Plasma

Medically Reviewed by Nayana Ambardekar, MD on November 20, 2022
Written by WebMD Editorial Contributors
2 min read

Plasma is the liquid part of your blood. You may have heard of red blood cells, white blood cells, and platelets. But plasma is also part of your blood.

One of its jobs is keeping your blood pressure in a healthy range. It also carries important proteins, minerals, nutrients, and hormones to the right places in your body.

Plasma is made up of about 90% water. It also has salts and enzymes. And it has antibodies that help fight infection, plus proteins called albumin and fibrinogen.

Plasma makes up the biggest part of your blood: about 55%. Even though blood appears red when you see it outside the body, plasma itself is a pale yellow color.

Plasma helps carry proteins, hormones, and nutrients to different cells in your body. These include:

  • Growth hormones that help your muscles and bones grow
  • Clotting factors that help you stop bleeding when you get a cut
  • Nutrients such as potassium and sodium that help your cells work

Plasma also helps your body:

  • Maintain normal blood pressure and blood volume levels
  • Get rid of the chemical waste from cells by dissolving it and carrying it away

Doctors can use plasma to treat different kinds of serious health problems.

Some of the elements in plasma, including the antibodies and chemicals that help your blood to clot, can help in medical emergencies like burns and trauma.

Other things that plasma donation is good for include:

  • Developing treatments. The antibodies and proteins can also be used to develop treatments for rare diseases, including some immune system problems.
  • Cancer. Adults and children with different kinds of cancer -- including leukemia -- sometimes need plasma transfusions.
  • Transplant surgery. Some people who get liver or bone marrow transplants need plasma.
  • Hemophilia. In this rare disorder, a person’s blood doesn’t have enough clotting factors, so donated plasma can help.

To donate plasma, you have to be at least 18 years old and weigh at least 110 pounds. You’ll need to get a physical examination and get tested for certain viruses like HIV and hepatitis.

Donating plasma is a little different from donating whole blood. When you donate whole blood, it goes straight into a collection bag and is later separated in a lab. When you donate plasma, the blood that’s drawn from your arm goes through a special machine to separate the different parts of your blood.

The parts that are left over, including your red blood cells, go back in your body, along with some saline (saltwater) solution. The process usually takes about 1 hour and 15 minutes.