Reader’s guide · First edition · September 2026 · Revised October 1, 2026
Semaglutide
A guide to the drug in Ozempic and Wegovy: the most-studied peptide in the world, a pill since 2025, a generic in Canada since June, and a vial market the FDA spent 2026 shutting down
Semaglutide is the GLP-1 that made the category. It has been an approved drug since 2017, first for diabetes and then for weight, heart disease, kidney disease, and liver disease, on trials that enrolled more people than every other peptide in this series combined. It is the one weight-loss injection with a daily pill, the first with a generic in a G7 country, and the one whose compounded copies the FDA has spent the last eighteen months removing from the market. This guide covers what it does, what the big trials showed, how it is dosed on the label, and what changes when the same molecule arrives as a compounded vial or a research-chemical powder.
Who this is for
Written for adults who are taking, or being offered, semaglutide in any form, and for anyone deciding between the brand, a compounded copy, and a vial. It summarizes the prescribing information, the published trials, and the regulatory position as of the edition date. It is not medical advice.
What semaglutide is7
GLP-1 is a gut hormone released after a meal that raises insulin when glucose is high, slows the stomach, and tells the brain to stop eating. The natural hormone lasts minutes. Semaglutide is a modified copy with two changes that protect it from breakdown and a fatty-acid tail that binds blood albumin, so one injection lasts a week. Its predecessor liraglutide lasted a day; its successor tirzepatide adds a second hormone. Semaglutide is the one in the middle, and the one with the most evidence.
| Product | Approved | For | Dose |
|---|---|---|---|
| Ozempic (injection) | 2017; heart 2020; kidney January 2025 | Type 2 diabetes, and reducing heart and kidney risk in it | 0.25 to 2 mg weekly |
| Rybelsus (tablet) | 2019 | Type 2 diabetes | 3, 7, or 14 mg daily |
| Wegovy (injection) | 2021; heart 2024; liver 2025 | Weight, and reducing heart risk with obesity; MASH | 0.25 to 2.4 mg weekly; a 7.2 mg dose marketed as Wegovy HD from 2026 |
| Wegovy pill (tablet) | December 2025 | Weight | 1.5 to 25 mg daily |
- Class
- GLP-1 receptor agonist; a 31-amino-acid peptide with a fatty-acid side chain
- Maker
- Novo Nordisk. Generic injections approved in Canada from April to June 2026; none in the United States, where patents run to 2031
- Forms in use
- Brand pens and tablets by prescription; compounded vials, now largely off the market; research-chemical vials of 5 to 30 mg, which are unapproved drugs
- Price
- About $349 a month cash for the injection through the maker's pharmacy, $149 to $299 for the pill by dose; list prices over $1,300; research vials $25 to $70
- Anti-doping
- Not prohibited; GLP-1 drugs are on WADA's monitoring program
The evidence is for the pen and the pill
Every number in this guide comes from the approved products, made under one manufacturer's controls and given by its label. The same molecule in a compounded vial or a research powder shares the name and the mechanism, and shares none of what the trials measured about purity, dose, or stability.
How it works7
Three effects, in order of how much they matter for weight. In the brain, semaglutide acts on appetite centers so that meals end sooner and food is less rewarding; users describe food noise going quiet. In the stomach, it slows emptying, so fullness lasts. In the pancreas, it raises insulin and lowers glucagon only when glucose is high, which is why it does not cause low blood sugar on its own and why it was a diabetes drug first.
| Where | What it does | What it explains |
|---|---|---|
| Brain | Reduces appetite and food reward | The weight loss, and why it returns when the drug stops |
| Stomach | Slows emptying | Fullness, nausea, and the warnings about anesthesia and intestinal blockage |
| Pancreas | Insulin up and glucagon down, only when glucose is high | Diabetes control without hypoglycemia, unless combined with insulin |
| Heart and kidney | Less inflammation and pressure on both, partly independent of weight | The SELECT and FLOW results |
Because the effect is on appetite rather than metabolism, semaglutide is a treatment, not a cure. The STEP 1 extension followed people who stopped after 68 weeks: they regained about two-thirds of the lost weight within a year, and the improvements in blood pressure and lipids went with it.
Body weight at 68 weeks on Wegovy 2.4 mg in adults with obesity, against 2.4% on placebo, in about 1,960 people
In adults with type 2 diabetes, where every GLP-1 drug loses less
Major cardiovascular events over about three years in 17,600 adults with obesity and heart disease but no diabetes
Kidney disease progression, kidney failure, or cardiovascular death in adults with diabetes and kidney disease
Body weight at 64 weeks on the 25 mg pill, in the trial that supported the December 2025 approval
Of lost weight regained within a year of stopping, in the STEP 1 extension
| Trial | Who | Result | What it settles |
|---|---|---|---|
| STEP 1 (2021) | 1,961 adults with obesity, no diabetes, 68 weeks | About 15% lost; a third lost more than 20% | The weight claim |
| STEP 2 (2021) | Adults with obesity and type 2 diabetes | About 10% lost | Diabetes blunts the effect |
| SELECT (2023) | 17,604 adults with obesity and heart disease, about 3 years | 20% fewer heart attacks, strokes, and cardiovascular deaths | The only weight-loss drug with a cardiovascular outcome trial |
| FLOW (2024) | Adults with diabetes and kidney disease | 24% less kidney progression and death | Kidney protection; approval January 2025 |
| OASIS 4 (2025) | 307 adults with obesity, 64 weeks, daily 25 mg tablet | About 17% lost | The pill matches the injection |
| STEP 1 extension (2022) | Participants after stopping | Two-thirds of the loss regained in a year | It is maintenance therapy |
Tirzepatide loses more weight, about 20% in its own trials and 25% in the head-to-head with CagriSema. Semaglutide's edge is the outcomes: nothing else in this category has shown fewer heart attacks in people without diabetes.
What this supports
That semaglutide, as the approved product, reliably produces double-digit weight loss for as long as it is taken, and reduces cardiovascular and kidney events in the people its trials enrolled. It is the best-evidenced peptide in this series by a wide margin, and the evidence belongs to the pen and the pill.
The label escalates slowly because the side effects are front-loaded and dose-related. Every step is held at least four weeks, and the label allows staying at a lower step, or dropping back, when nausea is bad. Most weight loss happens in the first six to nine months and then plateaus; the drug is then holding the loss, not adding to it.
| Weeks | Weekly dose | Purpose |
|---|---|---|
| 1–4 | 0.25 mg | Tolerance; not a treatment dose |
| 5–8 | 0.5 mg | First effective step |
| 9–12 | 1 mg | Escalation |
| 13–16 | 1.7 mg | Escalation; a maintenance dose for those who cannot tolerate 2.4 |
| 17 on | 2.4 mg | Maintenance |
Ozempic tops out at 2 mg; the pill escalates 1.5, 4, 9, then 25 mg daily. A missed injection is taken within five days or skipped; never doubled.
What the next table is, and is not
It expresses the label escalation for a 10 mg research vial, so the arithmetic can be checked against the pen. The pen delivers a fixed dose with no arithmetic; the vial is an unapproved drug whose strength no one has verified. Doses here are the label's, reported for the vial, not recommended.
- Vial
- 10 mg, as sold by research vendors; identity and quantity unverified unless a pharmacy dispensed it
- Water added
- 2 mL bacteriostatic water
- Concentration
- 5 mg/mL (5,000 mcg/mL). Use the same concentration for the whole course; a change between vials is the classic overdose path.
- Syringe
- 0.3 mL insulin syringe with half-unit marks for the first three steps; 0.5 mL from 1.7 mg
| Weeks | Weekly dose | Draw | Units | Used per 4 weeks |
|---|---|---|---|---|
| 1–4 | 0.25 mg | 0.05 mL | 5 | 1 mg |
| 5–8 | 0.5 mg | 0.1 mL | 10 | 2 mg |
| 9–12 | 1 mg | 0.2 mL | 20 | 4 mg |
| 13–16 | 1.7 mg | 0.34 mL | 34 | 6.8 mg |
| 17 on | 2.4 mg | 0.48 mL | 48 | 9.6 mg (about 1 vial) |
A 10 mg vial covers the first twelve weeks of escalation, or four weeks at maintenance. A mixed vial has no beyond-use date outside a pharmacy and will not keep for the months a slow escalation takes.
What each draw looks like · 0.5 mL (50-unit) U-100 insulin syringe
The plunger tip sits on the line for the dose. Units are marks on a U-100 syringe: 100 units is 1 mL. The picture assumes the concentration in the table above; a different amount of water changes every line.
- Nausea is worst in the week after each step up and fades; eating smaller meals, stopping when full, and avoiding fatty food are the label's own advice.
- Weight loss on the drug is a third lean mass unless resistance training and protein intake are kept up. That is true of every drug in this class.
- The plateau is not failure. At maintenance the drug is doing its job by holding weight that would otherwise return.
From 2022 to early 2025, semaglutide was on the FDA's drug shortage list, and the law allows pharmacies to compound copies of a drug in shortage. That window built an industry: telehealth companies, compounding pharmacies, and eventually research vendors selling the powder. The FDA declared the shortage over in February 2025, gave pharmacies until spring to stop, and spent 2026 enforcing it. The vial market outlived the legal basis for it.
| Source | What it is | Legal position, as of this edition |
|---|---|---|
| Brand pen or tablet | Novo Nordisk's product, by prescription | Approved. The only source the trials describe |
| Compounded vial, shortage era | A pharmacy copy made while the drug was in shortage | Lawful until April 2025 for 503A pharmacies and May 2025 for outsourcing facilities; not since, except for a documented patient-specific change |
| Compounded vial, 2026 | The same product, still sold by some clinics | The subject of more than fifty FDA warning letters in 2026; the largest telehealth companies have exited |
| Research-chemical vial | Powder from a chemical supplier, sold as not for human use | An unapproved new drug, whatever the label says |
The salt problem
The approved drug is semaglutide base. Some compounded and vendor products were made from semaglutide sodium or semaglutide acetate, salt forms that are not the approved active ingredient, have never been tested in people, and dose differently by weight. FDA warned about them in 2023. A vial label that says semaglutide does not say which one is inside.
- The documented harm from compounded vials is dosing error: patients drawing ten times the intended dose from a vial labeled in milligrams per milliliter, reported to poison centers and to the FDA through 2024 and 2025.
- The cash price gap that drove compounding has narrowed. The maker's own pharmacy sells the injection for about $349 a month and the pill from $149, and Canada approved generic injections in 2026 that the United States cannot import.
- In May 2026 the FDA proposed to exclude semaglutide, tirzepatide, and liraglutide permanently from the list of substances outsourcing facilities may compound in bulk. When final, the shortage door closes for good.
Reading a vial: the dose arithmetic11
The pen removes arithmetic; the vial reintroduces it, and the FDA's file of compounded-semaglutide injuries is a file of arithmetic errors. Doses are in milligrams, vials in milligrams, syringes in units, and the same 0.25 mg starting dose is 5 units in one vial and 25 in another.
units = (dose mg ÷ concentration mg/mL) × 100
A 10 mg vial reconstituted with 2 mL of bacteriostatic water is 5 mg/mL. A 0.25 mg dose is 0.05 mL, or 5 units on a U-100 insulin syringe; 2.4 mg is 0.48 mL, or 48 units. A pharmacy vial labeled 2.5 mg/mL puts the same 0.25 mg at 10 units.
| Water added | Concentration | 0.25 mg | 1 mg | 2.4 mg |
|---|---|---|---|---|
| 1 mL | 10 mg/mL | 2.5 units (not measurable) | 10 units | 24 units |
| 2 mL | 5 mg/mL | 5 units | 20 units | 48 units |
| 4 mL | 2.5 mg/mL | 10 units | 40 units | 96 units |
Pharmacy vials commonly came at 2.5 mg/mL or 5 mg/mL with the dose printed in units on the label; that label governs. Reconstituted powder from a vendor has no tested beyond-use date; refrigerate, and assume degradation within weeks.
Side effects and warnings7
Semaglutide's label is long because its trials were large enough to see rare things. Most of what it warns about is uncommon; the common problems are the stomach's, and they fade.
| Warning | What it means | How common |
|---|---|---|
| Nausea, vomiting, diarrhea, constipation | The stomach slowing down; worst at each step up | Very common; nausea in about 44% in STEP 1, most of it mild |
| Thyroid C-cell tumors (boxed warning) | Seen in rodents; not shown in people. Contraindicated with a personal or family history of medullary thyroid cancer or MEN 2 | Precautionary |
| Pancreatitis | Severe persistent abdominal pain; stop and seek care | Rare |
| Gallbladder disease | Gallstones with rapid weight loss | About 1 to 3% |
| Dehydration and kidney injury | From vomiting and diarrhea | Uncommon; preventable |
| Hypoglycemia | Only with insulin or sulfonylureas, whose doses need lowering | Common in that combination |
| Diabetic retinopathy complications | Rapid glucose improvement can transiently worsen eye disease | Diabetes only; monitor |
| Intestinal blockage (ileus) | Added to the label in 2023 | Rare |
| Aspiration under anesthesia | Food remaining in the stomach; added in 2025. Tell the anesthesiologist | Rare; procedural |
| Mood | Reviews by FDA and European regulators found no causal link to suicidal thoughts; the label asks for monitoring | Under study |
Pregnancy
Not for use in pregnancy, and the label advises stopping at least two months before trying to conceive, because the drug clears slowly. Weight loss itself improves fertility, which is how some pregnancies on semaglutide begin.
- Lean mass: a quarter to a third of weight lost on GLP-1 drugs is muscle unless protected with protein and resistance training.
- Interactions: slowed stomach emptying can change the absorption of oral drugs, which matters for narrow-margin ones like warfarin and for oral contraceptives on the pill form.
- The vial adds the risks the trials excluded: unverified strength, an unverified salt form, no sterility certification, and a syringe instead of a pen.
- Is this the brand pen or pill, a compounded vial, or a research vial? If compounded, what patient-specific change justifies it now that the shortage is over?
- Is it semaglutide base, or a sodium or acetate salt? Can the seller show a certificate of analysis that says which?
- What is the concentration, and what is my starting dose in units on this vial?
- Do I or my family have medullary thyroid cancer or MEN 2? Have I had pancreatitis?
- Am I on insulin or a sulfonylurea, and has the dose been adjusted?
- Am I pregnant, or planning to be within two months of stopping?
- What is my plan for protein and resistance training, and for the plateau?
- If I stop, do I know that most of the weight returns within a year, and what happens then?
The lawful versions, today
Wegovy and Ozempic pens and the Wegovy and Rybelsus tablets, by prescription, at cash prices that fell in 2025 and 2026. Tirzepatide as Zepbound for more weight loss. Once approved, CagriSema. Every one of them comes with a label, a fixed dose, and a manufacturer answerable for what is inside. The vial comes with a name.
Latest
Developments since this edition, newest first. Items here are dated and sourced; they update the guide without re-editing it.
Canada approves a third semaglutide generic
Health Canada approved Sandoz's generic Ozempic pens for type 2 diabetes, following Apotex's generic Ozempic launched May 14 and its generic Wegovy approved June 29. None can be imported into the United States, where patents run to 2031.
FDA tells Empower Pharmacy its semaglutide-B12 blend is a copy of an approved drug
FDA's warning letter says adding B12 to compounded semaglutide (and niacinamide to tirzepatide) does not make it meaningfully different from Ozempic or Wegovy. FDA called the claimed differences 'pretextual', faulted templated 'significant difference' notes on prescriptions, and cited sterile-manufacturing failures.
Wegovy pill 4 mg cash price rises from $149 to $199
The promotional price ended August 31. Self-pay is now $149 for 1.5 mg, $199 for 4 mg, and $299 for 9 and 25 mg tablets; the pen is $199 for the first two fills, then $349, and the 7.2 mg pen is $399.
Novo: Wegovy list price to fall about 50 percent on January 1, 2027
The half-year report also cites Canadian loss of exclusivity lowering realized prices, a Cipla generic Ozempic application now in U.S. patent litigation, and 2026 sales guidance of flat to minus 6 percent.
Comment period closes on FDA plan to bar bulk semaglutide compounding
FDA extended comments on excluding semaglutide, tirzepatide, and liraglutide from the 503B bulks list to July 30. A final determination has not been published.
References
- 1.Wilding JPH, et al. Once-weekly semaglutide in adults with overweight or obesity (STEP 1). N Engl J Med. 2021;384(11):989-1002.
- 2.Davies M, et al. Semaglutide 2.4 mg once a week in adults with overweight or obesity, and type 2 diabetes (STEP 2). Lancet. 2021;397(10278):971-984.
- 3.Lincoff AM, et al. Semaglutide and cardiovascular outcomes in obesity without diabetes (SELECT). N Engl J Med. 2023;389(24):2221-2232.
- 4.Perkovic V, et al. Effects of semaglutide on chronic kidney disease in patients with type 2 diabetes (FLOW). N Engl J Med. 2024;391(2):109-121.
- 5.Wilding JPH, et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide: the STEP 1 trial extension. Diabetes Obes Metab. 2022;24(8):1553-1564. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9542252/
- 6.Oral semaglutide at a dose of 25 mg in adults with overweight or obesity (OASIS 4). N Engl J Med. 2025. https://pubmed.ncbi.nlm.nih.gov/40934115/
- 7.Wegovy and Ozempic (semaglutide) prescribing information, 2025 revisions; Wegovy tablets, 2025. Novo Nordisk. https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/215256s024lbl.pdf
- 8.U.S. Food and Drug Administration. Semaglutide shortage resolved; compounding wind-down deadlines. February 2025.
- 9.U.S. Food and Drug Administration. FDA's concerns with unapproved GLP-1 drugs (salt forms, dosing errors); 2026 warning letters over compounded GLP-1 products. https://www.fda.gov/drugs/postmarket-drug-safety-information-patients-and-providers/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss
- 10.U.S. Food and Drug Administration. Proposed 503B bulks list excluding semaglutide, tirzepatide, and liraglutide. Federal Register, May 1, 2026.
- 11.Representative semaglutide research-vial listings and compounded-vial labels, September 2026; NovoCare cash pricing, 2026.
- 12.Health Canada. Canada approves first generic semaglutide for weight loss. June 29, 2026. https://www.canada.ca/en/health-canada/news/2026/06/canada-approves-first-generic-semaglutide-for-weight-loss.html