Blood Test

Last Reviewed: 21st June 2016.

What Is A Blood Test?

A blood test involves taking blood from you to test for the level of a naturally occurring

component (chemical or cell) or the presence of a chemical or cell that is not usually found in the body.

A test could be done to confirm a normal level of a blood component. It could also be done to look for a change in the quantity or indeed quality of such component or for the presence of abnormal components seen only when there is a disease or infection.

A blood test can be done to analyze your blood for signs of problems, such as abnormal electrolyte balance, abnormal kidney function, abnormal liver functions, anemia (lack of oxygen carrying red blood cells), low platelets, high amount of white blood cells, your blood group, drugs, and levels of different medications.

Today, blood tests can do many things, because doctors and scientists have identified many substances in the blood that can tell you if you have an infection, an autoimmune disease, a marker for cancer, inherited diseases, and even blood clots or heart failure. Blood tests are also used to tell your doctor if you are having a heart attack.

Blood would normally be taken from a vein in your arm, or by means of a prick to your finger or by any other convenient means, to carry out any such test.

Common Reasons For Blood Tests

Your doctor may find something on physical examination that made him or her decide there might be a problem and they might be able to find an answer by examining your blood for certain substances. You might have told your doctor about symptoms that you are experiencing which may have prompted the blood test or tests. Such symptoms may include:

  • Allergies
  • Fever
  • Weight loss
  • Jaundice (yellow color to skin and whites of the eyes)
  • Pain in a specific place
  • Weight loss
  • Shortness of breath
  • Fatigue
  • Chest pain
  • Skin rash

Common things that your doctor or your healthcare practitioner would want to check for in your blood would include:

  • Blood count for anemia (CBC)
  • White blood cell count
  • Platelet level
  • Stickiness of your blood or how thin your blood is
  • How well your blood clots
  • Your Kidney function
  • Liver Function
  • Bone profile
  • Crude evidence of infection or inflammation
  • How your immune cells are doing
  • Thyroid function
  • Blood sugar level (e.g to check for diabetes)
  • Normal bowel function e.g to check for pancreatitis or abnormal absorption of food like in celiac disease
  • Evidence of infection in your blood
  • Blood test for pregnancy
  • Test for evidence of cancer
  • Prostate test
  • Presence of abnormal levels of drugs or chemicals
  • Check for overdose
  • Check for inherited disease
  • Heart attack 
  • Blood group
  • Hormone level - e.g to confirm menopause or whether you are ovulating
  • For evidence of allergy
  • To unravel unexplained weight loss
  • Confirm or exclude heart failure
  • Look for  and identify bugs or parasites in the body or blood.

Common Blood Tests And What They Mean

The following are the common blood tests and what they mean:

1.  Full Blood Count (FBC) or Complete Blood Count (CBC)

This is a blood test to check your blood count. This is perhaps one of the most commonly done blood tests anywhere in the world.

In the UK and many part of the English speaking world, it is referred to as Full Blood Count or FBC. In North America, it is referred to as the Complete Blood count.

Under a FBC or CBC, your blood is checked for:

  • Haemoglobin Level. This is also called Hb. It is the substance in the blood that gives it the red colour. It is what carries oxygen in the blood to the body tissue and it is made from iron and protein. Normal hemoglobin level is about 12 to 16 in women and 14 to 18 in men. Low levels below 10 in anybody is referred to as anaemia or shortage of blood.
  • White Blood Count or WBC. White blood cells, if they are increased, can be an indicator of infection, or even types of leukemia. They are the cells your body normally produces in your bone marrow to protect you against infection. Normal levels of white blood cells in an adult Caucasian is 4000 to 11000 per dl and 2,500 to 8,500 in people of Afro-Caribbean extraction.
  •  Platelet Count. Platelets are the cells that form clots and help your body heal bleeding wounds by sticking together and forming a plug. However, platelets can also clog your blood vessels if they are narrowed by atherosclerotic heart disease, for example. A big clot will obstruct the blood vessels.

To do this blood test, a special tube will be drawn, usually from your arm vein. The blood is taken to the laboratory and put into a centrifuge. The blood is tested for the amount of hemoglobin in the red blood cells, which can help your doctor if you have anemia caused by iron deficiency, because iron is needed to produce the molecule heme, which carries oxygen in the red blood cells throughout your body to your tissues.

When your blood goes through the centrifuge, a spinner, the blood cells spin to the bottom to make a sediment, and the clear liquid on top is called plasma. The laboratory technicians will put the sediment under a microscope and will examine it and count how many red blood cells, white blood cells, and platelets are in the sediment per square millimeter.

Components of a complete blood count often tested includes:


  • MCV
  • MCHC
  • WBC

Normal Range in Health

  • 137 - 180 (Females 120 - 150)
  • 0.40 - 0.54
  • 82 - 100
  • 320 - 360
  • 150 - 400
  • 4.0 - 11.0 Whites (2 - 8.5 Blacks)
  • 2.0 - 8.0
  • 0.7 - 3.5
  • 0.0 - 1.0
  • 0.0 - 0.7
  • 0.0 - 0.2

2. Electrolytes And Urea Levels

Your body’s cells need certain molecules called electrolytes, in order to function. These are also referred to as blood salts. They include:

  • Sodium (Na)
  • Chloride (Cl-)
  • Potassium (K)
  • Bicarbonate molecules (HCO3)
  • Calcium
  • Magnesium
  • Phosphate
  • Urea
  • Urate or uric acid

These are also referred to DAX or blood urea nitrogen and electrolytes. They are required for the maintenance of electrical balance in your body, transmission of nerve impulses, blood pressure control, water balance and more.

Depletion of your blood salts or electrolytes could lead to:

  • Confusion
  • Low blood pressure
  • Vomiting
  • Swollen legs and ankles
  • Abdominal distension
  • Gout

Any abnormality in the natural level and balance of these chemicals could lead to illness. Illnesses like diarrhea and vomiting can also lead to excessive loss of these chemicals.

There are many reasons that your body has been unable to keep your electrolytes balanced, and one reason is that the kidney helps control the excretion and balance of these elements.

Kidney disease may keep you from having the right amounts of electrolytes for your cells to function.

Some drugs can also cause imbalances of electrolytes. As an example of what can happen if your electrolytes are out of balance, too much potassium can make your heart stop. In fact, in the United States, during executions, the condemned person is often given a "lethal injection" that contains excess potassium.  

Components of Electrolytes and Urea often tested include:



Normal Range in Health

  • 133-145 mmol/L
  • 3.3-5.1 mmol/L
  • 98-111 mmol/L
  • 2.10-2.55 mmol/L

3. Kidney Functions

Whether it is abdominal pain or indeed many other conditions, once there is imbalance of fluids and electrolyte or vomiting or diarrhea, the kidneys could be involved and injured, which can be noticed from doing a kidney function test. So this test is among the top blood tests often requested in most illness or conditions.

The components of kidney function test include:


  • UREA

Normal Range in Health

  •  50-120 umol/L
  •  3.0-9.0 mmol/L
  • 210-490 umol/L
  • >=60 mL/min/1.73m2

4. Liver Function test

Your liver is the site of many activities:

  • It stores carbohydrates to be made into sugar at a later date when you are not eating.
  • It produces bile, which helps you digest your food.
  • There are enzymes in the liver, which break down chemicals and drugs, called liver enzymes.
  • If, for example, you do not have enough of an enzyme produced in the liver, from proteins and parts of proteins called amino acids, then the drug will remain in your system and will not be eliminated, possibly causing too high of a dose.
  • Other chemicals from the liver may just indicate damage to your liver from alcohol or hepatitis. 

Testing for liver function is thus another very commonly requested blood test for abdominal pain and many other conditions.

Common components of liver function test include:



Normal Range in Health

  • 1-60 U/L
  • 33-48 g/L
  • 30-145 U/L
  • 11-63

Fatty liver disease, excessive alcohol intake, metabolic syndrome, drugs like statins are all common causes of elevated liver function test, especially the GGT.

5. Indicators of Inflammation

There are some chemicals in your blood that are released by damaged or injured cells. Such injury could be from infection, trauma, problems with the immune system, or even cancer. In many conditions that causes abdominal pain, important inflammatory markers or indicators of inflammation often tested in the blood include:

  • CRP (Cryo-Reactive Protein). This is a protein produced by the liver in response to inflammation - be it from infection or any other causes of inflammation. A normal level of CRP is between zero (0) to Eight (8). Levels higher than 10 indicates an ongoing acute inflammation.
  • ESR (Erythrocyte Sedimentation Rate). This is another marker of inflammation often checked in the blood. ESR could be raised in chronic inflammation too as in acute inflammation.

6. Tumor Markers

Cancer cells sometimes release special chemicals into the bloodstream, like prostate-specific-antigen (PSA), which can be used to help your doctor make a diagnosis of cancer, or confirm his suspicion. Tumour markers are a number of substances found in abnormal quantity, usually when there is the presence of a type of tumor or cancer in the body.

Though very high amount of any of these chemicals is likely to indicate the presence of a tumour,  they generally tend to have low level of accuracy in predicting the presence of cancers.

Tumor markers are best used to track recovery or recurrence in patients already diagnosed with a known cancer.

Common tumour markers requested in blood test include:

  • Prostate Specific Antigen (PSA)
  • Alpha Feto-Protein
  • Cancer Antigen 125 (Ca 125)
  • Carbohydrate Antigen 19-9 (Ca 19-9)
  • Carcinoembryonic Antigen (CEA).

7. Other Blood Tests

Every month, researchers are finding more chemicals in the blood to analyze to help your doctor make a diagnosis. Because a blood test is pretty simple to do, it is useful to be able to understand the purpose of all the chemicals in the blood.

Common and important blood tests that may be helpful in the diagnosis of abdominal pain and other related conditions include:

  • Albumin Level
  • Aldolase
  • Aldosterone Levels(Serum)
  • Alkaline Phosphatase
  • Alpha-1 Antitrypsin
  • ALT (SGPT)
  • Ammonia Blood Test
  • Amylase
  • Antinuclear Antibody Test (ANA)
  • Antistreptolysin O Antibody (ASO)
  • Ascaris Antibodies, IgE
  • AST (SGOT)
  • Babesia PCR
  • Blood Group (Blood Type) Test
  • BUN and Creatinine
  • CA 19-9 Pancreas Carbohydrate Antigen
  • Calcium Blood Test
  • Candida Albicans Antigen Test
  • Carcinoembryonic Antigen
  • Celiac screen - TTG
  • Ceruloplasmin (CER)
  • Cholesterol Panel
  • Cholinesterase Test
  • Chromogranin A
  • Clostridium difficile Toxins A & B
  • Coccidioides Antibodies
  • Complement C1 Esterase Inhibitor
  • Complement, Total (CH50)
  • Complete Blood Count (CBC) + Differential + Platelets
  • Comprehensive Digestive Stool Analysis 2.0 (CDSA)
  • Cortisol Level (Diurnal)
  • Creatine Kinase (CK)
  • Cytomegalovirus (CMV) Test
  • DNA Stool Test
  • Endomysial Antibody
  • Erythrocyte Sedimentation Rate (ESR)
  • Estradiol (E2)
  • Ferritin
  • Folate (Folic Acid) Levels
  • Follicle Stimulating Hormone (FSH)
  • Food Allergy Test
  • Glucose Blood Test
  • GGT Test
  • Glutathione Test
  • Growth Hormone, RIA
  • H. Pylori Blood Test
  • Hemochromatosis Genetic DNA Test
  • Hepatitis A Test
  • Hepatitis B Test
  • Hepatitis C Test
  • Hepatitis C Virus (HCV) Real Time PCR (Viral Load)
  • Herpes Varicella Zoster, IgG (Chicken Pox)
  • Homocysteine Test
  • Immunoglobulins
  • Iron Level
  • Kidney Function Test
  • Lactate Dehydrogenase
  • LH (Luteinizing Hormone)
  • Liver Function Test
  • Lupus Anticoagulant (PTT-LA)
  • Lyme Disease Test (Serology)
  • Magnesium Level
  • Mercury Level (Serum)
  • Mitochondrial (M2) Antibody
  • Mold Test
  • Phosphorus (Serum)
  • Potassium
  • Progesterone Test
  • Protein Electrophoresis (Serum)
  • Rheumatoid Arthritis Factor
  • Reticulocyte Count
  • Reverse T3 Test
  • Rocky Mountain Spotted Fever Screen
  • Testosterone Levels
  • Total Iron Binding Capacity (TIBC)
  • Transferritin
  • Thyroid Function Test
  • Toxic Heavy Metals
  • Troponin I
  • Zinc

If you are looking for a specific blood test - be it to check your Reverse T3, or Leaky Gut or any of the above test done and are having difficulty getting your doctor to order them, there is good news. You can now order most blood test directly yourself online from the comfort of your home - whether you are in any where in the USA, Canada, UK, rest of Europe or indeed anywhere in the world. Go to the True Health Labs and see what tests they currently have available and order your test. Yes, you can be in control of what you want tested.


  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
  • Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.


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