Medically reviewed by Dr. Ehtesham Ghani, Internal Medicine & Bariatric Medicine (ASBP). Last reviewed June 2026.
Semaglutide and tirzepatide are two of the most-discussed prescription medications in weight management today. If you are weighing one against the other, the most important thing to know is that the "better" option is not the same for everyone. The right choice depends on your medical history, how your body tolerates each medication, and your insurance coverage. At ThinFast MD, we have helped Illinois patients lose weight under physician supervision since 1984, and we evaluate both options in person across our four locations in Hinsdale, Arlington Heights, Brookfield, and Rockford. Here is an honest, side-by-side look to help you understand the differences before your consultation.
How are semaglutide and tirzepatide different?
The core difference is how each medication works in the body. Semaglutide is a GLP-1 receptor agonist, meaning it mimics a single hormone (GLP-1) that helps regulate appetite, slow stomach emptying, and signal fullness. It is the active ingredient in brand-name Wegovy and Ozempic. Tirzepatide is a dual agonist: it activates both the GLP-1 receptor and a second receptor called GIP. It is the active ingredient in Zepbound and Mounjaro. Both are taken as a once-weekly injection, and both are used alongside diet, exercise, and ongoing medical supervision rather than on their own.
Which one leads to more weight loss?
For the first time, a head-to-head clinical trial compared the two directly. In the SURMOUNT-5 trial published in the New England Journal of Medicine in 2025, participants taking tirzepatide lost an average of roughly 20% of their body weight at 72 weeks, compared with roughly 14% for those taking semaglutide, when each was combined with lifestyle changes. That made tirzepatide the more effective option on average in that study. However, "on average" is the key phrase. Individual results vary widely, and a meaningful number of people do well on semaglutide. These figures come from a controlled trial setting, not from any one patient, and are not a promise of any specific outcome for any individual.
If tirzepatide works better, why would anyone choose semaglutide?
Higher average weight loss is only one factor. Several real-world considerations can make semaglutide the better fit for a given patient. Tolerance matters: both medications can cause gastrointestinal side effects such as nausea, and some people tolerate one better than the other. Medical history matters, including conditions like type 2 diabetes, thyroid disease, PCOS, or a personal or family history that affects medication selection. Insurance coverage and supply also play a large role, because which medication is covered, and at what cost, differs from plan to plan. This is exactly why we review your full picture before recommending either drug. Our patients exploring these options often start with our pages on tirzepatide weight loss and GLP-1 semaglutide therapy to understand each medication on its own.
Are semaglutide and tirzepatide safe, and who should not take them?
Both medications are prescription-only and are appropriate for many patients, but they are not for everyone, which is why a medical evaluation comes first. According to FDA prescribing information, both semaglutide (Wegovy) and tirzepatide (Zepbound) carry a boxed warning regarding thyroid C-cell tumors observed in rodent studies; their relevance to humans has not been determined. Both are contraindicated in people with a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2), and neither should be used during pregnancy. The most common side effects are gastrointestinal, including nausea, vomiting, diarrhea, and constipation. Less common but serious risks can include pancreatitis and gallbladder problems. This is part of why an in-person history, physical, and lab review matters before starting either drug, so your physician can confirm a medication is safe and appropriate for you.
How does ThinFast MD decide which is right for me?
This is where in-person care makes a genuine difference. Many mail-order and telehealth-only services prescribe a medication after a brief online questionnaire, without ever examining you. At ThinFast MD, your evaluation includes a real history and physical exam, lab work, an EKG when appropriate, and a review of your metabolism and any conditions such as prediabetes, Hashimoto’s, or menopause-related changes. Dr. Ehtesham Ghani and our clinical team use that information to match you with the medication and dose that fit your body and history, not a one-size-fits-all script. We then monitor your progress over time and adjust as needed, which is something a pill-by-mail model cannot replicate.
Are compounded versions an option?
Depending on availability and clinical appropriateness, we offer both brand-name medications (Wegovy, Ozempic, Zepbound, Mounjaro) and compounded semaglutide, dispensed under physician oversight. We also offer other proven tools when a GLP-1 or dual agonist is not the best path, including phentermine and other appetite suppressants, OPTIFAST and OptitrimMD meal replacement, and lipotropic and B12 injections. The goal is always to build the safest, most effective plan for you, which your physician determines at your visit.
What does treatment cost, and is it covered?
Pricing and insurance coverage vary based on the medication, your plan, and your treatment plan, so we review costs and coverage directly with you at your consultation rather than quoting a number online. Our team will walk through what your insurance includes and what your options are at any of our four Illinois locations.
Frequently asked questions
Is tirzepatide always more effective than semaglutide?
On average, it produced more weight loss in one head-to-head study. In the SURMOUNT-5 trial (NEJM, 2025), tirzepatide produced about 20% average weight loss versus about 14% for semaglutide at 72 weeks. But individual results vary, and some patients do better on semaglutide based on tolerance and medical history.
Who should not take semaglutide or tirzepatide?
Per FDA prescribing information, both are contraindicated in people with a personal or family history of medullary thyroid carcinoma (MTC) or MEN 2, and neither should be used in pregnancy. Your physician reviews your history, exam, and labs to confirm a medication is safe for you before prescribing.
Are both medications taken the same way?
Yes. Both semaglutide and tirzepatide are given as a once-weekly injection, used together with diet, exercise, and medical supervision.
What is the actual difference between GLP-1 and GIP/GLP-1?
Semaglutide acts on one receptor, GLP-1. Tirzepatide acts on two, GIP and GLP-1, which is why it is called a dual agonist. Both help control appetite and fullness.
Can I switch from one medication to the other?
In some cases, yes. A switch may be considered based on tolerance, results, side effects, or coverage changes, and should only be done under physician guidance. Your ThinFast MD provider will advise whether a change is appropriate for you.
Do I need an in-person visit to start?
We recommend an in-person evaluation, including history and physical, labs, and an EKG when appropriate, because it lets us prescribe safely and personalize your plan. We also offer telehealth and online consults where suitable. Call (708) 485-4050 to get started.
This page is for educational purposes only and is not medical advice. Semaglutide and tirzepatide are prescription medications with contraindications and possible side effects, and are prescribed only when clinically appropriate following a medical evaluation; they are used together with diet, exercise, and ongoing supervision. Weight-loss figures are drawn from clinical trials and do not guarantee any individual outcome; individual results vary. Please consult a qualified clinician before starting, stopping, or changing any treatment.
Find your nearest ThinFast MD clinic
We serve patients across the Chicago suburbs and Rockford. Choose your nearest location — Hinsdale, Arlington Heights, Brookfield, or Rockford — or call (708) 485-4050 to book. See all service areas.
