Haemolysed Sample
The red cells in your sample broke, making some results unusable — a handling problem, not a health one.
What it means
The red blood cells in the sample have burst, spilling their contents into the surrounding fluid. That makes certain results — potassium in particular — falsely high and unusable.
It happens because of how the sample was taken or handled: a difficult vein, a narrow needle, drawing too fast, shaking the tube, or a delay before it reached the laboratory.
It says nothing whatsoever about your health. This is worth stating plainly, because being asked to repeat a test reliably sounds ominous and here it is not.
In practice
In a message or letter asking you to repeat a blood test, sometimes with the phrase "sample unsuitable" or "specimen rejected".
Occasionally only part of the panel is affected, and the rest of your results stand.
Why it matters
Simply have the test repeated — there is nothing to interpret.
If it happens repeatedly, mention that your veins are difficult and ask for a butterfly needle or a more experienced phlebotomist. Being well hydrated beforehand genuinely helps.
Do not read anything into it. It is one of the commonest reasons for a repeat request and the least concerning.
Clinically reviewed by Dr Mohammad Zubair Khan, GMC 7563469
Last reviewed
August 30, 2026