Medical Lab Technician Interview Questions

"I did my lab technology course because I liked biology and chemistry but didn't want a job where I'd be guessing. My clinical placement was in a busy hospital lab, and what hooked me was realising how many decisions depend on our numbers. A doctor might never meet us, but they're treating the patient based on a potassium or a haemoglobin we released. I like that responsibility. I also enjoy the detective side, when a result doesn't fit and you have to work out whether it's the patient, the sample or the analyser. I want to build solid experience across the core benches first, and later I'd like to specialise, probably in haematology."

"From what I read, you're a hospital lab running around the clock, with an emergency department and intensive care feeding you urgent samples. That means turnaround time and critical value calls really matter here, and that's the pace I trained in. I've worked in a reference lab setting too, where the work is high volume but mostly routine, and I missed the sense that a result I released at two in the morning changed what happened to a patient that night. I also saw that you run your own microbiology instead of sending it out, and I'd like to rotate into that bench eventually. So it's the pace, the patient impact and the chance to learn more benches."

"I've spent most of my time in clinical chemistry and haematology. In chemistry I can run the main analyser on my own, including daily maintenance, running QC and loading reagents. In haematology I run full blood counts, make and stain films, and I'm comfortable spotting when a film needs to go to a senior for review. I've done a rotation in microbiology, so I can set up routine urine and swab cultures, but I haven't read plates on my own yet, and I haven't worked in blood bank beyond observing crossmatches. That's my weakest area, and I'd want proper supervised training before I'd sign anything off there."

"At my last lab, two samples came up from the same ward in one bag. When I checked them against the requests, one tube had the right name but a date of birth that belonged to the other patient. It looked like the labels had been printed together and stuck on the wrong tubes. It would've been easy to assume a typo and swap them, but I had no way of knowing whose blood was in which tube. So I didn't process either one. I rang the nurse in charge, explained both samples needed to be recollected, logged them as rejected with the reason, and filled in an incident form. The ward later changed to printing labels one patient at a time, at the bedside."

"A doctor from the ward called, quite angry, because I'd rejected a potassium on a heavily haemolysed sample. He said he just needed a rough number. I explained that haemolysis releases potassium from the red cells, so the number could look dangerously high when the patient was actually normal, or hide a real problem, and either way he couldn't act on it. I didn't just say no, though. I offered to process a fresh sample the moment it arrived, and I suggested it be drawn gently with a larger needle. He calmed down once he saw I was trying to help, and the repeat came back normal. If he'd still insisted, I'd have passed it to my senior rather than argue."

"The first group is identity. If the tube has no label, only one identifier, or details that don't match the request form, I can't be sure whose blood it is, so it's rejected. The second is the sample itself: the wrong tube type for the test, a clotted sample in an EDTA or citrate tube, a citrate tube that isn't filled to the line, a haemolysed sample for tests that haemolysis affects, like potassium, or simply not enough to run the test. The third is transport: a leaking container, a sample that's too old, or one that wasn't kept cold or warm when the test needs that. Whatever the reason, I record the rejection, tell the ward and ask for a new sample."

"Every tube needs at least two patient identifiers, usually full name plus date of birth or hospital number, and never something like a bed number. It should also have the date and time of collection and who collected it, so we can trace it. The tube should be labelled straight after it's filled, at the bedside, with the patient in front of you, ideally after asking them to state their name and date of birth. If you label tubes beforehand, or take them away to label later, it's very easy to mix up two patients, and then the lab gets a perfectly labelled tube with the wrong person's blood in it. We can't detect that from the label. Blood bank samples usually have even stricter rules."

"Chain of custody is a documented, unbroken record of everyone who handled a specimen, from collection to result, so nobody can say it was swapped or tampered with. You need it when the result might be used legally, like workplace drug screening, alcohol testing for legal cases, or samples in an assault case. In practice, the specimen is collected under set conditions and sealed with a tamper-evident seal in front of the donor. The form is signed at each hand-off with the date and time, and the sample is stored somewhere secure with limited access. When it arrives, I'd check the seal is intact and the paperwork matches before opening it. If the seal is broken or there's a gap in the signatures, I'd document it and follow the policy, because the result may no longer hold up."

"Early on I loaded a rack of samples and later realised I'd put two tubes in each other's positions. The analyser read barcodes, so the results were fine, but on the manual ESR bench I'd written results against rack positions, and two were swapped. I noticed because one patient's result was wildly different from yesterday. I told my senior straight away, we reran both, and before the corrected results went out we rang the ward to say the earlier ones were wrong. I filled in an incident form. Since then I never record anything by position alone. I check the label against the worksheet as I write, even when it slows me down."

"First I'd confirm the right result, by rerunning the sample or checking what went wrong, so I don't correct it with another error. Then I'd tell my supervisor and phone the doctor or nurse caring for the patient straight away. I wouldn't just change it in the system, because they may already have given treatment based on the wrong number, and they need to hear it from a person. I'd explain what the original result was, what the correct one is, and ask them to read it back. Then the report is amended through the proper process, so it shows as corrected and the original stays on record. Finally I'd fill in an incident report and help work out why it happened, so it doesn't happen again."

"On an evening shift our main chemistry analyser threw a sample probe error and stopped mid-run, with a queue of emergency department samples waiting. I checked the error log first. It pointed to a clot in the probe, so I followed the manufacturer's steps to clean it and ran a check, but it failed again. Rather than keep fiddling, I moved the urgent samples to our backup analyser, which had passed QC that day, and told my senior. I rang the emergency department to warn them about a short delay on routine chemistry. Then I called the service line, and an engineer talked me through a probe replacement. After it passed QC we cleared the routine backlog. I logged the whole thing so the day team knew."

"When my last lab replaced its coagulation analyser, I was one of two people trained first. I did the manufacturer's training, then I rewrote the daily maintenance steps into a short bench card in plain language, which the rest of the team ended up using. Before it went live we ran patient samples on the old and new analysers side by side to compare the results, and we ran controls repeatedly to check precision. My senior reviewed the data and signed it off. I also had my own competency assessed before I reported anything alone. The part that surprised me was how different the error messages were, so I kept a notebook of the ones we met and what fixed them."

"First I'd stop releasing results from that run and read the exact error codes in the log, because they usually point somewhere. Then I'd work from simple to complex. Are reagents in date, loaded properly and not empty? Is there a clot or bubble problem with a sample, or is the probe blocked? Is the water supply and waste fine, and was the daily maintenance actually done? I'd follow the manufacturer's steps for that error rather than guess. If I can't fix it within a reasonable time, I'd call the service line and move urgent work to a backup. Once it's fixed I'd run QC before any patient samples, rerun the samples affected, and write it all in the instrument log."

"A full blood count flagged a delta check: the patient's haemoglobin had jumped a long way up since the day before, with no transfusion noted. The MCV was also quite different, which you rarely see change overnight. That made me think it might not be the same patient's blood. The label and request matched, so I rang the ward and asked who took it and how. It turned out two patients were bled at the same time and the tubes were labelled away from the bedside. I held the result, the ward recollected both patients, and the repeat matched the old pattern. It was logged as a wrong blood in tube incident, which matters a lot because the same mix-up in a transfusion sample could be fatal."

"I'd stop reporting glucose on that analyser straight away. Then I'd look for the cause rather than rerunning the control until it passes. I'd check the obvious things first: is the control in date, was it thawed and mixed properly, is this a new reagent or control lot, and when was the test last calibrated. If I find a reagent problem, I'd replace it, recalibrate if needed and run both control levels again. Once QC is back in range, I'd run the waiting samples. I'd also look at the last run with good QC and, with my supervisor, rerun some samples from after that point to see whether earlier results were affected. If urgent samples are waiting, I'd use a backup analyser and let the wards know about any delay. And I'd record everything."

"Calibration is setting the ruler. You run calibrators with known values, and the analyser uses them to work out how the signal it reads translates into a concentration. QC is checking the ruler is still right. You run control material with an expected range, usually at two or more levels, and if the results fall inside the limits you can trust patient results. Calibration is done on a schedule, or after things like a new reagent lot or major maintenance. QC is run every day or shift, and after every calibration, to prove the calibration worked. The controls should be separate material from the calibrators, otherwise you'd just be checking the analyser against itself."

"A Levey-Jennings chart plots each control result over time, with lines for the mean and one, two and three standard deviations. A shift is when results suddenly settle at a new level, above or below the mean. That usually follows a change, like a new reagent lot or a calibration. A trend is a steady drift in one direction over several days, which points to something slowly going off, such as a reagent breaking down or a lamp ageing. With Westgard rules, one control past two standard deviations is a warning. One past three, or one control above plus two and another below minus two in the same run, suggests random error. Two in a row past two on the same side, or ten in a row on one side of the mean, suggests systematic error."

"It should be treated exactly like a patient sample, run by whoever is on that bench, in a normal run, the normal number of times. The whole point is to show how the lab really performs on an ordinary day. If you give it to your best person, repeat it five times or phone another lab to compare answers, you get a good score but learn nothing, and in many places that kind of thing counts as serious misconduct. When a result comes back unacceptable, that's useful. It tells us something may be wrong with patient results too, so we investigate the cause, fix it, and record what we did. I'd rather have an honest poor score than a false good one."

"On a night shift I noticed a more experienced colleague had rerun a failed control three times until it came back in range, then carried on reporting without looking into why it failed. I was nervous because she'd trained me. I asked her quietly whether we should check the reagent, since it was a new lot, and she brushed it off. The problem was that any results since the last good control might be wrong. So I told the shift supervisor, calmly and just the facts. He reviewed it, they found the new reagent lot was reading low, and some results were rerun and corrected. It was awkward for a few days, but she later told me she was glad it was caught."

"I'd look at where the urgent requests come from. Resuscitation or intensive care samples and things like troponin or blood gases go first. Then I'd keep the analysers busy. I'd load the urgent samples, and while they run I'd sort the routine work into batches, so nothing sits waiting for me. I'd tell my senior early that we're falling behind rather than at the end of the shift, so they can move someone across or pause non-urgent work. If routine results will be late, I'd let the busiest wards know. What I wouldn't do is skip identity checks, sample checks or QC to save time. A fast wrong result is worse than a late right one."

"I'd say no, politely. Something like: I'm sorry, I can't look that up. I only open results I need for my work, and every look-up is logged. Your friend can get it from their own doctor or through the usual way the hospital releases results. Most people back off once you explain it, because they know they're asking for something they shouldn't. It doesn't matter that it's a colleague, or that the friend might have said it was fine. Patient results are confidential, and I'd be the one breaking the rules. If someone kept pushing or I saw it happening regularly, I'd mention it to my supervisor."

"I try to remember that the nurse on the phone is looking after the patient whose sample I'm holding. So when I reject a sample, I explain why in plain words and what they need to send, rather than just marking it rejected in the system. If we're running late, I'd rather ring the busiest wards before they chase us. I also think the lab should look for patterns. In my last job one ward kept sending underfilled coagulation tubes, so with my senior we took them a short guide and a few spare tubes to show the fill line, and rejections dropped. Small things like that make the relationship much better. It's not us against them."

"First I'd make sure the result is genuine. I'd look at the haemolysis index, check the calcium in case of EDTA contamination, compare with previous results and repeat it if my procedure says so. If it's real, it can't just sit in the system. If the ward phone isn't answered, I'd try the nurse in charge or another number for that ward, and if I still can't get anyone I'd bleep the on-call doctor for that team. If none of that works within our time limit, I'd tell my supervisor or the duty pathologist so someone senior takes it on. When I do reach someone, I give the patient's two identifiers and the result, ask them to read it back, and record their name, the time and the read-back."

"If I notice it as soon as I open the lid, I'd close it again straight away and leave it shut for a while so any aerosol can settle. In my last lab the procedure said thirty minutes. I'd warn people nearby and tell my senior. Then I'd put on gloves, a lab coat and eye protection, and I'd never pick up glass with my hands. I'd use forceps and put the pieces in a sharps bin. I'd remove the buckets, soak them and wipe the inside of the centrifuge with the disinfectant our procedure specifies, leaving it on for the full contact time. After that I'd check which sample broke, contact the ward to get it recollected, and fill in an incident report."

"I'd stop, go straight to the eyewash station and flush the eye with plenty of water, holding the eyelid open, for the full time our procedure says, usually around fifteen minutes. I wouldn't rub it. Then I'd tell my supervisor right away, because exposures need to be assessed quickly, and some treatment after exposure works best when it starts early. I'd note which sample it was, so the source patient's risk can be looked at under the hospital's policy, and I'd go to occupational health or the emergency department as our process says. After that I'd fill in the incident report. It would also make me ask why I was uncapping without eye protection or a splash shield, and fix that."

"I treat every specimen as if it could be infectious, because the label never tells you who has hepatitis or HIV. So I wear a buttoned lab coat and gloves at the bench, and eye protection or a splash shield when I'm uncapping or pouring. I change gloves when they're dirty or torn, and I don't touch shared phones or door handles with them on. I wash my hands when I take them off and before I leave the lab. No eating or drinking at the bench. Sharps go straight into the sharps bin without recapping, and waste goes into the right waste stream for our site. Anything that can make aerosols with a risky sample, like processing sputum for TB culture, is done inside a biological safety cabinet, never on the open bench. And I wipe down my bench at the start and end of the shift, and after any spill, with the disinfectant our procedure names, left on for its full contact time."

"Red cells hold a lot more potassium, LDH and AST than plasma does, so when they burst those results go up falsely. Phosphate and magnesium can be affected too. The red colour of free haemoglobin can also interfere with some tests that read colour. Most analysers give a haemolysis index, and each test has a limit above which we don't report it. Common causes are a very fine needle, pulling hard on a syringe, forcing blood through the needle into the tube, shaking tubes instead of gently inverting them, and difficult draws from lines. Rarely, the haemolysis is happening inside the patient, so if every sample from someone comes back haemolysed, that's worth flagging rather than just rejecting again."

"That pattern makes me think of EDTA contamination. Purple top tubes contain potassium EDTA, so if some gets into the chemistry sample, it adds potassium and it binds calcium, which makes calcium look very low. Magnesium can read low too, and so can alkaline phosphatase, because that enzyme needs metals that EDTA binds. It usually happens when tubes are drawn in the wrong order, or blood is poured from one tube into another. I'd check for haemolysis to rule that out, look at the patient's previous results and at the other analytes, and I wouldn't report the potassium and calcium. I'd ring the ward to explain and ask for a fresh sample. If it keeps happening from one area, I'd flag it so they get a reminder on the order of draw."

"The light blue tube contains sodium citrate, which stops blood clotting by binding calcium. It's designed for a fixed ratio of nine parts blood to one part citrate. When we test it, we add back a set amount of calcium to start clotting. If the tube is underfilled, there's too much citrate for the amount of plasma, so some of the calcium we add gets soaked up, and the PT and APTT come out falsely prolonged. A doctor could then think the patient is over-anticoagulated or has a clotting problem when they don't. So an underfilled citrate tube is rejected. I'd also check it isn't clotted, because a partly clotted sample has used up clotting factors and gives misleading results too."

"A clump flag with a surprisingly low count makes me doubt the number. Two common causes are a partly clotted sample and platelet clumping, which in some people happens because of the EDTA itself. The analyser counts a clump as one big cell, or misses it, so the count comes out low. First I'd check the tube for clots. Then I'd make a blood film and look, especially at the feathered edge, where clumps tend to collect. If I see clumps, I wouldn't release the count as it stands. I'd add a comment that the count is falsely low due to clumping and ask for a fresh sample, often in a citrate tube, remembering to correct that count for the dilution the citrate adds."