Definition – What is albumin?

Albumin is a protein that occurs in the human body, among other things. It belongs to the so-called plasma proteins and forms with 60% their largest part. It is produced in the liver and plays an important role in our water balance. Furthermore, it serves as a transport protein for degradation products and enzymes. A change in its value can provide information about possible liver damage or dehydration.

What is the function of albumin?

Albumin is a transport protein of the blood and transports various enzymes and degradation products. These include, for example, bilirubin, a breakdown product of haemoglobin, the red blood pigment of the red blood cells (erythrocytes). Since bilirubin is initially insoluble in water, it is bound to albumin to be transported in the blood to the liver, where it is finally made water-soluble by attaching an acid.

Other water-insoluble substances that are bound to albumin are fatty acids, trace elements, hormones, some vitamins, magnesium and calcium and even some drugs. These become water-soluble when bound to albumin and can thus be transported in the blood to their destination. Another task of albumin is to maintain the so-called colloid osmotic pressure.

80% of the colloid osmotic pressure is formed by albumin. The wall of our blood vessels is permeable to water. In order to prevent the water from flowing from the blood vessels into the surrounding cells, the colloid osmotic pressure mentioned above is required, which is produced by various proteins.

Since water always flows to the place with the higher particle concentration according to the principle of osmosis to create a concentration balance, it is held in the vessels by the proteins of the blood. If this were not the case, for example in the case of a lack of albumin, water would accumulate in the body tissue outside the blood vessels, so-called oedemas. A third function of albumin is to maintain and buffer the pH value of the blood. Albumin is able to release or bind hydrogen ions and can therefore influence the pH value. Would you like to read more about the pH value of the blood?

Where is albumin produced?

Albumin is produced in the liver. There about 12g albumin are produced per day. Deviations in the albumin value therefore provide information about the function of the liver. The liver plays a central role in the metabolism and therefore produces, in addition to albumin, components of the bile such as bile acids as well as some hormones and cholesterol. Would you like to learn more about the function of the liver?

Standard values of the albumin

The amount of albumin can be determined in blood, for example. The serum albumin thus determined should be between 3.5 and 5.4 g/dl. Depending on the laboratory, the values are also given in other units such as mg/dl.

In this unit, the albumin should accordingly be between 3500 mg/dl and 5400 mg/dl. Furthermore, albumin can also be determined in urine, as the body excretes a small amount of albumin daily through the urine. The albumin in the morning urine should be below 20 mg/l, whereas it should be below 30 mg in a 24-hour urine collection. Deviations in the values then provide information about the function of the kidneys, which are responsible for excreting the albumin.