CBC blood test

Complete Blood Count (CBC) Test

The Complete Blood Count (CBC) test is a blood test which measures the various components and characteristics of the blood, such as red and white blood cells, hemoglobin, hematocrit, platelets, and other substances. It is one of the most commonly ordered tests that serve as a broad screening tool to detect a variety of diseases and conditions, such as anemia, infection, and many other disorders. Anemia, infection and some other medical conditions can be diagnosed with help of this test.

Preparation for the Test

A CBC does not require any special preparation ahead of the test. However, if you are scheduled for a CBC test, you should inform your healthcare provider if you are taking any medication, such as aspirin or anticoagulants, as this may interfere with the results. You should also tell your healthcare provider of any bleeding issues you have. In some cases, you may need to stop taking certain medications before the test.


A CBC is usually performed by taking a small sample of blood from a vein in the arm. To collect this sample, a thin needle is inserted into a vein and then the blood is collected into a small vial. During the procedure, the patient may experience minor pain or discomfort. Then the collected blood sample is sent to the laboratory where it is analyzed using a specialized machine which looks at the different components and characteristics of the blood.


  • Differential Count – It looks at the number of each type of white blood cells. It helps to detect different types of infection or disease.

  • Complete Blood Count – It gives information about red and white cells, hemoglobin, hematocrit, platelets, and other substances present in the blood.

  • Platelet Count– It measures the number of platelets present in the blood. Platelets help to stop bleeding and help in clotting of the blood.


The procedure for a CBC is generally considered safe. Although it may cause slight pain or discomfort, there are no other major risks associated with it. Some people may develop an allergic reaction to the anticoagulant present in the vial, which may cause itching, redness, or swelling, but this is usually not dangerous.

Why it is done

The CBC test is usually used as a broad screening tool to help detect and diagnose a variety of conditions and diseases. It can be used to help diagnose anemia, infection, leukemia, and other disorders. It can also be used to monitor conditions such as diabetes and to check for any effects of treatments such as chemotherapy.

When it is done

A CBC test can be done at any time, but it is usually ordered by a healthcare provider when they suspect that a patient may be suffering from a certain medical condition, or when they want to monitor a certain condition. It is also often ordered when a patient is admitted to a hospital so that their blood counts can be monitored during their stay.