Side effects
GLP-1 red flags: when to call a clinician or 911
October 2, 2026 · 7 min read · Medically reviewed by Bryan Milton, MD · Reviewed October 2, 2026
The symptoms on the approved labels' warnings sections that should not be waited out, what they can indicate, and which number to call.
This is the article to read once and know where to find again. Most of what happens on a GLP-1 is mild and settles. The approved labels also carry a warnings section describing serious possibilities, and the point of knowing them is not anxiety — it is recognising the handful of symptoms that should not be waited out.
Call 911 for these
- Swelling of the face, lips, tongue or throat; trouble breathing or swallowing; a widespread rash with faintness. These are signs of a serious allergic reaction, which the labels list among their warnings.
- Chest pain, pressure or tightness, particularly with breathlessness, sweating, or pain spreading to the arm, neck or jaw. Do not assume it is reflux.
- Sudden severe abdominal pain with persistent vomiting, especially if you cannot keep any fluids down.
- Confusion, fainting, or a seizure, which can accompany severe low blood sugar.
Contact a clinician promptly for these
| Symptom | What the labels associate it with |
|---|---|
| Severe or persistent abdominal pain, sometimes felt in the back, with or without vomiting | Acute pancreatitis |
| Pain in the upper right abdomen, fever, yellowing of the skin or eyes, clay-coloured stools | Acute gallbladder disease, including gallstones |
| Persistent vomiting or diarrhea, reduced urination, dizziness on standing | Dehydration and acute kidney injury |
| Shakiness, sweating, confusion, hunger, fast heartbeat | Low blood sugar, particularly with insulin or a sulfonylurea |
| Changes in vision | Diabetic retinopathy complications in people with type 2 diabetes |
| A lump or swelling in the neck, hoarseness, trouble swallowing, shortness of breath | The boxed warning about thyroid C-cell tumors |
| Severe, ongoing stomach problems | Severe gastrointestinal disease, including delayed stomach emptying |
| New or worsening depression or thoughts of self-harm | Monitoring advised on one label |
The boxed warning, in plain terms
The approved semaglutide and tirzepatide labels carry a boxed warning about thyroid C-cell tumors seen in rodent studies. Whether this translates to humans has not been determined. What follows from it practically is that these medications are contraindicated in anyone with a personal or family history of medullary thyroid carcinoma, or with Multiple Endocrine Neoplasia syndrome type 2 — and that a lump in the neck, hoarseness or new trouble swallowing should be reported rather than watched.
Before any procedure with sedation
Tell the clinician performing it that you take a GLP-1, and say when your last dose was. The labels warn about pulmonary aspiration during general anesthesia or deep sedation, because these medications delay stomach emptying and food can remain when the stomach is assumed to be empty. This applies to surgery, colonoscopies, endoscopies and dental sedation. It is one of the most important practical things on the label and one of the most frequently missed.
Pregnancy
If you become pregnant or are planning to, tell your clinician promptly. These medications are not for use in pregnancy, and the labels address stopping before a planned pregnancy — which involves lead time, so it is a conversation to have early rather than late.
A note on compounded preparations
Everything above applies. GLP's clinicians screen against these same approved-label warnings and contraindications when prescribing a compounded preparation, and report anything unexpected to your care team. Compounded medications are not FDA-approved and are not reviewed by the FDA for safety, effectiveness, or quality.
Contact your care team about anything that concerns you, that is getting worse rather than better, or that stops you eating and drinking normally. Seek urgent care for severe or persistent abdominal pain (with or without vomiting, sometimes felt in the back), vomiting that will not stop, signs of dehydration, or yellowing of the skin or eyes. For swelling of the face or throat, trouble breathing, chest pain or any medical emergency, call 911.
This article is educational and is not a substitute for personalized medical advice. Whether any medication is appropriate for you is a decision for a licensed clinician who has reviewed your health history.