The episode title is literal; while the truths revealed (Peyton’s drug use, the heart condition) are necessary, they are undeniably painful for the characters to swallow.

One Tree Hill Season 2, Episode 8: "Truth, Bitter Truth" Review

Lucas and Nathan head to Charlotte for a Bobcats game. The trip has a heavy underlying purpose: Nathan is being tested for HCM, a genetic heart condition passed down from Dan. He urges a reluctant Lucas to do the same, highlighting the evolving bond between the brothers.