Difference between serum and plasma

The main difference between serum and plasma is that the liquid part of the blood, the blood plasma, consists of more than 90% water and 10% of substances dissolved in it. Blood plasma without clotting factors is called blood serum.

What is Plasma?

Plasma makes up about 55% of the overall blood volume. It is the liquid portion of blood and is 90% water. Other than water, plasma also contains fibrinogen (which contributes to the normal clotting of blood) and albumin (which acts to keep fluid in your bloodstream and prevent leaking into other tissues). The purpose of plasma in the blood is to transport all the proteins, nutrients, antibodies, hormones, etc. all over the body. As the plasma races around the body, cells will deposit their waste into the plasma, which contributes to another job of the plasma: waste removal.

Key difference between Serum and Plasma

What is Serum?

Put simply, the serum is plasma minus the clotting factors and blood cells. During the process of removing the clotting factors (achieved by centrifugation), the protein fibrinogen as described above is converted to fibrin. Fibrin is an insoluble protein that is used to assist in the repair of tissue damage by forming a clot over the wound which acts to hinder the flow of blood.

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What is blood plasma made of?


  • The largest proportion of the approximately 120 proteins that are contained in the blood plasma are made up of about 60% of the albumins. They maintain the osmotic pressure and thus prevent too much water from leaking into the tissue. Albumins are also the body’s transport proteins.
  • Other proteins, the globulins, mainly have defense functions. They make up the second large group of proteins. Immunoglobulins are called antibodies. They bind and mark microorganisms so that the body’s own defense system can better recognize them and turn them off.
  • Other proteins, such as fibrinogen and other enzymes or coagulation factors, are required for blood clotting. A number of hormones are also proteins.

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Other components of the blood plasma

Blood plasma also serves as a transport medium for metabolic products and for the substances dissolved in the plasma. Blood plasma supplies the necessary substances that are withdrawn from the blood on the spot. On the other hand, cells release metabolic degradation products to the blood plasma, which transports them for detoxification and excretion.

  • Nutrients: glucose, amino acids, lipids, vitamins
  • Minerals (electrolytes): sodium, calcium, potassium, magnesium, chloride, phosphate
  • Degradation products: e.g. B. creatinine, urea

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Blood plasma: determination of laboratory values

In medicine, deviations in the number of certain substances in the blood, which are measured in the laboratory, can be used to infer diseases. These substances, which are important for the detection of diseases, are known as laboratory values.

Blood plasma for treatment

The proteins contained in plasma are important for medical and pharmaceutical purposes. They are used in emergency medicine, but also to treat seriously and chronically ill people.

However, nowadays more and more proteins are produced by genetic engineering. Therefore, less and less donated blood is required for the preparation of proteins from blood plasma.

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Another major difference between serum and plasma is

Separation gels form a stable separation layer between the serum or plasma and the blood cells after centrifugation so that no cell constituents get into the serum even after days.

Advantages of separation gels:

  • longer shelf life at 4-8 ° C without disturbing influence by the cells (such as glucose breakdown or potassium release)
  • higher material yield in improved quality
  • reduced risk of confusion and infection
  • no coagulation if carried out correctly


  • Blood collection: tubes without additives, tubes with coagulant additives (beads, …), tubes with coagulation activators, and separating gel
  • Mix the sample well: tilt it 180 ° five times, do not shake!
  • Allow the sample to drain out for 20-30 minutes in an upright position
  • Centrifugation: after coagulation is complete, 10 min at 2000 × g
  • then separation of cellular components, unless a tube with separation gel was used
  • Supernatant: without coagulation factors (except calcium)

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  • Blood collection: tubes with anticoagulant additives (EDTA, citrate, Na-, NH4-, Li-heparin, hirudin …)
  • EDTA, citrate: bind calcium ions
  • Heparin: activates antithrombin III by binding
  • Hirudin: blocks thrombin by binding
  • It is essential to pay attention to the correct filling level in order to achieve the correct mixing ratios!
  • Mix the sample well: tilt it 180 ° five times, do not shake!
  • Centrifugation is possible immediately; 15 min at 2000 x g
  • then separation of cellular components
  • Supernatant: contains fibrinogen and other coagulation factors

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Another key difference between serum and plasma is:

A key difference between plasma and serum is that plasma is liquid, and serum is fluid. While most of the components are the same for both plasma and serum, plasma contains fibrinogen which is absent in serum. Both plasma and serum can be extracted from blood with the use of a centrifuge but it’s worth noting that serum is obtained after the clotting of blood, while plasma can be obtained before the coagulation of the blood. The serum is mostly used for blood typing but is also used for diagnostic testing. Plasma on the other hand, is mostly used for blood-clotting-related problems.

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