GLP-1 medicines: frequently asked questions

Frequently asked questions about GLP-1 medicines, with answers. The answers are general information; make decisions about your own treatment with your doctor.

Frequently asked questions

1. Who are these medicines for?

GLP-1-based medicines approved for weight management (such as semaglutide and tirzepatide) are generally for adults with a body mass index (BMI) of 30 or more, or 27 or more with at least one weight-related health problem. They are approved for use together with healthy eating and physical activity. Whether they are right for you is decided by a doctor who knows your health history.

• Examples of weight-related health problems: type 2 diabetes, high blood pressure, high cholesterol, sleep apnea, cardiovascular disease.
• These medicines are not used in some situations: if you or a family member has a history of medullary thyroid cancer or multiple endocrine neoplasia type 2 (MEN 2), if you have had a serious allergic reaction to these medicines before, or if you are pregnant or breastfeeding.

Questions to ask your doctor

• Are my BMI and my health suitable for this treatment?
• What other options do I have?

Sources: FDA-approved prescribing information, Indications and Contraindications: semaglutide · tirzepatide. EMA (European Medicines Agency) product information: semaglutide · tirzepatide.

2. What checks are done before starting?

Before you start, your doctor asks about your health history, examines you and orders the blood tests they think are needed. The aim is to see whether the medicine is right for you and whether anything needs extra care.

• Your health history: Have you had inflammation of the pancreas (pancreatitis), gallstones or gallbladder inflammation, kidney disease, diabetes-related eye disease, depression or an eating disorder? Have you ever had a serious allergy to a medicine?
• Your thyroid history: Do you or anyone in your family have medullary thyroid cancer or MEN 2?
• Medicines you take: Especially insulin and sulfonylurea diabetes medicines (risk of low blood sugar), and birth control pills taken by mouth. Tirzepatide can make these pills less effective; your doctor may suggest an additional method.
• Pregnancy: If you are planning a pregnancy or are breastfeeding, be sure to say so; when to stop the treatment is planned in advance. If you find out you are pregnant during treatment, tell your doctor straight away; the medicine needs to be stopped.
• Measurements: weight, height, waist circumference, blood pressure, pulse.
• Commonly ordered blood tests: fasting blood sugar and HbA1c, kidney and liver tests, cholesterol. Your doctor may order other tests if needed.

Questions to ask your doctor

• Which tests do I need before I start?
• Does it interact with the medicines I take?

Sources: FDA-approved prescribing information, Contraindications, Warnings and Drug interactions: semaglutide · tirzepatide.

3. How is the medicine used?

Most GLP-1 medicines used for weight management are pens injected under the skin once a week; some are injected every day. Your doctor or pharmacist can tell you which medicine is available in which form where you live. Each medicine has its own instructions for use. Do the first injection together with your doctor, nurse or pharmacist.

• Inject the weekly medicine on the same day each week. It can be taken at any time of day, with or without food.
• It is injected into the abdomen, thigh or upper arm. Change the injection site each time; you can choose a different spot within the same area.
• Store pens in the refrigerator (2–8 °C / 36–46 °F) and do not freeze them. How long a pen can be kept outside the refrigerator depends on the pen; follow the instructions in the box.
• Do not share your pen with anyone, even if the needle is changed. Throw used needles away in a puncture-resistant container.
• What to do if you miss a dose depends on the medicine; check the instructions for use or ask your pharmacist.

Questions to ask your doctor

• Can we do the first injection together?
• Who should I contact if I have side effects?

Sources: FDA-approved prescribing information and instructions for use: semaglutide · tirzepatide.

4. How often are check-ups done during treatment?

Your doctor decides how often you are checked, based on your health. Many doctors see their patients more often in the first months of treatment and then space visits out.

• Weight, waist circumference, blood pressure and pulse.
• Blood sugar and HbA1c (average blood sugar over three months), especially if you have diabetes or take insulin or sulfonylurea diabetes medicines; blood sugar can drop when these are combined.
• Kidney function, especially if you have had severe vomiting or diarrhea; losing fluid can strain the kidneys.
• Cholesterol and liver tests, if your doctor thinks they are needed.
• An eye examination if you have diabetes-related eye disease.
• Your mood: if you feel down or depressed, or have thoughts of harming yourself, tell your doctor straight away.

Don't wait for your check-up

• Severe pain in the upper part of your abdomen that does not go away, yellowing of the skin or eyes, fever or vomiting that does not stop: see a doctor straight away.
• Swelling of the face, lips, tongue or throat, shortness of breath, a widespread rash: this may be a serious allergic reaction; go to the emergency department straight away.
• A swelling or lump in the neck, hoarseness that does not go away, difficulty swallowing: tell your doctor.

If surgery or an endoscopy is planned, be sure to say that you take a GLP-1 medicine.

Questions to ask your doctor

• Which tests should we do, and how often?

Sources: FDA-approved prescribing information, Warnings and Precautions: semaglutide · tirzepatide.

5. How much weight did people lose on average in studies?

In large studies lasting 16–17 months, people taking semaglutide lost on average about 15 percent of their body weight; in the tirzepatide study, the average loss was between 15 and 21 percent. People on placebo lost around 2–3 percent.

• These results come from separate studies, measured in different participants over different periods. So they cannot be used to compare the two medicines with each other.
• These are averages. About 85–90 percent of participants lost at least 5 percent of their weight; some lost much more, some much less.
• Weight loss is faster in the first months; it usually starts to slow down and level off between one and one and a half years.
• In real life, results vary from person to person; taking the medicine regularly, side effects and breaks in treatment all affect the result.
• Some of the weight lost can be muscle; enough protein and strength exercise can help you keep your muscles.

Questions to ask your doctor

• What could be a realistic goal for me?

Sources: Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med. 2021;384(11):989–1002. · Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med. 2022;387(3):205–216.

6. What happens when you stop the medicine?

In studies, after the medicine was stopped, a large part of the weight lost came back within a year on average. That is why a decision to stop or reduce the medicine is planned together with your doctor, not on your own.

• In the extension of the semaglutide study (STEP 1), participants who stopped the medicine regained on average two thirds of the weight they had lost within a year. Improvements in blood pressure and blood sugar also largely returned to where they started.
• In a tirzepatide study, people who stopped the medicine started to regain weight, while those who continued kept losing weight.
• The answer to “I’ve reached my goal weight, can I stop?” differs from person to person. Long-term use, gradual reduction or stopping are options to discuss with your doctor.
• Also plan with your doctor how you will keep up eating well, staying active and tracking your weight when you stop.

Questions to ask your doctor

• What will we do once I reach my goal?
• What will we do if the weight starts coming back?

Sources: Wilding JPH, et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide: The STEP 1 trial extension. Diabetes Obes Metab. 2022;24(8):1553–1564. · Aronne LJ, et al. Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity (SURMOUNT-4). JAMA. 2024;331(1):38.

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Related: Gallstones on GLP-1 medicines: why the risk rises and how to protect yourself

Medical content review: Prof. Dr. Varlık Erol, Professor of General Surgery · Gila advisor. He reviewed the Turkish original; this English version is Gila's translation.

Last updated: November 1, 2026 · Editor: Sezen Soykut · support@gila.coach

This page is for information only and is not medical advice. Make decisions with your doctor.