wrecking ball with the word caffeine hitting on the word life

6 Negative Effects of Caffeine: What Are They and Why Are They Important to Know?

Do you have problems becoming fully alert in the morning without your coffee? I need caffeine in the morning to shake off my overnight sleepiness, and then I sometimes need some in the middle of the day because I start feeling tired. 

Lately, though, I’ve started wondering whether there are any negative effects of caffeine, and what those are. I began researching the benefits and drawbacks of caffeine, and I found some things that everyone should know. 

How Many People Consume Caffeine?

In the U.S., 80 to 90 percent of adults take caffeine in one form or another, usually via coffee or tea. Some people take caffeine pills either in place of coffee and tea or in addition to those drinks. If that sounds like a lot, consider that people consume even more caffeine in other countries like those in Scandinavia.

With so many people using so much caffeine, we all should know whether it’s really good for us to have so much of it in our systems. Unfortunately, the truth is that while caffeine does have some health benefits beyond the jolt of energy, it has some serious drawbacks, too.

The Negative Effects of Caffeine

What are the negative effects of caffeine? For a long time, I always thought of caffeine as a harmless substance. It’s certainly less harmful than drugs or alcohol and doesn’t cause diabetes the way too much sugar can. 

It’s not as harmless as we think, though. Science studies caffeine more than any other substance we take, and scientists have come to a widespread agreement about the negative effects of caffeine.

1. Anxiety and Agitation

Because caffeine is a stimulant, it can cause problems with anxiety and agitation. It blocks the production of a brain chemical that makes you feel tired, but it also increases adrenaline production. 

When you have too much caffeine, you start suffering from heightened agitation and anxiety due to the increased adrenaline. Your stress levels also rise, which adds to the problem. A small study found that men who took 300 mg of caffeine experienced significantly higher stress than those who took a placebo. 

If you consume too much caffeine, or you’re sensitive to it, you might also feel nervous and jittery, and you might notice that your hands shake. Feeling nervous, jittery, anxious, and agitated creates a recipe for unnecessary stress, which could make any stressful situations where you find yourself much worse.

2. Effects on Organs and Tissues

You may not notice, but caffeine does have some serious effects on your organs and tissues. Your heart, digestive system, muscles, bones, and more all see some impact from caffeine.

Main symptoms of Caffeine Overdose. Illustration about health check up diagram, negative effects of caffeine


One of the negative effects of caffeine is that you can get heart palpitations or even feel your heart begin to race. These things alone are probably nothing to worry about. However, if you have a heart condition, caffeine might be dangerous for you. You can develop an irregular heartbeat (arrhythmia) if you have an underlying condition.

There’s also evidence that caffeine can restrict blood flow to your heart, particularly during and after exercise. While this doesn’t make caffeine dangerous, per se, especially in moderate amounts, you should be aware of it.

If you experience anything like chest pain after drinking coffee, stop drinking it and contact your doctor.

Digestive System

You might have noticed that you experience more heartburn or nausea than usual if you have too much caffeine, or consume it when you aren’t used to it. I know I do. Caffeine increases the amount of acid in your stomach, which contributes to both heartburn and nausea. 

Also, extra caffeine goes straight to your liver and then your kidneys, increasing urination. Because of that, chronic dehydration is one of the negative effects of caffeine, especially if you consume large amounts of it. 

Can caffeine cause diarrhea, too? Yes, which will further dehydrate you. Indeed, one of the most significant negative effects of caffeine is dehydration.


Caffeine might be especially problematic for women, who are more susceptible to things like osteoporosis than men. There’s some evidence showing that high caffeine intake has a link to low calcium intake, and calcium intake is a significant factor in bone loss. 

However, there’s also a possibility that caffeine interferes with calcium absorption. Either way, you risk increased bone loss if you consume too much caffeine.

Brain Function

While caffeine does make you feel more alert for a time, too much can actually cause confusion. Anything that over stimulates your brain can lead to confusion and overall reduced mental function. 

a plastic brain on top of coffee beans

Can caffeine make you dizzy? Yes, but that’s usually a sign that you’ve ingested far more than your body can handle. 

None of this means you have to cut out your morning coffee unless you regularly experience these problems. You might just be more sensitive to caffeine than you thought, but you should see your doctor to ensure you don’t have other issues going on.

3. Problems with Sleeping

Insomnia is perhaps one of the most common negative effects of caffeine. If you have too much caffeine, it can and will affect your sleep.

The problem isn’t necessarily how easily you get to sleep, but rather, how long you stay asleep and your sleep quality. Many people drink a glass of wine or take a mild sedative before going to sleep, but they still have the stimulant in their system, affecting their ability to get truly restorative sleep.

You might not realize that caffeine affects your sleep this way. Even if your caffeine intake is low or moderate, you’ll have problems sleeping if you have it too late in the day. Caffeine can stay in your system for up to 24 hours, so if you regularly go to bed at 10 pm, even having one last cup of caffeinated coffee or tea in the afternoon can adversely affect your sleep.

If you consume too much caffeine regularly, you can wind up in a cycle of poor sleep and ever-increasing caffeine consumption to deal with the fatigue and other problems that poor sleep quality can cause.

Take it from someone who knows. I used to take caffeine pills to deal with fatigue every day. The more I took, the worse I slept, and the more tired I felt during the day. Eventually, I wound up in such a terrible cycle that I had to work with my doctor to bring my caffeine intake down and carefully monitor when I took it each day.

Here are some tips for a healthier sleep.

8 steps for healthy sleep. Medical, healthcare concept. Illustration of a cute girl in the bed.

4. Blood Pressure

If you don’t have blood pressure problems, you still might notice elevated blood pressure from your caffeine intake. Generally, the raised pressure is temporary, and it goes back down as the caffeine leaves your system. 

However, you might see a dramatic spike in your blood pressure, and there are several potential reasons for this. For instance, caffeine constricts your blood vessels, which will increase blood pressure. 

The fact that it increases your adrenaline may contribute to it as well. Since the effect is temporary, you probably won’t have a problem if your blood pressure is normal. 

If you already have high blood pressure, though, you should talk to your doctor about your caffeine intake. High blood pressure damages your arteries and increases your risk of heart attacks and strokes. Since caffeine will cause your blood pressure to spike, you might put yourself at unnecessary risk.

5. Tolerance and Addiction

Like many substances, we can easily develop an addiction to caffeine. Why? Because the longer you use caffeine, the more of it you feel you need for the same effect.

Caffeine works in a similar way to many other drugs. Sure, you feel more alert, feel good about things, have more energy, and even feel more sociable (which is a common effect of alcohol). 

While you might not develop what’s known as caffeine use disorder, you can still become dependent on it, including experiencing withdrawal symptoms. You might already know what some of those symptoms are, but you didn’t put them together with caffeine right away if you’re like me. These include:

  • Headaches
  • Fatigue
  • Irritability and poor overall mood
  • Feelings of fogginess
  • Problems concentrating

Interestingly enough, some of these symptoms also occur when you’ve had too much caffeine, including headaches, problems concentrating, and irritability.

6. Problems with Other Medication

Can you think of any people who aren’t taking some kind of medication regularly, whether it’s prescription or over-the-counter? You might experience some drug interactions with caffeine, whether your intake is excessive or not.

a pile of coffee beans and medication drugs and pills

For instance, if you’re taking an antidepressant like DULoxetine, your caffeine intake can increase the amount of the drug in your bloodstream, which then alters its effect on your condition. 

This is another area where you should check with your doctor, particularly if you’re getting new medication. Of course, your best bet is to always keep your doctor in the loop as to what medicines, supplements, and substances you regularly take so they know what possible interactions might occur.

How Much Is Too Much Caffeine?

I used to think there was no such thing as too much caffeine. Despite all the negative effects of caffeine, many of which I’ve experienced, and you may have as well, you might think caffeine is perfectly safe in any amount.

Unfortunately, that’s not true. Not many people consume so much caffeine that they end up in the hospital or just plain sick, but there is such a thing as too much.

The average adult ingests roughly 200 mg of caffeine daily. If you drink two five-ounce cups of your average, garden-variety coffee, or drink four 12-ounce colas each day, you’re getting approximately 200 mg of caffeine. 

Likewise, if you take a single caffeine pill, you’re getting 200 mg of caffeine.

However, many of us consume more than that. Unless you have health problems or take medication for which caffeine is bad, you can safely have up to about 400 mg per day. Keep in mind, though, that you might experience insomnia and disrupt the quality of the sleep you do get unless you have all of that early in the day.

Over 600 mg per day is probably too much for most people. At that point, you have too much in your system to eliminate before bedtime. You can also experience all the mental and physical problems that come with having too much of it. While caffeine affects everyone differently, you can reach a point at which too much is too much.

Why Do You Need to Know This?

We should all have as much information as possible about the effects the things we consume have on our bodies. Caffeine is not restricted, and it’s in so many foods and drinks that we tend to dismiss it. 

The truth is that nothing is perfectly safe, so we should also understand how these things might harm us. Since caffeine is a stimulant that affects our central nervous system, you should know potential caffeine hazards, including whether it will negatively interact with any of your medications and conditions, and more. 

You should also know when and if you should reduce your caffeine intake, or wean yourself off of it entirely.  

Does Caffeine Have Any Health Benefits?

The pros and cons of caffeine do not paint nearly as dire a picture as you might think. It does have some potential benefits, particularly if you consume it in coffee form. Coffee itself provides many benefits, caffeinated or otherwise. Besides improved alertness, here are some other benefits of caffeine.


Caffeine might give you some protection against dementia, particularly if you get it from drinking coffee. In adults 65 and older, many reported fewer symptoms when consuming between 250 and 300 mg of caffeine per day than those who only took 65 mg per day. 

You should keep in mind, though, that while you can attribute this to caffeine, it might also have to do with antioxidants or other nutrients found in coffee. It might be the combination of these things, too.

Improved Exercise

Many studies show that caffeine can improve muscle endurance and reduce fatigue during exercise. We’ve discussed many ways too much caffeine is bad for you. However, anywhere from 20 mg to 600 mg can help improve your ability to exercise.

Most of these studies involved high-performing athletes rather than regular people. Because of that, the effects of caffeine on your personal exercise may vary significantly from that in the studies. However, unless you’re consuming too much caffeine, it can’t hurt to see whether a jolt of caffeine before working out helps you.

Protection Against Certain Cancers

Observational work shows that caffeine may provide some protection against liver cancer, whether you suffer from liver disease or not. However, that, too, has to do with ingesting caffeine in coffee form. It’s entirely possible that caffeine, when combined with other nutrients found in coffee, work together to protect your liver from cancer regardless of your risk status.

Other Potential Benefits

Besides the above, there are other potential benefits, too: 

Weight Loss

If you’re trying to lose weight, caffeine might temporarily suppress your appetite, making it easier for you to avoid snacks that might sabotage your efforts. It might also stimulate your body’s ability to burn fat, which is your ultimate goal anyway.

Parkinson’s Disease

Your risk of Parkinson’s Disease may go down with caffeine intake as well. While these observations are tied more to coffee than caffeine, it still means your morning cup of coffee may give you some protection here and that the caffeine could play a role.

Cataracts and Other Eye Problems

You might know someone who’s had cataract surgery. Perhaps you’ve had cataract surgery yourself. Even if you have, caffeine might prevent further cataract development, and it might protect you against new ones. 

Also, there’s a condition dealing with eyelid spasms in which you blink incessantly and uncontrollably and wind up functionally blind because of it. Caffeine could protect you against this problem, too. 

Final Thoughts

I know how caffeine helps me wake up in the morning and stay alert during the day, and you know the same. And because we tend to assume caffeine is entirely safe, we don’t usually think of the side effects or potential long-term problems caffeine use may cause.

Generally, if you stay below 600 mg per day, you won’t experience most of the health issues caffeine can cause, unless you’re unusually sensitive to it. However, if you’re taking certain medications or have certain health conditions, then caffeine may not be the best thing for you.

Your best bet is to try and limit your caffeine intake to about 400 mg per day, and if you have any concerns, talk to your doctor. In fact, let your doctor know approximately how much caffeine you consume each day regardless of why you’re seeing them. It’ll help them head off any potential issues that could arise between your caffeine intake, your health, and your medicines.