Energy drinks can raise your blood pressure, disrupt your sleep, damage your teeth, and spike your anxiety, among other problems. A single 16-ounce can often packs 200 to 300 milligrams of caffeine (the FDA recommends no more than 400 mg per day for adults) plus roughly 40 grams of sugar. Here are ten specific ways that combination can affect your body.
1. Blood Pressure Spikes
Energy drinks raise blood pressure more than caffeine alone would explain. In a randomized trial published in the Journal of the American Heart Association, participants who consumed energy drinks saw their systolic blood pressure (the top number) jump by about 16 mmHg, compared to roughly 10 mmHg for a placebo with the same amount of caffeine. Diastolic pressure rose by nearly 10 mmHg. Those increases are significant enough to matter if you already have elevated blood pressure or an underlying heart condition, and the effect persists for several hours after a single drink.
2. Sleep Disruption
The caffeine in energy drinks has a half-life of about five to six hours, meaning half of it is still circulating in your bloodstream long after you finish the can. Research on college students found that energy drink consumers were nearly twice as likely to report short sleep duration compared to non-consumers. They were also 81 percent more likely to score poorly on standardized sleep quality measures and 53 percent more likely to experience daytime dysfunction from sleep loss. Even a single afternoon energy drink can delay the time it takes you to fall asleep and reduce total sleep time in a dose-dependent pattern: the more caffeine, the worse the effect.
3. Anxiety and Jitteriness
Caffeine stimulates your nervous system by blocking the brain chemical that makes you feel sleepy. At higher doses, that stimulation crosses over into anxiety. A large study of Korean adolescents found that those who consumed energy drinks excessively were 14 to 19 percent more likely to experience elevated anxiety overall. The link grew stronger as anxiety severity increased. Among males, the likelihood of severe anxiety was 93 percent higher in heavy consumers; among females, 62 percent higher. Even in adults, doses above 200 mg of caffeine can trigger a racing heart, restlessness, and the classic “wired but uncomfortable” feeling that mimics a panic response.
4. Tooth Enamel Erosion
Energy drinks are highly acidic, with pH levels ranging from 2.6 to 3.7. For reference, water is neutral at 7.0 and stomach acid sits around 1.5 to 3.5. That acidity attacks tooth enamel on contact. In laboratory testing, teeth soaked in popular energy drinks lost measurable enamel volume, with some brands causing more than twice the erosion of others. Unlike cavities, enamel erosion is irreversible. Your body cannot regrow enamel once it’s gone, leaving teeth more sensitive and more vulnerable to decay over time. Sipping slowly throughout the day, as many people do, extends the acid exposure and makes the problem worse.
5. Digestive Problems
The combination of caffeine, carbonation, and acidity in energy drinks can trigger your stomach to produce excess acid. This can cause heartburn, bloating, and nausea, especially on an empty stomach. For people prone to acid reflux, caffeine also relaxes the muscular valve between the esophagus and stomach, allowing acid to travel upward. Regular consumption can worsen existing reflux symptoms or create new ones.
6. Weight Gain and Blood Sugar Issues
A typical energy drink contains about 41 grams of sugar in a 12-ounce serving, slightly more than a cola. Larger 16- or 24-ounce cans can pack 55 to 80 grams. That sugar load hits your bloodstream quickly, causing a sharp spike in blood glucose followed by a crash. Over time, repeatedly flooding your system with that much sugar can promote insulin resistance, the precursor to type 2 diabetes. The high glycemic load of sweetened energy drinks can also contribute to weight gain, particularly when consumed daily as a habit rather than an occasional treat.
7. Kidney Stone Risk
Energy drinks create a perfect storm for kidney stones through several mechanisms working at once. Caffeine acts as a diuretic, promoting urination and potentially leading to dehydration. When you’re dehydrated, the concentration of stone-forming compounds like oxalate and uric acid rises in your urine. Sugar compounds the problem: fructose independently raises uric acid levels, and when urine pH drops below 5.5, uric acid crystals can bind together into stones. Sodium in energy drinks forces your kidneys to excrete more calcium, increasing the odds of calcium-based stones. Even the artificial sweeteners in sugar-free versions can raise oxalate levels in urine, so switching to “zero sugar” varieties doesn’t eliminate this risk.
8. Risks to Adolescent Brain Development
The teenage brain is still under construction, with the prefrontal cortex (the area responsible for decision-making, impulse control, and planning) among the last regions to fully mature. Researchers have raised concerns that regular caffeine exposure during this critical window could alter normal brain development. Animal studies show that caffeine exposure during equivalent developmental periods produces long-lasting changes in brain function. The American Academy of Pediatrics advises against energy drinks for children and teens entirely, citing both the caffeine and sugar content as concerns. Despite this, energy drinks are heavily marketed to young people, and consumption in this age group continues to rise.
9. Dangerous Interactions With Alcohol
About one in five college students report mixing alcohol with energy drinks in a given year, and the combination is riskier than either substance alone. Caffeine masks the sedating effects of alcohol, making you feel more alert and less drunk than you actually are. You don’t sober up; you just lose the internal cues that would normally tell you to stop drinking. The CDC reports that people who mix alcohol with energy drinks are more likely to binge drink, drive while impaired, sustain injuries, and engage in unprotected sex compared to those who drink alcohol without caffeine.
10. Emergency Room Visits
The consequences of energy drink overconsumption show up in emergency departments. SAMHSA tracked energy drink-related ER visits and found they doubled from roughly 10,000 in 2007 to nearly 21,000 in 2011. The most common complaints include heart palpitations, chest pain, seizures, and severe anxiety. These visits disproportionately involve young adults and people who consumed multiple cans in a short period or combined energy drinks with other stimulants or alcohol. Unlike coffee, which most people sip gradually, energy drinks are often consumed quickly, delivering a large caffeine dose in minutes rather than over the course of an hour.
How Much Is Too Much
The FDA considers 400 milligrams of caffeine per day a reasonable upper limit for most healthy adults. A single energy drink can contain 150 to 300 mg depending on the brand and size, so two cans can push you past that threshold before you factor in any coffee, tea, or chocolate you’ve also consumed. There is no established safe caffeine level for children. The practical takeaway is straightforward: if you’re drinking energy drinks daily, you’re likely exceeding recommended caffeine intake and consuming significant amounts of sugar or artificial sweeteners alongside it. The effects described above don’t require years of heavy use to appear. Many of them, from blood pressure changes to sleep disruption to digestive discomfort, can start with a single can.