Semaglutide
FDA-approved GLP-1 receptor agonist · once-weekly subcutaneous
Semaglutide is an FDA-approved GLP-1 receptor agonist — a long-acting copy of the gut hormone GLP-1 that the body releases after eating. It is sold as Ozempic and Rybelsus for type 2 diabetes and as Wegovy for weight management, and it lowers blood sugar and reduces appetite by switching on the GLP-1 receptor. Unlike most peptides in this library, it is a genuine approved medicine with real approved human doses and large clinical trials behind it: in the STEP-1 obesity trial the 2.4 mg dose produced about 15% mean weight loss over 68 weeks, and in the SELECT trial it cut cardiovascular events by roughly 20% in people with heart disease. The honest caveats marketing tends to skip: the gastrointestinal side effects are common (which is why the dose is raised slowly), a meaningful share of the weight lost is muscle rather than fat, and weight tends to come back after stopping — it is a chronic therapy, not a one-time fix.
The short version
Semaglutide is a man-made copy of GLP-1, a hormone your gut releases after a meal. GLP-1 normally tells the pancreas to make insulin, tells the stomach to empty more slowly, and tells the brain you are full — but the natural hormone is destroyed within minutes. Semaglutide is engineered to resist that breakdown and to stick to a blood protein (albumin), so a single dose lasts about a week.
It is an approved medicine, not a research chemical. The same molecule is sold under three brand names: Ozempic (a weekly injection for type 2 diabetes), Wegovy (a higher-dose weekly injection for weight loss), and Rybelsus (a daily tablet for diabetes).
Its effects are real and well-studied: substantial weight loss in obesity trials and fewer heart attacks and strokes in people with existing heart disease. But it is not magic — the side effects are mostly digestive, some of the lost weight is muscle, and the weight tends to return if you stop, so it is meant to be taken long-term.
Molecular identity
Specs
- Molecular weight
- 4113.58 g/mol
- Molecular formula
- C187H291N45O59
- Monoisotopic mass
- 4111.12 Da
- Molecular target
- GLP-1 receptor (agonist)
- Amino acids
- 31-residue backbone (94% homology to GLP-1(7-37))FDA Ozempic label
- Structure / class
- Acylated GLP-1 receptor agonist; Aib8, Arg34, Lys26 C18-diacid via γGlu/miniPEG linkerFDA label; PubChem CID 56843331
- CAS / UNII
- 910463-68-2 · 53AXN4NNHXPubChem CID 56843331; FDA UNII
- Brand / approval
- FDA-approved — Ozempic & Rybelsus (T2D), Wegovy (weight management)FDA label
- Regulatory status
- FDA-approved drug; WADA 2026 Monitoring Program (monitored, not prohibited)FDA / WADA 2026
Plain English
Mechanism
Semaglutide is a GLP-1 receptor agonist — "agonist" means a molecule that switches a receptor on, and GLP-1 (glucagon-like peptide-1) is an incretin, a gut hormone released after eating. By binding and activating the GLP-1 receptor it reproduces four linked effects of the natural hormone.
First, glucose-dependent insulin secretion: it tells the pancreas to release more insulin (the hormone that lowers blood sugar), but only when blood sugar is high. Because the effect switches off at normal glucose levels, semaglutide on its own rarely causes hypoglycemia (dangerously low blood sugar). Second, glucagon suppression: it lowers glucagon (the hormone that tells the liver to dump sugar into the blood), again only when glucose is elevated.
Third, slowed gastric emptying: food leaves the stomach more slowly, which blunts the post-meal blood-sugar spike and prolongs the feeling of fullness — this is also the root of the nausea and the interaction with oral drugs. Fourth, central appetite control: it acts on appetite-regulating regions of the brain (the hypothalamus and hindbrain) to reduce hunger and food intake, which is the main driver of weight loss. The net result is better glucose control plus reduced calorie intake, and downstream cardiovascular and kidney benefit.
Sources:DailyMed (Ozempic)PMID 27633186
Why people reach for it
Potential benefits
Semaglutide is the GLP-1 most people mean when they say "the weight-loss shot" — here's what actually draws them to it, with the honest trade-offs kept in view.
- Real, trial-sized weight loss — Its headline appeal — and unusually for this library, it's backed by large human trials: in STEP-1 the 2.4 mg dose produced about 15% mean body-weight loss over 68 weeks, driven mainly by genuine appetite reduction.
- Appetite that finally goes quiet — By acting on the brain's appetite centers and slowing the stomach, it dials down hunger and "food noise," which is why people find a calorie deficit far easier to hold than on willpower alone.
- Steadier blood sugar — As an approved type 2 diabetes medicine (Ozempic/Rybelsus), it lowers blood sugar by prompting glucose-dependent insulin and suppressing glucagon — and because that effect switches off at normal glucose, it rarely causes lows on its own.
- A proven heart-risk reduction — In the SELECT trial it cut major cardiovascular events by roughly 20% in people with established heart disease — a durable benefit that's the reason much of its long-term use is justified.
- A once-weekly rhythm that's easy to keep — Its ~7-day half-life means one injection a week on a fixed day — far less of an adherence burden than the older daily Liraglutide.
- A base that pairs cleanly with amylin — Because it works purely through the GLP-1 axis, it slots alongside Cagrilintide (the CagriSema pairing) for an additive, trial-backed step up in weight loss.
Sources:PMID 33567185PMID 37952131PMID 27633186DailyMed (Wegovy)DailyMed (Ozempic)
What people reach for Semaglutide for, based on what the trials report and how it's used — real approved outcomes, but paired with their honest costs (GI side effects, some lean-mass loss, regain after stopping), not a cure or a guarantee.
Implied timing
Best time to dose
Implied best time
Anytime (consistent, same day weekly)
Most people take Semaglutide on a fixed day each week — the day you hold it matters, the hour barely does.
- Its half-life is about 7 days, so blood levels are essentially flat between doses — there is no daily peak to line up with a meal or a clock. Picking one weekday and holding it (e.g. every Sunday) is what keeps levels steady; the exact time of day is up to you.
- Effects build over weeks, not hours: appetite suppression deepens across the slow titration and weight loss accrues over months, so no single dose's timing changes the outcome — consistency week to week does.
- It can be taken with or without food; meal timing does not affect the subcutaneous injection.
- The main day-to-day variable is early nausea, so some people choose a low-key day (a quiet weekend) for the dose, so any queasiness lands when it's least disruptive.
No study establishes an ideal time of day for Semaglutide — this is reasoned from its ~7-day half-life and how it's used. The usual peptide-dosing default is the midday-to-evening window, but for a once-weekly agent the real lever is the same weekday each week, not the hour.
Sources:DailyMed (Ozempic)
How to run it
Dosing & protocol
Semaglutide's titration IS the protocol. The dose is started low and stepped up every four weeks specifically to let the gut adapt and minimize nausea — rushing the ramp is how most GI side effects happen. The schedule below is the real FDA-approved Wegovy weight-management titration, which is also how off-label and research-vial use mirrors it. Subcutaneous injection, once weekly.
The approved Wegovy titration is the honest anchor here. Off-label or research-vial use of semaglutide mirrors this same ramp — the biology that demands slow titration does not change. WADA 2026: GLP-1 agonists including semaglutide are on the Monitoring Program (tracked, not prohibited). This is not a recommendation to self-medicate; the approved indication is a medical diagnosis requiring a prescriber.
Titration schedule
The slow ramp is not optional — it is the mechanism for tolerability. Each step is held for a minimum of 4 weeks before advancing.
- Weeks 1–4:
- 0.25 mg SC once weekly — starter dose for tolerability only; not yet a therapeutic weight-management dose.
- Weeks 5–8:
- 0.5 mg SC once weekly — first therapeutic step; most users notice some appetite suppression here.
- Weeks 9–12:
- 1.0 mg SC once weekly.
- Weeks 13–16:
- 1.7 mg SC once weekly.
- Week 17 onward (maintenance):
- 2.4 mg SC once weekly — the approved Wegovy maintenance dose (Ozempic T2D maintenance tops at 2 mg). Stay at the last tolerated step if GI side effects arise at a higher rung; the titration is a floor, not a fixed escalator.
Subcutaneous administration
Semaglutide is injected into subcutaneous fat once weekly. Site, rotation, and timing are the practical decisions.
- Injection site:
- Abdomen (at least 2 inches from the navel), outer thigh, or upper arm. Rotate sites week to week to prevent lipohypertrophy (fatty lumps from repeated use of one spot).
- Pen device (branded):
- Ozempic and Wegovy come as pre-filled prefilled auto-injectors (pens) — dose is dialed and injected; no reconstitution. Each pen covers the weeks in its dose range; follow the pen's label for cartridge changes.
- Research vial (lyophilized):
- Reconstituted vials (see calculator defaults: 5 mg vial + 2 mL bacteriostatic water = 2,500 mcg/mL) are drawn on a U-100 insulin syringe. At that dilution, 0.25 mg = 10 IU · 0.5 mg = 20 IU · 1.0 mg = 40 IU · 1.7 mg = 68 IU · 2.4 mg = 96 IU. The calculator adjusts for any vial size.
- Day of the week:
- Pick one consistent day each week (e.g. Sunday morning). Timing relative to meals is not critical for the subcutaneous injectable; inject the same day every week to keep serum levels steady. A ~7-day interval is the target; up to a 3-day shift on a given week is acceptable.
Duration / ongoing use
GLP-1 receptor agonists are not cycled like research peptides — they are designed as chronic therapy, and the evidence reflects that.
- Ongoing use:
- The approved indication assumes indefinite maintenance use. Weight loss continues to build over 6–12 months; cardiovascular benefit (SELECT trial data) accrued over ~4 years of use.
- On stopping:
- Weight regain is well-documented after discontinuation. The STEP extension data showed most participants regained a substantial portion of lost weight within a year of stopping — this is a characteristic of GLP-1 therapy, not a failure of the drug. Plan accordingly: if the goal is durable weight management, stopping has a predictable cost.
- Dose holidays:
- Short gaps (travel, supply interruption) of up to 2 weeks are generally tolerated without full re-titration. Longer interruptions may require dropping back one dose step and reclimbing to manage GI side effects.
Dose measurement (research vial)
If using a lyophilized research vial rather than an approved pen, the calculator defaults give the reference dilution.
- Standard dilution:
- 5 mg vial + 2 mL bacteriostatic water = 2,500 mcg per mL (2.5 mg/mL). On a 100-unit (1 mL) insulin syringe: 0.25 mg = 10 IU · 0.5 mg = 20 IU · 1.0 mg = 40 IU · 1.7 mg = 68 IU · 2.4 mg = 96 IU.
- Why this dilution:
- The 2 mL choice spreads the smaller starter doses (0.25–0.5 mg) across enough syringe units to measure accurately without drawing near-empty fractions. Use the on-page calculator to adjust for any vial size.
Substrate the signal needs
Nutritional cofactor precision
Semaglutide's cost profile defines the cofactor priorities: it cuts appetite hard (making protein targets hard to hit), slows gastric emptying (causing nausea and constipation), and causes a significant lean-mass loss with the weight. Mitigating those costs is the dominant work here. The amplify category is modest — the gut-biology changes semaglutide makes can be supported, not amplified, by diet.
Reasoned from GLP-1 pharmacology and mainstream weight-loss nutrition applied to semaglutide's known trade-offs — not a semaglutide supplement trial. Supplement doses are general evidence-based ranges, not semaglutide-specific findings.
SUPPLY: Protein + creatine + resistance training (lean-mass guard — the top priority)
The single most important thing to do alongside semaglutide. A large fraction of GLP-1-driven weight loss is lean mass, not fat — and with appetite suppressed this hard, getting enough protein is the main practical challenge.
- Protein target:
- 1.6–2.0 g per kilogram of body weight per day (roughly 0.7–0.9 g per pound). With appetite blunted, prioritize protein-first at every meal — eat protein before vegetables, vegetables before carbs. Protein shakes and Greek yogurt are practical ways to hit the number when eating volume is low.
- Creatine:
- 3–5 g creatine monohydrate daily — one of the most evidence-backed supplements for preserving lean mass during a caloric deficit. No loading phase required; 3–5 g/day is the maintenance dose. Take it at any consistent time.
- Resistance training:
- Non-negotiable complement. Without a signal to keep muscle, even adequate protein will not fully prevent lean-mass loss. 2–3 sessions per week of compound movements (squat, hinge, push, pull) is the minimum effective dose.
MITIGATE: Nausea + GI upset
The titration schedule (see Dosing) is the primary nausea tool — do not rush it. These supplements and habits reduce what the ramp cannot eliminate.
- Ginger:
- 1–2 g ginger (capsule or fresh) with meals, or ginger tea. Among the best-supported non-pharmaceutical options for GI nausea; acts on 5-HT3 receptors centrally and locally.
- Vitamin B6 (pyridoxine):
- 25–50 mg B6 with meals on high-nausea days. Classic adjunct for nausea (the mechanism behind B6 in morning sickness applies here too).
- Meal composition:
- Small, low-fat, protein-and-vegetable-forward meals during titration. High-fat, heavy meals sit in the slowed stomach the longest and trigger the worst nausea. Eat smaller portions more frequently if needed.
MITIGATE: Constipation
Slowed gastric emptying means slower whole-gut transit. Constipation is common, especially early in titration.
- Soluble fiber:
- At least 25–35 g total dietary fiber daily, emphasizing soluble sources (oats, psyllium, legumes, fruit). Soluble fiber feeds gut bacteria and adds bulk without the roughage of insoluble fiber that can worsen gut discomfort.
- Magnesium glycinate or citrate:
- 300–400 mg elemental magnesium at bedtime. Draws water into the colon and supports motility; glycinate or citrate is well tolerated vs oxide forms. Also helps sleep and the muscle-cramp pattern some users get in a deficit.
- Hydration:
- With less food volume, total fluid intake from food drops. Target 2–2.5 L water daily regardless of eating pattern; hydration and fiber work together.
MITIGATE: Electrolytes + micronutrient gaps
Eating much less means consuming much less sodium, potassium, magnesium, and vitamins — running low on any of them is quiet but cumulative.
- Electrolytes:
- Sodium, potassium, and magnesium are undersupplied when eating volume drops sharply. An electrolyte supplement (not a sugar-heavy sports drink) or deliberate inclusion of electrolyte-rich foods (avocado, leafy greens, nuts, broth) covers the gap. Fatigue and muscle cramps are the early signs of depletion.
- Daily multivitamin + targeted micronutrients:
- A broad-spectrum multivitamin as baseline insurance. Pay specific attention to B12 (lower with reduced animal-food intake), iron (especially for women), calcium, and vitamin D — nutrients where a deficit is easy and slow to emerge.
AMPLIFY: Gut microbiome support
The gut environment changes under semaglutide — slower transit gives bacteria more contact time with food. Supporting a favorable microbiome is the one amplification signal worth naming.
- Fermented foods and prebiotics:
- Daily fermented foods (yogurt, kefir, kimchi, sauerkraut, miso) and prebiotic fiber (garlic, onion, leeks, asparagus, oats). A well-fed gut microbiome produces short-chain fatty acids including butyrate, which support intestinal barrier integrity and endogenous GLP-1 production.
Sources:DailyMed (Wegovy)PMID 33567185
Combinations + timing
Stacking notes + timing windows
Semaglutide acts exclusively via the GLP-1 receptor. That narrows the stack universe: adding another GLP-1 or incretin agonist is redundant (same receptor, same axis). The useful partners hit the two gaps semaglutide leaves — insufficient lean-mass protection and GI tolerability during titration — or pair via a completely different satiety mechanism.
CagriSema (Cagrilintide + semaglutide) is the one trial-backed complementary combination; the others are mechanistically reasoned but not tested head-to-head as combinations. Stacking two GLP-1 agonists (semaglutide + tirzepatide, semaglutide + liraglutide) is receptor-level redundancy — additive side effects, not additive benefit. Doses here are reference points; the approved titration for semaglutide is the non-negotiable foundation regardless of what is stacked.
Semaglutide + Cagrilintide (CagriSema)
The one trial-backed complementary stack — different satiety hormones, different receptors, additive effect on weight loss.
- Why it works:
- Cagrilintide is an amylin receptor agonist. Amylin is a satiety hormone co-released with insulin that slows gastric emptying and suppresses appetite through a receptor entirely distinct from GLP-1. The two hormones act via complementary pathways — GLP-1 receptor + amylin receptor — so their combined effect is additive, not redundant. Phase 2 CagriSema trials (the fixed-dose combination) showed greater weight loss than either agent alone.
- The protocol:
- Cagrilintide 2.4 mg SC once weekly alongside the standard semaglutide titration. Both are given on the same injection day; they can be co-injected (separate syringes, adjacent sites) or a single fixed-dose pen when available. Note: cagrilintide itself requires its own titration — the combination is an investigational product and not yet standard of care.
- Outcome:
- Greater weight loss vs semaglutide alone; the target use case is weight management goals where semaglutide monotherapy plateau has been reached.
Semaglutide + Ipamorelin / CJC-1295 (lean-mass guard)
A GH secretagogue partner for the lean-mass deficit semaglutide creates — different axis entirely.
- Why it works:
- Semaglutide's caloric restriction pathway breaks down lean mass along with fat. Ipamorelin (a GHRP) and CJC-1295 (a GHRH analog) stimulate pulsatile growth hormone release, which favors fat mobilization and muscle preservation. GH and GLP-1 operate on separate receptor families — this is a genuinely complementary pairing, not the same lever.
- The protocol:
- Ipamorelin 200–300 mcg SC once daily at bedtime (the natural GH pulse aligns with sleep onset); CJC-1295 no-DAC 100–200 mcg SC alongside, or CJC-1295 with DAC 2 mg SC once weekly. Run the semaglutide titration as normal; add the GH secretagogue once the semaglutide dose has stabilized (week 5+) to reduce variable GI load during the titration ramp.
- Outcome:
- Weight loss steered more toward fat loss and less lean mass; particularly relevant for users who are already lean or who depend on muscle for athletic performance.
Semaglutide + BPC-157 (GI comfort during titration)
A gut-healing adjunct for the early titration window when GI side effects are most intense.
- Why it works:
- BPC-157 is studied for healing the gut lining and supporting GI motility in rodent models. Semaglutide's nausea and GI upset peaks during the 0.25–1.0 mg titration phase. BPC-157 does not share the GLP-1 axis; it works via NO-signaling and growth-factor pathways — a different lever aimed at the GI tissue being stressed during dose escalation.
- The protocol:
- BPC-157 250–500 mcg SC once daily during the first 8–12 weeks of the semaglutide titration ramp. Site rotation applies to both; they can be given as adjacent injections. Once steady-state semaglutide is well tolerated, BPC-157 can be tapered.
- Outcome:
- GI tolerability during the titration window; potentially smoother escalation through the nausea-heavy early steps. Reasoned from mechanism — not a tested combination.
Sources:DailyMed (Wegovy)PMID 33567185
Reconstitution math
Reconstitution calculator
Reconstitution calculator
Calculated for a 1 mL U-100 insulin syringe (100 units/mL).
Units per dose
10
Draw to this mark on a U-100 syringe
- Volume per dose
- 0.1 mL
- Doses per vial
- 20
- Concentration
- 2.5 mg/mL
One vial lasts
- Daily
- 20 days
- Every other day
- 40 days
- 5×/week
- 28 days
Research use only. Not for human consumption. Outputs are reference values based on research literature — verify all measurements independently.
From the studies
Side effects from research
Semaglutide carries an FDA boxed warning for thyroid C-cell tumors: in rodents it caused dose- and duration-dependent thyroid C-cell tumors, and it is unknown whether it causes these tumors, including medullary thyroid carcinoma (MTC), in humans. It is contraindicated in people with a personal or family history of MTC or with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).
The most common adverse effects are gastrointestinal — nausea, diarrhea, vomiting, constipation, and abdominal pain — which are dose-related and the reason the dose is titrated slowly. Other labeled warnings include pancreatitis (discontinue if suspected), gallbladder disease, acute kidney injury from dehydration during heavy GI symptoms, worsening of diabetic retinopathy in diabetics, and hypoglycemia when combined with insulin or sulfonylureas.
Two honesty points marketing tends to omit: a substantial fraction of the weight lost is lean (muscle) mass rather than fat, a recognized concern in the obesity literature; and weight is regained after stopping, so the benefit depends on continued use. None of this makes the drug unsafe in supervised use — it is approved and widely prescribed — but these are the trade-offs an honest summary has to state.
As reported in literature
Research dosing ranges
These are the doses tested in the major published trials, shown separately so the trial evidence is never mistaken for a recommended regimen. Unlike most peptides in this library, semaglutide's evidence base is large, randomized, and human — these are landmark cardiovascular-outcome and weight-loss trials, not animal data. All were given as the approved subcutaneous (under-the-skin) or oral forms under medical supervision.
| Dose | Route | Model | Outcome | Sources: |
|---|---|---|---|---|
| 0.5 / 1.0 mg | SC weekly | Human (SUSTAIN-6, T2D high CV risk, n=3,297) | Major cardiac events 6.6% vs 8.9% placebo; HR 0.74 (noninferiority) | PMID 27633186 |
| 2.4 mg | SC weekly (68 wk) | Human (STEP-1, obesity, no diabetes, n=1,961) | Mean weight −14.9% vs −2.4% placebo; 86.4% lost ≥5% | PMID 33567185 |
| 2.4 mg | SC weekly (~40 mo) | Human (SELECT, overweight/obese + CVD, n=17,604) | Major cardiac events 6.5% vs 8.0%; ~20% relative risk reduction | PMID 37952131 |
| up to 14 mg | Oral daily | Human (PIONEER 6, T2D high CV risk, n=3,183) | Major cardiac events 3.8% vs 4.8%; HR 0.79, non-inferior | PMID 31185157 |
Quick answers
Frequently asked
What is semaglutide?
It is an FDA-approved GLP-1 receptor agonist — a long-acting copy of the gut hormone GLP-1. It is sold as Ozempic and Rybelsus for type 2 diabetes and as Wegovy for weight management. It lowers blood sugar and reduces appetite by activating the GLP-1 receptor.
Is semaglutide the same as Ozempic, Wegovy, and Rybelsus?
Yes — all three are the same active molecule, semaglutide. Ozempic is the weekly injection for diabetes, Wegovy is the higher-dose weekly injection for weight loss, and Rybelsus is the daily tablet for diabetes. They differ in dose, form, and approved use, not in the underlying drug.
How much weight does semaglutide produce in trials?
In the STEP-1 obesity trial, the 2.4 mg weekly dose (Wegovy) produced about 14.9% mean body-weight loss over 68 weeks, versus about 2.4% on placebo, with most participants losing at least 5%. That is a supervised trial result paired with diet and lifestyle measures, not a guarantee.
Why is the dose increased so slowly?
The gastrointestinal side effects — nausea, diarrhea, vomiting — are dose-related. Starting low and stepping up over weeks (a titration ladder) gives the gut time to adjust and keeps those effects manageable. The starter doses are for tolerability and are not yet full treatment doses.
Is semaglutide banned in sport?
As of the 2026 WADA list, GLP-1 receptor agonists including semaglutide are on the WADA Monitoring Program — tracked but NOT prohibited. A possible future ban is under consideration. Some vendor sources incorrectly claim a current full ban; per WADA's own 2026 documents it is monitored, not banned.
Does the weight come back if you stop?
Largely, yes. Follow-up after discontinuation in the STEP program showed substantial weight regain, which is why semaglutide is understood as a chronic therapy rather than a one-time treatment. The benefit depends on continued use.
Primary sources
References
- PubChem CID 56843331PubChem CID 56843331 (Semaglutide, free acid)
- DailyMed (Ozempic)DailyMed — Ozempic (semaglutide) label
- DailyMed (Wegovy)DailyMed — Wegovy (semaglutide) label
- FDA NDA 213051FDA Rybelsus (oral semaglutide) label
- PMID 27633186Marso et al., NEJM 2016 (SUSTAIN-6, CV outcomes)
- PMID 33567185Wilding et al., NEJM 2021 (STEP-1, obesity)
- PMID 37952131Lincoff et al., NEJM 2023 (SELECT, CV outcomes)
- PMID 31185157Husain et al., NEJM 2019 (PIONEER 6, oral, CV outcomes)
- WADA 2026WADA 2026 Monitoring Program (GLP-1 agonists monitored, not prohibited)
Research use only · Not medical advice · Updated 2026-06-01