Complete Blood Count Definition

Complete Blood Count Definition

Complete Blood Count Definition

This article is different than our previous articles. Today, we will not talk about a disease, but about a test that is often used to diagnose problems.

Complete Blood Count Definition – CBC is the acronym for Complete Blood Count. When a doctor requests a CBC, he’s looking for the measurements of the various components in the blood. As we have discussed several times, there are various cells and elements that make up the blood, each one in different quantities. When something is not right in the body, the quantities may be different than usual. At times, a CBC will identify an illness when the symptoms are not clear enough, and sometimes it will just confirm a diagnosis that the doctor suspects. In this article, we will give you an understanding of what a doctor looks for on a CBC and what the terms and numbers mean.

What is Complete Blood Count?

A CBC looks primarily at the red blood cells, white blood cells, and platelets. It is also divided into sections for various forms of each type of cell. Blood for a CBC can be drawn from a vein in the arm or from a prick on the finger.

White Blood Cells, WBC:

White blood cells help the body fight infections. When bacteria or viruses enter the body, the white blood cells will resist them and kill them. WBCs are larger than red blood cells but fewer in number. When there is a bacterial or viral infection, the number of WBCs will rise quite quickly. The higher the numbers, the more widespread or serious the inflammation is. The usual number of WBCs is between 4500 and 11000 in one microliter of blood (4.5-11K / µL).

WBCs can be high because of infections, swelling, heart attack, stress, thyroid problems, and other illnesses. The use of corticosteroids and some other medications can also increase the count.

These numbers can be reduced due to viruses, some medications, alcohol use, and various diseases. The numbers can change by 2000 / µL because of exercise, stress, and smoking.

Children have higher levels of WBCs than adults.

The Five Types of WBC:

White blood cells are divided into five types. These types are: lymphocytes, monocytes, eosinophils, basophils, and neutrophils. Each type fights against different kinds of infections and each works a bit differently to protect the body. Some labs will report the numbers for each type and others will report the percentage values per type out of the entire white blood cell count. Higher or lower levels of each type can help identify an infection, an allergic reaction to medicine, and diagnose various diseases.

Red Blood Cells, RBC:

Red blood cells carry oxygen from the lungs around the body and bring back carbon dioxide to be removed and exhaled. If the numbers are low, the body may not be getting enough oxygen. When the numbers are too high, the cells can stick together, which also does not allow the oxygen to arrive where needed. Normal levels are between 4.7 and 6.1 million per microliter (4.4-5.0M / µL) for men, and between 4.2 and 5.4 million per microliter (4.2-5.4M / µL) for women.

Besides for the actual count, there are three other items figures measured as part of the RBC:

  1. Mean Corpuscular Volume (MCV) – This shows the average size of the red blood cells. It is given in femtoliters per cell. Normal range is 75.0-87.0 fL.
  2. Mean Corpuscular Hemoglobin, (MCH) – This measures the average amount of hemoglobin in each red blood cell. It’s measured in picograms per cell. Normal range is 25.6-27.6 pg
  3. Mean Corpuscular Hemoglobin Concentration, (MCHC) – This measures how concentrated the hemoglobin is in each cell. It’s measured in grams per deciliter of blood. Normal range is 33.4-37.0 g / dL.

All these numbers help diagnose anemia. Occasionally, Red Cell Distribution Width (RDW) will also be measured to determine if all RBCs are of the same size and shape.

RBCs can be higher due to smoking, lung problems, kidney problems, heart problems, alcohol use, liver problems, dehydration, and more. It may be lower due to anemia, stomach ulcers, intestinal problems, lead poisoning or reaction to chemicals or medicines. Not getting enough folic acid or vitamin B12 can cause anemia.

Sometimes a doctor will also look at the erythrocyte sedimentation rate (ESR). This measures how quickly the red blood cells sink to the bottom of the container in which the blood sample was taken. This can indicate swelling in the body and can help diagnose a problem when other results in the CBC are normal.


Hemoglobin fills the red blood cells. This is the substance that carries the oxygen and gives red blood cells their red color. The number is used to see if the person is anemic. Measured in grams per deciliter. Normal range is 13.5-17.5 g / dL for men and 12.0-15.5 g / dL for women.


This figure measures how many red blood cells are there as a percentage of the entire blood count. This measurement is also used to diagnose anemia. Normal range is 45% to 52% for men and 37% to 48% for women.


Platelets are the smallest cells in the blood and help the blood to coagulate. When a person bleeds, the platelets swell and stick together to close the cut or puncture. When there are not enough platelets, a person can bleed without stopping. Too many platelets can prevent the blood from flowing properly or cause blood clots, which can have extremely serious effects. Measured in units per microliter. Normal range is 150-350K / µL

When a person bleeds, has an iron deficiency, or there are problems with the bone marrow, higher levels of platelets can be seen.

The doctor may also look at how many platelets are in the blood as a percentage of the entire blood count. This may provide another way of diagnosing certain illnesses.

How to read a CBC Report?

It is important to note that each lab may have a slightly different scale for determining “normal” levels. The numbers are also different for men, women, and children. Each physician will also look at the numbers according to his experience and the patient’s health. There may be multiple reasons for higher or lower levels and, according to the symptoms or results of other examinations, the doctor will decide what is a problem and what is not.

The report will usually have a list of the blood units. Near each one there will be a number that shows the level for that component that was in the person’s blood. The next column will list the normal ranges. Some labs may indicate levels that are too high with an H and levels that are too low with an L. Others print the numbers in bold or write them to the right or left of the normal numbers. You can ask the doctor or nurse to help read the report a few times until you learn how to read it alone.

Complete Blood Count Treatment

Vitamins play an important role in a person’s health. It is important for each person, from childhood and on, to take a multi-vitamin, each according to their health and age, so that the body has from where to produce everything it needs. Taking a multi-vitamin can help all the blood components stay at the right levels. At times it is necessary to add other specific vitamins according to the needs of a patient. Taking the necessary vitamins even though there are no problems can help keep all blood cells at healthy levels. Even more, in the case of a disease, the cells may be strong enough to fight or recover if they are properly prepared for it.

If the CBC shows a problem, first follow all the doctor’s instructions. But be aware that vitamins can greatly add to the health of every part of the blood, and of the whole person.

Measurement table:

Here are the various measurements used in this article:

Base units:

Liter (L) – approximately 1.05669 quart.

Gram (g) – approximately 0.0352 of an ounce


Deciliter (dL) – 0.1 of a liter

Microliter (µL) – 0.000001 of a liter.

Femtoliter (fL) – 0.000000000000001 of a liter, a billionth of a microliter.

Picogram (pg) – 0.000000000001 of a gram.

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Interesting Facts

Complete Blood Count Definition

  • 16 ounces of blood can save three lives!
  • Every two seconds, one American needs a blood transfusion.

Complete Blood Count Definition

  • A newborn has about eight ounces of blood in his body.

Complete Blood Count Definition

  • There are about 100,000 miles of blood vessels in an adult.

Complete Blood Count Definition

  • A red blood cell can circulate the entire body in 30 seconds!


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