Hematologist
CION Cancer Clinics
Haemolysed or clotted blood sample: why the test must be repeated | CION Cancer Clinics
A haemolysed or clotted sample means the blood was damaged in the tube before testing, so the lab cannot give a reliable result and a repeat is needed. It usually reflects a difficult draw, poor mixing, heat or delay, not a problem with your health. Burst cells can make potassium look high, and clots can make platelets look low, which is why the old figure should not be used. At CION Cancer Clinics, our haematologist reviews abnormal blood reports with you, orders only the tests that answer your question and explains each result plainly.
BP
Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
17+specialists on panel
15,000+patients treated
35+centres across Telangana & AP
4.8★ / 800+Google rating
On this page
- What does "sample haemolysed" or "sample clotted" mean?
- What can go wrong with a blood sample?
- How does a damaged sample change the numbers?
- How can you help the repeat sample go well?
- What do people often misunderstand about a rejected sample?
- What do the words on the rejection note mean?
- What can this page not tell you?
- Common questions about haemolysed and clotted samples
The short answer
What does "sample haemolysed" or "sample clotted" mean?
It means the blood in the tube was damaged before it could be tested, so the lab cannot trust the result. A repeat sample is needed. In most cases it says something about the tube, not about your health.
Haemolysed, in plain words
Haemolysed means some red blood cells burst open inside the tube. When they break, they spill what is inside them into the liquid part of the blood. That spill changes several results, and it turns the liquid pink or red, which the lab can see. The most common causes are a difficult draw, a thin needle, shaking the tube, or heat and delay on the way to the lab.
Clotted, in plain words
Tubes for a blood count or a clotting test contain a chemical that stops the blood from clotting. If the tube was not mixed gently straight away, or the blood came slowly, small clots form. Clots trap platelets and other cells, so the count comes out falsely low.
Why the lab will not simply report it
A number from a damaged sample could look worrying when you are fine, or look normal when something needs attention. Rejecting it protects you from a decision made on a wrong figure.
A rejected sample is common. It is not a sign that anyone was careless with you, or that your blood is unusual.Reasons a sample is rejected
What can go wrong with a blood sample?
Labs reject samples for a handful of reasons. Your report or the message from the lab usually names which one.
Haemolysed
Red cells broke open in the tube. It happens more with small or deep veins, a slow draw, or blood pushed hard through a needle.
Tests most affected
- Potassium and some liver tests
- LDH, a marker of cell breakdown
- Some clotting tests
Clotted
Small clots formed in a tube meant to stay liquid. The platelet count and clotting tests cannot be read, and the blood count may be unreliable.
Gently turning the tube several times straight after filling prevents most clots.Not enough blood
Some tubes must be filled to a line, because the chemical inside is measured for a set amount of blood. An under-filled clotting tube gives a wrong result, so it is rejected.
Delayed, wrong tube or unlabelled
A sample that reached the lab too late, sat in the heat, went into the wrong coloured tube, or has a missing name cannot be matched safely to you or tested reliably.
Not sure whether this applies to you?
Ask an oncologistSide by side
How does a damaged sample change the numbers?
The result on the report
What a damaged sample can do to it
Potassium
Looks falsely high when red cells burst in the tube
Platelet count
Looks falsely low when small clots trap platelets
PT, INR and APTT clotting times
Can read wrongly if the tube clotted or was under-filled
LDH and some liver enzymes
Look falsely raised when cells break open
Before the repeat
How can you help the repeat sample go well?
Drink water and keep warm
Unless you have been told to fast from water, drink normally before the test. Warm arms and a well-filled body make veins easier to find, which means a smoother draw and less damage to the cells.
Tell the person taking blood
Say that the last sample was rejected, and whether your veins are usually hard to find. If you take a blood thinner, mention it. They may choose a different vein or a different needle.
Relax the arm
Avoid pumping your fist hard or keeping the band on for a long time. Both can damage the sample. Sit still and let the tube fill at its own pace.
Ask how it reaches the lab
For home collection, ask when the sample will be tested and how it is kept cool. A short, cool journey matters more than which lab does the testing.
Leave a number, we will call you
One field. No form to fill in, and no charge for the call.
Commonly believed
What do people often misunderstand about a rejected sample?
"Haemolysed means my blood cells are breaking down
inside my body."
Almost always, no. The word on a sample message means the cells broke in the tube. Cells breaking down inside the body is a separate condition, found with different tests, such as the direct Coombs test, and usually with symptoms like yellow eyes or dark urine.
"The lab just wants to charge me again."
A result from a damaged sample could lead to a wrong decision about your care. Ask the lab or collection service whether the repeat is charged. Many repeat at no extra cost when the fault was in collection or transport.
"The old number is close enough. We can use
it."
A figure from a damaged tube can be wrong in either direction. A high potassium could send you to an emergency ward for no reason. A falsely normal clotting time could hide a real problem. Wait for the repeat.
"If it happens twice, something is wrong with my
blood."
Repeated rejection is more often about difficult veins or transport. Still, tell your doctor. They may want the sample drawn at a hospital lab, or look for another cause.
On the lab message
What do the words on the rejection note mean?
- Haemolysed or haemolysis noted
- Red cells burst in the tube. Some results were withheld or marked as unreliable.
- Clot detected or clotted sample
- Small clots formed in a tube meant to stay liquid. The blood count or clotting test cannot be reported.
- QNS, quantity not sufficient
- Too little blood reached the lab for the test to be run correctly.
- Lipaemic
- The liquid part of the blood looked milky with fat, often after a meal. It can upset some results.
- EDTA tube or citrate tube
- The purple-top tube used for a blood count, and the blue-top tube used for clotting tests. Each has its own mixing and filling rules.
Being straight with you
What can this page not tell you?
This page cannot tell you what your repeat result will show. A rejected sample carries no information about your health, good or bad. Until the repeat is done, treat the question the test was meant to answer as still open.
If the test was urgent
Some tests are ordered because a decision is waiting on them, such as a platelet count before a procedure or a clotting test while on a blood thinner. Tell the doctor who ordered it that the sample was rejected, so the repeat can be done quickly. Do not change or skip any medicine while you wait. The treating team decides that.
If you feel unwell while waiting
The rejected sample does not change how to act on symptoms. Unusual bleeding, heavy bruising, a fever during chemotherapy, or feeling faint needs a doctor the same day, whatever the lab has or has not reported.
If rejection keeps happening
Tell your doctor. A haematologist, a doctor who treats blood conditions, can arrange the draw at a hospital lab and check for any cause beyond the tube.
Questions we are asked
Common questions about haemolysed and clotted samples
Is a haemolysed sample a sign of a disease?
Usually not. It most often happens during the draw or on the way to the lab. Rarely, red cells break down inside the body, but that is found through other tests and symptoms, not from a rejected tube. If you have yellow eyes, dark urine or new breathlessness, tell a doctor.
How soon should I repeat the test?
As soon as is practical, and sooner if the result was needed for a decision, such as before a procedure or during treatment. Ask the doctor who ordered the test how urgent it is. For routine checks, a repeat at your next convenient visit is usually fine.
Do I need to fast again for the repeat?
Only if the original test needed fasting. A blood count and most clotting tests do not. Some sugar and fat tests do. Follow the instructions for the tests being repeated, and keep drinking water unless you were told otherwise.
Why does this keep happening to me?
Thin, deep or scarred veins, often after many tests or chemotherapy, make a smooth draw harder. Long transport and heat add to it. Tell the person taking blood about past problems. Having the draw at a hospital lab, close to where it is tested, often helps.
Should I pay again for the repeat?
Ask the lab or collection service before the repeat. Many do not charge again when a sample is rejected because of collection or transport. Policies differ, so check rather than assume, and keep the rejection message as proof.
Can home collection cause a haemolysed sample?
It can, mainly through heat and delay rather than the draw itself. A good service keeps tubes cool and gets them to the lab quickly. Ask how long the journey takes, and book an early slot so the sample is not carried around all day.
My platelet count was low, then the lab said the sample clotted. Which is right?
The low figure cannot be trusted, because clots trap platelets and lower the count. The repeat decides. If you have unusual bruising, nosebleeds or bleeding gums while waiting, see a doctor the same day rather than waiting for the report.
I take a blood thinner. Does that affect the sample?
It makes the puncture bleed a little longer, and it makes accurate clotting tests matter more. It does not usually cause a rejected sample. Tell the person taking blood, press firmly on the spot afterwards, and keep taking your medicine as prescribed unless your treating team says otherwise.
Your Haematologist
Meet CION's haematologist. One specialist for your blood report and your plan.
Dr. Basudev Pokhrel reviews blood counts, transfusion needs and blood disorders, and works with the CION tumour board on blood cancers.
Want a specific doctor for your case? Mention them when booking.
Book Free ConsultationBook an appointment with our specialist
Share your name and number — we'll call you back within 30 minutes to schedule your consultation.
Sources
- NHS — Blood tests
- National Heart, Lung, and Blood Institute — Blood Tests
- National Cancer Institute — Understanding Laboratory Tests
- WHO — WHO guidelines on drawing blood
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
Why Blood Counts Vary Between LabsWhen two reports do not matchCoagulation Tests: PT, INR and APTTThe clotting tests most upset by a clotted tubeHome Blood Collection for Haematology TestsHow to get a reliable sample taken at homeDirect Coombs Test ExplainedThe test for red cells breaking down inside the body
Talk to us
Waiting on a repeat test?
Call the helpline if a rejected sample is holding up a decision about your care. We will help you reach the right specialist. One helpline serves every CION centre.