough water, and other factors can affect the results. Talk with your provider to learn what your results mean.

Is there anything else I need to know about a complete blood count?

A complete blood count is only one tool your health care provider uses to learn about your health. Your provider will consider your medical history, symptoms, and other factors to make a diagnosis. You may also need additional tests.

What is a Blood Differential Test?

A blood differential test measures the amount of each type of white blood cell (WBC) that you have in your body. White blood cells (leukocytes) are part of your immune system, a network of cells, tissues, and organs that work together to protect you from infection. There are five different types of white blood cells:

Neutrophils are the most common type of white blood cell. They are your body’s main defense against infection when bacteria, viruses, or other germs enter your body.

Lymphocytes include two main types of white blood cells: B cells and T cells. B cells fight off invading viruses, bacteria, or toxins. Certain T cells can target and destroy your body’s own cells, such as cancer cells and cells that have been infected by viruses.

Monocytes kill bacteria, viruses, and other germs that may make you sick. They also boost your body’s immune response and clear away dead cells.

Eosinophils defend against parasites and infections. They are also involved in allergies and help control inflammation (swelling and redness).

Basophils release enzymes during allergic reactions and asthma attacks.

However, your test results may have more than five numbers. For example, the lab may list the results as counts as well as percentages.

Other names for a blood differential test: Complete blood count (CBC) with differential, Differential, White blood cell differential count, Leukocyte differential count

What is it used for?

A blood differential test is often part of a general physical exam. Because the five types of white blood cell do different jobs, measuring them separately can give your health care provider important information about your health.

The test can also help diagnose a variety of medical conditions, such as:

Infections

Autoimmune diseases

Inflammatory diseases

Leukemia and other types of cancer

Why do I need a blood differential test?

A blood differential test is used for many reasons. Your provider may have ordered the test to:

Monitor your overall health or as part of a routine checkup.

Diagnose a medical condition when you have symptoms. For example, if you are feeling unusually tired or weak, or have unexplained bruising or other symptoms, this test may help uncover the cause.

Keep track of an existing blood disorder or related condition.

What happens during a blood differential test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

What do the results mean?

There are many reasons your blood differential test results may be higher or lower than normal. For example, a high white blood cell count may mean you have an infection, an immune disorder, leukemia, or an allergic reaction. A low count may be caused by bone marrow problems, reactions to medicines, or cancer.

But abnormal results don’t always mean you have a condition that needs medical treatment. Factors such as exercise, diet, alcohol level, medicines, and even a woman’s menstrual period can affect the results.

If your results seem abnormal, your provider may order more specific tests to help figure out the cause. To learn what your results mean, talk with your provider.

Is there anything else I need to know about a blood differential test?

Use of certain steroids may increase your white blood cell count, which can lead to an abnormal result in your blood differential test.

What is a Hemoglobin Test?

A hemoglobin test measures the levels of hemoglobin in your blood. Hemoglobin is a protein in your red blood cells that carries oxygen from your lungs to the rest of your body. If your hemoglobin levels are abnormal, it may be a sign that you have a blood disorder.

What is it used for?

A hemoglobin test is often used to check for anemia, a condition in which your body has fewer red blood cells than normal. If you have anemia, the cells in your body don’t get all the oxygen they need. Hemoglobin tests are measured as part of a complete blood count (CBC).

Why do I need a hemoglobin test?

Your health care provider may order the test as part of a routine exam, or if you have:

Symptoms of anemia, which include weakness, dizziness, and cold hands and feet

A family history of thalassemia, sickle cell anemia, or other inherited blood disorder

A diet low in iron and other minerals

A long-term infection

Excessive blood loss from an injury or surgical procedure

What happens during a hemoglobin test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You don’t need any special preparation for a hemoglobin test. If your health care provider has ordered other tests on your blood sample, you may need to fast (not eat or drink) for several hours before the test. Your health care provider will let you know if there are any special instructions to follow.

Are there any risks to the test?

There is very little risk to having a blood test. After the test, some people experience mild pain, dizziness, or bruising. These symptoms usually go away quickly.

What do the results mean?

There are many reasons your hemoglobin levels may not be in the normal range.

Low hemoglobin levels may be a sign of:

Different types of anemia

Thalassemia

Iron deficiency

Liver disease

Cancer and other diseases

High hemoglobin levels may be a sign of:

Lung disease

Heart disease

Polycythemia vera, a disorder in which your body makes too many red blood cells. It can cause headaches, fatigue, and shortness of breath.

If any of your levels are abnormal, it doesn’t always mean you have a medical condition that needs treatment. Diet, activity level, medicines, a menstrual period, and other factors can affect the results. You may also have higher than normal hemoglobin levels if you live in a high altitude area. Talk with your provider to learn what your results mean.

Is there anything else I need to know about a hemoglobin test?

Some forms of anemia are mild, while other types of anemia can be serious and even life threatening if not treated. If you are diagnosed with anemia, be sure to talk to your health care provider to find out the best treatment plan for you.