GLP-1 Side Effects by Body System: What Is Common and What Needs Care

Every prescription medication has possible side effects, and GLP-1 medications such as semaglutide and tirzepatide are no exception. Most effects are mild and settle with time, a few need a call to your provider, and a small number need urgent attention. This reference is organized by body system so you can find what applies to you quickly. It is educational and does not replace the information that comes with your own prescription.

Stomach and digestion

This is where most side effects occur, because these medications slow the emptying of the stomach.

Common: nausea, feeling full quickly, burping, heartburn, constipation, diarrhea, and occasional vomiting. They are most likely when you start or increase a dose and often ease over several weeks.

Call your provider if: symptoms keep you from eating or drinking normally, or do not improve.

Seek urgent care for: severe stomach pain that does not go away, vomiting that will not stop, or a swollen, hard abdomen with inability to pass stool or gas.

Gallbladder and pancreas

Less common: gallstones and gallbladder inflammation have been reported, as has inflammation of the pancreas.

Seek urgent care for: strong pain in the upper abdomen, particularly if it spreads to the back, with or without fever, vomiting, or yellowing of the skin or eyes.

Kidneys and hydration

Vomiting, diarrhea, or simply drinking too little can lead to dehydration, which can affect the kidneys.

Watch for: very dark urine, urinating much less than usual, dizziness when standing, or a racing heart.

What to do: keep up fluids, and contact your provider if you cannot.

Blood sugar

In people who do not take other diabetes medications, low blood sugar is uncommon. The risk rises when a GLP-1 medication is combined with insulin or a sulfonylurea.

Signs of low blood sugar: shakiness, sweating, confusion, sudden hunger, or a fast heartbeat.

What to do: ask your provider in advance how to recognize and treat it.

Injection site

Common: mild redness, itching, or a small bump where the injection was given.

What helps: rotating between the abdomen, thigh, and upper arm, and letting the alcohol dry before injecting.

Call your provider if: the area becomes increasingly painful, warm, or swollen.

Head, energy, and heart rate

Reported: headache, tiredness, and dizziness, often related to eating or drinking less. A modest increase in resting heart rate has also been observed with this class.

Call your provider if: you notice a pounding or racing heartbeat at rest, or dizziness that does not resolve with fluids and food.

Hair

Some people notice increased hair shedding a few months after starting. Temporary shedding is known to follow rapid weight change of any cause. It is usually short-lived, but mention it to your provider, who can check for other causes such as low iron or protein.

Eyes

People with diabetes and existing eye disease have been advised to keep up with eye examinations while on semaglutide. Separately, rare reports of sudden vision loss have been examined by regulators.

Seek urgent care for: any sudden change or loss of vision.

Mood

Tell your provider about any new or worsening low mood, anxiety, or thoughts of self-harm, as you would with any new medication. If you ever feel at risk of harming yourself, call or text 988 in the United States.

Thyroid

FDA-approved medications in this class carry a boxed warning about thyroid C-cell tumors seen in animal studies. They are not used in people with a personal or family history of medullary thyroid carcinoma or with Multiple Endocrine Neoplasia syndrome type 2.

Call your provider if: you notice a lump or swelling in the neck, hoarseness, or trouble swallowing.

Allergic reactions

Seek emergency care for: swelling of the face, lips, tongue, or throat, trouble breathing, a widespread rash, or fainting.

Situations that need advance planning

• Surgery or sedation. Tell your surgical and anesthesia team that you take a GLP-1 medication.
• Pregnancy. These medications are not used during pregnancy. Discuss timing with your provider if you plan to conceive.
• Birth control pills. Tirzepatide can make oral contraceptives less reliable around starting and each dose increase.

A note on compounded medications

The semaglutide and tirzepatide prescribed through Nu Image are compounded, which means they are not FDA-approved and have not been reviewed by the FDA for safety, effectiveness, or quality.

The FDA has received reports of side effects linked to dosing mistakes with compounded injectable products, where a person drew up more than intended. Confirm your dose in both milligrams and syringe units each time it changes.

How side effects are managed

Your provider has several options: keeping you at a dose for longer before increasing, lowering the dose, changing format, or stopping. Never adjust the dose on your own. Smaller meals, less fat, and steady fluids help with most digestive effects.

Reporting side effects

Tell your Nu Image care team about any side effect that concerns you. You can also report side effects directly to the FDA through its MedWatch program.

This content is for educational purposes only and is not medical advice, diagnosis, or treatment. It does not list every possible side effect. Compounded medications are prepared by state-licensed compounding pharmacies and are not reviewed or approved by the FDA for safety, efficacy, or quality. Prescription products require an online consultation with a licensed healthcare provider, who will determine whether a prescription is appropriate.