Plasma vs blood


Blood consists of several components, and plasma is one of these. The main components of the blood in a human are plasma, red blood cells, platelets and white blood cells.

Blood (also referred to as ”whole blood” in this context) contains roughly 55% plasma and 40-45% red bloo cells by volume. Plasma and red blood cells are thus the main components of our blood, by volume.

In some situations, donated plasma is given to patients instead of giving them whole blood. Plasma is also used to make certain medications. It is possible to donate plasma instead of donating whole blood. Whole blood is drained from you, but you get your red blood cells put back into your body as soon as the plasma has been separated out.


What is plasma?

Plasma is a mixture of water, sugar, fat, proteins and salts. When the non-plasma components have been removed from whole blood, the remaining plasma normally looks yellowish and it has a density of approximately 1.025 g/ml.

Up to 95 percent of the plasma´s volume is water. Other examples of what is found in plasma are glucose, oxygen, carbon dioxide, electrolytes (including Cl-, HC03-, Mg2+, Ca2+ and Na+), clotting factors, various hormones, and dissolved proteins (including serum albumins, globulins and fibrinogen proteins).

Plasma is vital to our circulatory system and carries out a range of tasks in the body. It helps maintain blood pressure and volume, transport proteins to places where they are needed, transport electrolytes to our muscles, and help maintain the correct pH value in the body.

Without sufficient amounts of plasma, our circulatory system collapses. Plasma is the intravascular part of the body´s extracellular fluid, and it is the main medium for excretory product transportation. A variety of substances are suspended in the plasma and moved around the body, including a range of important proteins. The intravascular osmotic effect that keeps the electrolyte concentration balanced in the body can not work without plasma, and plasma is also crucial for the immune system.

Why is whole blood red and plasma yellowish?

Blood is red because of the red blood cells. They contain a lot of hemoglobin, which is red.

When plasma is isolated from the other components of the blood, there are no longer any red blood cells present to bring that strong red colour. Plasma is yellowish because it contains bilirubin, carotenoids, transferrin and very small amounts of hemoglobin.

If the plasma is opaque instead of transparent, it is usually due to high levels of lipids.

How is plasma separated from whole blood?

Anticoagulant is added to a sample of fresh whole blood, and the blood is then centrifugated to separate it into layers. The top layer will be plasma.

Filtration or agglutination can also be used to separate blood plasma from the rest of the blood.

What is blood serum?

If you remove the clotting factors from blood plasma, you get blood serum.

What is donated plasma used for?

Plasma is commonly given to trauma, burn and shock patients. There are cases where a patient does not need to receive whole blood – getting a boost of plasma will be enough since the plasma increases blood volume, can prevent shock and helps with blood clotting.

There are also patients with certain serious health conditions that benefit from receiving plasma, such as some liver issues and clotting factor deficiencies.

Pharmaceutical companies rely on plasma to make treatments, such as:

  • Intravenous Immunoglobulin Therapy (IVIg)
  • Hyperimmuneglobulins to treat rabies, tetanus, dialysis patients and those who receive an organ transplant. Hyperimmuneglobulins are also given to pregnant women who have Rh incompatibility.
  • Clotting factor medications for patients with bleeding disorders
  • Alpha-1 Antitrypsin to treat patients with the hereditary disease genetic emphysema
  • Albumin can be extracted from plasma and given to trauma, burn and surgical patients