Do bipolar people ussualy deny their condition?

It can happen, yes: Bipolar disorder in mania can bring with it a sense of invulnerability, euphoria, and grandiosity. In this state a person may not realize s/he is ill, as it may not feel like suffering. People around the individual may see more clearly. Some may realize they need help, even though they don't like it. Bipolar is not the only psychiatric condition where denial can interfere with treatment.

Frequently: Because of the high energy and grandiosity during manic and hypomanic phases, bipolar folks often don't like to take mood stabilizers. Denial is involved in view of the dangers. In a sense the person is addicted to the euphoria and high energy, and it's easy to see how seductive that state can be.