If you have started researching GLP-1 weight loss medications, you have probably run into a second acronym that makes the picture more confusing: GIP. Some medications act on GLP-1 alone. Others are described as “dual agonists” that act on both GLP-1 and GIP. The difference is not just jargon. It shapes how the medication works, how much weight people tend to lose in studies, and how it feels to take.
Here is what each hormone actually does, why combining the two changed the field, and — just as important — why “more receptors” does not automatically mean “better for everyone.”
The short version: GLP-1 and GIP are two hormones your gut releases after you eat. Semaglutide activates the GLP-1 receptor only; tirzepatide is a “dual agonist” that activates both the GLP-1 and GIP receptors. In head-to-head research on the FDA-approved medications, the dual approach produced greater average weight loss — but the right medication is an individual clinical decision, not a ranking.
Start here: GLP-1 and GIP are both incretin hormones
When you eat, your gut releases hormones that signal the rest of your body that food is on the way. Two of the most important are GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide). Together they are known as incretin hormones. Both are released by specialized cells in the small intestine after a meal, and both help regulate blood sugar by prompting the pancreas to release insulin mainly when glucose is elevated.
The medications in this category are not foreign chemicals. They are engineered, longer-lasting versions of hormones your body already produces, designed to keep working for days rather than minutes.
What GLP-1 does
GLP-1 influences weight through a few coordinated effects:
- It slows gastric emptying. Food stays in your stomach longer, so you feel full sooner and stay full longer.
- It acts on appetite centers in the brain. Hunger signals quiet down, and many people describe a reduction in constant thoughts about food.
- It supports glucose-dependent insulin release and lowers the hormone glucagon, which together help steady blood sugar.
A GLP-1 medication such as semaglutide is a “GLP-1 receptor agonist.” An agonist is simply a molecule that switches a receptor on. Semaglutide activates one receptor: the GLP-1 receptor. For a closer look at the two best-known molecules side by side, see our guide on semaglutide vs. tirzepatide.
What GIP does — the more complicated hormone
GIP is also an incretin, but its role in weight regulation took far longer to understand and is still being actively researched. GIP receptors appear in fat tissue, the pancreas, and the brain.
For years GIP was something of a paradox: in certain contexts it had been linked to fat storage, which made it an unlikely candidate for a weight-loss therapy. Newer research points in a different direction. Activating the GIP receptor alongside GLP-1 appears to amplify appetite suppression through the brain’s own GIP-receptor signaling[4], influence how the body manages fat, and — notably — may improve tolerability by easing the nausea that GLP-1 activation on its own can trigger. Researchers are clear that the combination helps; they are equally clear that the exact mechanism is not fully settled.
Single agonist vs. dual agonist, in plain terms
The practical difference comes down to how many receptors a medication targets.
| Semaglutide | Tirzepatide | |
|---|---|---|
| Receptors targeted | GLP-1 only | GLP-1 and GIP |
| Drug class | GLP-1 receptor agonist | Dual GIP/GLP-1 receptor agonist |
| Core actions | Appetite reduction, slowed digestion, glucose-dependent insulin | The same GLP-1 actions, plus added GIP receptor activity |
| Typical form | Once-weekly injection (an oral form also exists) | Once-weekly injection |
A medication that activates one receptor is a “mono-agonist.” One that activates two is a “dual agonist.” Tirzepatide was the first dual GIP/GLP-1 agonist to reach the market, which is why the field now splits into single-target and dual-target options.
Does targeting both receptors produce more weight loss?
In clinical trials, on average, yes. The clearest evidence comes from SURMOUNT-5, the first head-to-head study comparing the two, published in the New England Journal of Medicine[1]. In that trial, participants taking tirzepatide lost roughly 20.2% of their body weight on average, compared with about 13.7% for semaglutide over 72 weeks — a meaningfully larger reduction. Earlier obesity and diabetes trials pointed in the same direction[2][3].
Two honest caveats. First, those are averages across study populations; individual responses vary widely, and some people lose more on a single-target medication than the averages would suggest. Second, comparing results across separate trials is unreliable, because different studies enroll different people and use different designs. Head-to-head data like SURMOUNT-5 is more trustworthy than stitching unrelated studies together.
One more piece of context matters, and it is easy to miss. These trials studied the FDA-approved, brand-name formulations of semaglutide and tirzepatide. Compounded preparations of these medications are a separate category: they have not been evaluated or approved by the FDA for safety or effectiveness, and the results above should not be assumed to apply to them. When you read a weight-loss percentage, it is worth knowing exactly which product was studied to produce it.
So is the dual agonist always the better choice? Not necessarily.
This is the part that marketing tends to skip. The right medication is a clinical decision, not a leaderboard. A physician weighs several things that a weight-loss percentage cannot capture:
- Your medical history and goals. What is appropriate and safe for your specific situation.
- Tolerability. Gastrointestinal side effects are the most common with both medications, and at comparable therapeutic doses the rates are broadly similar — but everyone’s body responds differently.
- Other medications you take. For example, tirzepatide carries specific manufacturer guidance about oral contraceptives that semaglutide does not[5], which matters for some patients.
- Access and sustainability. The best medication is one you can take consistently and stay on long enough to see results.
Plenty of people do very well on a GLP-1 medication alone. Starting with the “stronger” option is not the same as starting with the smarter one. The goal is the lowest effective approach you can tolerate and sustain.
Where compounded medication fits
At Elara, both compounded semaglutide and compounded tirzepatide are available through physician-guided care. Board-certified physicians review your medical history and determine whether a single-receptor or dual-receptor approach is appropriate, with medication dispensed through state-licensed 503A compounding pharmacies.
It helps to be clear about what compounded medication is. Compounded medications are prepared by a state-licensed pharmacy for an individual patient. They are not FDA-approved and have not been evaluated by the FDA for safety or effectiveness, and they are not the same as the branded products studied in the trials described above. A physician can explain what that distinction means for your care.
If you want to see how the evaluation and ongoing care actually work, here is how the program works, or you can explore the GLP-1 weight loss program.
Frequently asked questions
Is GIP the same as GLP-1?
No. Both are incretin hormones released after eating, but they act on different receptors and play different roles. GLP-1 reduces appetite and slows digestion; GIP’s role is more complex and appears to enhance those effects when it is activated alongside GLP-1.
What is a dual agonist?
A dual agonist is a medication that activates two receptors at once. Tirzepatide activates both the GLP-1 and GIP receptors, while semaglutide activates the GLP-1 receptor only.
Is a dual agonist always more effective?
On average, head-to-head trial data showed greater weight loss with the dual agonist. But individual results vary, and the right medication is a clinical decision based on your health history, how well you tolerate it, and your goals — not a fixed ranking.
Is oral GLP-1 as effective as the injection?
Oral and injectable forms differ in how the medication is absorbed and dosed, so they are not always interchangeable. Effectiveness depends on the specific medication, the dose, and how consistently it is taken. This is a good question to work through with a physician.
Which one is right for me?
That is a decision to make with a board-certified physician who can review your full medical history. No article can replace that evaluation.
References
- Aronne LJ, Horn DB, le Roux CW, et al. Tirzepatide as compared with semaglutide for the treatment of obesity (SURMOUNT-5). N Engl J Med. 2025;393(1):26–36. doi:10.1056/NEJMoa2416394
- Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). N Engl J Med. 2022;387(3):205–216. doi:10.1056/NEJMoa2206038
- Frías JP, Davies MJ, Rosenstock J, et al. Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes (SURPASS-2). N Engl J Med. 2021;385(6):503–515. doi:10.1056/NEJMoa2107519
- Zhang Q, Delessa CT, Augustin R, et al. The glucose-dependent insulinotropic polypeptide (GIP) regulates body weight and food intake via CNS-GIPR signaling. Cell Metab. 2021;33(4):833–844. doi:10.1016/j.cmet.2021.01.015
- Skelley JW, Swearengin K, York AL, Glover LH. Impact of tirzepatide and GLP-1 receptor agonists on oral hormonal contraception. J Am Pharm Assoc. 2024;64(1):204–211.e4. PubMed
This article is for general educational purposes and is not medical advice. Compounded medications are available only by prescription, following a medical evaluation, and are not FDA-approved. Individual results vary. Talk with a board-certified physician about whether GLP-1 therapy is appropriate for you.