A British man (54) who was a non-smoking, non-drinking avid runner, was left with permanent damage after a stroke, a result of consuming numerous energy drinks every day to stay alert for his job as a warehouse worker, reports CNN.
The senior author of a case report about him says that when the patient, who was super fit, suddenly experienced left-sided weakness, numbness and difficulties with balance, walking, swallowing and speech, a relative had immediately taken him to a nearby stroke clinic.
“His blood pressure was sky high – about 254 over 150 millimetres – yet when you looked at him you would never know it, because he looked so well. That’s why we call hypertension the silent killer,” said Dr Sunil Munshi, a consulting physician at Nottingham University Hospitals NHS Trust in the United Kingdom.
The paper was published last week in the journal BMJ Case Reports.
Normal blood pressure for adults is less than 120 over 80 mm HG (millimetres of mercury). BP of 180 over 120 or higher is considered a medical crisis that requires immediate emergency care.
“His left side was numb, and scans showed he’d had a stroke in the deeper part of the brain, the thalamus, which explains the unsteadiness,” Munshi said. “He was admitted, and we treated him with five different medications until his blood pressure dropped to 170.”
Back at home again, the man’s blood pressure continued to climb, reaching 220 despite numerous drugs. Munshi and his team searched for answers for weeks, running extensive tests that turned up negative. Then one day the man told Munshi about his energy drink habit.
“Each day he consumed eight highly potent energy drinks to stay alert for his job – two cans at four different times during the day,” the physician said. (The brand name was withheld from the study.)
“Each of the drinks contained 160 milligrams of caffeine. Suddenly the diagnosis was clear.”
Some energy drinks can have up to 500 milligrams of caffeine, compared with 30 milligrams in tea and 90 milligrams in coffee, said study first author Dr Martha Coyle, a resident doctor at Nottingham University Hospitals NHS Trust.
“In the UK, guidelines suggest 400 milligrams of caffeine a day, between two and four cups,” Coyle said. “This gentleman was consuming 1 200 to 1 300 milligrams, three times the amount.”
Just weeks after stopping his consumption of the energy drink, the man’s BP returned to normal. Today, years after the incident, he is healthy but still lives with the aftermath of his stroke.
“I obviously wasn’t aware of the dangers of energy drinks,” he told his doctors. “I have been left with numbness in my left hand and fingers, foot and toes even after eight years.”
Combinations of ingredients ‘cause havoc’
It’s not just high levels of caffeine. Today’s energy drinks also contain blood pressure-boosting ingredients such as the amino acid taurine, Munshi said.
“Energy drinks that contain caffeine plus taurine produce significantly higher blood pressure than caffeine alone,” he said. “They also contain high levels of glucose – we know sugar damages the blood vessels in diabetes, which leads to heart damage.”
Typically, they also contain ginseng, which affects metabolism, and guarana, a plant thought to contain caffeine at twice the concentration of a coffee bean, according to the study.
Milder stimulants such as theophylline, found in cocoa, and theobromine, found in tea, are often included as well, Coyle said.
Such energy drinks can cause cardiac arrhythmias, damage the endothelium, the tissue that lines blood vessels, and aggregate blood platelets, Munshi said.
“When platelets are aggregated, especially in the setting of high glucose, they can produce blood clots,” he said. “Young people are often willing to try energy drinks, especially in combination with other drugs like cocaine or methylamphetamine, which have similar effects, and all of these drugs together can cause havoc.”
Medical literature is full of examples of the harms of energy drinks, so this case, while startling, is not an isolated event, Munshi said.
“We have seen other patients who developed an irregular heartbeat (atrial fibrillation),” he said.” Another patient developed an intracellular haemorrhage in the brain, while yet another had a stroke in the brain due to a blood clot.”
Munshi believes doctors should become more aware of the impact of energy drinks and ask about use during regular check-ups, “especially when people come at a younger age with cardiovascular problems or strokes”.
Study details
Energy drinks, hypertension and stroke
Martha Coyle and Sunil Munshi.
Published in BMJ Case Reports on 9 December 2025
Abstract
A man in his 50s, normally fit and well, had an ischaemic thalamic stroke confirmed on MRI, manifesting with left-sided weakness, numbness and ataxia. Admission BP was 254/150 mm Hg. All tests for secondary hypertension were normal. After 72 hours as an inpatient, starting antihypertensives reduced the systolic BP to 170 mm Hg; however, after discharge, his BP rose again and remained persistently high despite up-titration of antihypertensives to five medications. After further questioning, the patient revealed an average daily consumption of eight cans of energy drink, each containing 160 mg caffeine, a habit which had not been specifically asked about during admission. On cessation of this consumption, his BP normalised and antihypertensives were successfully withdrawn. This article explores what we can learn from this case about whether energy drink consumption could be a risk factor for stroke and cardiovascular disease, and therefore the importance of targeted questioning in clinical practice, and greater public awareness.
BMJ Case Reports article – Energy drinks, hypertension and stroke (Open access)
See more from MedicalBrief archives:
‘Robust’ link between insomnia and energy drinks – Norwegian study
Caffeine levels in energy drinks spark calls for ban
Serious health risks to energy drinks — Harvard study
Energy drinks notably diminish blood vessel function in young adults