A Healthy Man Suffered a Stroke and Permanent Damage After Drinking Eight Energy Drinks a Day, Doctors Warn

“Silent killer”: Blood pressure hit 254/150

At the clinic, doctors found his blood pressure was “sky high” — about 254/150 mm Hg — even though he looked well. Dr. Sunil Munshi, a consulting physician at Nottingham University Hospitals NHS Trust, said the reading is a reminder that hypertension can be symptomless until it becomes a crisis.

Normal adult blood pressure is under 120/80. A reading of 180/120 or higher is considered a medical crisis requiring immediate emergency care.

Scans showed the man had suffered a stroke in a deep part of the brain called the thalamus, which helped explain the unsteadiness and coordination issues. He was admitted to hospital, and clinicians used five different medications to bring his blood pressure down to around 170.

Doctors couldn’t find a cause — until one lifestyle detail emerged

After he returned home, his blood pressure climbed again — reaching about 220 despite multiple drugs. Munshi and his team ran extensive tests for weeks, but results were negative and they couldn’t identify a typical medical cause.

Then the man shared a key detail: to stay alert at work, he was consuming eight highly potent energy drinks every day — two cans at four different times during the day. The brand was not named in the report.

Each drink contained 160 mg of caffeine. That means he was taking in roughly 1,200–1,300 mg of caffeine daily — more than three times typical recommended adult limits.

How much caffeine is considered “too much”?

In the UK, guidance commonly cited for adults is around 400 mg of caffeine a day (roughly two to four cups of coffee, depending on strength). Study author Dr. Martha Coyle noted that the man’s intake was about triple that amount.

In the United States, the FDA also cites 400 mg per day as an amount not generally associated with negative effects for most healthy adults: FDA: How much caffeine is too much?.

Health Canada similarly recommends no more than 400 mg of caffeine daily for adults and publishes cautionary labelling guidance for caffeinated energy drinks: Health Canada: Cautionary labels on caffeinated energy drinks.

Why energy drinks may push blood pressure higher than caffeine alone

Doctors say the risk isn’t just caffeine quantity — it’s also the combination of stimulants and sugar. Munshi warned that energy drinks commonly include blood-pressure-boosting ingredients such as taurine, and that beverages containing caffeine plus taurine may raise blood pressure more than caffeine alone.

Many energy drinks also contain high levels of glucose (sugar). Clinicians noted that sugar is known to damage blood vessels in diabetes and can contribute to cardiovascular harm over time.

The report also discussed other commonly added ingredients, including ginseng (which can affect metabolism) and guarana (a plant stimulant thought to contain caffeine at higher concentrations than coffee beans), along with milder stimulants such as theophylline (found in cocoa) and theobromine (found in tea).

According to the clinicians, these combinations may contribute to issues such as cardiac arrhythmias, damage to the endothelium (the lining of blood vessels), and platelet aggregation. When platelets clump — particularly alongside high sugar — blood clots can form, which can raise stroke risk.

Doctors also cautioned that some people — especially younger users — may combine energy drinks with stimulants like cocaine or methylamphetamine, which can intensify cardiovascular strain and “cause havoc.”

Blood pressure normalized after stopping — but stroke damage remained

Just weeks after quitting energy drinks, the man’s blood pressure returned to normal levels. However, years later he still lives with the aftermath of his stroke.

In a patient statement included in the report, he said he was not aware of the danger and that he has been left with numbness affecting his left hand and fingers, foot and toes — even eight years after the incident.

Not an isolated event, doctors say

Munshi said medical literature contains multiple examples of potential harms linked to energy drinks, so the case should not be seen as a one-off. He noted other patients have developed atrial fibrillation (an irregular heartbeat), intracranial hemorrhage (bleeding in the brain), and strokes related to blood clots.

He argues clinicians should ask about energy drink consumption during routine checkups — particularly when people present at a younger age with cardiovascular problems or stroke-like symptoms — because the drinks have become “more potent” over time.

The authors also proposed increased regulation of energy drink sales and advertising, which they say is often targeted at younger people.

Read the medical case report

The case report was published in BMJ Case Reports. You can view details here: BMJ Case Reports: “Energy drinks, hypertension and stroke” (PDF available from BMJ site as well).