Three peptides. Three generations of the same science. One decision that’s easier than it looks once you see how they actually differ.
Semaglutide came first. Tirzepatide followed with stronger results. Retatrutide is the newest, and it’s showing the biggest numbers in clinical trials so far. All three work with your body’s natural appetite and metabolism signals rather than against them, which is why side effects tend to be manageable and results tend to hold when you have real support around the treatment.
Here’s what each one is, how they compare, and how to think about which fits where you are right now.
Semaglutide — the original
- ~14.9% average body-weight reduction at 52 weeks
- Targets GLP-1 (one pathway)
- Weekly injection
- Best for: first-timers, or anyone sensitive to side effects
Tirzepatide — the upgrade
- ~22.1% average body-weight reduction at 52 weeks
- Targets GLP-1 + GIP (two pathways)
- Weekly injection
- Best for: plateaued on semaglutide, or want stronger results
Retatrutide — the newest
- ~25.9% average body-weight reduction at 52 weeks
- Targets GLP-1 + GIP + glucagon (three pathways)
- Weekly injection
- Best for: want the newest science, comfortable with a compounded option
Semaglutide: the original
Semaglutide is a GLP-1 receptor agonist. It mimics a hormone your gut already produces after meals, which tells your brain you’re satisfied, slows how fast your stomach empties, and helps stabilize blood sugar.
The result: you feel full sooner, stay full longer, and stop thinking about food constantly.
Trial participants averaged around a 14.9% reduction in body weight at the 52-week mark. Real-world results vary based on dose, diet, activity, and how consistently you show up for the treatment. Side effects are usually mild and taper as your body adjusts, most commonly nausea, constipation, or headache in the early weeks.
If you’re new to peptide therapy, semaglutide is often the smart starting point. The science is well established, the safety profile is well documented, and it gives your body a chance to adapt before you consider anything stronger.
Tirzepatide: the upgrade
Tirzepatide activates two receptors instead of one. It hits GLP-1 (like semaglutide) and also GIP, a second gut hormone that helps regulate appetite and how your body handles sugar and fat. Two levers instead of one.
That dual action shows up in the numbers. Trial participants averaged around a 22.1% reduction in body weight at 52 weeks, a meaningful step up from semaglutide’s ~14.9%. It tends to work well for people whose progress on semaglutide stalled out or who wanted stronger results from the start.
The dosing schedule is the same: one weekly injection. Side effects are broadly similar to semaglutide (nausea, constipation, or headache in the early weeks), with one addition specific to tirzepatide — some people notice a mild reaction at the injection site. All of it usually settles as your body adjusts.
One reason tirzepatide has become popular in weight loss programs is the flexibility. It works well at standard doses and also at microdoses. A microdose is a smaller, more gradual amount that keeps side effects even lower. It’s a real option for people who are sensitive or who simply want to ease in.
Retatrutide: the newest
Retatrutide adds a third receptor to the picture. GLP-1, GIP, and glucagon. That third pathway also plays a role in how your body burns fat and manages energy. Three receptors, three coordinated signals.
Phase 2 trial results have been striking. Trial participants averaged around a 25.9% reduction in body weight at the 52-week comparison mark, and because the trial timeline is shorter than semaglutide’s and tirzepatide’s, the eventual results with longer treatment may still climb.
Retatrutide is a good fit if you’re comfortable being early on a treatment with strong but still developing data, and you want to work with the newest science available.
Not Sure which one is Right?
That’s exactly what the consultation is for. Come in, talk it through with a provider, and leave with a plan. No pressure to decide today.
Beyond the scale
Weight is the headline, but these peptides act on core metabolic pathways, so the benefits reach further than a number on a scale. All three help lower A1C, reduce appetite and cravings, help reverse insulin resistance, and lower the risk of type 2 diabetes or a major cardiovascular event. That’s the shared baseline.
Here’s what each one adds beyond that.
What semaglutide is best at:
- Lowering blood glucose and HbA1c. The most effective of the three at moving these numbers.
- Reducing appetite. The most effective of the three at appetite suppression.
What tirzepatide adds
- Regulating and lessening sugar cravings
- Decreasing bone resorption (helps prevent age-related bone loss)
- Raising HDL (“good” cholesterol) and lowering triglycerides
- Lowering inflammation markers like IL-6 and hsCRP
- Improving brain fog and concentration by reducing glucagon secretion
- Supporting healthy intestinal microbiota, which affects GI health and aging
What retatrutide adds:
Everything tirzepatide adds, plus:
- The lowest risk of hypoglycemia among the GLP-1 receptor agonists
- The strongest impact on inflammation, with added support for liver and kidney function
None of these are reasons to start peptide therapy on their own. The primary reason is still sustainable weight change under medical supervision. But they’re a big part of why this class of medication has moved so quickly from a diabetes treatment to a broader metabolic-health tool.
How to actually choose
The right peptide depends less on which one has the biggest trial number and more on where you are right now — your history, your goals, and how your body has responded to things before. That’s a conversation, not a formula.
When you come in, the first thing your provider should do is listen. What are you hoping to change? Have you used a GLP-1 before, and how did it feel? Do you want to ease in gently, or move at a faster pace? From there, they’ll talk you through how each option fits what you’ve described.
For a lot of people new to peptide therapy, that points toward semaglutide — a gentler, well-established starting point. If your progress has stalled or you want a stronger response, tirzepatide often makes sense, with the microdose option keeping it comfortable. And for someone who wants the newest science and is at ease being early on a compounded option, retatrutide is worth talking through. Which one is right isn’t something we decide for you before you’re in the room.
You also don’t have to get it perfectly right on day one. Peptide therapy is adjustable: doses can be titrated, and you can move between peptides as your body and goals change. What matters most is starting with a provider who takes time to understand where you’re headed and adjusts the plan alongside you.
Getting started at Radiance Medspa
At Radiance Medspa in Vinings, all three peptides are available through our Getting Started Program. That’s four in-person visits with a provider who injects your dose, answers your questions, and adjusts the plan as you go.
A few things that make the experience simpler:
- Pre-dosed vials. Every dose is prepared and pre-measured for you. No drawing up medication yourself. No guessing on volume. No math at home. You show up, we inject.
- Flat pricing. The program costs the same regardless of your standard dose, so you can adjust up or down without changing what you pay. Microdose tirzepatide is offered at a lower price point for people easing in.
- Bloodwork if needed. Depending on your health history, bloodwork may be recommended before starting. It isn’t included in the program cost, but we’ll walk you through what’s needed and where to get it done.
The program is designed to make peptide therapy less confusing and more supported. You’re not sent home with a vial and a Google search. You’re seen, injected, and checked in with, four times.