Dr Petcha

How Long Does A Cup Of Coffee Keep You Awake?

Just when you are about to retire from work, your boss calls you and asks you to work on a presentation to be handed in tomorrow. It is a pretty bad situation but whether you want it or not, now you are in for an all-nighter. What do you do? You go to the kitchen, make yourself a hot cup of coffee, and get to work. But will this cup of coffee help you get through the night? How long does it actually keep you awake? Let’s find out. 

How does coffee actually work?

As you go about your day working and doing other activities, your brain starts to create an enzyme called adenosine. This enzyme binds with the A1 receptors in your brain causing you to feel tired and sleepy.  Coffee, on the other hand, contains a very popular substance called caffeine which is a central nervous system stimulant. Caffeine acts as an anti-dote to adenosine and counters the feeling of tiredness and lethargy making you more active and alert. 

How long does a cup of coffee keep you awake?

This depends on the amount of caffeine in your cup of coffee. Every cup of coffee is made differently. Some people prefer coffee with milk while others just enjoy black coffee. So naturally, the caffeine content in coffee is different for different people. But generally speaking, 250 ml of brewed coffee can have up to 96 mg of caffeine content in it. 

Now, onto the main question. How long does this actually keep you awake? Well, caffeine is a substance that is quickly absorbed by your system. The caffeine content in your blood is at its peak after 15-45 minutes of consumption and you can immediately start feeling its energizing effects. Once it has entered your system, caffeine does not leave easily. The half-life of caffeine is around 5-6 hours, meaning that you will still feel its effects even after 6 hours of consumption. 

Now, these are general figures but the effects of caffeine can be different on different people. People who consume coffee regularly can develop resistance to it and hardly notice any effects of caffeine. Others can be so sensitive to caffeine that they cannot sleep even hours after consuming it. The effects of caffeine on you depend on your individual metabolism.

What about other beverages?

Coffee is not the only substance with caffeine in it. Several other popular beverages like tea, soft drinks and energy drinks also contain caffeine in varying amounts. A cup of black tea which is around 240 ml can contain up to 45 mg of caffeine. This is way less when compared to coffee but, if you need that energy for short periods of time then black tea could be your go-to. 240 ml of soft drinks contain up to 22 mg of caffeine. Popular energy drinks like Red-Bull can pack around 70-80 gm of caffeine in a 248 ml serving which is roughly the same as coffee. Monster energy drinks might contain a little more. 

However, you have to keep in mind that soft drinks and energy drinks come with a lot of sugar content in them. Coffee and tea are always better options if you need some instant bolts of energy. 


It is okay to take a cup or two of coffee when you cannot avoid an all-nighter. But in usual circumstances, it is recommended to stay away from caffeinated drinks in the evening. They can linger around in your system for 5-6 hours leading to disturbed sleeping patterns. So use caffeine only when it is absolutely needed.