Whether or not you know you have bisexual clients, you almost certainly already do. Health care providers should think carefully about what you need to know and what questions you want to ask. For example, HIV is spread through bodily fluids, therefore whether or not a person is at risk for HIV depends on their behavior, not their identity. You cannot determine someone's HIV risk by asking their sexual orientation. You can learn more by asking about their sexual behavior.
Bisexuals can be monogamous or non-monogamous.
It is a mistake to assume that because someone has the potential to be attracted to men and women, they must have twice as many sex partners.