Blood plasma is a light yellow liquid that makes up about half of a person’s blood. Blood plasma is vital for fighting infection, maintaining correct blood pH levels, helping blood to clot, and transporting and eliminating waste products.

Many people can donate blood plasma, which can help treat infections and conditions and save lives.

Read on to learn about blood plasma, what it contains, its crucial functions to keep the body healthy, and how to donate blood plasma.

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Whole blood contains red blood cells, white blood cells, and platelets suspended in blood plasma. Blood plasma is a yellowish liquid that makes up around 55% of blood.

Aside from water, which makes up around 91–92% of blood plasma, the main components of blood plasma are:

  • Plasma proteins: These proteins, which include globulin and albumin, help control pressure within a person’s circulatory system.
  • Coagulants: Coagulants help with blood clotting, which is an important process that slows down bleeding. The most common plasma coagulant is fibrinogen. This coagulant is the primary component of a blood clot.
  • Electrolytes: These include potassium, sodium, calcium, chloride, and bicarbonate. Scientists understand that electrolytes have many functions around the body. In blood plasma, they help regulate blood pH levels.
  • Immunoglobulins: Immunoglobulins make up around 20% of the total proteins in blood plasma. The immune system produces immunoglobulins to fight parasites, fungi, viruses, and bacteria.

Learn more about blood components and what they do.

Which protein is the most important buffer in blood plasma?

Red blood cells in blood plasma contain the protein hemoglobin. Healthcare professionals consider hemoglobin one of the most important proteins for respiration (breathing) because it regulates levels of carbon dioxide and oxygen in the blood. Iron inside hemoglobin binds to oxygen. This allows hemoglobin to carry oxygen from the lungs to the rest of the body.

Hemoglobin also picks up carbon dioxide waste. It carries it to the lungs, where the person breathes out the waste.

Red blood cells and the hemoglobin protein are essential in providing vital oxygen throughout the body. Doctors test hematocrit levels to check a person’s red blood cell count, which may affect their health.

Here is what to know about hematocrit levels and testing.

Blood plasma has many functions, and different blood plasma components play different crucial roles. In addition to the functions mentioned above, scientists recognize these other important roles of blood plasma and the components in blood plasma. These include:

  • Transporting nutrients: Our body contains millions of cells. As our cells grow, repair themselves, and carry out their functions, they need nutrients. Blood plasma can absorb nutrients from the digestive system and transport them around the body. These nutrients include fats, amino acids, vitamins, and glucose.
  • Managing waste products: When cells carry out their functions, they often form waste products, which can be damaging to the body in larger quantities. Blood plasma can absorb these waste products and send them to the skin or kidneys for processing and excretion.
  • Respiration: Our cells need a steady supply of oxygen, and they release carbon dioxide. Red blood cells, along with hemoglobin in blood plasma, help carry oxygen from the lungs to the body’s cells, and carbon dioxide from those cells to the lungs.
  • Transporting hormones: Hormones act as signals from one part of the body to another. Hormones can affect many bodily processes, such as metabolism and growth. Blood plasma can carry hormones around the body.

Plasma viscosity is a measure of the blood’s thickness. The amount of proteins in the plasma affects its thickness. Doctors may measure the viscosity of blood to detect or monitor inflammation. Doctors may also use a plasma viscosity test to diagnose inflammatory conditions.

As with any other part of the body, blood plasma requires maintenance. As a 2021 review explains, the kidneys help to filter blood plasma. This process happens when blood plasma flows through a part of the kidney called the Bowman’s capsule. The Bowman’s capsule removes excess blood cells, platelets, and proteins from blood plasma.

Learn more about the kidneys’ vital role in health.

Donated blood plasma can be very helpful to medicine. It can help treat various health conditions. Scientists can also use donated blood plasma in their research to better understand how blood plasma works and to develop new vaccines and treatments.

Treating conditions

One important use of blood plasma is in the treatment of infectious diseases such as chickenpox. For example, when someone has the chickenpox virus, their body will develop specific immunoglobulins to fight it off. If the person donates blood plasma shortly after having chickenpox, their blood plasma will contain a greater concentration of those immunoglobulins, which scientists can use to develop vaccines.

Similarly, people who have recovered from COVID-19 have produced antibodies to SARS-CoV-2. These antibodies can protect against reinfection. Known as convalescent plasma, plasma donated from people who recovered from COVID-19 may help others with the disease fight the virus, according to the Food and Drug Administration (FDA).

A 2021 review lists many other important medical uses of donated blood plasma, including treating:

  • autoimmune conditions, such as Guillain-Barré syndrome, myasthenia gravis, multiple sclerosis, systemic lupus erythematosus, and Hashimoto’s disease
  • blood disorders, such as blood clotting disorders
  • liver diseases, including Wilson’s disease and acute liver failure
  • neurological disorders and stroke, including viral or bacterial infections of the brain and inflammation of the brain and spinal cord

Transplant rejection

Doctors may try using donated blood plasma to help treat transplant rejection in people who have had a liver, kidney, or heart transplant. Doctors also use donated blood and blood plasma to treat drug overdoses, poisonings, trauma, burns, and shock.

Blood types

While all types of donated blood can save lives, the American Red Cross urges people who have the AB blood type to donate blood plasma. Healthcare professionals consider AB blood plasma universal because it can be given to anyone regardless of their blood type and without having to test the recipient’s blood type. This is particularly critical when a person needs a blood plasma transfusion during an emergency situation.

Read more on blood types.

Donating blood plasma is a simple and safe procedure. As the American Red Cross explains, donating blood plasma is similar to donating whole blood or any blood product.

Most donation places require that a person is in good health to donate blood. Upon arrival, a medical professional will ask a person about any existing conditions and medications they take.


The FDA recommends that a person meet some basic requirements to donate blood. These include:

  • having a normal temperature
  • meeting the minimum age requirement for the state
  • meeting the minimum weight requirement
  • having a normal blood hemoglobin level
  • not having infections that can transmit through the blood
  • not having donated blood within the past 8 weeks

To donate blood plasma, a person sits in a reclining chair. A healthcare professional will insert a needle into the person to draw blood from a vein.

A special machine will filter out the red blood cells and platelets and safely return these blood components to the donor’s body. What is left is donated blood plasma. This process takes around 1 hour 15 minutes.

Read more about what blood plasma donation involves.

Side effects

While donating blood is a safe procedure, blood donations can sometimes cause temporary side effects, such as:

  • dizziness
  • feeling faint
  • sweating
  • weakness
  • loss of consciousness
  • nausea
  • vomiting

A person can prepare for donating blood and minimize the risk of side effects by eating nutritious foods, drinking plenty of fluids, and getting rest before donating blood. Blood donations are perfectly safe for most people.

Learn about what to do after donating blood.

Blood plasma is an essential part of the blood. The components of blood plasma perform many crucial body functions.

Doctors use donated blood and blood plasma to treat many conditions and in emergency situations. Donated blood plasma and other blood products often improve and save lives. Donating blood plasma is a safe and simple procedure.