What Is Blood Plasma?

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Blood plasma is the liquid component of blood. Approximately 55% of blood is plasma. The rest is red and white blood cells and platelets (small cells that help with clotting).

Plasma is a straw-colored liquid that plays an important role in the body's functions. These include regulating blood pressure and blood volume, helping with clotting and immunity, transporting nutrients, eliminating waste, and maintaining a proper pH (acid/base) balance.

Blood plasma components and transfusions can also help people with injuries and medical conditions. Donations of blood plasma can be lifesaving.

This article will discuss the makeup of blood plasma, how it functions, and key things to know about blood plasma donation.

A lab professional takes a blood tube out of a centrifuge, showing the yellow plasma separated from the blood cells

Nicola Tree / Getty Images

Blood Plasma Makeup

While plasma mainly consists of water and salts absorbed through the digestive tract, it also contains other important elements.

The main components of blood plasma are:

  • Coagulants: Coagulants help to slow down bleeding when there is a cut or injury. They work by helping the blood thicken and clot over the injured blood vessel. Fibrinogen is one such coagulant found in plasma that helps blood clot.
  • Electrolytes: Electrolytes (electrically charged compounds and minerals) help regulate pH levels in the blood. Common electrolytes found in plasma include sodium, chloride, calcium, potassium, and bicarbonate.
  • Plasma proteins: Plasma proteins, such as albumin and globulin, help to regulate blood pressure. Plasma proteins also play a role in overall health, regulating metabolism, immune response, and hormone levels.
  • Immunoglobulins: Immunoglobulins (Ig; also called antibodies) are proteins produced by white blood cells that play an important role in the body’s immune response. They fight bacteria, viruses, and other organisms and substances that could cause disease.

Blood plasma differs from blood serum. Serum is the liquid part of blood after the blood has clotted. Plasma still contains clotting factors while these are depleted in serum.

Blood Plasma Function

Blood plasma plays a crucial role in blood flow throughout the body and helping with other body functions.

Blood plasma supports the functions of the body by:

  • Providing nutrients: The body’s cells need nutrients to grow, repair, and carry out their individual functions. Plasma helps to deliver nutrients absorbed from the digestive system throughout the body.
  • Aiding in respiration: The plasma is the liquid medium in which red blood cells are carried to the lungs to bind oxygen and release carbon dioxide, then to the body's tissues to release oxygen and bind carbon dioxide, and then back to the lungs. These gases are dissolved in the plasma as part of this process.
  • Removing waste: As cells perform their daily functions, waste is created. This waste is transported by blood plasma to the kidney, lungs, and skin for excretion.
  • Transporting hormones: Hormones are molecules produced in the endocrine system that send signals to different organs and cells. Hormones are transported through the blood to help regulate various functions such as metabolism and growth.

Donating Blood Plasma

Blood plasma is a vital part of life, and plasma donations are just as important as whole blood donations. In fact, some of the plasma used in medical treatments comes from plasma separated from whole blood donations.

However, plasma can also come from a process called plasmapheresis, which is a mechanical process of separating desired components from whole blood while the donor is connected to an apheresis machine.

If plasmapheresis is used, plasma is collected while the cellular portion of the blood is returned back to the donor.

Uses of Donated Plasma

Blood plasma can be separated into different components and used to treat a variety of conditions, including:

  • Trauma: People who have experienced severe burns or trauma may receive a blood plasma transfusion to increase blood volume, prevent shock, and aid in the blood clotting process.
  • Clotting factor deficiencies: People with various bleeding disorders may be deficient in specific clotting factor proteins. These can be produced from donated plasma and given to replace the factors their bodies do not produce.
  • Primary immune deficiency disorders (PIDDs): PIDDs are rare genetic disorders that impair the immune system's function. People with PIDDs often experience frequent infections that aren't helped by antibiotics. Intravenous immunoglobulin from blood plasma can help the immune system fight infection.
  • Alpha-1 antitrypsin (AAT) deficiency: People with AAT deficiency (also called genetic emphysema), a condition that affects the lungs, are deficient in AAT. Infusion of AAT from blood plasma can slow the progression of the disease and damage to the lungs.
  • Infections and viruses: Certain conditions, such as rabies and tetanus, can be treated with hyperimmune globulins produced from plasma.
  • Rh-factor incompatibility: Pregnant people whose Rh-negative blood type is incompatible with their fetus's blood can be given RhoGAM (Rho(D) immune globulin) to prevent developing antibodies that could threaten future pregnancies.

Is Donating Plasma Good for You?

Blood plasma donation is safe. The procedure and machine used to separate the plasma have been approved by the Food and Drug Administration (FDA).

A benefit of donating plasma is that you get a mini checkup each time you donate. You may also be compensated for your donation. Knowing that your plasma will go to help treat people with many medical conditions is also beneficial.

There is also some evidence that regular plasma donors may see a decrease in total and low-density lipoprotein (LDL) cholesterol, considered "bad" cholesterol. In another study, people who donated plasma experienced lower blood pressure for up to 14 days after donation, suggesting that those who donate on a regular basis may be able to stabilize their blood pressure.

AB Elite Donors

While anyone can donate plasma, people with type AB blood are highly encouraged to donate. AB blood types are universal plasma donors, meaning their plasma donation can be used in people with any blood type.

Plasmapheresis as Treatment

Not only can plasmapheresis be used to collect plasma from healthy donors, but it can also be used to treat disease. Plasmapheresis may be used as part of the treatment for a variety of conditions. These include:

  • Some blood clotting or platelet disorders: Some disorders affecting blood clotting and platelet function are treated by plasmapheresis.
  • Wilson’s disease: This conditions can lead to an overaccumulation of copper in the blood and affect the liver. Plasmapheresis is believed to remove the copper and slow damage to the liver. 
  • Organ transplant. Plasmapheresis can help prevent the body from rejecting a transplanted organ.
  • Neurological conditions. Conditions like Guillain-Barré syndrome, myasthenia gravis, and multiple sclerosis affect the central nervous system. Blood plasma donations are believed to remove autoantibodies caused by these conditions that cause injury to the central and peripheral nervous systems. 


Blood plasma is the liquid portion of blood. It contains proteins, electrolytes, immunoglobulins, and coagulants which all play a role in the body’s functions. Blood plasma is responsible for delivering nutrients, removing waste, respiration, regulating blood pressure, and transporting hormones.

Blood plasma transfusions and components produced from donated plasma can be lifesaving when used to treat blood clotting disorders, liver failure, trauma, and burns. As universal donors, people with type AB blood are encouraged to donate plasma.

14 Sources
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