Does Coffee Dehydrate You?

A steaming cup of coffee is a morning staple for many people. However, you may have heard that caffeine can actually dehydrate you. In this case, it is easy to be second-guessing your morning routine. While it is true that consuming caffeine can keep you up at night, there is much more to understanding caffeine and its effects.

Understanding Caffeine

Caffeine is the world’s most consumed psychoactive substance. These days caffeinated beverages take many forms. It is popular due to its mood-enhancing properties. People also consume it to elevate both their mental and physical performance.

Once consumed, caffeine enters your bloodstream. It then reaches your liver, where it is broken down and distributed to the rest of your body–this is how it affects your brain function. Similarly, this is also how it affects your kidneys by increasing the blood flow in that region, and what allows it to function as a diuretic.

What is a Diuretic?

Any substance that causes an increase in the passing of urine is known as a diuretic. Any drink, including water, when consumed in large volumes, acts as a diuretic. An important fact to note is that while urinating is a loss of body water, it doesn’t always correlate with dehydration.

Depending on the amount of urine output that occurs after consumption, at best, a drink can be classified as a poor rehydrator. Caffeine is known to be a diuretic in the same sense. However, it is quite a weak diuretic as you can build up a tolerance to its effects.

Caffeine does cause your kidneys to flush out extra sodium and water through urine. However, you should be used to these changes within just four to five days.

What Does the Research Say?

Before we get into the research, we first need to understand how hydration is measured. Generally, it is measured as a balance between how much fluid the body retains out of the consumed amount.

These studies are nowhere near recent. In a study conducted way back in 1928, participants were given varying doses of caffeine. The study focused on a comparison between people who consumed no caffeine, people who consumed a low dose (approx. half a cup of coffee), and regular users (one cup of coffee per day).

The results suggested that while there was some increased urination, people tended to adjust quite quickly to these changes.

Similarly, a second study included a subject group of 59 people. The study lasted for about 11 days and also focused on the effect of caffeine on fluid loss. Each subject was given a dosage of 3mg per day, which is about two to three cups of coffee.

This intake gradually altered to a dose of no coffee, one cup to two cups. The results spanned not just the amount of urine output but also the color. Despite all these criteria, it was concluded that there were no irregular effects seen in terms of fluid loss.

These studies suggested that regularly consuming caffeinated drinks would not lead to chronic dehydration. Both these tests looked into regular consumption that went up to at least two cups per day without noting any significant dehydration.

Are You Dehydrated?

Poor hydration has been linked to multiple health problems. By now, we are all aware of how important drinking water is. A disruption in proper hydration can cause fluctuations in not just moods but also brain function. It can lead to adverse effects on your reasoning skills, sluggish performance, and cause harmful effects on your immunity.

It is especially harmful to the more susceptible population, such as growing children, older people, or people with compromised immunity. Headaches are the most common sign of dehydration.

Other symptoms can be fatigue, dizziness, muscle cramps, nausea, digestive issues, and so on. If these symptoms persist despite rehydration, you will need to consult a medical professional.

Verdict – Nope, Coffee Does Not Dehydrate You

The main concern with your caffeine intake will most likely be the sugar levels. The coffee consumption can, in truth, help add to your daily water intake. Your body is more than capable of absorbing the fluids you need and discarding the rest.

For your coffee intake to have a significant effect on your fluid output, you would need to consume at least 500 mg of it every day. This amounts to about 1.2 liters or 5 cups of coffee. However, if you still find yourself suffering from headaches after your coffee, it might not be from dehydration.

It is also likely that you are more sensitive to caffeine. Even if it is dehydration, it most likely has nothing to do with your coffee intake.


As far as hydration goes, coffee is a strange competitor. While it may not be the optimal choice, it adds to your total water consumption and does not dehydrate you. The effects of any substance are largely subjective. This means that a certain degree of self-experimentation will be needed for you to figure out what dosage works best for you.

The same curiosity goes with tea dehydration dubiety. So what is the answer? Find yourself here.