Black lips and black tongue may be related to chronic hypoxia, digestive diseases, hepatitis B and other factors, as follows: 1. hypoxia: if the blood supply is insufficient or the oxygen content in the blood is low, hypoxia and cyanosis will occur, which is common in the lips and the ends of the fingers and toes. 2. Digestive system diseases: such as indigestion, constipation and so on. When the body’s digestive function declines, the food in the stomach and intestines cannot be eliminated in time and stays in the body. Over time, toxins will also slowly accumulate, then there may be lips, tongue coating black and so on. 3. Hepatitis B: When there is serious damage to the liver, liver function will also decline, resulting in an increase in the body’s melanin, resulting in black lips and tongue. If the situation of black lips and tongue persists, it is recommended to consult a doctor in a timely manner, complete the relevant examinations, identify the cause of the disease, and be targeted treatment.