Once consumed, caffeine is quickly absorbed from the gut into the bloodstream.

From there, it travels to the liver and is broken down into compounds that can affect the function of various organs.

That said, caffeine’s main effect is on the brain.

It functions by blocking the effects of adenosine, which is a neurotransmitter that relaxes the brain and makes you feel tired.

Normally, adenosine levels build up over the day, making you increasingly more tired and causing you to want to go to sleep.

Caffeine helps you stay awake by connecting to adenosine receptors in the brain without activating them. This blocks the effects of adenosine, leading to reduced tiredness.

It may also increase blood adrenaline levels and increase brain activity of the neurotransmitters dopamine and norepinephrine.

This combination further stimulates the brain and promotes a state of arousal, alertness, and focus. Because it affects your brain, caffeine is often referred to as a psychoactive drug.

Additionally, caffeine tends to exert its effects quickly.

For instance, the amount found in one cup of coffee can take as little as 20 minutes to reach the bloodstream and about 1 hour to reach full effectiveness.

Caffeine’s main effect is on the brain. It stimulates the brain by blocking the effects of the neurotransmitter adenosine.