A complete blood count may be done as part of a regular physical examination. A blood count can give valuable information about the general state of your health. You do not need to do anything before having this test.
If this blood test is done on a baby, a heel stick will be done instead of a blood draw from a vein. The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch. There is very little chance of a problem from having a blood sample taken from a vein. The normal values listed here—called a reference range—are just a guide.
These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
Normal values for the complete blood count CBC tests depend on age, sex, how high above sea level you live, and the type of blood sample. Your doctor may use all the CBC values to check for a condition. For example, the red blood cell RBC count, hemoglobin Hgb , and hematocrit HCT are the most important values needed to tell whether a person has anemia, but the red blood cell indices and the blood smear also help with the diagnosis and may show a possible cause for the anemia.
To see if the white blood cell WBC, leukocyte count is good and how the cells look on the smear, your doctor will look at both the number WBC count and the WBC differential. To see whether there are too many or too few of a certain type of cell, your doctor will look at the total count and the percentage of that particular cell. There are normal values for the total number of each type of white cell. Pregnancy can change these blood values. Your doctor will talk with you about normal values during each trimester of your pregnancy.
In general, a normal hemoglobin level is about one-third the value of the hematocrit. Reasons you may not be able to have the test or why the results may not be helpful include:. Current as of: September 23, Gabica MD - Family Medicine. Author: Healthwise Staff.
Medical Review: E. This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.
Your use of this information means that you agree to the Terms of Use and Privacy Policy. Learn how we develop our content. To learn more about Healthwise, visit Healthwise. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated. Top of the page. Test Overview A complete blood count CBC gives important information about the kinds and numbers of cells in the blood, especially red blood cells , white blood cells , and platelets.
White blood cells protect the body against infection. If an infection develops, white blood cells attack and destroy the bacteria, virus, or other organism causing it. White blood cells are bigger than red blood cells but fewer in number. When a person has a bacterial infection, the number of white cells rises very quickly. The number of white blood cells is sometimes used to find an infection or to see how the body is dealing with cancer treatment. White blood cell types WBC differential.
The major types of white blood cells are neutrophils , lymphocytes, monocytes, eosinophils, and basophils. Immature neutrophils, called band neutrophils, are also part of this test. Each type of cell plays a different role in protecting the body.
The numbers of each one of these types of white blood cells give important information about the immune system. Too many or too few of the different types of white blood cells can help find an infection, an allergic or toxic reaction to medicines or chemicals, and many conditions, such as leukemia. A low count can mean you have an increased risk of getting an infection. White blood cell differential dif looks at the types of white blood cells in your blood.
There are many different types of white blood cells. Each of them protects you from different types of infections. Hemoglobin Hgb measures the amount of this oxygen-carrying protein in red blood cells. This level is low in people with anemia. Hematocrit Hct measures how much of a given volume of whole blood is made up of red blood cells. In healthy men, 41 percent to 50 percent of blood is red blood cells.
A low white blood cell count leukopenia may be caused by a medical condition, such as an autoimmune disorder that destroys white blood cells, bone marrow problems or cancer. Certain medications also can cause white blood cell counts to drop. If your white blood cell count is higher than normal, you may have an infection or inflammation. Or, it could indicate that you have an immune system disorder or a bone marrow disease.
A high white blood cell count can also be a reaction to medication. For specifics about what your complete blood count results mean if they fall outside the normal ranges, talk to your doctor.
Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission. This content does not have an English version. This content does not have an Arabic version. Overview A complete blood count CBC is a blood test used to evaluate your overall health and detect a wide range of disorders, including anemia, infection and leukemia.
A complete blood count test measures several components and features of your blood, including: Red blood cells, which carry oxygen White blood cells, which fight infection Hemoglobin, the oxygen-carrying protein in red blood cells Hematocrit, the proportion of red blood cells to the fluid component, or plasma, in your blood Platelets, which help with blood clotting. Request an Appointment at Mayo Clinic.
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