Suddenly spitting blood in the mouth has many too many reasons, to diagnose exactly where the blood comes from, for example, stomach bleeding will spit blood, nasal bleeding may backflow into the mouth to spit blood, pharyngeal inflammation may also be congested, bleeding, teeth and gums inflammation may also bleed. Whether the blood comes from the nasopharynx, the stomach, or from the mouth, it takes a very clear judgment to figure out the cause of the disease and the relative treatment, so bleeding in the mouth is more of a problem. Overall if it is darker in color and also accompanied by food gastric juices, it is definitely bleeding from the stomach. But if it is fresh blood and also mixed with phlegm, there is a possibility that the bleeding is coming from the pharynx. If the bleeding comes from the mouth, from the gums or teeth, usually the amount of bleeding is not very large, and when you suck hard, you will feel the smell of blood coming out of the teeth, it should be from the inflammation and bleeding of the gums. Some people don’t need to make efforts, when brushing teeth, you can also see bleeding on the top of the toothbrush, usually from the inflammation of the gums, you can go to the hospital for dental cleaning, anti-inflammatory treatment. Other bleeding may be obviously related to trauma and should be easier to determine.