Some facts about blood tests

Blood tests...

Some time ago a man re-attended my surgery to obtain the results of some blood tests. During the course of the conversation he enquired about his blood group. I told him that I didn’t know what his blood group was because we hadn’t specifically requested the particular test that would have identified it. He had assumed that his blood group would have been automatically identified as part of routine blood testing.

That consultation was a repeat of an experience that I have had many times during my career as a general practitioner. Many people assume that once their blood is tested the doctor receives a result sheet that contains an A to Z of everything that is normal or abnormal in their blood.

Variety of tests

Today’s doctors have powerful investigative tools at their disposal but before investigation begins the doctor needs to specify which tests are to be performed. The doctor also needs to decide which laboratory he should send the sample to. Should the sample go to haematology or should it go to endocrinology or even biochemistry? Perhaps the test required is so specialised that it has to go to a special laboratory such as the Virus Reference Laboratory in University College Dublin. Sometimes the doctor may need to send separate blood samples to different sections within the one laboratory complex. The doctor also needs to decide if the blood sample should be taken after a period of fasting by the patient.

For example if the doctor wants to test for cholesterol and other fat levels in the blood it is usually recommended that the person attend in the morning having fasted from their evening meal of the night before. Fasting ensures that the test is measuring the true level of cholesterol in the blood and is not skewed by having a full Irish breakfast shortly before the sample is extracted. I can never mention the full Irish breakfast without thinking of Terry Wogan’s description of it as 'a coronary on a plate'.

So, what happens to your blood after it has been extracted from your arm? The first step is to put the sample in a sealed glass tube with a patient identification label on it. The tubes are colour coded for particular tests. Some are plain dry glass tubes and others are slightly moist because they contain a special anticoagulant that stops the blood from clotting in the tube. The patient identification details are completed on the label on the tube and a separate laboratory request form is completed which specifies which tests are to be performed. Each laboratory department usually has its own distinct and separate request form.

Wrong test result

Once the sample is received in the laboratory the details on the sample and the request form are crosschecked. If there is any disparity between the two or if the identification details are unclear or illegible the sample is discarded and not subjected to testing. The implications of giving the wrong test result to the wrong person are too serious to permit otherwise. In that eventuality the doctor is informed and a fresh blood sample is taken from the patient and resubmitted for testing.

The sample is then sent to the particular laboratory specified on the request form. For example if the GP suspects that the person might be anaemic the sample is sent to haematology and an FBC or full blood count is requested. The haematology department specialises in analysing disorders of the blood. Blood samples for FBC analysis are sent in a glass tube containing anticoagulant. This chemical agent stops the blood from clotting, which would render the sample useless because of the clumping of the cellular elements in the blood that occurs in the clotting process.

The FBC gives information on the size, shape, colour and quantity of the various cells that form the blood. It also gives information on the haemoglobin level, which is the oxygen carrying protein in the blood. Approximately one dozen individual elements are measured in the special automated analyser that performs the FBC.

Blood group

The FBC is one of the most commonly performed blood tests however; it will not give any information about a person’s blood group. That needs to be requested and tested for separately. Similarly if you want to find out about your blood glucose level a separate fasting sample of blood will need to be sent to biochemistry. The biochemistry department is concerned with measuring various chemical elements within the blood. Many of the samples that are sent to biochemistry are sent in dry glass tubes. The sample is usually spun down in the laboratory in a special device called a centrifuge. This device separates the serum or liquid element from the cellular elements in the blood. The various chemical elements in the blood are contained in the serum.

The biochemistry department can perform a diverse range of tests that give information on such important matters as kidney and liver function. Again it is necessary for the doctor to specify which tests he wishes to have performed. If the doctor were to request information on liver function he would receive a printout containing information on the protein level in the blood as well as the level of bilirubin plus various chemical enzymes, which can give valuable information on possible liver damage.

The department of endocrinology is concerned with measuring hormone levels such as thyroid function, male and female sex hormone levels, adrenal gland hormones and the levels of particular trigger hormones that control hormone output from the individual endocrine glands. For example if a doctor has requested hormone studies on a menopausal female he will receive a measurement of oestrogen and progesterone levels as well as FSH (follicle stimulating hormone) and LH (luteinising hormone), which are both produced by the pituitary gland and regulate hormone production in the ovaries.

Immune system

The immunology department has assumed increasing importance in recent years and can provide very valuable information on many different aspects of function within the immune system. It also provides testing facilities for the various autoantibodies that are involved in various autoimmune diseases. Autoimmune diseases occur when the immune system develops antibodies against various tissues within the body thereby reacting against them as if they were a foreign invader. The laboratory can test for the presence of specific autoantibodies and can give an indicator of the severity of the disease. Autoimmune diseases include such diverse conditions as rheumatoid arthritis, failure of the adrenal glands and particular forms of thyroid disease.

New technology

Hospital laboratories are very efficient and the referring doctor usually receives test results within a week of sending the sample to the laboratory. More specialised tests that require the services of a specialised laboratory may take a little bit longer. This time interval will be eroded even further within the near future as GP surgeries become electronically linked to hospital laboratories thereby permitting electronic transfer of test results. Desktop technology will also increasingly allow GPs to analyse blood samples in the surgery without needing to involve the hospital laboratory.

Blood testing is a technological marvel of the modern age. It is mind boggling to think of the amount of information that can be extracted from a teaspoonful of blood. However, before your mind gets too boggled remember that the request form needs to specify which tests are to be performed. If you are concerned about a particular element in your blood tell your doctor so that the item can be included on the request form. Don’t assume that the item will be tested for automatically.

Dr Leonard Condren is the medical editor of


Noel and Maura(mosne) - 13/03/2002 20:31

Very informative

Ruth(ruthking) - 13/03/2002 23:14

You have answered a lot of my questions in this article - thank you.

Anonymous - 14/03/2002 19:00

I had a blood test done to check if I was anaemic, the result was clear, the doctor said that my haemoglobin was also clear, what is that if the spelling is correct.

Anonymous - 17/03/2002 16:14

As a medical scientist I am delighted to see that some effort has been made to simplify and explain the processes which occur in the pathology laboratory. I congratulate you on a well written and thought-out article. Two small points on minor issues: Glass tubes are rarely if ever used in labs any more. All blood tubes should now be plastic to avoid breakages. Also the first picture in the article shows a doctor transferring blood from a srynge to a blood container - this practice has been shown to distort some test results (e.g. coagulation studies) and should be avoided. To answer the question from a previous writer - haemoglobin is the molecule contained in red cells that binds to oxygen and thus transports it around the body.Haemaglobin testing is part oft he FBC test as described in the article and is the most commonly requested laboratory test in the world. An important component of haemoglobin is the iron molecule. If you are iron deficient for example your haemoglobin level drops and so does ones ability to transport oxygen from the lungs around the body. This will result is a person feeling tired and pale as oxygen is needed as a 'fuel' for all the cells in the body. Iron deficient anaemia is quite common in some populations such as pregnant women and in the elderly. It can also sometimes be seen in some vegatarians if they do not plan a proper diet. Another common anaemia is B12 and Folate deficient anaemia. The absence of these nutrients from the diet can cause red cells to expand in size to a point where they lose their ability to function correctly.

nuala(nualaduggan) - 21/03/2002 13:23

thank you for your help

Anonymous - 01/05/2002 12:55

Could you tell me if there is a test called SR Test and if so what is it ?

Anonymous - 07/05/2002 22:02

reason for very high E.S.R.106

roni(ronienright) - 29/05/2002 19:15

My doctor has told my husband that his blood is a little rich and will have to do a further blood test. What could this mean ?

Anonymous - 06/06/2002 15:26

My doctor has sent a blood test off to check my white cells? Why would she need to do this?

Anonymous - 07/06/2002 20:22

i had been feeling extremely depressed, tired, anxious and irritable for some time. i attended my doctor and requested a hormaonal test (i had read about it somewhere). when the results came back, my oestrogen levels were under 150. i was told by my doctor that this was extremely low and that all the symptoms above were probably as a result of this. the doc put me on the pill and after a few days, i began to feel so much better, better than i had in years. can low oestrogen levels really make one feel so bad ??? i would really appreciate feedback.

Anonymous - 10/06/2002 13:43

Because of raised blood pressure my GP putme on a course of medicine.At the same time he took ablood sample and this was repeated nearly three weeks later. i am due to visit him again next Monday to discuss the results of the tests.What are these tests designed for?

Anonymous - 11/06/2002 22:38

Thanks to you, I now can ask my G.P. to do specific blood tests, as I have had Lupus for the past three years, and never knew exactly what these blood tests were for.If anyone out there has Lupus, I would like to be in contact with them as I feel support is very important.

Anonymous - 10/09/2002 14:33

I underwent some blood tests at my local county hospital to be told three months later that they had "lost" halve of them within the same hospital on the way to their lab. I am not aware of the particular tubes that went "missing" or their relevance however I would have thought it would be routine to inform my GP/myself so the tests could be done again. I had to endure another set of blood tests three months later when I was informed of their "mishap". Obviously, I was considered important enough to be advised considering the test results would have been available within seven days to them. This is just another calamity of my dealings with this Hospital and The Health Board who manage it.

Anonymous - 10/09/2002 14:37

Please ignore first regarding blood tests lost as a sentence should read I wasn't considered important enough whereas I have it down as was considered which is incorrect and changes the context of the subject. The second has the correct wording

mary(caseym) - 02/10/2002 17:36

Could anyone tell me if it is possible to have a saliva hormone test done in this country.Approx 1 year ago I heard an article on "Nationwide" in relation to infirtile couples and heard that saliva hormone tests would be carried out by a private agency - approved by the government.Despite umpteen calls to health boards, dpt. of health, Irish Medicine Board I have been unable to get any information.Can anyone help please. Mary

fbloggs - 29/05/2003 02:49


dave(stapleton) - 29/05/2003 19:11

Is a blood test for prostate sufficient to detect any abnormality?

Anonymous - 01/06/2003 19:42

Prior to a recent operation I had blood sample sent to the hospital Haemotolgist and got the results. One result called WBC showed 10.8 and the range is 4.0 - 10. Is my reading serious?

Anonymous - 06/08/2003 13:15

Employees of my company (medical devices) handle explanted human tissue (bench testing) & recently, one of the team raised a concern in terms of blood borne pathogens. Where can we learn more about this & receive professional training to ensure we are following best practices. Who for example trains doctors/nurses etc? Regards.

Anonymous - 04/09/2003 00:10

I was told that my folate level was 2 by a dentist and this was due to medication for epilepsy (phenytoin). Can I increase my folate level by just taking a folic acid tablet? Should I have my blood monitored as I read recently that a low folate level is very serious, esp. with regard to dementia? Should I change my epilepsy med?

jean(jeanlennon) - 04/09/2003 19:06

I attended an endocrinologist some time ago (due to extreme fatique) who did bloods and diagnosed ME due to extremely low levels of DHEA in the Adrenal Glands i.e. 0.6. No GP that I have spoken to ever heard of DHEA. The upper level I am told should be 10.0. Also he told me I have low oestrogen and progesterone levels and was menopausal. I asked my GP to repeat these tests and they were normal. Can these fluctuate? Can we trust our Doctors????????

ken(ZJH12880) - 26/04/2004 14:15

I need to know the clinics or hospitals in Dublin where I can have my blood tested. Are these generally private or are they state provided tests.

Anonymous - 01/02/2005 13:31

I went for blood tests about six months ago and I was put on iron and folic acid. But went to the doctor only yesterday for a prescription but have been told I am anaemic and need vitamin B12 injections and need to double my intake of iron and folic acid. Should this not have been actioned six months ago?

Anonymous - 05/05/2005 17:18

Hello Im just wondering what is the easiest way of getting a full blood test done. I want to find out am I lacking in any nutrients. From time to time I feel a bit lethargic and people have commented to me on how pale i look from time to time. Ive had a simple 5 minute blood test done in a mobile clinic about a year ago and it showed that I was not lacking in iron and that my glucose levels were OK. I was diagnosed with irritable bowel syndrome 5 years ago which I still have. Could this be connected with feeling lethargic and pale from time to time.

James(HAP28635) - 16/05/2005 13:59

A blood test has shown that my liver function is high.I've got to attend for an ultra-sound in St.James's in July.Can it be serious?

martin(IJV30004) - 21/06/2005 22:20

Here's a novel idea...let's have a 'centre of excellence' for blood..where all blood donations are comprehensively screened for all known symptoms..then people can donate blood regularly..with the full knowledge that they will receive a 'free' blood report..on a regular basis. This would assuredly relieve the paucity of supplies that is so topical at the moment. Chances of this being implemented? won't be offered such short odds in a bookies!!

Anonymous - 25/08/2005 09:59

I have recently undergone blood tests, i was tested for diabetes, it came back clear, new results confirmed that my blood count is low, is this dangerous and why does it happen??

Anonymous - 03/09/2005 11:45

My mum has just got her blood results back and it showed that her enzyme level is moderately high although her diet is healty enough and she is not a drinker. What could this mean.

Anonymous - 04/09/2005 14:13

Many thanks for posting my message but how do I actually get an answer to this message and where do I look on this website.

mary(CMA25690) - 13/09/2005 17:03

Can anyone tell me what 'factor 5 leydon' blood test is?

biddy - 08/11/2005 19:42

my gp took blood tests yesterday and sent them to the lab he rang me back today and said my blood is very serious it is only 7 and it should be 13 what would be wrong

biddy - 09/11/2005 19:54

thank you for posting my message but i just want to know how do i find my answer to this message or where do i look for it on the medical web site and many thanks again

Chuckles - 10/11/2005 11:23

hi biddy, the way this site works is that you post your question and hopefully some other person will have been through a similar experience or be able to pass on some information. Unfortunately I can't help you as I have not had any problems with my blood, but maybe somebody else might.

biddy - 12/11/2005 20:36

thank you very much chukkles

NH - 30/03/2006 10:34

I have just called my GP to get the results of blood tests & was told my Grammits (Probably spelt wrong) is very high & this is to do with kidney & liver. I went complaing of numbness / weakness in hands & feet, confusion /tiredness. I am really concerned now. I am 31, hope to hear something really soon.

Matej - 11/04/2006 13:20

My mother had brest cancer removed last year. In her last blood-test results SR value vas too high (20 mm/h)- I`d like to know what does that mean. And secondly CA15-3 marker value was 16,5 U/ml - is that normal or does it indicate some problems? Thank you.

katie - 18/07/2006 00:19

what does 10.4 reading of bloods means and carino embryonic antigen what type of a blood test is that

martin - 22/08/2006 15:16

I got a blood test done and was told that there is too much iron in my blood and its affecting my liver. I now have to go for more tests in hospital, so I am left in the dark. I don\'t know the cause of this, so if there\'s any one out there with the same problem that could tell me about it, even the name of it, please let me know. Thank you

Anon - 26/08/2006 14:31

Martin, the tests they are doing in the hospital will tell them (and you) exactly what is causing too much iron. It could be something very minor and/or it could be a condition called Haemachromatosis (which is also called the Celtic Disease as it is more common in people of celtic origin). If it is haemachromatosis, don't worry as all it means is that you will have blood taken regularly until the iron levels are back to normal & after that they will monitor you regularly. Don't worry!

shel - 26/08/2006 16:45

hi martin thats called haemachromatosis its when you have too much iron and it causes problems its usually can get leaflets on it from your local gp or takes ages for them to get results of this so id advise you to get medical history from your immediate family to see if anyone else has the same problem,then go to your doctor and get him to refer you to hospital for further blood tests you'll also need to get a liver test...

Andra - 28/08/2006 08:52

My wife went to her GP for a general check up. The GP took blood and said the results will be ready in a few days. 1 week later my wife gets a call and told the samples have been misplaced and she needs to take blood again. She takes blood for a second time and 1 week later we get a call saying the samples have again been misplaced and blood needs to be taken again!! The reason for this she was told is that the lab misplaced her blood sample. Is this a common scenario I wonder? Blood taken 3 times because twice it was misplaced? The doctor apparently was hardly apologetic about the whole episode and she has a respected practice in Dublin. I just find it very strange and also confirms my belief that doctors are becoming the most arrogant profession out there with never the need to apologise when things go wrong.

Mary - 28/08/2006 16:48

Andra, sadly it's not uncommon. In my own experience so much depends on the lab. it as my work GP who told be that there is a path. lab attached to a particular hospital which he never uses becuase the results are slow, samples are misplaces and they are unreliable. In my personal opinion, doctors do not apologise for mistakes becuase they feel that you may think they are then accepting blame and doctors, so many of them do not like to accept blame.

Anonymous - 16/02/2007 16:48

A friend has been diagnosed with Haemachromotasis last year. Since then his health has gone down hill. Are there other ailments that can occur from having it?

Anon - 16/02/2007 19:09

Haemochromatosis is a very common illness in Ireland and is also very easy to treat. It is caused by too much iron and the treatment is to have blood taken usuallly weekly or monthly to begin with (which can be done in a few hours as a day patient). If the condition is left untreated, the build up of iron in the blood will cause complications for many of the other organs but this takes a long number of years. So, it depends on the age of your friend. I am sure they must have checked out your friends general condition after they diagnosed the haemochromatosis so they would know if there was any other problems. If there are no other organs involved (and I would hope that there isn't at this point) then its just a matter of having blood taken regularly and the condition will not cause any further problems. I hope that is of help to you. Its not as serious a condition as it sounds once it has been diagnosed. Good luck.

Anonymous - 06/03/2007 17:23

I have had blood tests carried out and my B12 was 60. My doctor started me on B12 injections and sent my bloods away again, this time they came back at 2000, I didnt have the second injection but did the bloods again and they have come back at 294. She is now sending me to a Haemotologist as she is puzzled. Should I be worried?

pingu - 21/03/2007 09:49

i have just had blood test taken and they have come back normal, however i suffer with depression and have extremely irregular menstrual cycle, how come nothing comes up on the blood tests? doctors dont seem to be able to determine any diagnosis for irregular cycles, what tests should you ask for

Anonymous - 21/03/2007 10:00

An irregular mentrual cycle won't come up on blood tests nor will depression unless they use specific test to detect medication levels. With regard to your menstrual cycle, depending on your age, you will need hormone testing. If you are not of menopausal age and it's not contra-indicated for any health reason it wou;ld be well worth your while investigating the pill to regulate your cycle.

Anonymous - 02/04/2007 22:21

Have been told by neuro to have acantocyte blood film and have it three times - why? Also suggested to have ABGA blood test. What will this show? I have neuro symptoms and tested pos for parkinsons but they are not too sure if it is parkinsons as my symptoms are not typical

salsa - 19/04/2007 11:41

Ok, but how is a basic blood test done????

Cathy - 19/04/2007 12:19

Salsa, your GP is very unlikely to have a pathology service as part of their clinic so it will need to be sent to a lab (usually attached to a hospital) in order to be analysed. This could take anything from a couple of days to a a couple of weeks

fee - 25/07/2007 15:08

i was at the doctor this morning for the results of my haemochromaosis test. They said that I have the both C282Y and H632D heterozygous and I have been referred to another clinic as I am adopted and there is no other family history. Is it likely from this diagnosis that I have it? Also I have been suffering with sweling and aching in my knees and I got a colonic done and they think I also have IBS. Anyones advice welcome!

Ducks - 04/08/2007 21:49

I have crohns disease and ? PD, in Jan and Feb my Prolactin was high, in Feb my ANA was 1/800 and again in July |ANA was 1/800. My CK is rising and now is 294, my thyroid is not functioning and I take replacement. I feel so ill all the time every time I ask the docs why such a blood test is raised he/she just says ah its alright, except they're not saying that about the CK but in such an ill person with so much wrong can the ANA really be a false positive TWICE? As the last ANA was in July when I can I acceptably ask for another. I feel very poorly again now and would like to ask for another ANA and CK? Is this too much to ask. Lupus sufferers advice on the ANA greatly appreciated

Niibro - 02/01/2014 13:23

I am a lab. professional and i just want a quick info on the report format on HVS.

I want to know if when clue cells are seen on a wet mount, which suggests BV, can the gram stain have a lot of gram positive bacilli?

I need someone to send me the report format on HVS either here or to my email: Thanks a lot.

Spider - 23/06/2015 13:07

what does high infection level in blood tests result mean, ??????????

Shiva Gopi - 25/10/2017 13:33

Great here to see the facts about the blood test. We also must be fasting before blood tests. Because, if we eat anything then our blood observes nutrients then the reports do not represent actual one. Maybe it's not a fact about blood test but this is helpful who think about why do we need fasting before blood test.

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