Heart experts have issued an urgent warning to millions of Americans who use weight-loss injections after the sudden death of an apparently healthy 19-year-old was linked to the medication.
Speaking to the Daily Mail, doctors are calling for patients offered the blockbuster drugs to be screened for underlying heart conditions that could increase the risks associated with the injections.
Of particular interest are myocardial bridging and long QT syndrome – two often silent but common cardiac abnormalities.
Both can go completely unnoticed for years, causing few obvious symptoms, meaning patients may have no idea they are affected until they undergo a heart test.
But experts warn that when these conditions are combined with serious side effects Weight loss medications – especially persistent vomiting, which can cause dehydration and dangerous disturbances in the body’s electrolytes – can put vulnerable patients at risk of a potentially fatal abnormal heart rhythm and sudden cardiac arrest.
Doctors are now calling for better screening of patients before they are prescribed the drugs and for warning labels to be updated to alert doctors to the potential danger.
It follows the death of a law student Josephine Nasr, 19, who died alone in her London dormitory in September 2025 after taking tirzepatide – the drug found in Mounjaro and Zepbound.
It is part of a wave of new weight-loss drugs, including semaglutide, sold under brand names such as Ozempic and Wegovy, that have transformed the treatment of obesity.
Josephine Nasr, 19, was a law student who died after taking a weight-loss drug that she did not medically need. An inquest in London ruled that vomiting from the drug depleted her electrolytes, causing a fatal arrhythmia, exacerbated by an undiagnosed heart condition
Collectively, they are known as GLP-1 drugs because they mimic GLP-1, a naturally occurring gut hormone that helps control blood sugar levels and appetite.
Josephine, a California native, had been prescribed a generic form of tirzepatide, not a branded version, after a telehealth consultation, despite being only slightly overweight and not obese.
An inquest ruled that vomiting induced by the medication caused a severe electrolyte imbalance which, combined with undiagnosed myocardial bridging, led to fatal cardiac arrest.
Josephine had no idea she had the heart defect, which was only discovered after her death.
Dr. Michael Aziz, an internist at Lenox Hill Hospital in New York City, said, “Patients with underlying heart conditions may be particularly vulnerable if they experience severe vomiting while taking the medications.”
Vomiting can cause levels of crucial electrolytes such as potassium and magnesium to drop, which in turn can disrupt the electrical signals that keep the heart beating normally.
While this can happen to anyone who becomes severely dehydrated, Dr. Aziz said the consequences can be much more dangerous in someone whose heart is already prone to abnormal rhythms.
“The risk is much higher for people with heart disease,” he told the Daily Mail.
He said patients with myocardial bridging or long QT syndrome were among those of particular concern and called for the potential danger to be reflected in the drugs’ warning labels.
“I think the FDA should have a labeling update on this,” he added.
Dr. James Chao, a board-certified surgeon, said heart risk is a concern and patients starting weight-loss injections should have basic heart and blood tests before starting treatment.
He said this should include an electrocardiogram, or ECG, which records the heart’s electrical activity and can flag abnormalities, including long QT syndrome and other heart rhythm problems.
Patients should also undergo a basic metabolic panel, he said: a routine blood test that measures levels of substances including potassium and other electrolytes that are crucial for maintaining a normal heart rate.
“Tack on a paragraph, then propose a basic ECG and a basic metabolic panel and you change medications at almost no cost to the system,” Dr. Chao told the Daily Mail.
Currently, neither myocardial bridging nor long QT syndrome is listed by the FDA as a contraindication to any major GLP-1 medications.
In fact, the only formal contraindications to tirzepatide are a personal or family history of a rare form of thyroid cancer called medullary thyroid carcinoma, a related condition called multiple endocrine neoplasia syndrome type 2, or a previous severe allergic reaction to tirzepatide or its ingredients.
The FDA-approved label does warn that tirzepatide can cause serious gastrointestinal problems and that vomiting and diarrhea can lead to dehydration and possibly serious kidney problems.
Josephine was prescribed the drug despite being only moderately overweight, not obese, and having no known health problems. Her hidden heart defect would only be discovered after her death
But it does not specifically warn that severe vomiting and the resulting loss of electrolytes may pose a particular danger to people vulnerable to abnormal heart rhythms.
Myocardial bypass is a birth defect in which part of a coronary artery – one of the blood vessels that supply blood to the heart – tunnels through the heart muscle instead of running along its surface.
It’s surprisingly common. Studies using detailed imaging suggest that some degree of myocardial bridging may be present in as many as one in three adults, representing tens of millions of Americans.
For most people it is harmless and never causes symptoms. In fact, a standard ECG will often appear normal in someone with the condition.
“The majority of people who have it will go through life without knowing they have it or ever getting tested,” Chao said.
But in a small proportion of patients, the heart muscle surrounding the artery can squeeze it as the heart contracts, restricting blood flow. The condition has been associated with dangerous cardiac arrhythmias and, in rare cases, sudden cardiac death.
Long QT syndrome, meanwhile, is a disorder of the heart’s electrical system that is thought to affect about one in 2,500 people, or about 135,000 Americans.
The condition causes the heart to take longer than normal to electrically reset itself between beats, leaving some patients vulnerable to unsynchronized heart rhythms called torsades de pointes, which can cause fainting, cardiac arrest or sudden death.
As with myocardial bridging, patients may appear completely healthy.
But in someone already vulnerable to dangerous cardiac arrhythmias, experts fear that a severe electrolyte depletion could trigger a medical emergency.
Josephine’s death has also shed light on another growing problem: the use of powerful weight-loss drugs by people who are not obese.
Tirzepatide is approved for weight loss in adults with a BMI of 30 or higher, or in people with a BMI of at least 27 who also have a weight-related health condition, such as high blood pressure or type 2 diabetes.
But the rapid growth of online prescribing has made GLP-1 drugs increasingly accessible to people looking to lose relatively small amounts of weight — including some who would not have qualified for the large trials used to determine the drugs’ safety and effectiveness.
This is important because much of what doctors know about the side effects of these medications comes from studies of people who are obese, or overweight and have related health problems.
For example, in the landmark SURMOUNT-1 study of tirzepatide, participants had an average BMI of about 38 at the start of the study. Nearly all were obese and none were of normal weight.
The study found that tirzepatide is effective for weight loss, but critics point to several limitations: the study lasted only 72 weeks, did not track what happened after patients stopped taking the drug, and excluded people with type 2 diabetes.
Yet gastrointestinal problems were already common. About one in three patients experienced nausea, while about one in five had diarrhea and about one in eight vomited, depending on the dose.
There is also evidence that body weight may influence exposure to tirzepatide, with lighter patients experiencing higher concentrations of the drug than heavier patients receiving the same dose.
Dr. James Chao said this can be especially important if a patient develops persistent vomiting.
Smaller people generally have less body water, meaning that the same amount of fluid lost through vomiting may represent a greater portion of the body’s reserves.
“Lighter users just get exhausted faster,” he told the Daily Mail.
The resulting dehydration can disrupt levels of electrolytes such as potassium and magnesium, which are essential for maintaining the heart’s normal electrical rhythm.
At the same time, the calculation of benefits and risks becomes more difficult to justify as patients move further away from the population for which the drugs are intended.
In obese patients, tirzepatide can cause significant weight loss and reduce the risk of serious obesity-related diseases. But there is much less evidence showing these benefits in normal-weight people who just want to get thinner.
Dr. Chao added: ‘If someone is obese, losing weight can provide enormous health benefits, which may justify accepting a very small risk of a serious complication.
“But if you’re already at a healthy weight, those benefits largely disappear, while the potential risks of taking the drug don’t disappear.”
Josephine’s case illustrates the concern. Despite not being obese, she had been prescribed tirzepatide in California in the summer of 2025, before returning to London for her second year at university.
Just a week after returning to Britain she contacted her family to say she was experiencing nausea and vomiting. Her sister attempted to arrange medical attention and when she could no longer reach her, a welfare check was requested.
Josephine was later found collapsed on the bathroom floor of her university building, with an empty bottle of the weight-loss drug nearby.
Dr. Chao believes her death could ultimately force online providers to implement stricter controls before dispensing the drugs.
“I have no doubt that telehealth platforms will be forced to adopt this by default, whether they like it or not.”
