If a patient has black lips, there are several reasons: 1. The most common factor is cardiogenic factors, such as coronary atherosclerotic heart disease, cardiac insufficiency or myocarditis, pericarditis, etc. In cases where there is an obvious lack of blood supply to the heart, there will be poor peripheral circulation and the lips will have a black-purple color. 2. Factors of lack of oxygen, such as pulmonary hypertension, chronic pulmonary heart disease, chronic 3, if the patient has poisoning, such as nitrite poisoning, then there will be a significant reduction of hemoglobin in the body, which will also lead to the black color of the mouth and lips.