Important Safety Information

Last updated: October 19, 2026

Read this information before starting semaglutide or tirzepatide, and whenever your prescription changes. Both are prescription medicines with potentially serious risks. Your licensed healthcare provider determines whether treatment is appropriate for you.

This page provides general education, not personalized medical advice or a complete list of risks. Follow your prescriber’s instructions and the information supplied by your dispensing pharmacy. Safety information for FDA-approved products helps explain risks associated with these ingredients; it does not establish the safety or effectiveness of a compounded preparation.

Important warning: risk of thyroid C-cell tumors

FDA-approved semaglutide and tirzepatide products carry a boxed warning about thyroid C-cell tumors. These medicines caused thyroid tumors, including medullary thyroid carcinoma (MTC), in rodents. It is not known whether they cause these tumors in humans.

Do not use semaglutide or tirzepatide if you or anyone in your family has ever had MTC, or if you have Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). Tell your provider promptly about a lump or swelling in your neck, persistent hoarseness, trouble swallowing, or shortness of breath.

Who should not use these medicines

Anyone with a personal or family history of MTC or with MEN 2.
Anyone who has had a serious allergic reaction to the prescribed medicine or any of its ingredients. Tell your provider and pharmacist about all medication allergies and check the ingredients of your specific preparation.

These medicines should not be used for weight loss during pregnancy. They are not a treatment for type 1 diabetes or diabetic ketoacidosis. They are not recommended for people with severe gastroparesis (severely delayed stomach emptying). Your provider must assess other conditions and risks before prescribing.

Serious side effects and symptoms to act on

Inflammation of the pancreas (pancreatitis): Stop the medicine and seek medical care right away for severe, persistent stomach pain that may spread to your back, with or without vomiting.
Gallbladder problems: Seek prompt medical care for upper stomach pain, fever, yellowing of the skin or eyes, or clay-colored stools.
Dehydration and kidney injury: Nausea, vomiting, and diarrhea can cause fluid loss and worsen kidney function. Contact your provider promptly if you cannot keep liquids down, urinate much less than usual, or feel very dizzy.
Severe stomach or intestinal problems: Seek medical care for severe or persistent stomach symptoms, a swollen abdomen, ongoing vomiting, or inability to pass stool or gas.
Low blood sugar (hypoglycemia): Risk is higher with insulin or sulfonylureas. Symptoms can include sweating, shakiness, hunger, headache, fast heartbeat, dizziness, confusion, or blurred vision. Follow your clinician’s plan for checking and treating low blood sugar. Severe symptoms require emergency help.
Serious allergic reactions: Stop the medicine and get emergency help for trouble breathing, swelling, fainting, or a severe rash with other symptoms.
Vision changes: Tell your provider promptly about changes in eyesight, especially if you have diabetes or diabetic retinopathy. Sudden vision loss requires urgent medical evaluation.
Increased resting heart rate: Tell your provider if your heart races or pounds while you are at rest, particularly during semaglutide treatment.

Common side effects

Common side effects include nausea, diarrhea, vomiting, constipation, stomach pain, indigestion, and decreased appetite. Some people also experience belching, reflux, bloating, fatigue, or injection-site reactions. Side effects may occur when starting treatment or increasing a dose.

Contact your provider if symptoms persist, worsen, or interfere with eating or drinking. Do not increase your dose to speed up weight loss or change treatment on your own.

What to tell your provider before treatment

Share your complete medical history, including pancreatitis, gallstones, kidney disease, severe digestive problems, diabetes, diabetic eye disease, thyroid conditions, allergies, and any planned surgery or procedure. Tell your provider about all prescription medicines, over-the-counter medicines, vitamins, and supplements.

Other weight-loss or diabetes medicines: Do not combine semaglutide and tirzepatide, or use them with another GLP-1 medicine or another product containing the same active ingredient. Discuss any other weight-loss treatment with your provider.
Insulin and sulfonylureas: Your provider may need to adjust these medicines to reduce low blood sugar risk. Do not adjust them yourself.
Medicines taken by mouth: Semaglutide and tirzepatide slow stomach emptying and can affect absorption of oral medicines. Some medicines may require closer monitoring.
Anesthesia and deep sedation: Delayed stomach emptying can increase the risk of stomach contents entering your lungs during a procedure. Tell your surgical and anesthesia teams that you take this medicine, even if you follow fasting instructions. They should give you individualized instructions about treatment before the procedure.

Pregnancy, breastfeeding, and contraception

Weight-loss treatment offers no benefit during pregnancy and may harm an unborn baby. Stop weight-loss treatment and contact your provider if you become pregnant. Tell your provider if you are planning a pregnancy.

Semaglutide: Stop at least 2 months before a planned pregnancy because the medicine stays in the body for a long time.
Tirzepatide: Discuss when to stop before trying to conceive. Tirzepatide can make oral hormonal contraceptives less effective. Switch to a non-oral contraceptive method or add a barrier method for 4 weeks after starting tirzepatide and for 4 weeks after every dose increase.
Breastfeeding: Discuss potential effects on your baby and milk supply with your provider before starting or continuing either medicine. Recommendations depend on the specific product and your circumstances.

Important information about compounded medications

Compounded semaglutide and compounded tirzepatide are not FDA-approved. The FDA does not review compounded drugs for safety, effectiveness, or quality before they are marketed. They are not FDA-approved generic versions of Ozempic®, Wegovy®, Mounjaro®, or Zepbound® and should not be assumed to be interchangeable with those products.

Compounding may be appropriate for an individual patient whose medical needs cannot be met by an available FDA-approved drug, subject to applicable law. Discuss FDA-approved alternatives and why a specific compounded preparation is being considered. Availability is subject to prescribing, pharmacy, and regulatory requirements.

Verify every dose: Vial concentrations and syringe markings can differ. Confirm the prescribed dose in milligrams, the concentration in milligrams per milliliter, and the exact volume or syringe units with your pharmacist. Never copy a dose or syringe measurement from another person or a previous vial.
Ask before injecting: If your label, instructions, vial, or syringe is unclear or different from what you expected, contact the dispensing pharmacy before use. Do not estimate or convert doses yourself.
Check the ingredients: Semaglutide sodium and semaglutide acetate are different active ingredients from the semaglutide base used in approved drugs. The FDA has raised concerns about the use of these salt forms. Added ingredients, such as vitamins, do not establish that a compounded combination is safe or effective.
Handle medication safely: Follow the pharmacy’s storage, refrigeration, and beyond-use instructions. Contact the pharmacy about damaged packaging, temperature concerns, particles, or unexpected changes in appearance before use. Never share medication, needles, or syringes; use a new needle and syringe for each injection and dispose of them in a sharps container.
Missed doses or treatment breaks: Ask your prescriber or pharmacist for instructions specific to your preparation. Do not double a dose or restart at a previous high dose without guidance.

Questions, reporting side effects, and further reading

For treatment questions or side effects, contact your prescribing clinician through your patient account. For dosing, ingredients, storage, or dispensing questions, contact the pharmacy listed on your prescription label. Online messages are not an emergency service.

You can report suspected medication side effects or product problems to FDA MedWatch or call 1-800-FDA-1088 (1-800-332-1088). Reporting does not replace medical care.

Always review the current medication information provided with your prescription. Your individual preparation may have additional precautions that are not listed here.