Quick Answer
The most common GLP-1 side effects are digestive: nausea, fullness, constipation, diarrhea and sometimes vomiting, especially when starting or increasing the dose. They often improve with time and simple adjustments. Less common but serious side effects, such as pancreatitis, gallbladder problems and dehydration, need prompt attention, so it helps to know the warning signs.
Who this is for: adults starting or taking a GLP-1 medication such as semaglutide or tirzepatide, and anyone considering one.
Common Side Effects
Most side effects come from the way GLP-1 medications slow stomach emptying and reduce appetite.[1] Common ones include:
- Nausea and feeling full quickly
- Constipation or diarrhea
- Vomiting, usually mild and occasional
- Heartburn, burping or bloating
- Decreased appetite
- Fatigue or headache, especially early on
These tend to be strongest in the first weeks and after each dose increase, and many people find they ease over time. This is one reason doses are increased gradually.
Tips to Reduce Digestive Side Effects
- Eat smaller meals and stop when you first feel full
- Eat slowly and avoid lying down right after meals
- Limit greasy, fried, very rich or very sweet foods
- Drink fluids throughout the day to stay hydrated
- Include fiber and fluids to help prevent constipation
- Limit alcohol
- Tell your provider if side effects are hard to tolerate, since the dose or schedule may be adjusted
Most side effects are digestive and tend to ease over time.
Less Common but Serious Side Effects
These are uncommon, but it is important to recognize them:[1]
- Pancreatitis: severe, persistent pain in the upper abdomen that may spread to the back, with or without vomiting
- Gallbladder problems: pain in the upper right abdomen, fever, or yellowing of the skin or eyes
- Dehydration and kidney problems: ongoing vomiting or diarrhea can lead to dehydration, which can affect the kidneys
- Low blood sugar: more likely if you also take insulin or certain other diabetes medications
- Allergic reactions: swelling of the face, lips or throat, or trouble breathing
GLP-1 medications carry a warning about thyroid C-cell tumors seen in animal studies. They should not be used by people with a personal or family history of medullary thyroid cancer or multiple endocrine neoplasia type 2.[1]
Other Things to Know
- Surgery and procedures: because these medications slow stomach emptying, tell every provider, including anesthesia teams, that you take one before any procedure
- Pregnancy: these medications are not used during pregnancy, so talk with your provider before trying to conceive
- Birth control: some GLP-1 medications can affect how well oral birth control pills work, particularly when starting or increasing the dose, so ask whether a backup method is needed
- Muscle and nutrition: eating much less can make it harder to get enough protein, so prioritize protein and strength training
- Hair shedding: rapid weight loss can cause temporary hair shedding
How We Manage Side Effects at Lake Forest Regenesis
Allana screens for health conditions and medications that affect whether a GLP-1 medication is appropriate before treatment begins. Doses are increased gradually, and you are encouraged to report side effects early so the plan can be adjusted, whether that means slowing the dose increase, changing eating habits or pausing treatment. Follow-up visits check both progress and how well you are tolerating the medication.
When to See a Provider
Seek urgent care for severe, persistent abdominal pain, pain with fever or yellowing of the skin or eyes, vomiting that prevents you from keeping fluids down, signs of dehydration such as dizziness or very little urine, or signs of an allergic reaction. Call 911 for trouble breathing or swelling of the throat. Contact your provider for a lump or swelling in the neck, trouble swallowing or persistent hoarseness.
Starting a GLP-1 or having side effects? We screen before starting, raise doses gradually and adjust your plan as needed.
Frequently Asked Questions
How long does nausea last on a GLP-1 medication?
For many people, nausea is strongest in the first few weeks and after dose increases, then improves. Tell your provider if it does not.
Can I take something for nausea or constipation?
Often, yes. Your provider can recommend options that are safe with your other medications.
Should I stop the medication if I have side effects?
Do not stop without talking to your provider unless you have a serious symptom that needs urgent care. Many side effects can be managed with adjustments.
Do I need to tell my surgeon I take a GLP-1 medication?
Yes. Because these medications slow stomach emptying, your care team may give you specific instructions before anesthesia or procedures.
References
- MedlinePlus. Semaglutide injection. U.S. National Library of Medicine. Read the drug information
This article is for general education and is not a substitute for individual medical advice. See our medical disclaimer.
