Blood Test : Complete Blood Count (CBC), Types, Preparation & Procedure

What is a CBC?

A complete blood count, also known as a CBC is a simple and widely used test to detect certain diseases that may impact your health.

A CBC examines whether there are any decreases or increases in the blood cell count. Normal values can vary based on your age and gender. The lab report you receive will inform you of the typical range for your gender and age.

A CBC can assist in diagnosing various illnesses, ranging from anemia and cancer to infection.

The three types of blood cells.

Monitoring changes in your blood cells will help your doctor assess your overall health as well as detect conditions. The test tests the three main kinds of blood cells.

Red blood cells

Red blood cells transport oxygen to your whole body and eliminate carbon dioxide. A CBC CBC examines two parts of the red blood cells in your body:

  • hemoglobin: oxygen-carrying protein
  • Hematocrit: the percentage of the red blood cells found in your blood

Hemoglobin levels that are low and hematocrit are usually signs of anemia an illness that can occur when blood is low in iron.

White blood cells

White blood cells can help your body fight off infections. A CBC determines the amount and kinds of cells called white present in your body. Any changes or fluctuations in the amount or type of cells called white may be an indication of infection as well as inflammation or cancer.


Platelets aid in preventing blood clots and managing to bleed. If you notice that a cut isn’t bleeding, the platelets do their job. Any change in platelet levels can make you more susceptible to bleeding that is excessive and could be an indicator of a serious medical issue.

What is the time to have a CBC required?

Your doctor could request the CBC to conduct your routine checkup or if you experience unusual symptoms like bleeding or bleeding. A CBC can assist your doctor to perform the following.

  • Assess how well you are overall. Many doctors will require a CBC to provide an overview of your overall health. A CBC will also allow your doctor to detect any health issues.
  • Find out if you have a medical concern. The doctor might recommend a CBC in the event that you experience unexplained symptoms such as fatigue, weakness or fever, swelling, redness, bleeding, or bleeding.
  • Check for a health issue. Your doctor might regularly make CBCs to track your health condition in the event that you’ve identified a disease that impacts blood cell counts.
  • Be aware of the treatment you are receiving. Certain medical treatments may affect the number of blood cells in your body and you could need regular CBCs. Your doctor can assess whether the treatment you are receiving is effective, based on your CBC.

Preparing for a CBC

Wear an oversized short-sleeved or a shirt with sleeves that can easily roll up.

You are able to take a normal diet and drink before taking a CBC. But, your doctor might ask you to be fasting for a certain amount of time prior to the test. It’s normal if the blood sample is used to conduct additional tests. The doctor will provide specific guidelines. What occurs during CBC?

In a CBC the technologist will take blood samples from an area typically, from within your elbow, or from the palm side of your hands. The test takes only about a minute. The technician:

  1. cleanses your skin using an antiseptic wipe
  2. Place an elastic band, or tourniquet, over your upper arm to aid in the vein to expand by supplying blood
  3. Inserts a needle into your body and then collects an amount of blood in at least one vial
  4. The elastic band is removed
  5. The area is covered with a bandage that stops bleeding.
  6. Then label your samples and send them off to an analysis lab

A blood test may be uncomfortable. When the needle pokes the skin, you may experience a pinching or a prick sensation. A few people feel faint or lightheaded when they look at the blood. Afterward, you might experience tiny bruising. However, it will heal in a matter of days.

The majority of CBC results are accessible within a couple of hours to a full day following the test.

For babies

In infants the nurse will generally clean to the sole of your feet using a tiny needle referred to as a lancet, to poke the foot. Nurses will gently squeeze the heel, and take a tiny amount of blood to be placed in a vial and used to be tested.

What does the result have to do with it?

The results of tests will differ according to the number of blood cells in your body. Here are the typical results for adults. However, the labs you use may give minor variations:

Blood component Normal levels
Red Bood Cell (RBC) In men: 4.32-5.72 million cells/mcL
In women: 3.90-5.03 million cells/mcL
Hemoglobin (HB) In men: 135-175 grams/L
In women: 120-155 grams/L
Hematocrit In men: 38.8-50.0 percent
In women: 34.9-44.5 percent
White Blood Cell (WBC) Count 3,500 to 10,500 cells/mcL
Platelet Count 150,000 to 450,000/mcL

A CBC does not constitute a final test for diagnosis. Blood cells that are either excessively high or low can be a sign of an array of health conditions. Specific tests are required to determine the cause of a particular condition. The conditions that can create an imbalance in CBC and could require additional tests may include:

  • iron, or any other vitamin, and mineral deficiencies in iron or other minerals and vitamins
  • bleeding disorders
  • heart disease
  • autoimmune disorders
  • Bone marrow issues
  • Cancer
  • Inflammation or infection
  • reaction to medications

If your CBC has abnormal levels the doctor might require a blood test in order to confirm the results. They might also recommend other tests to further assess your health and confirm the diagnosis.

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