What does the bars above the health bar mean?

The bars over top of your health bar shows the current boost level from using consumables. Each bar corresponds to a different level of boost:

• Level 1:+1% Health Regen per 8 Seconds
• Level 2:+2% Health Regen per 8 Seconds
• Level 3:+3% Health Regen per 8 Seconds and +2.5% Movement Speed Bonus
• Level 4:+4% Health Regen per 8 Seconds and +6.2% Movement Speed Bonus

You can increase the your boost level by using the following consumables
(see image below for more detail):

• Energy Drinks: 1.5 bars of boost (40% of total boost)
• Pain killer: 2 bars of boost (60% of total boost)
• Adrenaline Shot: 4 bars of boost (100% of total boost)

One thing to keep in mind is that the effects of using the consumables is cumulative, so drinking two energy drinks will get you to around 80% of your boost bar (slightly less, as the bar degrades while you drink the second energy drink).

Boost amount source

They are boosts. They come from both energy drinks and painkillers.

First 2 bars (the leftmost) are slight health improvements, meaning they can slowly heal you until the bar decays. You get faster health regeneration in the second bar. The third bar is a speed boost, meaning you run and move slightly faster. The fourth is even more speed increase and health regeneration.

Good luck! Get those chicken dinners!