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What Does a Hospital Medical Lab Technologist Do?

If you're like most people, you have no idea what goes on behind closed doors of your local hospital laboratory. I found out about Medical Laboratory Technology and after taking the program, I have been working as a registered Medical Laboratory Technologist at a core lab for a little more than a year.

I'm going to write about what I do now because not many people understand it. When I say that I am a "lab tech," they think it means that I take blood and that is all. People who only take blood are called phlebotomists and we have no such people employed at my lab. We do have lab assistants and while a large portion of their job involves blood collections.

Most of my work as a Medical Laboratory Technologist is done "behind the scenes" and happens after a patient's blood has been drawn. It is analogous to being part of the lights and camera crew on a movie set - an important group but not part of what the public sees so tends to be undervalued and forgotten. That's too bad because a movie would not happen without them, much like patient health care would be very different without the lab. You may have heard that approximately 80% of all medical decisions are based on laboratory results that Medical Lab Technologists provide. Hopefully I'll be able to demystify a little about the role of a Medical Laboratory Technologist.


When I was in Med Lab Tech school, I studied the five main departments of Medical Laboratory Technology: Microbiology, Chemistry (Urinalysis is a subset of this), Blood Bank, Hematology and Histology. I now work in a core lab, so I get to practice in all of these departments except Histology which has designated staff. In larger hospital labs, there are designated staff for each department but in a core lab like where I work, techs rotate through most departments which can be challenging given the constant changes.

Obviously my descriptions below relate to the happenings of my particular lab but would more or less apply to most core labs as well. I'm only going to describe the main tests that we do so my descriptions are far from all-inclusive:

The inside of a blood bank fridge. There are guidelines that must be followed for how much blood should be in inventory at each lab based on typical usage. We must constantly monitor our supplies.

The inside of a blood bank fridge. There are guidelines that must be followed for how much blood should be in inventory at each lab based on typical usage. We must constantly monitor our supplies.

Blood Bank:

Here we test for blood types (ABO group and Rh factor) on mostly all patient samples that come into the department. There are a few reasons we may do this. One of them is in the testing of pregnant women. If a woman carrying a baby is Rh negative it means that she lacks the Rh protein on her blood cells. If the baby she is carrying is Rh positive, the baby carries the Rh protein (inherited from the father) on its blood cells and if that Rh factor crosses over the placenta into the mother's bloodstream, the mother's immune system can become activated and start attacking her own baby. This can cause complications with the baby (it can be fatal), especially in subsequent pregnancies.

By detecting this situation early in the blood bank, such mothers can be given a drug that will prevent them from potentially harming their babies.

When a patient needs a blood transfusion (due to bleeding, anemic conditions, etc.), he/she must be given blood that is compatible and will not cause adverse reactions (administering the wrong blood type can be fatal). In the blood bank laboratory, we do crossmatches which involves taking a sample of the patient's blood and mixing it with a sample of the blood that has been selected for transfusion. The idea is that if the two bloods do no react adversely in the laboratory (in vitro) that they will not react adversely inside the patient's body (in vivo).

It is not always that simple though because before we do the crossmatch, we check the patient's sample for antibodies. This means that we are checking the patient's blood for certain proteins that may cause that person to react adversely to some blood products. If there are antibodies present, we must find out specifically which antibody or antibodies are there so that we can make sure to select blood products for transfusion that will not react with those antibodies. This is called "antibody investigation" and is not actually performed in my lab. If we discover that antibodies are present, we refer the sample to Canadian Blood Services (CBS) for the investigation.

A normal blood smear in the hematology department. This is what we see under the microscope.

A normal blood smear in the hematology department. This is what we see under the microscope.


Hematology literally means "the study of blood" and the main test here is a Complete Blood Count (CBC). A CBC actually consists of many tests and the main ones are: white cell count, red cell count, hemoglobin and platelets.

What happens is patient CBC samples get placed on our analyzers which test the blood for the aforementioned components plus some others. We must then review all results in the computer before we "verify" or accept them after which time they are available to the patient's physician. If there are any results that are really abnormal or that are very different from that patient's recent history, we must call the doctor directly and/or fax paperwork immediately. We then put a drop of that patient's blood on a glass slide, stain it with special hematology stain, and view it under the microscope.

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As sophisticated as our analyzers are, we still must do a lot of work under the microscope for some patients in order to make sure that there is nothing the analyzers have missed. There are some things that we can only find out about by looking under the microscope. We have certain criteria and if they are met, the slide will go to our lab pathologist for further review.

CBCs can alert a physician to many things such as infections, internal bleeding, reactions to chemotherapy, inabilities to clot properly, etc. As with most lab tests, they are often just a "piece of the puzzle" that doctors use to aid in diagnosis and/or treatment.

There is another part of hematology called coagulation that would be a separate department in larger labs but in mine, coagulation is under the general department of hematology. Coagulation deals with the ability of a patient's blood to clot. Some people who are especially prone to clots are put on drugs to thin their blood making it less likely to clot in their arteries. The problem is that if the blood is thinned out too much, it can put that patient at risk of hemorrhage or massive bleeding with just the smallest of injuries. It's a delicate balance. The main tests we do are called PT (prothrombin time) and PTT (partial thromboplastin time) depending on what type of blood thinning drug(s) the patient is on and/or what situation exists.

This is what urine looks like under the microscope. There are white cells and red cells here.

This is what urine looks like under the microscope. There are white cells and red cells here.


This is the simplest part of the core lab to work in and it primarily deals with the analysis of urine for the detection of Urinary Tract Infections (UTIs). Each sample of urine that we receive in Urinalysis gets placed on our analyzer. If certain criteria are met such as the presence of white cell enzymes, red cells, turbidity, protein or bacteria, the sample gets viewed under the microscope for further analysis. If enough bacteria or white cells are visible, the urine sample is sent to microbiology for culture (I'll explain this further in the micro section).

There are a few other sediments we must be on the lookout for in urinalysis. One of the most important is "casts." There are several different types of casts and they can indicate anything from recent exercise (not clinically significant) to renal disease (obviously much more clinically significant).

An example of what a microbiology plate looks like with bacteria growing on it. This one happens to be E.coli which is the most common cause of UTIs.

An example of what a microbiology plate looks like with bacteria growing on it. This one happens to be E.coli which is the most common cause of UTIs.


The micro department is concerned with the detection and identification of infection-causing bacteria. Since I work in a core lab, we generally work with pretty basic samples and the types of bacteria we see are usually fairly predictable (not always). Anything "really weird" gets sent to our reference lab.

A few examples of samples we set up for culture here are: urine, stool, throat swabs, MRSA ("super bug") swabs, vaginal swabs, wound swabs, sputums, etc. A few examples of what that bacteria we are looking for cause are: UTIs, food poisoning, vaginal colonizations that can be passed onto a baby causing disease like pneumonia, lung infections, and colonizations in catheters and tracheas that are connected to a patient.

To set up a culture, we take a bit of our sample and put it on special microbiology plates that contain the necessary nutrients to grow certain types of bacteria. We then incubate the plates at the appropriate temperature and oxygen environment. The next day, we look at the plates to see what has grown. Reading plates is a bit of a learning curve but with some experience, one can start to recognize what is clinically significant from what is not.

One of the difficult parts about reading plates is that not everything that grows on the plate is necessarily "bad bacteria." You probably know that our bodies are covered with bacteria inside and out and this is our "good bacteria" or normal flora. There can be a fine line between what is normal flora and what is not. To make it more complicated, bacteria that would be considered normal flora in small amounts can be considered disease-causing or pathogenic bacteria in larger amounts. There are many factors involved here but that's what makes it interesting.

Once we have picked out the clinically significant bacteria on the plates, we have to identify what it is and also what antibiotics will work for the patient to kill off that bacteria. To do this, we scrape a little bit of it off the plate and put it into saline. This creates a liquid bacteria suspension that we put on our analyzer. Around 10 hours later, our analyzer tells us what bacteria is present based on a huge database of known bacteria that is in its software. It also provides an antibiotic susceptibility for that organism.

Microbiology is the department that in my opinion requires the most interpretation and judgment call making (there can be a lot of interpretation required in blood bank as well). Each plate we look at is different and it can be difficult to apply a set of rules to each situation we encounter. We must judge each plate on a case-by-case basis. Many times, we will ask our fellow techs for their opinions about a particular plate or situation. It's great to be able to learn from techs with years of experience. There's definitely always more to be learned in the micro department as there is in all departments of the lab.

A typical analyzer in the chemistry department. Here you can see a new tech or maybe a student receiving some training. Every time the lab gets a new analyzer, we must go through training to learn how to use it.

A typical analyzer in the chemistry department. Here you can see a new tech or maybe a student receiving some training. Every time the lab gets a new analyzer, we must go through training to learn how to use it.


Chemistry is the most automated of all the departments - that means that here you will find the greatest number of analyzers and there are no microscopes and few manual interpretations involved. A few examples of some of the main tests we do here are: glucose, cholesterol, thyroid hormones (TSH and FT4), electrolytes, liver enzymes, certain drugs, troponin (heart enzyme), etc. The results we provide here can hep with anything from diabetes management to liver and kidney function to confirming whether or not a patient has had a heart attack.

Simply put, in the chemistry department, we take our patient chemistry samples, put them on our analyzers, wait for results and if the results look okay, we file them in the computer or if results are too high or too low, we phone and/or fax the results. Like anything, it's not really that simple. While the analyzers we have are sophisticated pieces of equipment, they do not always work as they are supposed to. We have to be very careful to watch out for analyzer malfunctions, error codes, inappropriate temperature and humidity conditions, etc.

Opening up a chemistry analyzer reminds me of opening up the hood of your car and looking inside (i.e. a mound of parts and wires). There are many pieces that all have to be working properly in order for us to be able to rely on the results that these analyzers produce. There are daily, weekly, monthly and as-needed maintenance procedures we must perform to ensure that our analyzers are working up to snuff. Some of that involves cleaning probes, monitoring/changing reagents, and running Quality Control (QC).

Quality Control is so important that it's worth saying a few words about. QC involves running samples with results that are already known (usually these are purchased from a medical diagnostics manufacturing company). We put these samples on our analyzers and if the results fall within an acceptable range, it means that our Quality Control for that run passed and that our analyzer is working properly and it is safe to use for patient results.

If QC fails, it alerts us that something may be wrong with the analyzer and we CANNOT release patient results until we figure out what is going on and fix it. This often involves a lot of troubleshooting, sometimes calling our technical support line, and reviewing QC charts. There is some form of Quality Control in all departments and it is very important everywhere - in chemistry though, at least where I work, it is the most involved and seems to require the most constant attention.

Most labs, unless very small, are open 24 hours a day, 7 days a week. This is the case where I work which means that I work shifts. During the day, there are normally around 8 technologists present and often around 4-5 lab assistants. On day shift, techs are scheduled to work in one department only (ex. hematology) but if it happens to be busy in another department, we use common sense and help out where needed.

On evening and night shift, however, there is only one tech and one lab assistant working. On evenings, the workflow is usually moderately busy. Some evenings though it is so slow that there is almost nothing to do while other evenings it is so insanely busy that it is very hard to keep up with what's coming in and one almost goes on auto-pilot mode just to get the work done. We cannot take breaks or supper when it is like this but at least it is not like this every shift. On nights, this is when we do the bulk of our maintenance work. There usually are not many patient samples we run at night but the maintenance can take all night to perform depending on how well it goes. Ideally, the maintenance goes really well and only takes up half the night.

Overall, I enjoy my career as a Medical Laboratory Technologist. There is satisfaction in knowing that my work is helping to provide many pieces of the puzzle that will ultimately lead to patient diagnosis and/or treatment. As you hopefully have gathered from my article, there is more involved in the field than most people are aware of (as is the case with many jobs that appear simple on the surface). Next time you stop by your local lab to have your blood drawn, you might now consider what is involved "behind the scenes" and have more respect for the whole process, not just the part that you see.


nr on June 30, 2015:

Hi, would it be detrimental to me if i chose to do a bachelor's degree of medical laboratory scientist but do not really work well with microscopes or will we be taught how to use them properly?

Tim Sandle from London, United Kingdom on January 05, 2014:

Fascinating insight...

yodastyle on August 13, 2012:

It's nice to read the work of someone else who takes just as much pride in their work as they find enjoyment from educating people about what it is that we do. It really can be an elegant field. Thank you.

PurpleOne (author) from Canada on October 04, 2010:

reddog1027: I'm so happy that you can relate to this and actually use it! Us lab techs are so far behind the scenes sometimes that the average person just doesn't have an opportunity to understand what we do. Thanks again!

reddog1027 from Atlanta, GA on October 04, 2010:

Thank you, thank you, thank you! I am bookmarking this hub so when I tell people what I do for a living and they reply "so your a nurse, huh'". Now I can just hand them this hub. Problem solved. Great hub.

labchef on February 01, 2010:

Hi PurpleOne,

I enjoy reading your lens. Hubpages need more lens like this. This will help new college student know about the career ahead of them. I've worked in laboratory for a little while. Right now, I am writing software for laboratories - like LIMS mentioned in the comments posted by johncurio.

PurpleOne (author) from Canada on December 30, 2009:

johncurio - to be honest with you, I had never even heard of the term LIMS until I read your comment. Just doing some quick reading online, it appears to be similar to LIS. I can't speak for all of Canada, but where I live in Canada at least, the name of the LIS software that we use is Meditech. Does that make sense to you? Perhaps you can explain this to me more in detail... are you a lab tech as well?

johncurio on December 30, 2009:

No mention here about the laboratory regulation... which LIMS system do you use? In the UK we've been great fans of STARLIMS web based lims for some time.. i'd be interested to see what you use in Canada

Starlims can be found here (

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