Decreased protein is generally defined as serum albumin falling below the normal reference range, which is also known as hypoproteinemia. The four common causes of hypoproteinemia are inadequate intake, excessive consumption, excessive loss, and a problem with protein synthesis, which is the inability to synthesize. Inadequate intake is generally due to various reasons for poor eating, insufficient food intake, low protein, so that not enough protein is absorbed, and gradually hypoproteinemia will occur. Excessive protein loss is mainly common in diseases such as nephrotic syndrome, where a large amount of proteinuria occurs, a large amount of protein is lost from the urine, and hypoproteinemia occurs. Excessive consumption is a hypoproteinemia caused by a relative lack of protein due to fever or a state of stress, where protein consumption is significantly higher than usual and production is insufficient. Decreased protein synthesis is mainly seen in liver function abnormalities, cirrhosis, and inability to effectively synthesize albumin resulting in hypoproteinemia. The above four conditions are the common causes of protein decline.