How Long Do Dogs Bleed When They Are in Heat?

In general, females from smaller dog breeds go into heat earlier than large-breed dogs. Some large bitches do not experience a heat until they are two years old. As dogs age, the duration of the bleeding phase often becomes longer. Some dogs experience bleeding for more than a month. There is no age when a dog naturally stops the heat cycle. The only way to stop a bitch from going into heat is through surgical spaying.