GLP-1s tied to elevated risk of fainting, dizziness, reveals research

Northwestern Medicine scientists have identified a safety concern associated with GLP-1 drugs. Using health record data, the research team tracked more than 42,000 adults already taking at least two types of blood pressure medications. After starting GLP-1s, these patients experienced higher rates of dizziness, fainting and other events related to low blood pressure, also known as hypotension.

These hypotensive episodes were most common among patients aged 65 and older and those with diabetes, the scientists found.

The peer-reviewed findings will be presented on Saturday (June 13) at ENDO 2026, the Endocrine Society’s annual meeting.

The study authors stress that the widely used drugs remain highly beneficial for many patients. “I’m a big proponent of GLP-1s, they are huge,” said study senior author Dr. Micah Eimer, clinical assistant professor of medicine in the division of cardiology at Northwestern University Feinberg School of Medicine and a Northwestern Medicine cardiologist.

“I'm just saying, let’s watch out for hypotensive events in select patients because I think there’s the potential to do harm,” added Eimer, who launched this study after noticing many patients on GLP-1s complaining of dizziness and fainting. “I am particularly worried about the risk to patients who obtain GLP-1s without direct and ongoing clinical supervision.”

Eimer’s team analyzed the health records of more than 42,000 adults taking at least two classes of antihypertensive medications who initiated semaglutide, tirzepatide or liraglutide. The scientists tracked hypotensive events over six, 12 and 24 months after patients started GLP-1 therapy and compared them with rates before GLP-1 initiation. Hypotensive events included dizziness, fainting, falls, low blood pressure diagnoses, systolic blood pressure readings below 90 mm Hg and prescriptions for medications used to treat hypotension.

A hypertensive patient on a GLP‑1 for sleep apnea is available for interview to discuss how it made him dizzy.

Key findings

• Within six months of starting GLP-1 therapy, the rate of hypotensive events increased from 8.7% to 10.2%
• The increased risk remained significant at 12 months, with hypotensive events rising from 13.6% to 14.3%
• Adults age 65 and older accounted for 53% of hypotensive events despite representing 37% of the study population
• Patients with Type 2 diabetes made up 75% of those experiencing hypotensive episodes but only 63% of the overall cohort
• In secondary analyses, the scientists found that weight loss alone did not explain the increased risk, suggesting other mechanisms of action may be at play

Below is a Q&A with study senior author Dr. Micah Eimer, who says additional studies are needed to confirm the results.

Q: Why did you decide to investigate this?

“I use a lot of GLP-1s because they are shown to reduce the risk of dying from heart disease by up to 20% depending on the population. And I noticed a series of patients on GLP-1s complaining of lightheadedness, dizziness and fainting. They had low blood pressure on my examination. Hypotension is the most dreaded potential side effect of treating hypertension and actually far more dangerous. And I started thinking that there was a pattern there that needed to be investigated.”

Q: Your study found a 1.5% increase in hypotensive events in patients six months after starting GLP-1s. How significant is this?

“It is statistically significant, and the consequences of hypotension can be terrible. People die from that. You can hit your head, or you can crash your car or break your hip. So, it’s a very bad outcome when it happens. Plus, part of the take-home from our abstract is that this is preventable. This is something that clinicians should be looking for and it’s recognizable. All we’re proposing to clinicians is, ‘Hey, think about the patients who are at risk and have a strategy to monitor and mitigate that risk.’”

Q: What about patients on GLP-1s? What is the take-home message for them?

“Here’s the other problem: A lot of patients are getting these drugs not from treating physicians necessarily. If I’m a patient, and I go to an online prescriber and they start sending me this drug, they’re not checking my blood pressure. They’re not asking me if I’m lightheaded or dizzy. So, I also want patients to think, ‘Hey, that’s true. I started this drug three months ago. I’ve lost 30 pounds, and now I feel like I’m going to faint every time I stand up. What could that be?’”

Q: In a way, your study found that GLP-1s are, at times, working too well?

“Yes, that’s why our abstract title asks, ‘Too much of a good thing?’ When I’m talking to patients about going on these drugs, they’re like, ‘I don’t want to go on another medicine.’ I say, ‘You know what? If you take this GLP-1, you can get rid of one or two blood pressure medicines. You can probably get rid of a blood sugar medication; you can probably cure your sleep apnea.’ So, I’m a big proponent of GLP-1s, they are huge. I’m just saying, let’s be careful in select patients because I think there’s the potential to do harm.”

Q: You found that hypotensive events were most common among patients over 65 and those with diabetes. Why are these patients most at risk after starting GLP-1s?

“Three things could be happening here. Older patients are just more susceptible to changes in blood pressure. Older patients have stiffer arteries, more blockages in their arteries and may get much more symptomatic from a change in blood pressure. The other thing is that patients with diabetes may have autonomic dysfunction, that’s a known complication of diabetes, so they don’t regulate blood pressure well. Finally, there are mechanisms of action of these GLP-1s that we don’t completely understand.”

The study is titled, “GLP1 Receptor Agonists and the Risk of Significant Hypotension Among Patients with Metabolic Cardiovascular Renal Disease: Too Much of A Good Thing?”