9 Surprising Side Effects of Too Much Caffeine

How much caffeine should you be drinking? You’ve probably heard that it’s bad for you to drink too much coffee, but how bad can it really be? If you’re like most people, you probably want to know all the details, from how much is too much to what could happen if you do drink too much caffeine. To answer all of your questions about caffeine side effects, read this article to find out exactly what happens when you consume too much of this popular stimulant in your coffee or tea every day.

1) High blood pressure

Any substance that can increase your heart rate or blood pressure is going to put you at risk for an elevated blood pressure. If you’re worried about high blood pressure, consider cutting back on caffeine. Interestingly, one study showed that decaf coffee (which has about 3mg per cup) may still have some health benefits; so perhaps a small amount of regular coffee isn’t all bad either. Just don’t overdo it!

2) Paranoia

More than half of people who consume 400 to 600 mg of caffeine daily, or roughly three to five cups of coffee, report feeling jittery at some point. While that may be tolerable for some coffee lovers, a 2005 study in The Journal of Clinical Psychiatry showed that consuming as little as 300 mg of caffeine (about two cups) could trigger manic symptoms in individuals with bipolar disorder—and that doesn’t even take into account how stress can exacerbate your anxiety.

3) Insomnia

Caffeine’s energizing effect makes it easy to fall asleep and stay asleep, which may make you think that drinking coffee makes for a good sleep aid. But if you overdo it, your caffeine tolerance will go up, making it increasingly difficult to fall or stay asleep. Some studies have shown that consuming more than 400 milligrams of caffeine can result in insomnia.

4) Headaches

Aside from fatigue, headaches are perhaps one of caffeine’s most well-known side effects. If you start experiencing headaches after consuming a lot of caffeine, make sure to cut back on how much you’re taking in. Not only will it reduce your risk for headaches, but cutting back may also help you lose weight and boost your mood.

5) Insulin resistance

Excessive caffeine consumption can lead to insulin resistance, a precursor to diabetes and obesity. Once you develop insulin resistance, your body becomes less sensitive to insulin, requiring more and more in order to lower blood sugar levels. In some cases, even high levels of caffeine aren’t enough. If you suffer from or are at risk for type 2 diabetes or metabolic syndrome, reducing your intake of coffee and other caffeinated beverages may be necessary for better health.

6) Poor memory and learning

A number of studies on humans have shown that high doses of caffeine may reduce cognitive function, especially verbal memory. One study even suggested that those who regularly consume more than 500 milligrams (mg) a day—about five cups of coffee—have lower brain volume.

7) Depression

High doses of caffeine have been linked to depression. A 2013 study found that people who drank more than four cups of coffee a day were more likely to experience depression, anxiety, and fatigue. While it’s too early to say definitively why there’s a link between high-caffeine intake and mental health problems, some researchers suggest that caffeine can actually prevent restful sleep and contribute to feelings of depression.

8) Negative moods

There are a few studies that suggest that caffeine can negatively impact our mood and emotional well-being. While it's not clear whether or not caffeine is solely responsible for these feelings, a recent study found that drinking caffeinated coffee resulted in lower levels of positive emotions, such as happiness and life satisfaction. On top of that, some researchers have linked higher consumption to anxiety disorders.

9) Heart palpitations

Caffeine is a stimulant, so consuming too much can be dangerous for your heart. For example, in a 2010 study published in Journal of American Heart Association researchers found that consuming as little as 500 mg — just over one cup — could lead to arrhythmias (irregular heartbeats). So whether you drink coffee every day or carry around an energy drink with you everywhere you go, overdoing it on caffeine can have serious consequences.