Are you playing the version or the Definitive Edition ? What platform are you on (PC, Xbox, or PlayStation)?
If you are tired of staring at a red screen or dying in one hit, here is how to fix the Mafia 2 health bug for good. Understanding the Health Bug mafia 2 health bug fix
Buy any food item. The animation of eating often forces the health bar to update. Are you playing the version or the Definitive Edition