Semaglutide: What It Is, Where to Get It Prescribed, and What It Costs

Semaglutide is a GLP-1 receptor agonist: a synthetic analogue of glucagon-like peptide-1, a hormone released by the small intestine after a meal. Native GLP-1 is cleared within minutes by the enzyme DPP-4, which is why the hormone itself was never a practical drug. Semaglutide keeps most of the native sequence and changes three things: an unnatural amino acid at position 8 that blocks DPP-4, a substitution at position 34, and a fatty-acid chain at position 26 that binds the peptide to albumin. Those changes stretch the half-life to roughly a week, which is what makes once-weekly injection possible.

It is not a stimulant. It works on receptors the body already uses to register that a meal has been eaten.

Semaglutide was developed by Novo Nordisk and is sold in the United States under three brand names, each with its own FDA approval: Ozempic, a weekly injection for type 2 diabetes (5 December 2017); Rybelsus, a daily tablet for type 2 diabetes (20 September 2019); and Wegovy, the higher-dose weekly injection for chronic weight management (4 June 2021). Wegovy's label has since grown: cardiovascular risk reduction (8 March 2024), non-cirrhotic MASH with fibrosis (15 August 2025), an oral 25 mg tablet (22 December 2025) and a 7.2 mg injection sold as Wegovy HD (19 March 2026).

The compounded product Pepti prescribes contains the same active ingredient, prepared by a state-licensed pharmacy to an individual prescription. It is not any of those brands and does not carry their approval.

It is not a substitute for eating and moving differently; every large trial ran it alongside a reduced-calorie diet and increased activity. It is not a short course with a permanent result: the trial that stopped the drug and kept watching reported most of the weight coming back. It is not for type 1 diabetes. And it is not interchangeable with tirzepatide, which acts on two receptors rather than one.

GLP-1 receptors on pancreatic beta cells trigger insulin secretion only when blood glucose is elevated; the signal switches off as glucose normalises, which is why semaglutide on its own rarely drives blood sugar too low. It also suppresses glucagon, which tells the liver to release stored glucose. This is the original diabetes mechanism, demonstrated in the SUSTAIN programme.

Semaglutide slows the rate at which the stomach empties, particularly early in treatment. Fullness lasts longer and post-meal glucose rises more gradually. The same action explains the most common side effects (nausea, fullness, constipation) and is why anaesthesiologists ask about GLP-1 use before a procedure.

GLP-1 receptors in the hypothalamus and brainstem regulate hunger and satiety, and human feeding studies describe reduced hunger, fewer cravings and lower energy intake. Patients most often describe "food noise" going quiet rather than feeling forcibly full. In the weight-management trials this mechanism carries most of the weight change.

SELECT reported fewer major cardiovascular events in people without diabetes, with the effect appearing before much weight had been lost, so investigators describe it as partly independent of weight. ESSENCE reported improved liver histology in MASH. How much of either is weight-mediated remains open.

STEP 1, in the New England Journal of Medicine in 2021, randomised 1,961 adults with overweight or obesity and no diabetes to weekly semaglutide at the full trial dose or placebo for 68 weeks, both with lifestyle intervention. Mean weight change was −14.9% against −2.4%.

STEP 2, in The Lancet in 2021, ran the same design in 1,210 adults with type 2 diabetes: −9.6% against −3.4%. STEP 3, in JAMA in 2021, added intensive behavioural therapy for 611 adults: −16.0% against −5.7%. STEP 5, in Nature Medicine in 2022, followed 304 adults for two years: −15.2% against −2.6%. STEP 8, in JAMA in 2022, compared weekly semaglutide with daily liraglutide: −15.8% against −6.4%.

STEP 4, in JAMA in 2021, is the trial worth reading before starting. 803 adults reached the maintenance dose over 20 weeks and were then randomised to continue or switch to placebo for 48 weeks. Those who continued lost a further 7.9%; those switched to placebo regained 6.9%, along with most of the improvements in blood pressure and lipids. Semaglutide works while it is being taken, in the way a blood-pressure medication does.

SUSTAIN-6, in the New England Journal of Medicine in 2016, randomised 3,297 people with type 2 diabetes at high cardiovascular risk to semaglutide or placebo for 104 weeks. Major adverse cardiovascular events occurred in 6.6% against 8.9%. The same trial reported more diabetic retinopathy complications (3.0% against 1.8%), the source of the label's retinopathy warning.

SELECT, in the New England Journal of Medicine in 2023, is the largest trial of the compound: 17,604 adults aged 45 and over with established cardiovascular disease and a BMI of 27 or more, without diabetes, followed for a mean of 39.8 months. Cardiovascular death, heart attack or stroke occurred in 6.5% against 8.0%, a 20% relative reduction, and the basis of the March 2024 cardiovascular indication.

ESSENCE, in the New England Journal of Medicine in 2025, randomised 1,197 people with biopsy-confirmed MASH and stage 2 or 3 fibrosis to semaglutide or placebo. At 72 weeks, 62.9% of the semaglutide group had resolution of steatohepatitis without worsening fibrosis against 34.3%, and 36.8% had fibrosis improvement against 22.4%. The trial continues to 240 weeks; the August 2025 liver approval rests on this interim result.

SURMOUNT-5, in the New England Journal of Medicine in 2025, randomised 751 adults with obesity and no diabetes to tirzepatide or semaglutide at maximum tolerated doses for 72 weeks; tirzepatide produced −20.2% against −13.7%. It was open-label, a limitation, but the direction is consistent with the two drugs' separate trials.

Multiple large randomised placebo-controlled phase 3 trials in obesity, type 2 diabetes and established cardiovascular disease; a two-year maintenance trial; a withdrawal trial; a liver-histology trial; one head-to-head against tirzepatide; and post-marketing experience in millions of patients. This is the standard of evidence a drug needs for FDA approval, and semaglutide has it several times over.

• It does not establish that a compounded vial performs identically to the branded pen. No trial has tested compounded semaglutide; the case that the same molecule at the same dose behaves the same way is pharmacological inference.
• It does not establish what happens after stopping, beyond most weight returning within a year.
• It does not establish benefit below the trial BMI thresholds (27 with a weight-related condition, or 30).
• It does not establish safety in pregnancy.
• Trial figures are averages at the full trial dose with lifestyle support; an individual on a lower dose without that support should not expect the trial number.

Semaglutide is an FDA-approved active ingredient. Ozempic, Rybelsus and Wegovy are approved drug products, with the label expansions dated above.

Semaglutide injection went onto the FDA's drug shortage list in 2022, and while a drug is on that list federal law allows compounding pharmacies to prepare it. On 21 February 2025 the FDA declared the shortage resolved, giving 503A pharmacies until 22 April 2025 and 503B outsourcing facilities until 22 May 2025 to stop compounding, distributing and dispensing products that are essentially copies of the approved ones.

Shortage-based compounding has ended. What remains is the ordinary 503A pathway that exists for every drug: a state-licensed pharmacy may compound for an identified patient where the prescriber has determined that the compounded product differs from the commercial one in a way that matters for that patient, such as a strength or dosage form that is not sold. The FDA updated its guidance on what counts as "essentially a copy" on 1 April 2026, noting that semaglutide appears on neither the 503B bulks list nor the shortage list.

On 30 April 2026 the FDA proposed to exclude semaglutide, tirzepatide and liraglutide from the 503B bulks list, having not identified a clinical need for outsourcing facilities to compound them from bulk substances. That is a proposal, not a final rule: it was published in the Federal Register on 1 May 2026, the comment period was extended to 30 July 2026, and no final determination had been published as of the date above. It concerns 503B facilities, which make large batches without patient-specific prescriptions; it does not by itself change the 503A framework under which a pharmacy compounds for a named patient.

The FDA has also policed marketing: warning letters to telehealth companies in September 2025, 30 more on 3 March 2026 and 25 in June 2026, objecting to websites implying a compounded product was equivalent to or approved like the brand, or hiding which pharmacy made it. That is why this page says plainly: compounded semaglutide is not FDA approved and is not Wegovy or Ozempic.

So the accurate description today is: an approved active ingredient; no more shortage-based compounding; patient-specific 503A compounding on a physician's prescription still lawful where the prescriber documents the clinical reason; and a pending 503B proposal that would not directly change that.

Treatment starts at the lowest strength, a tolerance dose rather than a treatment dose. Most people notice reduced appetite within one to two weeks; gastrointestinal effects cluster in the days after each step up. Weight change in the first month is modest and not a measure of what the drug will do at maintenance dose.

Dose escalation continues at roughly monthly intervals as tolerated, and the appetite effect becomes consistent. In the STEP trials weight loss was steepest through roughly week 20.

Weight loss continues but slows; in STEP 1 the curve flattened around week 60. A plateau is the drug reaching equilibrium, not stopping working. This is where physicians consider holding, stepping up, or reconsidering the plan.

STEP 5 reported weight maintained at two years on continued treatment. STEP 4 reported most weight returning within a year of stopping. Semaglutide is a maintenance treatment, and the long-term plan is something to agree with your physician early.

Semaglutide is the one product on this site where the vial changes as the dose changes. Each strength is a separate vial concentrated so that one weekly dose is a single draw: 0.25 mL for the 0.25 mg rung, 0.50 mL for the 0.5 mg and 1 mg rungs, 0.68 mL for 1.7 mg, 0.40 mL for 2 mg and 0.50 mL for 2.5 mg. The volume is printed on your medication.

Directions are written in millilitres and insulin-syringe units because that is what you read off the barrel: 0.25 mL is 25 units on a U-100 syringe. Because concentration differs between vials, the units for one strength are not the units for another; never carry a number over from a previous fill.

Subcutaneous means into the fat layer: abdomen, thigh or upper arm, rotated. Once weekly means the same day each week. Treatment starts at the lowest strength and the physician steps up, typically at roughly four-week intervals as tolerance allows; never on your own.

At one draw per week, each dose-specific vial holds about four weekly doses, which is why refills run on a 28-day cycle and why a step up arrives as a new vial. One vial per fill, always.

Refrigerated, and it ships that way in insulated packaging with ice packs. Beyond-use dating runs from first puncture and is on the label. A vial that has frozen should not be used.

Same active ingredient; different product. Ozempic and Wegovy are FDA-approved drugs made by their manufacturer in a fixed-dose pen. Compounded semaglutide is prepared by a state-licensed pharmacy to an individual prescription, is not FDA approved as a finished product, and has not been the subject of any of the trials above. The strengths on this page are not the branded strengths, the kind of patient-specific difference a prescriber documents when compounding is appropriate. A physician who considers the branded product the right choice for you will say so.

Semaglutide acts on the GLP-1 receptor alone; tirzepatide acts on GLP-1 and GIP receptors. In SURMOUNT-5 tirzepatide produced more weight loss. Semaglutide has the longer track record, the larger outcomes trials (SELECT, ESSENCE) and the lower price. Side-effect profiles are similar. Which one a physician prescribes depends on history, tolerability, goals and cost rather than the head-to-head figure alone.

Not alternatives. Semaglutide changes appetite and energy intake, with large human trials behind it. Tesamorelin, sermorelin and CJC-1295 / Ipamorelin act on the growth hormone axis and are described around body composition, with much thinner human evidence. Someone whose problem is appetite and weight is in semaglutide's territory; someone near a healthy weight is not.