A complete blood count, or CBC blood test is an easy and very common type of blood test a doctor can order to screen for certain disorders that can affect the health of a patient.
A CBC helps to find if there are any increases or decreases in the blood cell counts of the patient.
Normal values tend to vary depending on the age and gender of the patient.
Moreover, the lab report will tell the normal value range for the given age and gender of the patient.
It is important to note that CBC can help to diagnose a broad range of conditions, ranging from anemia and infection to cancer.
A CBC blood test will help the doctor to measure several components and features of the blood.
These include red blood cells, which carry oxygen, number of white blood cells which fight infection, and hemoglobin the oxygen-carrying protein in red blood cells.
Furthermore, it also measures hematocrit, the proportion of red blood cells to the fluid component or plasma in the blood, and platelets which help with blood clotting.
Keep on reading.
Uses of CBC Blood Test
A complete blood count or CBC blood test can help and the doctor can order them for a number of reasons.
These include:
Review the Overall Health: The doctor can recommend a complete blood count as part of the routine medical examination to monitor the general health of the patient.
Moreover, it will help to screen for a number of disorders like anemia or leukemia
Diagnose Medical Condition: A doctor can suggest this blood test if the patient is experiencing:
- weakness
- fatigue
- fever
- inflammation
- bruising
- bleed
It is important to note that a complete blood count can help the doctor to diagnose the cause of these signs and symptoms.
In case the doctor suspects that patient has an infection, this test can also confirm the diagnosis.
Monitor a Medical Condition: In case a doctor diagnoses a patient with a blood disorder that affects blood cell count, the doctor can use complete blood counts to monitor the condition of the patient.
Monitor Medical Treatment: This test can help to monitor if the medication a patient is taking is affecting blood cell counts or not.
Learn more about Blood Test: All You Need to Know here.
The Three Basic Types of Blood Cells
Measuring changes in the blood cell levels can help the doctor to elevate the overall health and detect disorders in a patient.
The test will measure the following basic types of blood cells:
Red Blood Cells
RBC carries oxygen throughout the bremovesd remove carbon monoxide.
A CBC blood test will measure two components of the red blood cells:
- hemoglobin: oxygen-carrying protein
- hematocrit: percentage of red blood cells in the blood of the patient
Low levels of hemoglobin and hematocrit are often signs of anemia, a condition in which blood is deficient in iron.
White Blood Cells
White blood cells help the body fight infection.
Moreover, a CBC will measure the number and types of white blood cells in the blood of the patient.
Any abnormal increases or decreases in the number of types of white blood cells can be a sign of infection, inflammation, or cancer.
Platelets
Platelets help the blood clot and control bleeding.
When a cut stops bleeding, it is because platelets are doing their job.
Any changes in platelet level can put the patient at risk for excessive bleeding and can be a sign of a seriuos medical condition.
When will a Doctor order CBC Blood Test?
A doctor can order a CBC blood test as part of a routine checkup or if the patient is experiencing unexplained symptoms.
These can include bleeding or bruising.
A CBC can help the doctor to do the following:
Evaluate the Overall Health of the Patient
A number of doctors will order a CBC test so that they can have a baseline view of the health of a patient.
A CBC can also help the doctor screen for any health problems.
Diagnose a Health Problem
A doctor may order a CBC in case a patient is experiencing unexplained symptoms.
These include weakness, tiredness, fever, redness, swelling, bruising, or bleeding.
Monitor a Health Problem
A doctor can regularly order CBCs to monitor the condition of the patient if they diagnose them with a disorder that affects blood cell counts.
Monitor the Treatment
It is important to note that certain medical treatments can affect blood cell counts and can require regular CBCs.
The doctor can evaluate how well a treatment is working for a patient depending on the CBC.
Getting Ready for CBC
It is important for the patient to wear a short-sleeved shirt or a shirt with sleeves that they can easily roll up.
A patient can usually eat and drink normally before a CBC.
However, in some cases, the doctor may require the patient to fast for a specific amount of time before the test.
This is common if the blood sample needs to be used for additional testing.
The doctor can also give further specific instructions to the patient as well.
Fasting before Blood Test
It is important to note that fasting before certain blood tests can help to make sure that the test results of a patient are accurate.
In case the doctor needs to determine vitamins, minerals, fats, carbohydrates, and proteins that make up all food and beverages that affect blood-level reading, they can cloud the results.
However, not all blood tests will need a patient to fast beforehand.
Certain lab tests that will need a patient to fast are:
- blood glucose test
- liver function test
- cholesterol test
- triglyceride level test
- high-density lipoprotein, HDL level test
- low-density lipoprotein, LDL level test
- basic metabolic panel
- renal function panel
- lipoprotein panel
When a doctor prescribes a patient for a new blood test or does not mention whether or not they should fast or for how long, they can ask the doctor.
Some tests like fecal occult blood tests do not need a patient to eat but do limit certain foods.
These include red meats, broccoli, and even some medications that can cause a false positive test.
Therefore, it is important for the patient to always follow the advice of the doctor when preparing for a test.
Learn more about Esophageal pH Screening for Heartburn here.
The Procedure for CBC Blood Test
During a CBC, a lab technician will draw blood from the vein of the patient, often from the inside of the elbow or from the back of the hand.
The test often takes only a few minutes.
Moreover, the technician will:
- clean the skin of the patient with an antiseptic wipe
- places an elastic band, or tourniquet, around the upper arm to help the vein swell with blood
- insert a needle in the vein and collect a blood sample in one or more vials
- remove the elastic band
- cover the area with a bandage to stop any bleeding
- label the sample and send it to the lab for analysis
A blood test, however, can be slightly uncomfortable.
When the needle punctures the skin, the patient may feel a prick or pinching sensation.
While some people may also feel faint or light-headed when they see blood.
Afterward, the patient may have minor bruising, but it tends to clean up within a few days.
Most CBC results are often available within a few hours to a day after testing.
For Infants
In the case of young infants, a nurse will often sterilize the heel of the foot and use a small needle: a lancet to prick the area.
Then the nurse will then gently squeeze the heel and collect a small amount of blood in the vial for testing.
Interpreting the Results
Test results can vary depending on the blood cell count of the patient.
The following table shows the normal results for adults, but different labs may deliver slight variations:
| Blood component | Normal levels |
| red blood cell | In men: 4.32-5.72 million cells/mcL In women: 3.90-5.03 million cells/mcL |
| hemoglobin | In men: 135-175 grams/L In women: 120-155 grams/L |
| hematocrit | men: 38.8-50.0 percent women: 34.9-44.5 percent |
| white blood cell count | 3,500 to 10,500 cells/mcL |
| platelet count | 150,000 to 450,000/mcL |
It is important to note that a CBC blood test is not an effective diagnostic test.
Blood cell counts that are either too high or too low can signal a wide variety of conditions.
With the help of a specialized test, the doctor can diagnose a specific condition.
Conditions that can cause an abnormal CBC and require additional testing are:
- iron or other vitamins and mineral deficiencies
- bleeding disorders
- heart disease
- autoimmune disorders
- bone marrow problems
- cancer
- infection or inflammation
- reaction to medication
In case CBC shows abnormal levels, the doctor can recommend another blood test to confirm the results.
Moreover, they can also order another blood test that will help further evaluate the condition of the patient and confirm a diagnosis.
Final Thoughts
A complete blood count CBC blood test can give information to the health care provider about the blood and overall health of th patient.
CBCs help providers diagnose, monitor, and screen for a wide range of diseases, conditions, disorders, and infections. Moreover, the provider will take a sample of blood and the lab results are often ready within a few days.
