The Hidden Health Risk Lurking in Your Energy Drink

A new case study links excessive energy drinks with stroke.

December 11, 2025

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It seems innocent enough to sip on an energy drink when you’re feeling wiped. But a surprising new case study just linked the common habit to stroke.

There’s a major caveat of this BMJ Case Reports paper to point out upfront—namely that the patient regularly tossed back eight energy drinks a day. Still, it probably didn’t occur to him that this habit could give him a stroke.

But the findings are raising all kinds of questions about the link between energy drinks and stroke, and if your health might be at risk if you sip one of these a day. With that in mind, we tapped a neurologist, cardiologist, and toxicologist to break down how energy drinks can lead to a stroke, plus the safest way to approach these drinks going forward.

The case report starts out as a medical mystery.

As the report explains, the patient was a “normally fit and well” man in his 50s who went to the hospital after developing weakness on his left side, numbness, and clumsiness. An MRI confirmed that he suffered an ischemic stroke, which happens when a blood clot blocks an artery that supplies oxygen and nutrients to the brain.

His blood pressure was sky-high when he was admitted—254/150 mm Hg. Normal blood pressure is considered less than 120/80 mm Hg; anything higher than 180/120 mm Hg is a hypertensive emergency, according to the American Heart Association (AHA), and he was well above that.

The man spent 72 hours in the hospital, where doctors were able to get his blood pressure down. But after he was released, his blood pressure shot back up and stayed high, even after doctors put him on five different medications. It wasn’t until the man was questioned about his diet that doctors discovered that he regularly drank eight cans of energy drinks, which contained 160 milligrams of caffeine each. Once he stopped having those drinks, his blood pressure normalized and he was able to get off the medications.

The case report co-authors stressed that the findings raise the need for greater public awareness that you can, in fact, have a stroke from energy drinks.

How can energy drinks lead to a stroke?

The caffeine in these drinks is definitely a factor, Carolyn A. Cronin, MD, PhD, division chief of vascular neurology at Vanderbilt University Medical Center, tells SELF. “Energy drinks contain high doses of caffeine, and sometimes other agents [like taurine] as well, that can increase blood pressure,” she explains. “Elevated blood pressure causes damage to blood vessels throughout the body, but the brain is particularly susceptible.”

That higher blood pressure can cause changes in the lining of small arteries in the brain, according to Dr. Cronin. “This can lead to thickening in some spots and thinning in others, which in turn can put people at risk for both blockages (ischemic strokes) and bleeding (hemorrhagic strokes),” she says.

But caffeine isn’t the only issue. "Energy drinks often contain large amounts of glucose—sugar—which is believed to be a risk factor for blood vessel damage and blood clotting disorders that may also increase the risk of stroke," Kelly Johnson-Arbor, MD, a toxicologist at MedStar Health, tells SELF. "Sugar-free energy drinks are not necessarily healthier or safer, as some studies have shown that the blood-clotting risk is heightened even after consumption of sugar-free energy drinks."

These strokes can come on fast too. “They can cause pretty sharp spikes in your blood pressure, elevations of your heart rate, and can constrict blood flow to the brain,” Kevin Shah, MD, cardiologist and program director of heart failure outreach at MemorialCare Heart & Vascular Institute at Long Beach Medical Center in Long Beach, CA, tells SELF. “All of this can create a perfect storm that can put people at risk for a stroke.”

When you do the math, this patient was downing 1,280 milligrams of caffeine a day. “That is well over the recommended amount of caffeine per day,” Jamie K. Alan, PhD, an associate professor of pharmacology and toxicology at Michigan State University, tells SELF. (The Food and Drug Administration recommends having no more than 400 milligrams of caffeine a day.)

Something else to consider, per Dr. Cronin: Elevated blood pressure usually doesn’t cause any symptoms, so this can creep up on you. “People may not know that it is happening and that this damage is being done to their blood vessels until something severe like a stroke happens,” she says.

What this suggests about your energy drink use going forward

Every person’s caffeine tolerance is different, making it hard to give blanket recommendations around how many energy drinks are okay to have a day. “The dose that is safe for one person may be too much for another, depending on their baseline blood pressure, genetics, and other medical conditions,” Dr. Cronin says. “As with most things in life, moderation is key.” Meaning, an energy drink a day is unlikely to give you a stroke, but having nearly a case on a daily basis is pushing it.

If you want a safe baseline to follow, Dr. Alan suggests aiming to have 200 milligrams of caffeine a day or less. “Some people may need to consume less because of other conditions like hypertension, so make sure you talk to your healthcare provider for an individual recommendation,” she says. “Some people might be just fine consuming slightly more.” (Again, the FDA says most people are generally okay to have up to 400 milligrams of caffeine a day.) Something else to consider: Some energy drinks contain a lot of added sugar, which can raise your risk of developing type 2 diabetes and other health issues.

While you’re giving your energy drink consumption a second look, Dr. Cronin also recommends getting your blood pressure checked here and there, along with basic lab tests, even if you’re otherwise healthy. (These are usually done at annual physical exams.) “It is not uncommon for patients to present with stroke and report that they have no medical conditions and take no medications, but have not seen a doctor for many years,” Dr. Cronin says.

But if you enjoy energy drinks, Dr. Shah says it’s okay to have them in moderation—the odd can is unlikely to give you a stroke. “But some people have underlying health risks and higher amounts of energy drinks could certainly put them at risk for a stroke,” he says. So sticking to a can a day or less is really the safest way to go.