What is plasma?

Your blood can be separated into four components, one of them being plasma. The other three are:

  • red blood cells
  • white blood cells
  • platelets

Plasma makes up about 55 percent of your blood. It carries out several key functions in the body, including transporting waste products.

Read on to learn more about plasma, including what it’s made of and its many functions.

Plasma contains about 92 percent water. This water helps to fill up blood vessels, which keeps blood and other nutrients moving through the heart.

The remaining 8 percent of plasma contains several key materials, including:

  • proteins
  • immunoglobulins
  • electrolytes

When blood is separated into its key components, including red blood cells and plasma, plasma looks like a yellow-tinged fluid.

One of plasma’s main functions is the removal of waste from cellular functions that help to produce energy. Plasma accepts and transports this waste to other areas of the body, such as the kidneys or liver, for excretion.

Plasma also helps maintain body temperature by absorbing and releasing heat as needed.

In addition to transporting waste and regulating body temperature, plasma has several other key functions that are carried out by its different components:


Plasma contains two key proteins called albumin and fibrinogen. Albumin is vital for maintaining a balance of fluid, called oncotic pressure, in the blood.

This pressure is what keeps fluid from leaking into areas of the body and skin where less fluid usually collects. For example, people with low albumin levels may have swelling in their hands, feet, and abdomen.

Fibrinogen helps to reduce active bleeding, making it an important part of the blood-clotting process. If a person loses a lot blood, they’ll also lose plasma and fibrinogen. This makes it harder for blood to clot, which can lead to significant blood loss.


Plasma contains gamma globulins, a type of immunoglobulin. Immunoglobulins help the body fight off infections.


Electrolytes conduct electricity when dissolved in water, hence their name. Common electrolytes include sodium, potassium, magnesium, and calcium. Each of these electrolytes plays a key role in the body.

When you don’t have enough electrolytes, you can have a range of symptoms, including:

When people lose a lot of blood, often due to a traumatic accident or surgery, they also lose a lot of plasma. Given all the functions of plasma, this can have serious effects on someone’s health. This is why organizations collect plasma in addition to whole blood.

How it’s done

There are two ways to donate plasma. The first is by donating whole blood. A laboratory then separates the blood components, including plasma, as needed.

The other way involves donating only plasma. This is performed through a method known as plasmapheresis. A machine draws blood from a vein into a centrifuge. A centrifuge is a machine that spins rapidly, which separates plasma from other blood components.

Plasma is naturally lighter than many other components, so it tends to rise to the top during this process. The machine will keep the plasma and send other components, such as red blood cells, back into your body.

Donated plasma keeps for about a year. It’s usually kept frozen until it’s needed.

Who can donate

Each laboratory or blood bank may have different requirements regarding to who can donate plasma.

Generally, donors must:

  • be between the ages of 18 to 69
  • weigh at least 110 pounds
  • have not donated plasma in the last 28 days

The 28-day rule allows the donor’s body to heal and repair itself. This provides about 13 opportunities to donate plasma per year.

If you live in the United States, the American Red Cross can help you find a blood donation site. Learn more about the side effects of donating plasma and important safety tips.

Plasma is an important part of blood that helps with everything from regulating body temperature to fighting infection. Not having enough plasma can have serious health consequences, which is why people can donate plasma for use in others.