What is albumin? Definition, functions, and why it matters for your health

Did you know that albumin is one of the most important proteins in human plasma and plays a key role in your overall health? Human albumin is a fascinating protein with many important roles. It maintains fluid balance in the bloodstream, it transports essential endogenous and exogenous molecules and is important in diagnostics and medical treatments. In this article, we will explore the types, functions and clinical significance of albumin.

What is albumin?

Albumin is the most abundant protein in plasma. It is made exclusively by liver cells, also known as hepatocytes and comprises 50% to 60% of the proteins in plasma of healthy people.

Albumin creates a kind of pressure that keeps fluid inside the blood vessels and influences fluid balance between the former and surrounding tissues. 

It also acts as a type of biological carrier, transporting essential molecules through the bloodstream. In medicine, albumin levels are used in routine blood testing to assess liver function, kidney health and nutritional status.

The importance of albumin in health and medicine

What does albumin do?

• Regulates oncotic pressure and fluid balance: the Albumin molecule is too large to pass through the blood vessel walls, which creates a kind of pressure that keeps fluid inside the blood vessels and prevents it from leaking into surroundings. This is the oncotic pressure that helps to maintain stable blood pressure and circulation, reduces the risk of edema (swelling due to the movement of fluid from the bloodstream into the tissues) and supports tissue hydration and oxygen delivery.
• Transports proteins: Albumin acts as a carrier protein, binding to and transporting essential substances, endogenous ones including hormones, fatty acids, bilirubin (a substance produced in the liver during breakdown of red blood cells), as well as exogenous ones such as drugs. It facilitates the distribution, activity and metabolism of these compounds throughout the body. By binding to drugs, albumin can regulate the amount of drug available to exert its therapeutic effect.
• Removal of toxic substances: Albumin binds to waste products and toxins, aiding in their removal from the body. It helps to protect cells by reducing the effects of harmful molecules called free radicals and reactive oxygen and nitrogen species, which can cause damage to the body.
• Nutritional Reserve: Albumin serves as a source of amino acids, the building blocks for proteins, for tissue repair and other metabolic processes.

Types and classifications of albumin

The three main types of albumins used in medicine, biotechnology and research are human serum albumin (HSA), bovine serum albumin (BSA) and recombinant albumin. 

1. Human serum albumin (HSA)

HSA is the most abundant plasma protein. It is essential in maintaining oncotic pressure, transporting molecules and regulating fluid balance. 

1.1 Medical and therapeutic applications:

Albumin therapy is widely used in critical care and disease management, particularly in conditions where fluid balance, protein levels or removal of toxic substances are not functioning normally. These are the main applications:

• Treatment of low albumin levels: Albumin infusions help restore normal plasma protein levels in patients with malnutrition, kidney disease or liver disease.
• Liver cirrhosis and fluid management: In advanced liver disease, albumin therapy is used to reduce fluid accumulation and support proper blood flow.
• Burns and trauma care: plasma expanders containing albumin are essential in treating severe burns, blood loss and septic shock, as they help stabilize blood volume and prevent low blood volume.
• Severe infections and sepsis: Intravenous albumin therapy is used along with antibiotics and fluids to improve the condition of patients with severe infections and failure of multiple organs.

1.2 Diagnostics and laboratory testing

Albumin is essential in medical diagnostics, where it is used to test how well organs are functioning and if diseases are getting worse (progressing).

• Albumin blood tests:
  • They measure the amount of this protein in blood and are used to evaluate kidney and liver functions. Albumin levels often decline in chronic liver disease and kidney failure.
  • These tests help monitor nutritional status in critically ill or malnourished patients.
• Albumin-to-globulin ratio (A/G ratio test):
  • A/G ratio tests are a useful diagnostic marker for chronic infections, autoimmune diseases (diseases where the patient’s immune system attacks their own body, e.g., lupus, rheumatoid arthritis, etc.), kidney disease, liver disease and multiple myeloma.
• Urine albumin test:
  • This test detects early kidney damage in patients with diabetes or high blood pressure by measuring small amounts of albumin in the urine. This occurs before more severe symptoms develop.

1.3 Pharmaceutical development and biotechnology

Albumin’s stability and binding properties make it highly valuable in making drugs and vaccines and in biotechnology research.

2. Bovine serum albumin (BSA)

BSA, derived from cattle plasma, is a highly versatile protein used extensively in biotechnology, diagnostics and pharmaceutical research. While structurally similar to HSA, it is mainly used in laboratory and industrial settings rather than in human medicine. 

Common applications in research and industry:

• Laboratory research: BSA is commonly used as a protein standard in biochemical testing and experiments.
• Diagnostics and vaccines: BSA functions as a stabilizer in vaccines, diagnostic testing kits and laboratory experiments using enzymes. Human albumin is also used for this purpose. 
• Nutrient and cell growth support: BSA serves as a supplement for growing cells to use in research studies.

3. Recombinant albumin

Recombinant albumin is a genetically engineered albumin produced using mammalian cells, yeast and other production media. It is used to make drugs and vaccines and can be tailored to specific medical uses.

Common applications in therapeutics and biotechnology:

• Therapeutic uses: Recombinant albumin is used in delivery of drugs throughout the body, and in wound healing.
• Biopharmaceutical manufacturing: It enhances the stability of some types of drugs and vaccines.
• Tissue engineering and 3D bioprinting: It is used as a scaffold material in the regeneration of organs outside the body and in the creation of artificial tissues.
   

Albumin life cycle: from synthesis to breakdown

Albumin follows the following biological cycle from synthesis to breakdown:

Synthesis

Liver cells called hepatocytes produce 12–14 grams of albumin daily to maintain plasma protein levels. The production of albumin is influenced by nutrition, hormonal regulation and liver function.

Circulation

Albumin is then released into the bloodstream, where it circulates and carries out its functions. These include maintaining oncotic pressure and binding and transporting essential endogenous molecules and drugs. 

Break down and recycling

Albumin lasts a long time in the blood. It has a half-life of approximately 21 days, which means that every 21 days, half of the albumin your blood will be gone. After this, it is broken down by various tissues, including the liver, muscle and kidneys. Albumin is converted into amino acids from which it was made. These amino acids can be reused by the body for making proteins and other processes. 

Excretion

The end products of albumin degradation such as urea, are removed from the body, in the urine.
 

In conclusion, Albumin is a cornerstone of modern medicine and biotechnology, with extensive applications in clinical therapeutics, diagnostics and drug development. In critical care, disease detection or pharmaceutical innovation, its versatility and functional properties make it an irreplaceable component in healthcare and life sciences.

Want to learn more about related topics? Explore our medical glossary here.