Briatney Portillo, the 20-year-old Bronx woman who suffered a heart attack recently after attempting the as-seen-on TikTok “dry-scooping” pre-workout ritual, only now knows why ingesting pre-workout powder without diluting it with water is so dangerous.

Pre-workout powders can increase endurance and energy during a workout if they contain appropriate ingredients and when taken properly. Most include amino acids, protein, caffeine, creatine, B vitamins and artificial sweeteners. Caffeine, as every coffee drinker knows, notably affects the heart when you’ve had one cup too many. A cup of coffee contains about 95 milligrams of caffeine. Some pre-workout powders contain extreme amounts, up to 500 milligrams per serving.

“When you ingest caffeine so quickly and such a large amount (in pre-workout powders), it can cause very dangerous, sudden rises in heart rate and blood pressure,” says Amanda Zaleski, an exercise physiologist with the Hartford HealthCare Heart & Vascular Institute’s Department of Preventive Cardiology. “This increases our risk of irregular heartbeats, otherwise known as arrhythmias. All of which increases our risk for a cardiovascular event like a heart attack or stroke.”

Portillo, in an interview with BuzzFeed, said she at first experienced chest pain, nausea and lightheadedness, then felt good enough to report to work. There, she said, “I started sweating a lot and was drenched . . . then my chest pain came back and this time it was more intense. The pain went to my back and to my left arm. My left arm went slightly limp, so I knew those were symptoms of a heart attack. I called 911 and the ambulance came.”

Portillo was lucky. Doctors told her she had suffered an NSTEMI — or non-ST segment elevation myocardial infarction — which is less damaging to the heart than a typical heart attack, known as a STEMI. The difference: The artery is partially blocked in an NSTEMI and fully blocked in a STEMI.

Zaleski cautions users that pre-workout supplements are not regulated by the Food and Drug Administration.

“So this means these powders could potentially be laced with banned substances like stimulants, steroids or other toxic ingredients,” she says. “You’re dealing with some serious ingredients. It goes right to the bloodstream if you’re not going to dilute it with water.”