Albumin is the most important protein in human plasma and its main role is to maintain the body’s nutrition and osmotic pressure. The liver is the main site for synthesizing albumin. If the raw materials for synthesizing albumin are reduced, such as malnutrition, long-term failure to eat and timely replenishment, it can cause a decrease in albumin. If there are problems with the liver, such as hepatitis, cirrhosis, or severe liver failure, the liver’s ability to synthesize albumin is reduced, which can cause a decrease in albumin. In addition, some special diseases, such as chronic kidney disease, can cause a large amount of protein loss due to kidney damage, and the lost protein is the small molecule albumin, which can also cause a decrease in albumin. In addition, some chronic diseases, such as serious infections, serious wounds that do not heal after surgery, long-term consumption, such as malignant tumors, cachexia, can cause an increase in the consumption of albumin, resulting in a decrease in albumin. Low albumin can cause swelling, such as subcutaneous swelling, swelling of the limbs, or fluid in the chest or abdomen. Therefore, albumin, as the most important protein in the body, is synthesized by the liver and can be reduced due to various diseases, nutritional status or various reasons, such as loss of albumin.