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Why Would My Blood Given For A CBC Test Clot Really Soon?

Posted on Thu, 15 Jun 2023

Question: First I have to say I suffer from health anxiety and tend to doubt what my dr tells me. Three weeks ago I had a CBC done at my dr, along with a full liver panel and a sed rate test, everything was fine. But I have gotten obsessed with doing a bleeding and coagulation test. My dr said I do not need one, but I went to another lab and had one done two weeks after my dr visit. The lab is not local they send the tubes six hours away. Anyway the lab said my blood was clotted and they called me back for a redraw. I did that last week and again my blood clotted. They didn't know why and just said to talk to my dr. I spoke to my drs nurse who told him what happened. He wants me to come in this week but not do any labs he is aware of my OCD and his nurse said he wants to talk to me about all of this. Any idea what would cause my blood to clot twice when my CBC two weeks prior was ok?

Answered by Dr. Shailja Puri (1 hour later)

Brief Answer:
Proper mixing of blood with anticoagulant will prevent clotting of blood.

Detailed Answer:

Hello,

The blood sample for bleeding and coagulation tests is drawn in citrate tubes (tubes with sky blue cap). These tubes are different from those used to perform CBC.

CBC is done on blood sample drawn in EDTA or lavender colored tube caps. Blood should not clot in both citrate and EDTA blood tubes.

Most common cause of clotting of blood in citrate tubes is inadequate mixing of blood and anticoagulation i.e. citrate.
I suggest you to give the blood sample again and check for proper mixing of blood with anti-coagulant although this is job of phlebotomist who draws the blood.

I addition, the plasma needs to be separated from red blood cells as soon as possible. Thus, the citrate blood sample needs to be centrifuged to separate the light yellow colored part from heavy red colored red blood cells.

Hope I have answered your query. In case you have more queries, I will be glad to answer.

Thanks and take care.

Regards,
Dr. Shailja Puri
Pathologist and Microbiologist

Above answer was peer-reviewed by : Dr. Prasad

Follow up: Dr. Shailja Puri (1 hour later)

So if it is not separated till six hours or more later would that affect the specimen? What is the likelihood I would have a blood disorder that causes rapid clotting but it not be evident on my CBC?

Also I have no symptoms of excessive clotting. This is the only time I have had this issue and it's been twice in a week. Not sure if I need to be really concerned about this or not.

Answered by Dr. Shailja Puri (9 hours later)

Brief Answer:
Blood separates as soon as blood is collected in citrate tube.

Detailed Answer:

Hello,

The blood separates as soon as it is collected in citrate tube.
Whether you have any clotting disorder or not cannot be confirmed at this point.

A couple of investigations are required before concluding anything.
I suggest you to consult a hematologist.

Hope I have answered your query. Let me know if I can assist you further.

Thanks and take care.

Regards,
Dr. Shailja Puri
Pathologist and Microbiologist

Above answer was peer-reviewed by : Dr. Kampana

Follow up: Dr. Shailja Puri (4 hours later)

Ok I have an appt with my dr this week he is an internist. Is there any reason why my blood would of clotted fine with my CBC but not with the bleeding test?

Answered by Dr. Shailja Puri (2 hours later)

Brief Answer:
The most common reason for clotting of blood is improper mixing.

Detailed Answer:

Hello,

The most common reason for blood clotting in EDTA or citrate tubes is improper mixing.

Hope I have answered your query.

Thanks and take care.

Regards,
Dr. Shailja Puri
Pathologist and Microbiologist

Above answer was peer-reviewed by : Dr. Prasad