Terrifying heart risks of weight-loss drugs taken by millions of Americans: Experts reveal little-known fatal side effect after death of 19-year-old student

An urgent warning to millions of Americans using weight-loss injections has been issued by heart experts after the sudden death of a seemingly healthy 19-year-old was linked to the medication.

Speaking to the Daily Mail, physicians are calling for patients offered the blockbuster drugs to be screened for underlying heart conditions that could cause the risks associated with the shots to spiral.

Of particular concern are myocardial bridging and long QT syndrome – two often-silent, yet common heart abnormalities.

Both can go completely unnoticed for years, causing few obvious symptoms, meaning patients may have no idea they are affected until they undergo cardiac testing.

But experts warn that when these conditions are combined with severe side effects from weight-loss drugs – particularly persistent vomiting, which can cause dehydration and dangerous disturbances in the body’s electrolytes – vulnerable patients may be 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 physicians to the potential danger.

It follows the death of law student Josephine Nasr, 19, who died alone in her London dorm room in September 2025 after taking tirzepatide.

The California native had been prescribed the drug following a telehealth consultation, despite being only slightly overweight, not obese.

An inquest ruled that vomiting triggered by the medication caused a severe electrolyte imbalance which, combined with undiagnosed myocardial bridging, led to a fatal cardiac arrest.

Nasr had no idea she had the heart abnormality, which was only discovered after her death.

Dr Michael Aziz, an internal medicine physician at Lenox Hill Hospital in New York City, said: ‘Patients with underlying heart conditions may be particularly vulnerable if they suffer severe vomiting while taking the drugs.’

Vomiting can cause levels of crucial electrolytes such as potassium and magnesium to plummet, 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 could be far more dangerous in someone whose heart is already susceptible to abnormal rhythms.

‘The risk is very much higher for people with a cardiac condition,’ 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 that,’ he added.

Dr James Chao, a board-certified surgeon, said the heart risk was a ‘worry’ and that patients starting weight loss shots should be required to undergo basic cardiac and blood testing 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 to maintaining a normal heartbeat.

‘Tack on a paragraph, then suggest a baseline ECG and basic metabolic panel and you change medicine for almost zero 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 for any major GLP-1 weight-loss medication.

In fact, tirzepatide’s only formal contraindications are a personal or family history of a rare type of thyroid cancer called medullary thyroid carcinoma, a related condition called multiple endocrine neoplasia syndrome type 2, or a previous serious allergic reaction to tirzepatide or its ingredients.

The FDA-approved label does warn that tirzepatide can cause severe gastrointestinal problems and that vomiting and diarrhea can lead to dehydration and potentially serious kidney problems.

But it does not specifically warn that severe vomiting and the resulting loss of electrolytes could pose a particular danger to people vulnerable to abnormal heart rhythms.

Myocardial bridging is a congenital abnormality in which part of a coronary artery – one of the blood vessels supplying the heart – tunnels through heart muscle instead of running along its surface.

It is surprisingly common. Studies using detailed imaging suggest some degree of myocardial bridging may be present in as many as one in three adults, which would equate to 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 individuals who have it will pass through life without knowing they have it or ever being 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 linked to dangerous heart rhythm disturbances and, rarely, sudden cardiac death.

Long QT syndrome, meanwhile, is a disorder of the heart’s electrical system thought to affect around one in 2,500 people, or roughly 135,000 Americans.

The condition causes the heart to take longer than normal to electrically reset itself between beats, leaving some patients vulnerable to out-of-sync heart rhythms called torsades de pointes, which can cause fainting, cardiac arrest or sudden death.

As with myocardial bridging, patients can appear completely healthy.

But in someone already vulnerable to dangerous arrhythmias, experts fear that severe electrolyte depletion could trigger a medical emergency.

Nasr’s death has also shone a light on another growing concern: 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 above, or those 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 wanting to lose relatively small amounts of weight – including some who would not have qualified for the major trials used to establish the drugs’ safety and effectiveness.

This matters because much of what doctors know about the side effects of these medications comes from studies involving people with obesity, or those who were overweight and had related health problems.

In the landmark SURMOUNT-1 trial of tirzepatide, for example, participants had an average BMI of around 38 at the start of the study. Nearly all were obese and none were normal weight.

The trial showed tirzepatide is effective for weight loss, but critics point to several limitations: the study ran for just 72 weeks, it didn’t track what happened after patients stopped the drug, and it excluded people with type 2 diabetes.

Yet gastrointestinal problems were already common. Around one in three patients experienced nausea, while diarrhea affected roughly one in five and vomiting up to around one in eight, depending on the dose.

There is also evidence that body weight can influence exposure to tirzepatide, with lighter patients experiencing higher concentrations of the drug than heavier patients given the same dose.

Dr James Chao said this could be particularly important when a patient develops persistent vomiting.

Smaller people generally have less total body water, meaning the same amount of fluid lost through vomiting can represent a greater proportion of their body’s reserves.

‘Lighter users are just quicker to deplete,’ he told the Daily Mail.

The resulting dehydration can disturb levels of electrolytes such as potassium and magnesium, which are essential to maintaining the heart’s normal electrical rhythm.

At the same time, the benefit-risk calculation becomes harder to justify as patients move further away from the population the drugs were designed to treat.

For patients with obesity, tirzepatide can produce substantial weight loss and reduce the risk of serious obesity-related disease. But there is far less evidence demonstrating those benefits in people of normal weight who simply want to become thinner.

Dr Chao added: ‘If someone has obesity, there can be enormous health benefits from losing weight, which may justify accepting a very small risk of a serious complication.

‘But if you’re already a healthy weight, those benefits largely disappear while the potential risks of taking the drug do not.’

Nasr’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 of university.

Just a week after arriving back in the UK, she contacted her family to say she was suffering from nausea and vomiting. Her sister tried to arrange medical help and, when she could no longer reach her, a welfare check was requested.

Nasr was later found collapsed on the bathroom floor of her university accommodation, with an empty vial of the weight-loss drug nearby.

Dr Chao believes her death could ultimately force online providers to introduce more rigorous checks before handing out the drugs.

‘I have no doubt telehealth platforms will be forced to adopt this as standard whether they like it or not.’