Semaglutide
The one entry on this list that's a mainstream, FDA-approved medication. Not a research peptide.
What is semaglutide?
Semaglutide is a GLP-1 receptor agonist and the most clinically validated compound in this library. It is an analog of human glucagon-like peptide-1, re-engineered to resist rapid breakdown so it can be dosed once a week. Unlike almost everything else here, it is fully FDA-approved: as Ozempic and Rybelsus for type 2 diabetes, and as Wegovy for chronic weight management. Same molecule, different brand names and approved doses.
How semaglutide works
Semaglutide mimics GLP-1, a hormone your gut releases after you eat, and it acts in several places at once. In the hypothalamus it activates the appetite-suppressing POMC and CART neurons and quiets the hunger-driving NPY and AgRP neurons, which lowers hunger and raises fullness. In the stomach it slows gastric emptying, so meals stay with you longer. In the pancreas it prompts insulin release only when blood sugar is high and lowers glucagon, which is how it controls blood sugar without the crash risk of insulin itself. The appetite effect is what drives the weight loss. The glucose effect is what makes it a diabetes drug.
What the research shows
The evidence base here is unusually deep for anything in this library. In the STEP 1 trial, adults with obesity taking 2.4 mg weekly lost an average of 14.9% of body weight over 68 weeks, compared with 2.4% on placebo. For type 2 diabetes, the SUSTAIN program showed strong, durable reductions in A1c alongside weight loss. This is not preliminary animal work. It is large, randomized, human-trial evidence, which is exactly what most peptides on this list do not have.
Dosage and how it is used
Semaglutide follows a fixed, gradual titration. The standard weight-management schedule steps up every four weeks: 0.25 mg, then 0.5, 1.0, 1.7, and finally 2.4 mg weekly, reaching the full dose around week 16 to 20. The 0.25 mg starting dose is not therapeutic. It exists purely to let your gut adapt and blunt the nausea. If a step is rough, the guidance is to hold or slow down rather than push through, because rushing the titration does not speed up results.
→ How to reconstitute semaglutide: calculator, units to draw & storage
Side effects and safety
The side effects are overwhelmingly gastrointestinal and cluster during the escalation phase. In pooled STEP data on the 2.4 mg dose, nausea affected about 44% of people, diarrhea about 30%, vomiting about 25%, and constipation about 24%. Most of it is mild to moderate and eases within a week or two of each dose increase. Semaglutide also carries a boxed warning for thyroid C-cell tumors based on rodent studies, and it is contraindicated in anyone with a personal or family history of medullary thyroid carcinoma or MEN 2.
- Research depth: extensive. Human clinical trials: yes, large and randomized.
- GI side effects are common but usually transient and tied to dose increases.
- Prescription medicine in the US. Verify current legal and regulatory status independently.
Frequently asked questions
How much weight can you lose on semaglutide?
In the STEP 1 trial, adults with obesity on the 2.4 mg weekly dose lost an average of 14.9% of their body weight over 68 weeks, versus 2.4% on placebo. Individual results vary widely, and weight tends to return if the medication is stopped without lasting lifestyle change.
Why does semaglutide start at 0.25 mg?
The 0.25 mg dose is a tolerability step, not a therapeutic one. It lets your gastrointestinal tract and appetite signaling adapt to GLP-1 stimulation gradually, which sharply reduces nausea and dropout compared with starting at a full dose.
What are the most common side effects?
Nausea, diarrhea, vomiting, and constipation, in that rough order. They are most intense right after a dose increase and usually settle within one to two weeks. Persistent or severe symptoms are a reason to slow the titration, not push through it.
Is semaglutide the same as Ozempic and Wegovy?
Yes, it is the same molecule. Ozempic and Rybelsus are approved for type 2 diabetes, and Wegovy is approved for weight management at a higher 2.4 mg dose. The brand differences are about approved use and dosing, not the drug itself.
How long does semaglutide take to work?
Appetite changes often show up within the first few weeks, but meaningful weight loss builds over months as the dose escalates. Trial results are measured at 68 weeks, so it is a gradual process rather than a quick fix.
References
Track Semaglutide in Peptide AI
Log your doses, connect labs and wearables, and let the AI show you how Semaglutide is affecting your biomarkers over time.
Download the appEducational information only. This is not medical advice. Peptide AI is an informational and tracking platform. Everything on this page is for general education. It is not a substitute for professional medical advice and is not a recommendation to use any compound. Many peptides listed here are research compounds the FDA has not approved for human use. Talk to a qualified, licensed healthcare provider before you start, change, or stop any protocol.