Primus Pathology Laboratory

Everything About a Blood Test

Last Updated on July 10, 2022 by Dr. Neeraj Gujar


Regular blood tests are a great way to monitor your overall health and well-being. Regular testing intervals can help you see how your body changes over time. It also enables you to make informed health decisions.

A blood test is used to measure or examine cells, chemicals, proteins, and other substances in the blood. One of the most popular lab tests is blood testing, also known as blood work. It usually is a part of a routine checkup. However, blood tests can also help to:

  • Diagnose and treat certain health conditions
  • Monitor a chronic condition such as High Cholesterol or Diabetes
  • Learn if treatment is effective for your disease
  • Check how your organs work, including the liver, kidneys, heart, etc.
  • Help diagnose clotting or bleeding disorders
  • Check to see if your immune response is struggling to fight infections

Why Is the Blood Test Done?

A blood test can help your doctor assess the health of different organs. A blood test can reveal malfunctions in organs such as your thyroid, liver, and kidneys.

In addition, your doctor may also perform blood tests to identify markers of disease and other health conditions, such as:

  • Diabetes
  • Anemia
  • Cancer
  • HIV
  • Coronary heart disease
  • Evaluation for any lifestyle diseases
  • Monitoring the treatment and disease activity in chronic or infectious diseases

A blood test can also determine if someone is at risk for developing heart disease even if they don’t have it. Other blood tests are available to determine if your medications are being taken correctly or how well your blood is clotting.

In short, your doctor can order a blood test for many health scenarios and conditions.

When To Get a Blood Test Done?

Your doctor may recommend a routine blood test during your annual physical exam. In certain cases, additional testing may be necessary in case if,

  • You are experiencing persistent, unusual symptoms. It could range from fatigue to weight gain and new pain.
  • You want optimal health. Understanding your blood levels can help you adjust your diet and exercise plan to achieve healthy habits.
  • Reduce your chance of developing any illness. Having regular blood tests to detect early warning signs can help with the treatment. Blood tests can diagnose many health conditions related to the heart, lungs, and kidneys.

If you are interested in having certain tests performed, talk to your doctor first.

According to guidelines, the frequency you need to have a physical exam depends on your age.

  • Ages 18-39: At least once every 5 years
  • Ages 40-49: Every 2 to 3 Years
  • For those 50 years and over: Every 1 to 2 Years

It is recommended to have a minimum of a lipid test at age 20 and every five years for those at low risk for heart disease. People at higher risk for heart disease may need to have their lipids tested more often.

If your blood pressure is consistently above 135/80, you should also get a glucose test. People over 50 years old should have a fecal and occult blood test annually to screen for colorectal carcinoma.

How To Get Tested?

Your doctor can prescribe you a blood test as a part of a routine checkup or diagnose a health issue.

Before the Blood Test

Most blood tests don’t require any special preparations. Some tests may require you to fast for several hours. In case of any specific instructions, your health care provider will let you know the same. Always consult with your healthcare provider for any specific instructions to be followed while giving a sample of your blood.

During the Blood Test

A trained technician or nurse collects the blood sample and is transported to the laboratory with adequate precautions for testing and analysis. It takes only a few minutes to collect your blood sample.

To perform a blood test, the healthcare professional will:

  • Cleanse the area from where they will draw the blood.
  • Tying a rubber band around your upper arm to make your veins visible.
  • To draw blood, insert a needle into a vein on the inside of the arm.
  • When the collection is complete, remove the needle from your skin and take the rubber band off of your arm.
  • Use a bandage, clean cotton, or medical tape to cover the area.

There are other ways too for performing a blood test:

  • A finger-prick test: The test involves pricking the tip of your finger to collect a small amount of blood. The finger prick test is used to perform at-home tests and quick tests. Rapid tests are quick and easy tests that require very little equipment.
  • A heel stick test: This procedure is used most often for newborns. A heel stick test is when a healthcare provider cleans your baby’s heels with alcohol and pokes the heel with small needles. The provider will take a small amount of blood from the area and apply a bandage.
  • An arterial blood test: The test measures oxygen levels. Blood drawn from an artery has higher oxygen levels than blood from a vein. That is why blood is drawn from an artery rather than a vein for the test. The provider may cause sharp pain by inserting the needle into your artery to collect the blood sample.

Blood samples collected in test tubes

After The Blood Test

There are very low risks or after-effects related to a finger prick, heel-stick, and venipuncture blood test.
But they can lead to:

  • Slight discomfort or pain where the needle is inserted
  • A feeling of fainting due to blood loss
  • Vein puncture

Although collecting blood from an arterial is more painful than from a vein, it is still possible to avoid complications. There may be some bleeding, swelling, or soreness around the site where the needle was inserted. You should not lift heavy objects for 24hrs after the test.

What is the average time it takes to see results?

It may take a few hours or days for results to be available, and are variable, subject to the availability of facilities. This is a summary of the time it may take to complete some common tests.

  • Complete Blood Count (CBC): 24 Hours
  • Basic Metabolic Panel 24 Hours
  • Complete Metabolic Panel: 24 to72 hours
  • Lipid Panel: 24 Hours

The timing of your tests will depend on where they are performed and how many you have. You may not receive the full results if you order multiple tests.

Sometimes, a lab will directly hand over the results to your doctor. They will then review it and give it to you.

Interpreting Results

Although every laboratory and test-providing organization may have their results reported differently, they all include basic components and comply with prevailing laws and regulations.

Some of this information may include administrative content such as the name and date of the person who performed the blood test and the name and address of the doctor who ordered it.

You can use the following to understand the results.

  • Quantitative results. Results are usually written numerically when the test measures the quantity of something. For example, a test measuring the level of cholesterol in your blood.
  • Abnormal markers. A lot of laboratory reports will include some type of marker to indicate if the result is out of the normal range and, therefore, abnormal. If your results are highly abnormal, you might see the letters H and L. You will usually get a call from the doctor in this situation.
  • Specific reference range. This reference range is usually written next to your numerical result in your laboratory report. You can then see where you fall within the range.

10 Most Common Blood Tests

Let’s take a closer look at some of the most common blood tests.

  1. Complete Blood Count (CBC)

A routine CBC test is done to check for 10 components in every major cell of your body: red blood cells and white blood cells.

Red blood cell count, hemoglobin, and hematocrit are important components of this test.

The typical range of results is shown below. However, every laboratory may have a slightly different range.

ComponentNormal range
RBC Count (cells responsible for carrying oxygen)male: 4.3–5.9 million/mm3female: 3.5–5.5 million/mm3
WBC Count (immune system cells)4,500–11,000/mm3
Platelet Count (Substances that control the clotting)150,000–400,000/mm3
Hemoglobin (protein that carries oxygen and carbon dioxide)male: 13.5–17.5 grams/deciliter (g/dL); female: 12.0–16.0 g/dL
Hematocrit (RBC percentage in the blood)male: 41–53%; female: 36–46%

These components could indicate an abnormal level of activity, such as:

  • Vitamin B6 and B12 deficiencies
  • Clotting problems
  • Anemia (iron deficiency)
  • Infection
  • Blood cancer
  • Immunity system disorders

Your doctor may then consider follow-up tests to diagnose the underlying cause of the abnormal ranges.

  1. C-reactive Protein (CRP) Test

CRP is a protein made by the liver when your tissues are inflamed. A high level of CRP can indicate inflammation due to several factors, including:

  • Viral or Bacterial infection
  • Autoimmune diseases like rheumatoid arthritis and Lupus
  • Diabetes-related inflammation
  • Cancer
  • Inflammation caused by physical trauma or habits such as smoking

The higher level indicates a higher risk of developing heart disease.

  • 0.3m/dL: Normal
  • 0.3 to 2.0 mg/dL: minor elevations can be associated with body mass index (BMI) or conditions like depression, insomnia, or sex.
  • 1.0-10.0 mg/dL: moderate elevation often caused by systemic inflammation such as an autoimmune disease or heart attack.
  • >10.0mg/dL: marked elevation usually caused by a serious or viral infection, major trauma, or systemic vasculitis
  • >50.0mg/dL: severe elevation often caused by an acute bacterial illness
  1. Kidney Function Test

A kidney function test, also named a basic metabolic panel (BMP blood test), usually tests for levels of 8 compounds in blood.

  • Calcium
  • Sodium
  • Potassium
  • Glucose
  • Carbon dioxide
  • Chloride
  • Blood Urea Nitrogen (BUN)
  • Creatinine

Depending on what the test is measuring, you may need to fast for up to 8 hours before the blood draws.

Abnormal results may indicate:

  • Diabetes
  • Kidney disease
  • Hormonal imbalance

Your doctor will perform follow-up tests to confirm a diagnosis.

  1. Liver Function Test

Liver function tests or comprehensive metabolic panels (CMPs) include all measurements of a BMP and additional substances that are related to liver function such as:

  • albumin
  • total protein
  • Alkaline phosphatase (ALP) – is an enzyme found mainly in the bones and liver.
  • Alanine aminotransferase (ALT) – is an enzyme found in the liver.
  • Aspartate Aminotransferase (AST) – is an enzyme found in the liver as well as other tissues of the body.
  • Bilirubin –a waste product of the breakdown of red blood cells. The liver removes it.

A CMP blood test can draw the same conclusions as a BMP test for the common substances. Yet, in the CMP test, you may also see other abnormalities because of the extended substance coverage.

  1. Lipid panel

This lipid profile test measures the levels of two types of cholesterol:

  • High-density Lipoprotein (HDL), also known as “good” cholesterol
  • Low-density lipoprotein (LDL), also known as “bad” cholesterol

HDL is considered “good” as it helps to eliminate harmful substances from the blood and helps the liver break them down into waste. LDL can lead to plaque in your arteries and increase your risk of developing heart disease.

This test may require you to fast for up to 8 hours.

These are the ranges for each type.

HDLMore than 60 mg/dLmale: Less than 40 mg/dL; female: Less than 50 mg/dL (low)
LDLMore than 160 mg/dLLess than 100 mg/dL (optimal)
  1. Thyroid panel

A thyroid panel or thyroid function test checks the quality of your thyroid’s production and response to hormones such as:

  • Triiodothyronine (T3): Together with T4, it regulates your heartbeat and body temperature.
  • Thyroxine (T4): Together with T3, it regulates your metabolism, and how you grow.
  • Thyroid-stimulating hormone (TSH): This regulates the hormones your body releases.

Your thyroid gland is a small gland located in your neck. It regulates bodily functions such as your mood, energy, and overall metabolism.

These are the normal ranges for the thyroid test:

  • T3: 80-180 ng/dL
  • T4: 0.8 -1.8 ng/dL
  • TSH: 0.5-5 mIU/L

NOTE: A significant Physiological (in normal people) variation up to 15mIU/L is commonly noted in TSH Values.

These hormones may be abnormally high in certain conditions such as:

  • Thyroid growth disorders
  • Immune disorders of the thyroid gland
  • Generalized metabolic disorders of the body
  • Other major illnesses
  1. Coagulation panel

Lab technician at her desk working

Coagulation test measures how well your blood is clotting and how long it takes to clot. The prothrombin activity (PT) test and D-dimer test are examples.

Clotting is an important process that stops bleeding from a cut or wound. But a clot in a vein, artery, or brain can cause serious damage. It can also block blood flow to the brain, heart, and lungs. This could lead to a stroke or heart attack.

The results of coagulation tests will vary depending on your health and any other conditions that could affect clotting.

These test results can be used to diagnose.

  • Excessive bleeding (hemophilia)
  • Leukemia
  • Liver conditions
  • Thrombosis
  • Vitamin K deficiency
  1. Tests for sexually transmitted infections

A blood sample can help diagnose many sexually transmitted infections (STIs). For a more precise diagnosis, these tests can be combined with urine samples and swabs from infected tissue.

These STIs can all be diagnosed by blood tests

  • HIV
  • Herpes
  • Gonorrhea
  • Chlamydia
  • Syphilis

After contracting an HIV infection, blood tests may not always be accurate. You may need to wait up to a month for a blood test to detect HIV infection.

  1. Cardiac biomarkers

Enzymes are proteins that aid your body to accomplish certain chemical processes such as breaking down foods and clotting blood. They are vital for many functions in your body. An abnormal level of enzymes can be a sign of many conditions.

Common enzymes that are tested for muscle and cardiac diseases include:

  • Creatine kinase (CK): This enzyme is mainly found in the brain, heart, and skeletal muscles. CK can seep into the bloodstream in increasing amounts when there is muscle damage.
  • Creatine Kinase-MB (CK-MB): These enzymes can be found in your heart. After a heart attack or any other injury to the heart, they may increase in blood.
  • Troponin: This enzyme is known to cause heart damage and can leak into the bloodstream.

These are the ranges of normal enzymes listed above:

  • CK: 30-200 U/L
  • CK-MB: 0-12 IU/L
  • Troponin: Less than 1 ng/mL
  1. Cancer Marker Test

This test looks for tumor markers in the blood. The cells produce a substance, known as cancer markers, in response to cancer in the body.

A blood test for cancer helps in different phases of cancer treatment like:

  • Screen people at high risk for cancer
  • Plan your treatment
  • Help in finding if cancer has spread to other tissues
  • Help in predicting the likely outcome of the disease
  • Check to see if cancer has come back even after a successful treatment

There are different cancer marker tests that your healthcare advisor can order depending on the symptoms. Some of them are:

  • CA 125 (cancer antigen 125) – Tumor marker for ovarian cancer
  • CA 15-3 and CA 27-29 (cancer antigens 15-3 and 27-29) – Tumor marker for breast cancer
  • PSA (prostate-specific antigen) – Tumor marker for prostate cancer
  • CEA (carcinoembryonic antigen) – Tumor marker for colorectal cancer, and also for cancers of the lung, stomach, thyroid, pancreas, breast, and ovary
  • AFP (Alpha-fetoprotein) – Tumor marker for liver cancer, and cancers of the ovary or testicles
  • B2M (Beta 2-microglobulin) – Tumor marker for multiple myeloma, some lymphomas, and leukemias

Where can I get the blood test done?

Different centers offer you diagnostic services such as blood tests. Many hospitals have a laboratory you can visit to order tests. Some laboratories offer walk-in services. Some may need to make an appointment.

You may also be able to have blood tested at these other locations:

  • Private labs: Hospitals might use private laboratories to offload testing from their laboratories or when a specialized test may be required. Many times, your health insurance plan will require that you use a particular laboratory to have the test covered.
  • Point of care: These are situations where you might need a blood test while you’re receiving medical care. This typically includes your doctor during an appointment. This can include tests performed at a military or cruise ship clinic, as well as in an ambulance.
  • Direct access testing: Also referred to as direct to consumer. It allows you to order your test online without the need for a referral from a doctor. The test is performed in a laboratory or they provide you tests at-home option for this purpose.
  • Home testing: It is possible to get a few tests from a pharmacy, and then take them at home. Some tests may require a prescription, while others might be available over-the-counter. These include blood glucose monitoring, which is for diabetics, and the fecal-occult blood test, which screens for colorectal carcinoma. All home tests must be approved by the FDA before they can be purchased.

Final Takeaway

A blood test can give you a snapshot of your overall health. They are also a great way to detect illness early and see how your body reacts to different treatments. Routine blood tests are something that many people have at least once per year. Discuss with your doctor any additional tests that may be required to maintain your health.

Once you have a proper idea of the blood tests required, you can book an appointment either at a diagnostic center or for a blood test at a home facility to go ahead with the test.


What can be detected in a blood test?

A blood test can detect different chemicals and hormonal levels in the blood. The tests can give providers information about your organs, such as the heart, kidneys, liver, etc.

Which blood test should you have annually?

The blood tests that you should consider doing annually are:

  • Complete Blood Test (CBC)
  • Comprehensive Metabolic Panel (CMP)
  • Hemoglobin A1C (HbA1C)
  • Lipid Panel (ideally with particle size)
  • Thyroid Panel (or at least a TSH test)
  • Vitamin D
  • Anemia Panel (or iron, ferritin, folate, and vitamin B12)
How long does a blood test take?

It usually takes 5-10 minutes. Sometimes it can take longer to locate a vein. Dehydration, the experience of the phlebotomist, and the size of your veins all can affect how fast a blood draw can take place.

What does a full blood count include?

It usually takes 5-10 minutes. Sometimes it can take longer to locate a vein. Dehydration, the experience of the phlebotomist, and the size of your veins all can affect how fast a blood draw can take place.

What is the alarming level of platelets?

A platelet count below 150,000 per microliter is considered to have thrombocytopenia. This means that the platelet count is lower than normal. A platelet count below 50,000 is considered to be very low. Below 10,000 is considered severe hemoglobinemia, which can lead to internal bleeding.


by Dr. Neeraj Gujar

Dr. Neeraj Gujar has done his M.D. in Pathology from Government Medical College. He has worked at various organisations such as Breach Candy Hospital and Tata Memorial Hospital along with many other private organisations. During his working career, he realised the pressing need for exceptional quality diagnostic services. A diagnostic centre that can consistently give accurate results verified by a consultant doctor (M.D. Pathologist) on which your doctor can depend. This has been the founding principle of Primus Pathology and Diagnostics.

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