AcademiaAgriculture & FarmingHumanitiesSocial SciencesSTEM

Understanding Your Blood Tests & Biochemistry

Updated on April 25, 2016
Source

"Blood is that fragile scarlet tree we carry within us". ~Osbert Sitwell

The majority of us at some time have had blood taken, but how many people actually understand:

  • Why the blood test is being carried out?
  • What the blood test is looking for?
  • Understand the results when they come back?

This article will explain, in basic terms, the composition of human blood. The most common blood tests carried out and why doctors, nurses and other professionals need the information tests provide. In addition this will help you to have a better insight in to what blood tests reveal about your health.

There are hundreds of different blood tests carried out - some for general tests others are more specialised.
There are hundreds of different blood tests carried out - some for general tests others are more specialised. | Source
A test tube sample showing the different components of human blood.
A test tube sample showing the different components of human blood. | Source

Human blood - the basic compilation

The blood has two main components:

  1. plasma
  2. blood cells.

This texture allows substances such as oxygen, carbon dioxide, nutrients, enzymes and other products to be carried to all organs, tissues and cells of the body.

  • Plasma is made up of approximately 91-92% water. The other 8% consists of blood plasma proteins and traces of other elements. Not only does the plasma transport blood cells but it also acts as a conductor of heat. Plasma is not a clear liquid but is more straw coloured.


  • Within the blood there are three kinds of blood cells - red cells, white cells and platelets.


  • Red blood cells, (RBC) account for approximately 99% of all the blood cell categories. The scientific name for a red blood cell is - erythrocyte


  • The red colouring comes from haemoglobin. This is a red pigment that carries oxygen in the blood.


  • White blood cells, (WBC), fight disease and infections within the body by producing anti-bodies that destroy harmful organisms.


  • Platelets form clots when there is injury in order to prevent blood loss from the body. However, if clots develop inside the body for some reason - due to disease for example - then the clots are called a thrombosis and can be dangerous.



White blood cells within the blood plasma fighting infection.
White blood cells within the blood plasma fighting infection. | Source
Red blood cells as seen under a microscope. The shape and number of your blood cells is one investigation that may be carried out to determine your state of health.
Red blood cells as seen under a microscope. The shape and number of your blood cells is one investigation that may be carried out to determine your state of health. | Source

Why Are Blood Tests Taken?

There are many reasons why your doctor may want to take a blood test, but some of the most common are listed below:

  • To test for or confirm the presence of an infection or virus.
  • To test the health of certain organs in the body such as the liver and kidneys. The amount of certain substances found in your blood can tell a doctor whether or not your body organs are in good health.
  • To assess your general over all health.
  • To check for medication levels in your blood. This is particularly important for very toxic drugs such as digoxin and lithium that can easily build up in the blood causing severe side effects.
  • Blood tests can also be used for genetic testing. These look for disorders such as cystic fibrosis.

Lastly, don't be confused by the various bottles with coloured tops that are used. They are only for identification purposes at the laboratory. A specific colour of bottle means that the doctor would like a particular test to be carried out.

Blood samples in vials with different coloured tops. These colours tell the laboratory what tests to carry out.
Blood samples in vials with different coloured tops. These colours tell the laboratory what tests to carry out. | Source
Both red and white cells as well as platelets are analysed to determine the state of health of a person.
Both red and white cells as well as platelets are analysed to determine the state of health of a person. | Source
A modern laboratory showing the machines that analyse all the components of human blood.
A modern laboratory showing the machines that analyse all the components of human blood. | Source

The Main Types of Blood Test & What They Mean

Obviously this article can't cover the numerous blood tests available. However, by understanding the most common, it should help to give you a clearer picture of blood tests in general.

In addition, these tests are the names common to the UK. In other countries they may be referred to differently, but the routine tests are used for similar purposes.

Full Blood Count (FBC)

This test is a universal standard when a patient visits a local doctor or is in hospital. This test will give an overall view of your general health. Basically the different types of blood cells that we mentioned earlier - red, white and platelets - will be counted and compared against what should be normal values for the person's age and sex. The FBC can not give a clear cut diagnosis. However, it can give a good indication of problem areas in the body.

An FBC can signal up the following issues:

  • If the red cell count is found to be too low then this could be due to anaemia.
  • If you have too many red cells within the count then this signifies a potential health problem in a number of areas in the body. For example in respiratory disease. Because the body is not getting enough oxygen into the body due to inflamed lungs, to compensate, the body will produce higher numbers of red cells to try to increase the amount of oxygen into the body. But this is only an example and there are a number of conditions where the red count is increased.
  • If the FBC finds that your white cell count is low this could indicate a problem with over all blood cell production in the bone marrow. A low white count could also be an indication of other conditions such as leukaemia.
  • If your white cell count is high this is nearly always an indication that the body is responding to some form of infection or virus. What the FBC can't say is where or what that infection is. Further tests such as Blood Culture would be carried out.
  • When your platelet count is low this could suggest that a virus is present in the body. Viruses such as Rubella (German measles) are often responsible for a low platelet count. In other cases low platelets can indicate an autoimmune condition such as Lupus. An autoimmune condition is one where the immune system, for some reason, attacks healthy body tissue.
  • If your platelet count is found to be higher than normal this can be an indication that an inflammatory condition such as rheumatoid arthritis is present. Another condition that can cause a high platelet count is when the organ of the body called the spleen is damaged. The spleen is responsible for removing damaged or old blood cells from the body.

Electrolyte test

Electrolytes are essential minerals found in the body. The body cannot function properly without them. An electrolyte test is used to measure their levels in your blood. The important functions that electrolytes carry out are:

  • Assist in moving nutrients into cells and removing waste products out of them.
  • Helps to maintain a healthy water balance in your body
  • Assists in maintaining the levels of acid and alkali in your body

There are three main electrolytes that can be measured with an electrolyte test:

  • Sodium
  • Potassium
  • Chloride

Raised or lowered levels of any of these electrolytes can have a number of possible causes:

  • If you have high sodium levels this can be an indication of various conditions such as - dehydration, kidney disease and diarrhoea. *Hypernatremia is the medical term for high sodium levels in the blood.
  • When the sodium levels are very low this may indicate some of the following - poorly controlled diabetes, liver disease, a dietary deficiency in sodium and pneumonia. Some types of medication can also cause low sodium levels. This is particularly the case with some anti-convulsants that are used to treat epilepsy. *Hyponatremia is the medical term for low sodium levels in the blood.
  • High levels of potassium could be an indication of kidney failure. However there are some medications used to treat high blood pressure that can also cause potassium levels to rise. *Hyperkalaemia is the medical term for raised potassium levels.
  • Low levels of potassium are usually the result of excessive sweating or conditions where there are prolonged bouts of vomiting and diarrhoea. *Hypokalaemia is the medical term for low potassium levels.
  • High chloride in the blood is usually found with some types of kidney disease. However, raised chloride is also found in excessive diarrhoea and in people who have overactive parathyroid glands. These glands help to regulate the amount of calcium in your body. *Hyperchloremia is the medical term for high levels of chloride in the blood.
  • When the chloride levels are very low this is also an indication of various types of kidney disease. But can also be brought on by heavy sweating and vomiting. *Hypochloremia is the medical term for low chloride levels in the blood.

When you visit someone in hospital and they have an intravenous infusion - bags of fluid on a stand, with a tube going into their hand/arm - then frequently these bags of fluid contain electrolytes. Other infusions contain substances such as glucose, anti-biotics and other drugs.

Blood glucose test

Blood glucose tests are used firstly to diagnose diabetes and secondly to monitor the glucose levels in the blood of people who have already been diagnosed with the condition.

Diabetes will occur when either the body cannot produce enough insulin to control glucose levels or when the insulin that is produced does not work effectively. Insulin is a hormone that the body produces to convert glucose into energy.

Blood gas test

A blood gas test is used to check two things:

  • firstly how acid or alkaline your blood is
  • secondly the balance of both oxygen and carbon dioxide in the blood

Why are these important?

If you have an imbalance in either acid/alkaline or carbon dioxide/oxygen then this could indicate that your lungs are not functioning properly. Secondly, there may be a problem with your ability to breakdown food into energy. This process of breaking down food to release energy is known as metabolism.

An imbalance of oxygen and carbon dioxide can be an indicator of conditions such as pneumonia, COPD - chronic obstructive pulmonary disorder and similar illnesses. Hyperventilation can also cause an imbalance in the blood gases.

Metabolic causes of alkaline-acid imbalances could be caused by conditions such as diabetes, kidney disease or excessive vomiting.

Blood cholesterol test

Although we hear a lot of bad news about cholesterol it is in fact a vital fat required by the body. Problems only arise when there are excessive amounts of cholesterol. This can lead to serious life threatening conditions such as CVD (cardio-vascular system disease) leading to strokes, heart disease/heart attack. The medical term for excess cholesterol in the blood is hyperlipidaemia. Normally this blood test is only carried out if your doctor feels that you may be at risk of having a stroke or developing heart problems.

Liver function test

A liver function blood test is one of the most common tests to be carried out by a doctor. This test helps to check the health of the liver and to diagnose some liver conditions. Disease of the liver can be diagnosed in this way because when damaged or inflamed the liver releases a special enzyme into the blood that can be detected. In addition, the liver produces numerous proteins. When the levels of these proteins in the blood are low this can also indicate that the liver may be diseased.

Liver conditions that can be indicated when this blood test is carried out are:

· Hepatitis - this means an inflammation of the liver.

· Cirrhosis - when the normal structure of the liver is damaged, scar tissue is formed.

  • Alcoholic liver disease - basically the liver has been severely damaged by excess alcohol. This condition can also cause other diseases to develop such as hepatitis and cirrhosis.

Blood cultures - these type of tests will show up numerous health issues within the body.
Blood cultures - these type of tests will show up numerous health issues within the body. | Source

Human liver

There are various blood tests that can be carried out to find out if the liver is diseased. One of the most common is the 'liver function test'.
There are various blood tests that can be carried out to find out if the liver is diseased. One of the most common is the 'liver function test'. | Source

Human kidneys

Blood tests can say much about the health of the kidneys.
Blood tests can say much about the health of the kidneys. | Source

Test your knowledge


view quiz statistics

What Does Your Biochemistry Mean?

The bio-chemistry of your blood is the different substances and their levels that the blood usually carries in solution.

If your doctor, nurse or pharmacist shows you your own biochemistry form you may see elements such as the following - this is not exhaustive and only an illustration:

  • Hg - haemoglobin
  • RCC - red cell count
  • WCC - white cell count
  • eGFR - estimated Glomerular Function Test or creatinine clearance test - is a number given based on your blood test for creatinine. This shows how well your kidneys are working.
  • Creatinine - this is a nitrogenous organic acid found in most animals and this substance helps to supply energy to the body cells. It is normally excreted by the kidneys. Therefore, if levels in the blood are high, this could be an indication that the kidneys are not working properly.
  • CorCal - corrected calcium. This is the result of how much calcium is in the blood. The amount is usually corrected to allow for the amount of calcium that binds to albumin in the body. High or low levels of calcium in the blood can indicate various diseases and conditions.
  • Albumin - is a protein made by the liver. It helps to regulate the osmotic pressure in the blood. A low albumin level is an indicator not only of malnutrition but many other conditions and diseases such as liver disease and inflammation.
  • Na - sodium
  • K - potassium
  • po4 - phosphorus. This is a vital mineral required by the body for both healthy new growth of bone and for normal functioning of all cells in the body. Depending on whether the levels of po4 are high or low is an indication of problems in the body. For example, high levels could indicate kidney disease. Whereas low levels might be an indication of sepsis.
  • Urea - is a waste product formed during the breakdown of proteins in the body. It is sometimes called urea nitrogen. Like creatinine it is usually excreted in the urine by the kidneys. High levels of urea can indicate that the kidneys are not working properly. However it’s usually the creatinine levels that are preferred for estimating proper kidney function.
  • Bilirubin - is a yellow coloured substance that results from the natural breakdown of haemoglobin. This yellow pigment gives urine its familiar colour. It’s also responsible for the yellowish tinge around bruises and the yellow skin colour in people who have jaundice. High levels of bilirubin in the blood can be an indication of liver disease.

This explanation is a simplified one and your doctor may well ask a laboratory to test other body substances not listed here. But those above are among the most common.

I hope this article has been helpful in giving you more information about why blood tests are needed and what health professionals are looking for in your blood. However, as always, this article is not intended to replace the advice of your doctor. If you have any concerns about your health speak to them as soon as you can.

©Seeker7(Helen Murphy Howell) August 5th 2013

© 2011 Helen Murphy Howell

Comments

Submit a Comment

  • Kosmo profile image

    Kelley 5 years ago from California

    I've often wondered about blood tests. Thanks very much for the informative hub. Hey, I haven't had a blood test in many years. Am I overdue? Later!

  • Seeker7 profile image
    Author

    Helen Murphy Howell 5 years ago from Fife, Scotland

    Hi Kosmo,

    Many thanks for stopping by and glad that you found the hub interesting.

    As to blood tests being overdue - I only ever allow those needles near me when it's absolutely necessary. If you feel okay, as you said 'later!'LOL!

  • Cloverleaf profile image

    Cloverleaf 5 years ago from Calgary, AB, Canada

    Hi Seeker7 you did an excellent job of presenting this well researched and thorough hub - I love the use of your pictures!!

    Great stuff voted up and interesting.

    Cloverleaf.

  • Seeker7 profile image
    Author

    Helen Murphy Howell 5 years ago from Fife, Scotland

    Hi Cloverleaf,

    Lovely to hear from you and many thanks for the vote up. I use photos, then if folks find the writing boring they can always look at the pictures!! But really glad you found it interesing - many thanks again.

  • Eiddwen profile image

    Eiddwen 5 years ago from Wales

    a very interesting hub which i am sure will benefit many readers.

    I vote up and thank you for sharing.

    Take care

    Eiddwen.

  • Seeker7 profile image
    Author

    Helen Murphy Howell 5 years ago from Fife, Scotland

    Hi Eiddwen,

    It's always a pleasure to hear from you and many thanks for the vote up. It would be a nice bonus if people did find the hub useful at some point.

    Many thanks for the visit.

  • Stacie L profile image

    Stacie L 5 years ago

    everything I wanted to know about blood but was afraid to ask!

    good hub!

  • Seeker7 profile image
    Author

    Helen Murphy Howell 5 years ago from Fife, Scotland

    Hello Stacie L,

    Many thanks for visiting the hub and for the positive comment. The blood can be very daunting not to mention the blood tests themselves. But hopefully learning more about the tests and their indications lessens the fear rather than adding to it.

  • shai77 profile image

    Chen 5 years ago

    Thanks for the useful info :-)

    You have great Hubs my friend :-)

    Rated and voted.

  • Seeker7 profile image
    Author

    Helen Murphy Howell 5 years ago from Fife, Scotland

    Hello to you Shai77,

    Many thanks for stopping by and for the rate+vote. It really is appreciated, but more importantly, glad that you found the hub useful. Many thanks again!!

  • K H Camp profile image

    K H Camp 5 years ago from Atlanta, GA

    Great hub! You have a ton of helpful info here! Rated and voted.

  • Seeker7 profile image
    Author

    Helen Murphy Howell 5 years ago from Fife, Scotland

    Hi K H Camp

    Many thanks for stopping by and glad that you enjoyed the hub. My aim was to include information that is not always explained to patients but these tests are always mentioned to them causing a great deal of confusion and at times anxiety.

    Many thanks again and for the vote up - much appreciated!

  • jenn-zee profile image

    jenn-zee 5 years ago from Toronto, Ontario

    Very comprehensive and well-organized overview!

  • Seeker7 profile image
    Author

    Helen Murphy Howell 5 years ago from Fife, Scotland

    Hi jenn-zee,

    Lovely to hear from you and glad that you enjoyed the hub!

  • Lady_E profile image

    Elena 5 years ago from London, UK

    Interesting. I would like to Bookmark this to read/study again. It's important we know these things.

    The photos are very useful too.

    Thanks.

  • Seeker7 profile image
    Author

    Helen Murphy Howell 5 years ago from Fife, Scotland

    Hi Lady_E,

    Lovely to hear from you and many thanks for stopping by and leaving a comment.

    I'm glad that the hub was of interest and that it will be of use to you in the future.

    Many thanks!

  • Sunshine625 profile image

    Linda Bilyeu 5 years ago from Orlando, FL

    Hi Seeker7! This bloody hub is outstanding :) VERY informative and detailed! My husband is starting a cancer treatment next week called Provenge and I've been hearing about red, white, platelets, Tcells, etc.... most are foreign language BUT now you have placed them all together for me to print and take with me to the blood bank and oncologist so I know what they heck they are talking about! Thank you VERY much!!!

  • Seeker7 profile image
    Author

    Helen Murphy Howell 5 years ago from Fife, Scotland

    Hey Sunshine! Sorry to hear about your hubby being ill - but he is good hands now!

    There is so much jargon in the medical world that it's like a different language to most people. However, armed with a little knowledge it's amazing how easily everything suddenly makes sense and there is no realy mysteries involved.

    Many thanks again for your lovely comment - and I will be thinking about you and your hubbby - Bright Blessings to you both!

  • Austinstar profile image

    Austinstar 5 years ago from Somewhere in the universe

    Excellent hub on lab tests. One thing I would like to clarify - "don't be confused by the various bottles with coloured tops that are used."

    The colours of the tubes indicate exactly what type of anti-coagulant is inside the tube, not what tests are done on the tube. However the different types of anti-coagulants are used because they are the most compatible with the different types of tests. IE - It leads to very erroneous test results if you use EDTA (a lavender top) tube to test for calcium levels as calcium is the main ingredient in EDTA. Lithium heparin is the anti-coagulant of choice when ordering electrolyte or calcium testing. I hope this made sense.

    I know this because I am the lab geek who runs the tests :-) And thanks for letting everyone know we are badly overworked.

  • Seeker7 profile image
    Author

    Helen Murphy Howell 5 years ago from Fife, Scotland

    Hi Austinstar,

    Lovely to hear from you and many thanks for stopping by and leaving such an interesting comment.

    I totally agree with you about the tubes and their colours. However, I had to decide - since the article is for non medical folks - whether to keep it simple or add in more facts about this issue. I decided to go for simplicity. However, I'm sure your comment will be read by those visiting the hub and find your clarification very helpful and interesting.

    Many thanks again for your visit - much appreciated!

  • Austinstar profile image

    Austinstar 5 years ago from Somewhere in the universe

    True, it is a minor point. And everyone does wonder why we have to have so many tubes of blood. "Why can't you take just one?" Is a frequent question. But as I am a perfectionist or "anal retentive" as they say, I just had to say something.

    Now I'm curious about why the UK adds a "a" to hematology??? (heamatology) or a "u" to colors? Just a thought. I'm being facetious here. :-)

  • Seeker7 profile image
    Author

    Helen Murphy Howell 5 years ago from Fife, Scotland

    Hi Austinstar,

    LOL! The same question must be asked by patients all over the world 'why can't you just take one' is the classic!

    Working in the medical field there is nothing wrong with being a perfectionist. For the most part we have to be like that - and there's nothing wrong with you 'saying something'. For me it opens up the topic and makes it more informative for people who want to know more. I'm sure you're the same when writing your own hubs - what to leave in, what to leave out, it can be a bit of a nightmare!

    Okay as to the words with the 'a' and 'u' - I have no earthly idea except that it makes them much more difficult to spell! I think it goes back, probably to the origins of the English language - much of the English language does originate, I believe, from Anglo-Saxon and funny spellings are possibly a throw back to that. But I'm afraid this is not my field. I have to say that the American spellings are much easier to remember, bascially because they spell how they sound - which makes sense to my dull brain! I don't think you are being facetious - it's an interesting point and there's maybe even a hub somewhere in there! LOL!

    It was great to hear from you again - your comments are appreciated and very interesting!! Thank you!

  • Seeker7 profile image
    Author

    Helen Murphy Howell 4 years ago from Fife, Scotland

    Hello ausmedus, many thanks for stopping by and glad that you enjoyed the hub - many thanks for the fanmail as well, greatly appreciated!

  • profile image

    jamesjohnson1 3 years ago

    Great hub. Got to know a lot of new things about the blood tests. Thanks for the hub. http://www.ilsbio.com/

  • Seeker7 profile image
    Author

    Helen Murphy Howell 3 years ago from Fife, Scotland

    Hi, many thanks for your visit and glad you enjoyed the hub!

  • Glenn Stok profile image

    Glenn Stok 23 months ago from Long Island, NY

    Every year when I get my annual physical, I ask for a copy of my blood work. I keep that so I can compare one year to the next. I see things that the doctor never bothers to explain. He's okay as long as everything is between normal limits.

    But I like to pay attention to see if a pattern is developing, such as one thing getting closer to an extreme. I knew of many of the blood related items, but not all. Your hub helped give me a more complete understanding.

Click to Rate This Article