GLP-1GIPGCG
Semaglutide
Single agonist
MADE SIMPLE
More receptors does not automatically mean “better.” Each mechanism changes the benefit-risk picture.
Single agonist
Dual agonist
Triple agonist • investigational
Results from controlled trials cannot be assumed for unregulated products. For educational purposes only. Not medical advice, diagnosis, treatment, or prescribing guidance. Research and regulatory information can change over time.
HOW THEY WORK
Activates receptors in the pancreas, gut, and brain. It increases glucose-dependent insulin release, lowers glucagon, slows gastric emptying, and signals fullness to appetite centers in the brain.
A second incretin hormone. It supports insulin secretion after meals and is studied for how it adds to GLP-1 effects on appetite, glucose, and fat metabolism.
Adding glucagon-receptor activity is studied for increasing energy expenditure and liver fat use. It is the third pathway targeted by retatrutide.
Unlike growth-hormone peptides that aim to mimic natural pulses, weekly incretin medicines provide a more continuous signal, which is suited to appetite regulation and glucose control.
COMPOUND PROFILES
Mechanism: GLP-1 receptor agonist.
Brand examples: Ozempic (type 2 diabetes), Wegovy (chronic weight management).
Evidence: about 15% average weight loss at 68 weeks (STEP 1) and 15.2% at 104 weeks (STEP 5) at 2.4 mg weekly.
Labeled titration: starts at 0.25 mg once weekly and is increased stepwise, usually every 4 weeks, to a 2.4 mg maintenance dose for weight management.
Watch for: GI effects are most common in the first weeks and after dose increases; appetite can drop enough to undercut protein intake; gallbladder issues with long-term use.
Mechanism: dual GIP and GLP-1 receptor agonist.
Brand examples: Mounjaro (type 2 diabetes), Zepbound (weight management).
Evidence: up to 20.9% average weight loss at 72 weeks on 15 mg (SURMOUNT-1), and about 25% total at 88 weeks in SURMOUNT-4 for people who stayed on treatment.
Labeled titration: starts at 2.5 mg once weekly, increased in 2.5 mg steps every 4 weeks as tolerated, up to 15 mg weekly.
Watch for: GI distress early on; large, high-fat meals often worsen nausea; adequate protein matters to limit lean-mass loss.
Mechanism: triple GLP-1, GIP, and glucagon receptor agonist.
Evidence: Phase 2 showed up to 24.2% average weight loss at 48 weeks. The Phase 3 TRIUMPH-1 trial (topline results, May 2026) reported 19.0%, 25.9%, and 28.3% average loss at 80 weeks on 4, 9, and 12 mg, and 30.3% at 104 weeks on 12 mg.
Doses studied: once weekly, reached by gradual escalation, up to 12 mg in trials.
Watch for: at 12 mg, nausea (42%), diarrhea (32%), constipation (26%), and vomiting (25%) were reported; 11.3% stopped due to side effects. It is not FDA approved as of this update.
*Approval applies to specific branded products and indications only. Trial percentages are averages for people in controlled studies, not predictions for any individual or for unregulated products.
RESEARCH OUTCOMES
Slower gastric emptying and brain satiety signaling reduce hunger, portion size, and food cravings.
Glucose-dependent insulin release and lower glucagon improve fasting glucose and HbA1c, which is why several of these medicines began as diabetes treatments.
These are the compounds with the largest average weight loss in human trials, including reductions in visceral and subcutaneous fat.
Part of the weight lost is lean mass. Trials and guides alike stress high protein intake and resistance training to help preserve muscle.
In trial extensions, many people regained a large share of lost weight after stopping. These medicines are studied as long-term treatments, not short “cycles.”
Dual and triple agonists show larger average losses, but higher doses also brought more GI side effects and discontinuations.
SIDE EFFECTS & RISKS
Nausea, vomiting, bloating, diarrhea, and constipation. These are usually worst during the first weeks and after each dose increase, which is why doses are escalated slowly.
Pancreatitis, gallbladder problems (watch for persistent abdominal pain), and significantly delayed stomach emptying. People with a history of pancreatitis are generally not candidates.
Approved GLP-1 medicines carry a boxed warning about thyroid C-cell tumors and are not used in people with a personal or family history of medullary thyroid carcinoma or MEN 2.
Strong appetite suppression can lead to low protein intake, fatigue, and muscle loss over extended periods.
MONITORING
Tracks insulin sensitivity and glucose control.
Liver health, especially relevant with multi-pathway agonists.
Weight loss and metabolic changes can shift cholesterol and triglycerides.
Overall systemic health, kidney function, and electrolytes—important if vomiting or diarrhea occur.
Body composition, strength, and protein intake help show whether weight lost is fat or lean mass.
A baseline before starting and periodic rechecks (often every 8–12 weeks) are a common approach.
KEY PRINCIPLES
Semaglutide, tirzepatide, and retatrutide are dosed once a week by subcutaneous injection, ideally on the same day each week, any time of day.
Every program escalates gradually. Faster increases mostly add side effects, not results.
These compounds act on overlapping receptors. Combining two GLP-1-based compounds is not how any were studied.
The largest fat-loss results are best supported by adequate protein and strength training to protect muscle.
Approved products are made under FDA oversight. For anything else, identity, dose, and sterility are unknown without independent third-party testing (COA with lot number), sealed sterile vials, and cold-chain shipping. Warm, sticky, or unlabeled product is a red flag.
Because of dose titration, bloodwork, and serious-risk screening, GLP-1 medicines are prescribed and monitored by licensed clinicians.
QUICK ANSWERS
Peptide medicines that mimic GLP-1, a gut hormone that helps control appetite and blood sugar. Some also target GIP and glucagon receptors.
Semaglutide and tirzepatide are approved in specific branded products for specific uses. Retatrutide is still investigational as of this update.
Average trial weight loss has been highest for retatrutide, then tirzepatide, then semaglutide—but semaglutide has the longest safety record, and side effects rise with potency and dose.
Standard employment drug tests are not designed to detect them. Sport-specific anti-doping rules change, so athletes should check current WADA and league lists.
Content review: September 18, 2026. Sources: STEP 1 (NEJM) • SURMOUNT-1 (NEJM) • Retatrutide Phase 2 (NEJM) • TRIUMPH-1 topline (Lilly). For educational purposes only. Not medical advice, diagnosis, treatment, or prescribing guidance. Research and regulatory information can change over time.
DOSE ESCALATION
Incretin drugs are started at a low dose and increased in steps, usually every 4 weeks. The low starting doses mainly help the body adjust and reduce stomach side effects. They are not expected to produce the full result.
| Compound | Source | Weekly steps | Step interval |
|---|---|---|---|
| Semaglutide Wegovy (weight) | FDA label | 0.25 → 0.5 → 1 → 1.7 → 2.4 mg | Every 4 weeks |
| Tirzepatide Zepbound / Mounjaro | FDA label | 2.5 mg start, then +2.5 mg steps up to 5, 10, or 15 mg maintenance | At least 4 weeks per step |
| Retatrutide Not FDA approved | Phase 2 trial (NEJM 2023) | Most arms started at 2 mg (some at 4 mg) and stepped up to 1, 4, 8, or 12 mg | About every 4 weeks |
| Eloralintide Not FDA approved | Phase 2 trial (Lancet 2025) | Fixed arms of 1, 3, 6, or 9 mg, plus escalation arms (3 → 6 → 9 mg and 6 → 9 mg) | Stepwise |
| CagriSema Under FDA review | Phase 3 REDEFINE trials | Both components stepped up together to 2.4 mg + 2.4 mg | About every 4 weeks |
Labels allow a longer stay at a step when side effects are hard to tolerate. Not everyone needs the top dose. The goal is the lowest dose that works and is tolerated, decided with a prescriber.
Never double up. After several missed weeks, ask a prescriber whether to restart at a lower dose.
Approved pens deliver fixed, pre-set doses. Vials require the concentration math on our Peptide Math page, where a single decimal error can mean a much larger dose.
THE NEXT PATHWAY
Amylin is released by the same pancreatic beta cells that make insulin, right after meals. It slows stomach emptying, increases fullness through the brainstem, and lowers glucagon after meals. That makes it a natural partner to GLP-1 drugs.
The first amylin analog, FDA approved in 2005 for people with diabetes who use mealtime insulin. It is short-acting and injected before meals, which limited how widely it was used.
A long-acting amylin analog dosed once weekly (Novo Nordisk). In the REDEFINE 1 trial, cagrilintide alone produced about 11.8% average weight loss at 68 weeks.
Cagrilintide 2.4 mg + semaglutide 2.4 mg in one weekly injection. REDEFINE 1: 20.4% average loss at 68 weeks vs 3.0% on placebo (22.7% among people who stayed on treatment). The FDA application was filed in December 2025.
A selective amylin-receptor agonist (Eli Lilly). In a 48-week Phase 2 trial, weekly doses of 1–9 mg produced 9.5% to 20.1% average weight loss vs 0.4% on placebo. Phase 3 trials are underway.
Common side effects in amylin trials were nausea, other GI effects, and fatigue, and they were more frequent at higher doses and with faster escalation. None of the long-acting amylin drugs above were FDA approved at our last content review. Check the FDA’s current status before relying on this.