The reasons for patients’ dark lips are as follows: 1. Heart disease, that is, problems with the circulatory system, are mostly seen in heart rate failure, as well as coronary heart disease, angina pectoris and pulmonary heart disease. These can lead to insufficient oxygen supply to the body’s tissues, resulting in a darkening of the mouth and lips, mostly black and purple. 2, mostly seen in patients with abnormal kidney function. Some patients with chronic kidney disease will have pigmentation for various reasons, making the mouth and lips dark. 3, digestive system problems, mostly seen in prolonged gastritis, indigestion, decreased appetite, constipation, diarrhea, bloating. These abnormalities of the digestive system can also lead to color changes in the mucous membrane of the mouth and lips and the appearance of dark lips. Clinically, the color change of the lips and the condition can be combined to make a reasonable diagnosis and treatment.