Hemolyzed Specimen vs Clotted Specimen
A guide for accurate blood collection, specimen handling, and test results
Have you ever had a blood specimen rejected as “clotted” or “hemolyzed”?
Blood samples becoming clotted or hemolyzed happens very frequently, but it can be prevented if properly understood.
In simple terms: Hemolysis is when red blood cells are damaged and rupture. Clotting is when blood does not properly mix with anticoagulant, causing fibrin strands or cellular clumps to form in the tube.
Both issues affect test accuracy, delay results, and may require recollection. Understanding the difference helps improve specimen collection and patient safety.
1. What is Hemolysis?
Hemolysis refers to the rupture of red blood cells. When this happens, hemoglobin and other intracellular components leak into the plasma or serum.
This can alter the chemical composition of the specimen. For example, potassium, LDH, AST, magnesium, and phosphate levels may appear falsely elevated. Hemoglobin pigments may also interfere with certain laboratory instruments or analytical processes.
Hemolysis is not just a visual issue. If serum or plasma appears pink or reddish, it may indicate that the specimen no longer accurately reflects the patient’s condition.
Typical Appearance of a Hemolyzed Specimen
After centrifugation, plasma or serum may appear pink, reddish, or darker than usual. There are typically no visible clots or fibrin strands. Hemolysis can occur in any tube, but is most commonly problematic in serum tubes (SST, Red top).
How does hemolysis occur?
Hemolysis can occur when blood cells are exposed to excessive physical stress. Common causes include using a needle that is too small, pulling the syringe plunger too forcefully, shaking tubes vigorously, leaving the tourniquet on too long, or repeated attempts on difficult veins. Tapping the skin to make veins more visible can also cause hemolysis.
It can also occur after collection
Even if the blood draw was successful, poor specimen handling can damage the sample. Vigorous shaking, delayed processing, exposure to extreme temperatures, repeated freezing and thawing, and rough transportation can all cause red blood cell destruction.
2. What is a Clotted Specimen?
A clotted specimen is one in which fibrin strands, clumps, or cellular material have formed inside the tube. This is especially problematic in tubes containing anticoagulants such as EDTA, sodium citrate, or heparin.
These tubes are designed to prevent clotting. However, the additive must come into contact with the blood quickly and evenly. If the tube is not inverted immediately or mixed sufficiently, small or micro clots can form.
What might you see?
You may observe clumps, fibrin strands, or irregular solid material in the tube. Sometimes clots are very small and may not be detected until the specimen is examined in the laboratory.
Why do clots form?
Common causes include not inverting the tube immediately, insufficient mixing, underfilling the tube, delayed processing, or using the wrong tube for the test.
Hemolysis vs Clotting: Key Differences
| Condition | What Happens? | Common Cause | Impact on Testing |
|---|---|---|---|
| Hemolysis | Red blood cells rupture and release internal contents into plasma or serum. | Physical stress during collection or handling | May falsely elevate chemistry values such as potassium, LDH, and AST. |
| Clotting | Fibrin strands or cellular clumps form inside the tube. | Poor or delayed mixing with anticoagulant | Leads to inaccurate cell counts and specimen rejection. |
Easy way to remember: Hemolysis is a cell damage issue. Clotting is usually a mixing or anticoagulant issue.
Proper Tube Mixing Technique
Tubes containing additives must be gently inverted immediately after collection. This allows the additive to mix evenly with the blood.
The goal is to prevent clotting without damaging red blood cells. Gentle inversion helps distribute additives evenly. In contrast, shaking the tube can damage cells and increase the risk of hemolysis.
- Invert tubes containing additives immediately after collection.
- Gently turn the tube completely 180 degrees and return it to the upright position.
- Follow the recommended number of inversions for each tube type.
- Never shake the tube forcefully.
How to Prevent Hemolysis and Clotting
Protect red blood cells
Use an appropriate needle size, avoid excessive suction, do not shake tubes, avoid leaving the tourniquet on too long, and handle specimens gently during transport and processing.
Mix additives properly
Fill tubes to the proper volume, invert immediately after collection, follow recommended inversion guidelines, and avoid processing delays with anticoagulant tubes.
Why It Matters in Real Practice
Both hemolysis and clotting can alter test results, delay diagnosis, and require repeat blood collection. For patients, recollection can mean more discomfort, longer waiting time, and delayed treatment.
Good specimen quality begins at the bedside or in the phlebotomy chair. Collection technique, tube fill volume, mixing, labeling, transport, and processing all affect the final test result.
Most specimen errors do not occur during testing. They occur before the specimen reaches the analyzer.
What Students Learn at DMS
At DMS Care Training Center, students in the Phlebotomy Technician and Medical Assistant programs learn how to safely and accurately collect and handle blood specimens.
- The difference between hemolyzed and clotted specimens
- Common tube additives and their purposes
- Proper tube inversion and specimen mixing technique
- How phlebotomy technique affects test results
- Specimen handling, transport, and patient safety
- How to reduce recollection and pre-analytical errors
Accurate test results begin with accurate blood collection.
Phlebotomy Technician CPT Program
DMS Care Training Center offers a 12-week Phlebotomy Technician program designed to help students build practical clinical blood collection skills.
Students practice specimen collection, tube handling, safety procedures, patient care skills, and preparation for the NHA CPT certification exam.
Learn More About the CPT ProgramStart Your Healthcare Career Here
DMS provides hands-on healthcare training for students preparing for real clinical environments.
Contact: admin@dmscare.org · 469-605-6035
Visit the DMS Website
