Most jaundice is characterized by yellowing of the skin and mucous membranes, which can be detected by visual observation; however, occult jaundice can only be detected by laboratory tests. Normal serum total bilirubin levels range from 1.7 μmol/L to 17.1 μmol/L. When the total bilirubin level exceeds the upper limit of normal, the skin and mucous membranes may become jaundiced. When the bilirubin level exceeds the upper limit of normal, it causes yellowing of the skin, mucous membranes, sclera and other epithelium, which is called jaundice. When bilirubin is between 17.1 μmol/L and 34.2 μmol/L, it is not easy to be detected clinically and is called hidden jaundice; when it exceeds 34.2 μmol/L, symptoms such as yellowing of the mucous membranes are typical. Detection of jaundice is mainly through laboratory testing of blood bilirubin levels, and can be combined with liver and gallbladder ultrasound, abdominal X-ray or CT, liver puncture biopsy and other tests to diagnose the cause of the disease. Cell phones do not currently have testing capabilities. Jaundice may be caused by hemolysis, cirrhosis, cholestasis, etc. If jaundice is suspected, it is recommended to go to the hospital in time.