The causes of low serum prealbumin are commonly attributed to malnutrition, gastrointestinal diseases, abnormal liver function or nephrogenic hypoproteinemia. 1. Malnutrition: patients lose weight and diet or do not eat, which will lead to a decrease in prealbumin. 2. Digestive tract diseases: patients can not absorb and digest well and lack of raw materials for protein production, such as gastric cancer, colorectal cancer and liver cancer and other diseases. 3. Abnormal liver function: if the patient suffers from liver diseases, such as alcoholic liver, fatty liver, drug-induced liver, hepatitis B, cirrhosis, liver cancer, etc., all of them will lead to the decrease of prealbumin synthesis, and the prealbumin in the blood test will be reduced. 4. Nephrogenic hypoalbuminemia: Due to the damage of the normal excretion barrier of kidney, a large amount of serum albumin is excreted from urine, and the total amount of protein lost is higher than the amount of protein ingested in the normal diet, thus leading to low albumin. It is recommended that the patient go to the hospital in time to find out the cause of low serum pre-protein and treat it under the guidance of the doctor.