GLP-1s and gastroparesis: separating the noise from the signal

The 2023 case reports

In mid-2023, individual case reports surfaced of severe gastroparesis in patients taking GLP-1s, including a high-profile pre-surgical case where stomach contents from days earlier complicated anaesthesia. The reports prompted regulatory reviews and a great deal of media coverage.

In subsequent labelling updates, the FDA added language clarifying that delayed gastric emptying is an expected mechanism of action and a known side effect, and added language about ileus (severely slowed bowel movement) to the prescribing information for some GLP-1s. (Wegovy label updates, 2023 to 2024.)

The volume of case reports has not, so far, translated into a large signal in population-level analyses. The most-cited 2023 cohort study using the PharMetrics health insurance database reported a relative risk increase of gastroparesis on GLP-1s but with an absolute risk below 0.1% per year, meaning fewer than 1 in 1,000 users developed clinical gastroparesis. (Sodhi M et al., JAMA 2023.)

What gastroparesis actually is

Gastroparesis is a clinical diagnosis, not just "slow stomach emptying." It involves:

• Significantly delayed gastric emptying confirmed by a gastric emptying study (a 4-hour scan after a labelled meal)
• Symptoms that interfere with daily life: nausea, vomiting, early satiety, bloating, abdominal pain
• Symptoms persisting for at least three months in the formal diagnostic criteria

Most people on a GLP-1 experience slower stomach emptying. That is the drug working. Very few meet the diagnostic threshold for gastroparesis. Distinguishing the two is the job of the clinician.

The signs that matter

The pattern that should prompt a real conversation with your prescriber:

• Persistent vomiting that does not improve with dose pause or titration slow-down
• Inability to eat enough to maintain even basic caloric needs: losing weight involuntarily past your target
• Severe early satiety: feeling full after a few bites, every time, for weeks
• Vomiting undigested food from hours earlier
• Worsening over time rather than improving (most GI side effects improve as your body adapts)

If you have any of these, this is not a "log a symptom and see how it goes next week" situation. This is a same-week prescriber call.

Who is at higher risk

Risk factors that increase the chance of clinical gastroparesis on a GLP-1:

• Pre-existing diabetes, especially long-standing type-2 diabetes, where autonomic neuropathy may already affect stomach motility
• Personal history of gastroparesis from any cause: this is essentially a contraindication
• High-dose GLP-1 rather than starting or middle doses
• Use of other medications that slow GI motility (anticholinergics, some antidepressants, opioids)

A woman without any of these risk factors, on a moderate GLP-1 dose, who is following standard titration, is at very low risk.

What your prescriber will do

If symptoms of clinical gastroparesis are real, the standard approach:

1. Pause or reduce the GLP-1. Most cases improve within 4 to 8 weeks of stopping.
2. Investigate other causes. A gastric emptying study, blood tests, sometimes endoscopy to rule out other explanations.
3. Manage symptoms. Antiemetics, dietary adjustments (small frequent meals, low fat, low fibre during the acute phase), sometimes prokinetic medications.
4. Decide whether to resume. If symptoms fully resolved after stopping, some prescribers will try a lower dose. If they did not, a different class of weight-loss intervention is the path forward.

Pre-surgical considerations

The 2023 cases that drew attention often involved patients undergoing anaesthesia. Anaesthetic complications can arise when a "fasting" patient actually has retained stomach contents because of GLP-1-induced slowing.

In 2023, the American Society of Anesthesiologists issued guidance:

• Consider holding the GLP-1 for at least one weekly dose before elective surgery (for daily GLP-1s, the recommendation was different).
• For urgent surgery in patients taking GLP-1s, anaesthesiologists may use techniques (such as ultrasound to assess stomach contents) to manage aspiration risk.

If you have any surgery planned, tell every relevant clinician you are on a GLP-1, including:

• The surgeon
• The anaesthesiologist (pre-op visit or pre-op call)
• Your primary care doctor

(See ASA guidance, Updated 2024.)

Most cases are not gastroparesis

For every woman who develops clinical gastroparesis on a GLP-1, hundreds have nausea that improves with titration adjustment, dozens have persistent fullness that resolves over weeks, and a smaller number have moderate GI symptoms that respond to dietary changes.

The common pattern is not the rare one. But the rare one is real, and recognising it early is the difference between a manageable side effect and a serious complication.

What to do with this

With a history of gastroparesis the calculator does not give you a deficit. It shows your maintenance figure, the full derivation, and a clear line saying this needs supervision, which is the useful thing a website can do here.

See what it will show you

Sources

1. Sodhi M et al. Risk of Gastrointestinal Adverse Events with GLP-1 Receptor Agonists for Weight Loss. JAMA 2023. JAMA
2. FDA Prescribing Information, Wegovy. Label
3. American Society of Anesthesiologists. Updated guidance on perioperative GLP-1 management. 2024. ASA
4. Camilleri M. Clinical guideline: management of gastroparesis. Am J Gastroenterol 2013. PubMed

Medical disclaimer: Severe or persistent GI symptoms belong with your prescriber within days, not weeks. See our full medical disclaimer.