You couldn't live without your morning cup of coffee — or five. Am I right? It's what gets you out of bed in the morning, helps you shake off sleepiness and sharpens your mind so you can get stuff done.
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"Caffeine is a stimulant. For most people, consuming a reasonable amount will cause minimal side effects," says Sunitha Posina, MD, an internal medicine doctor in Stony Brook, New York. (A "reasonable amount," she says, is about one or two cups per day.)
That said, if you overdo it on the caffeine or are especially sensitive to it, you can experience uncomfortable mental and physical effects.
OK, if you're so hopped up and jittery on caffeine that you're struggling to hold your cup, then you probably know you're drinking too much. But there are other signs and symptoms of too much caffeine that you might not directly connect with your cup of joe.
1. Digestive Issues
Caffeine is a drug, and consuming too much for your body can overstimulate your central nervous system, leading to what's called caffeine intoxication. Symptoms include restlessness, nervousness, insomnia, irregular heartbeat and gastrointestinal distress, according to a March 2020 paper in the Journal of Caffeine and Adenosine Research.
What's more, "caffeine can trigger the production of gastrin, which increases the movement of your colon," Dr. Posina says. Not only might you have an upset stomach or nausea, but you might get diarrhea, too.
2. Irritability and Anxiety
Caffeine gives you that wake-up effect because it blocks adenosine, a chemical in your body that makes you feel tired, Dr. Posina explains.
If you're taking in too much caffeine or drinking it too late in the day, it can easily affect how well you sleep at night. Lack of sleep is a recipe for general crankiness during the day, but it can also fuel anxiety disorders, according to the Anxiety and Depression Association of America.
According to the U.S. Food & Drug Administration (FDA), you might also just generally feel unhappy when you drink too much java.
The funny thing about caffeine is that it's both a treatment for headaches and a cause of them.
You'll find caffeine added to headache and migraine meds, as it helps constrict blood vessels to ease head pain, per the National Headache Foundation.
However, headache is a common symptom of caffeine withdrawal. You might notice a headache after drinking more or less coffee than usual, or at different times than you're used to.
You expect that it'll perk you up, but drinking too much coffee can cause "rebound fatigue," Dr. Posina says.
"You feel really energized after drinking caffeine, but when the effects wear off, you have this rebound that leaves you much more tired. The only way to avoid it is to continue to drink coffee, but if you did that, you'd never sleep," she says.
Having "jitters" is the result of changing blood pressure and a rising heart rate, which can happen after consuming caffeine.
6. Flu-Like Symptoms
Drinking caffeine throughout the day can lead to caffeine withdrawal, which is a medical diagnosis that appears in the DSM-5 and refers to what happens to your body when it's coming off of a steady stream of caffeine. (The DSM-5 is a manual providing guidance on diagnosing mental disorders).
In addition to things you might expect, like irritability or headache, flu-like symptoms (think: nausea, muscle pain) can also occur.
So, How Much Caffeine Is Too Much?
The FDA recommends capping caffeine at 400 milligrams per day, which comes out to about four to five cups of home-brewed coffee. For reference, a tall (12-ounce) coffee at Starbucks contains 235 milligrams of caffeine. The amount of caffeine in your brand of coffee may vary.
If you notice that you're more sensitive to caffeine, though, you might want to stick with a lower amount. Dr. Posina recommends limiting caffeine to 250 milligrams per day to keep potential side effects to a minimum.
Some people might even feel that one cup per day is too much for them, she says. In that case, try a half-caff or a small latte (a single shot of espresso contains just 75 milligrams of caffeine).
Do You Have a Caffeine Problem?
If you're having symptoms of too much caffeine but are having trouble cutting back, you might have caffeine use disorder.
The Journal of Caffeine and Adenosine Research study noted above looked at more than 1,000 caffeine-consuming adults and found that 8 percent likely had the disorder.
If you're concerned about your caffeine intake or find it's having a negative effect on your health, talk to your doctor to strategize ways you can cut back.
- Encyclopedia of Psychopharmacology: “Caffeine Intoxication”
- Current Addiction Reports: “Caffeine Use Disorder: A Review of the Evidence and Future Implications”
- National Headache Foundation: “Does Caffeine Trigger or Treat Headaches?”
- American Psychiatric Association: “DSM-5: Frequently Asked Questions”
- Starbucks: “Pike Place Roast”
- Anxiety and Depression Association of America: “Sleep Disorders”
- U.S. Food & Drug Administration: “Spilling the Beans: How Much Caffeine is Too Much?”
- Starbucks: “Caffe Latte”
- Journal of Caffeine and Adenosine Research: “Prevalence and Correlates of Caffeine Use Disorder Symptoms Among a United States Sample”
Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.