For some scientists, the difference between serum and plasma is just nomenclature. On more than once occasion we’ve had to ask customers, “Do you mean serum or do you mean plasma?” only to hear, “either one” or “aren’t they the same thing?” Let us clear up the confusion.


Serum vs. Plasma: What’s the Difference?

Serum and plasma both come from the liquid portion of the blood that remains once the cells are removed, but that’s where the similarities end.

Serum is the liquid that remains after the blood has clotted.

Plasma is the liquid that remains when clotting is prevented with the addition of an anticoagulant.

This is not an insignificant difference.



The Importance of Clotting

The clotting process activates a cascade of proteases, which results in the conversion of prothrombin to thrombin, an enzyme that converts fibrinogen into fibrin to clot blood. Platelets are activated in the process and release a set of compounds, which naturally alters proteins in the serum.

To collect plasma, an anticoagulant is added to the centrifuged whole blood, which can impact testing. EDTA is the most commonly used anticoagulant in clinical diagnostic labs. EDTA chelates the calcium needed for clotting, but can also inhibit other enzymes. There are many other anticoagulants in use such as citrate, heparin, and fluoride, each with appropriate uses.

When to Use Serum, Plasma or Both

Whether you’re developing a diagnostic test, supplementing a cell culture, or running a research assay, we recommend using both serum and plasma so you can observe how different sample types behave. If you use only one, you could be misled by false results.

For example, clotting factors in serum or the platelets and cellular elements that contaminate plasma could interfere with or alter your results. If your results are the same for serum and plasma, then you have more flexibility in sample usage.

View all of our available serum and plasma samples, including normal donors, diabetic donors, RA donors, SLE donors, and donors with other disease states.


  1. Why is plasma volume more than serum volume in blood? (approximately 15-20% more plasma obtainable from whole blood than with serum) Thanks

    • I think that may be a technical difference, not an actual difference in volume. You can get more serum if you allow the clot to contract, which it will do over the course of an hour or so. The platelets in the clot will pull it together tightly and squeeze the serum out. Also, we usually collect all the liquid when we’re separating serum and then we do a second spin to get rid of the free red cells. Otherwise when we are collecting serum we leave some behind just to avoid the rbc.

  2. Please sir, I need a clarification on some issues
    1) what are the biochemical parameters used
    2) when talking about biochemical parameters which of this do you use blood, plasma or serum.
    I will be grateful if my questions are treated with utmost urgency.
    Thank you for your time

    • I would refer you to the table that details a few of the differences between plasma and serum. We did not discuss the use of whole blood in this post, only the differences between plasma and serum.

  3. Hi, Thank you for useful information. I am interested to measure CK and LDH for my research study. I see many studies have used serum and some have used plasma to measure these enzymes. My subjects are mice.
    Do you have any suggestion on that which one should I use?


    • If one is looking for the virus then nasal or nasopharyngeal swabs are preferred. Serum or plasma can be used for detection of antibodies to the virus.

  4. how long the antibodies for COVID 19 will last, as now we asking blood donation to get plasma from recovered patients with COVID 10 , and can Donner donate more than one time

    • There are reports that the antibodies to Covid-19 do not last. I would assume that the therapeutic plasma collections are only done when they know the donor still has antibody in circulation. Plasma collection can be done more frequently than donation of red blood cells so depending on the volume collected a donor can donate several times.

    • Plasma can be more easily collected than the same volume of serum. Remember that serum is what you get after clotting of whole blood so it is only present in vivo after injury.

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