313. Blood from One’s Own Mouth
46:3 If one bites into a loaf of bread or some similar type of food and his gums bleed onto the food, the piece that got blood on it must be cut off and thrown away. If one’s gums are bleeding, he can suck it because only blood separated from the body is problematic. He may only do so on weekdays, however, and not on Shabbos. (This is because of a Shabbos issue, not a kashrus issue.)
46:4 If blood is found in the milk, such as if they came out together when milking the animal, an authority must be consulted.