Plasma vs. Serum: Understanding the Differences in Blood Components

Blood, the life-sustaining fluid that courses through our veins, is composed of various components, each with specific functions. Plasma and serum are two fundamental substances found in blood, and while they are closely related, they serve different purposes in the context of medical analysis. Understanding the distinction between plasma and serum is crucial in clinical diagnostics. These components are separated from whole blood for laboratory tests.

Plasma vs. Serum: The Main Differences

Key Takeaways

  • Plasma is the liquid component of blood with clotting factors; serum is similar but without those factors.
  • Serum is used for various diagnostic tests because it does not contain clotting proteins.
  • The choice of plasma or serum for testing depends on the test’s purpose and the substances being measured.

Plasma vs. Serum: Understanding the Differences in Blood Components Pin

Basics of Blood Components

Definition of Plasma

Blood plasma is the liquid portion of your blood. It’s a yellowish fluid that makes up about 55% of your blood’s total volume. Plasma primarily consists of water (~90%), but it also contains dissolved proteins, glucose, clotting factors, mineral ions, hormones, and carbon dioxide. These components are vital as they carry out the task of transporting substances throughout your body.

Definition of Serum

Serum refers to the fluid that’s left after the removal of blood cells and clotting proteins from plasma. It contains the same basic components as plasma excluding the clotting factors such as fibrinogen. Serum is used in various diagnostic tests as it provides important information about your body’s physiological and pathological state.

Differences Between Plasma and Serum


Plasma is the liquid portion of your blood that is a light yellowish liquid. It’s made up of:

  • Water: about 90%
  • Proteins: including albumin, fibrinogen, and immunoglobulins
  • Electrolytes: like sodium and potassium
  • Hormones
  • Gases: such as oxygen and carbon dioxide
  • Nutrients: including glucose and fatty acids

On the other hand, serum is plasma that’s been allowed to clot, and therefore lacks clotting factors. It contains:

  • Water
  • Proteins: but not fibrinogen
  • Electrolytes
  • Hormones
  • Gases
  • Nutrients

Coagulation Factors

Plasma includes all the coagulation factors, which are essential for blood clotting. These are a series of proteins (factors I through XIII) that work in a cascade to heal injuries.

Serum, however, is devoid of these coagulation factors because they are used up during the clotting process that leads to serum separation from blood.

Separation Process

To separate plasma from your blood:

  • Blood is typically collected in a tube containing an anticoagulant.
  • It is then centrifuged before coagulation occurs.
  • Plasma, being less dense, is found at the top layer and can be easily isolated.

For serum:

  • Blood is collected without an anticoagulant.
  • It’s left to clot, which usually takes about 30 minutes.
  • After clotting, blood is centrifuged to separate the serum which appears as the clear liquid at the top.

Plasma vs. Serum: Examples

Example Sentences Using “Plasma”

  • The patient received a plasma transfusion to help manage their clotting disorder.
  • Blood plasma contains important proteins that help in the clotting process and immune response.
  • During the procedure, they separated the plasma from the rest of the blood components for testing.
  • Plasma donation is critical for producing medicines for those with certain chronic illnesses.
  • The plasma from recovered patients may contain antibodies that can help treat people with certain infectious diseases.
  • plasma exchange may be performed to remove harmful substances from a patient’s blood.
  • Doctors measured the levels of certain drugs in the patient’s blood plasma to adjust the dosage accurately.

Example Sentences Using “Serum”

  • The lab technician centrifuged the blood sample to separate the cells from the serum.
  • Antibodies are typically found in the serum portion of the blood.
  • For the test, we only need a small amount of serum, which can be extracted from a blood draw.
  • The doctor ordered a serum electrolyte panel to check for any imbalances.
  • Serum iron levels can indicate whether a person has anemia or iron overload.
  • After the clotting factors have been removed, what remains is called blood serum.
  • The medical researcher used serum from patients to study the response to the new vaccine.

Related Confused Words With Plasma or Serum

Plasma vs. Blood

Plasma is the liquid component of blood, making up about 55% of its volume. It is a straw-colored fluid that contains water, electrolytes, proteins, hormones, and waste products. Plasma plays a crucial role in transporting nutrients, hormones, and proteins throughout the body, as well as in maintaining blood pressure and pH balance.

On the other hand, blood refers to the entire fluid connective tissue that circulates in the body. It consists of plasma, red blood cells, white blood cells, and platelets. While plasma is the liquid portion, blood also contains cellular components that are responsible for oxygen transport, immune response, and blood clotting.

Serum vs. Moisturizer

Serum and moisturizer are both skincare products, but they serve different functions and have distinct formulations.

A serum is a lightweight product that contains a high concentration of active ingredients. Serums are designed to penetrate deeply into the skin to deliver targeted benefits such as anti-aging, brightening, or hydrating effects. They typically have a thin, liquid or gel-like consistency and are applied after cleansing but before moisturizing.

A moisturizer, on the other hand, is a thicker cream, lotion, or ointment that is primarily intended to hydrate the skin by forming a barrier on the skin’s surface. This helps to prevent water loss and protect the skin from environmental factors. Moisturizers may also contain some active ingredients, but their main purpose is to lock in moisture and maintain the skin’s natural barrier function.

Frequently Asked Questions

What distinguishes plasma and serum in terms of their components?

Plasma is the liquid component of blood containing water, salts, enzymes, antibodies, and other proteins. It includes clotting factors, which are absent in serum. Serum is similar to plasma but has had the clotting factors and fibrinogen removed following blood clotting.

Why might plasma be chosen over serum for certain tests?

Plasma is preferred when clotting factors need to be assessed. Since it contains these factors, it is used in tests like coagulation studies, where the ability of blood to clot is important.

How do serum and plasma differ in their preparation procedures?

To prepare plasma, blood is collected in tubes containing an anticoagulant and centrifuged. The anticoagulant prevents clotting. Serum is obtained by allowing the blood to clot first and then centrifuging to remove the clot, resulting in a clear fluid without clotting factors.

Can you explain why serum lacks clotting factors, unlike plasma?

Serum lacks clotting factors because it is separated from the clotted components of blood. During clotting, fibrinogen converts to fibrin and is removed along with other factors that facilitate clotting, leaving behind the liquid serum.

What types of tubes are typically used for collecting plasma versus serum?

Plasma is usually collected using tubes that contain anticoagulant agents, often with a light blue or green top, while serum is collected in tubes without anticoagulants, typically with a red or gold top.

In the process of centrifugation, how does the method differ when separating serum from plasma?

When centrifuging for plasma, the blood is mixed with an anticoagulant and spun down quickly to prevent clotting. For serum, the blood is allowed to clot first at room temperature and then centrifuged, allowing the liquid serum to be separated from the clot.

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Last Updated on January 6, 2024

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