
Semaglutide
Semaglutide (GLP-1 Receptor Agonist)
Also called Ozempic, Wegovy, Rybelsus, semaglutida
The appetite regulator
Semaglutide is a once-weekly injection sold as Ozempic for type 2 diabetes and Wegovy for weight loss, with a daily tablet version called Rybelsus. It copies a gut hormone that tells your brain you are full. It is an approved medicine, and it is the only weight-loss drug shown to cut heart attacks and strokes.
A weekly injection sold as Ozempic for diabetes and Wegovy for weight loss. It is a rebuilt copy of a hormone your gut releases after eating, the one that tells your brain you are full, engineered to last a week instead of minutes. It is also the only weight-loss drug shown to cut heart attacks and strokes rather than just weight.
- Half-life
- About a week, which is why it is weekly
- Route
- One injection under the skin, once a week; an oral tablet also exists
- Typical dose
- 0.25 mg to start, stepped up every 4 weeks toward 2.4 mg
- Availability
- Vetted vendors
Tested in several human trials
5,178 papers · 317 clinical trials
What people use Semaglutide for
Reported uses, roughly in order of how often they are the reason someone goes looking. Whether it works for any of them is a separate question, answered under each one.
- Type 2 diabetes
- Its first approved use, sold as Ozempic.
- Heart attack and stroke prevention
- The result that sets it apart: a 20% reduction in serious cardiovascular events in people with heart disease and obesity but no diabetes.
- Kidney disease
- Tested in people with obesity and chronic kidney disease without diabetes.
Mechanism of Action
How Semaglutide works
There is a hormone your gut releases when you eat, called GLP-1, whose job is to tell your brain you have had enough. It works, and then it disappears within minutes. Semaglutide is that hormone rebuilt so it lasts about a week.
Three things happen at once
The first is appetite. It reaches the parts of the brain that set hunger, and the usual description from people taking it is not willpower but silence: the constant low-level negotiation about food stops.
The second is your stomach. It empties more slowly, so a meal keeps feeling like a meal for longer.
The third is insulin, and the detail here is genuinely clever. It only prompts insulin when blood sugar is actually raised. Older diabetes drugs pushed insulin regardless, which is how people ended up shaky and sweating between meals. This one responds to the situation instead.
The result that matters most
Weight loss is what it is famous for, at around 15% of body weight over 68 weeks. But the more important trial was not about weight at all. In 17,604 people with existing heart disease and obesity, it cut the rate of heart attacks, strokes and cardiovascular death from 8.0% to 6.5%.
That is the difference between a drug that changes a number on a scale and one shown to change what happens to you. No other weight-loss compound has that result.
The honest catch
Gut side effects are common, mostly while the dose is climbing, and they are the usual reason people stop. And as with tirzepatide, stopping brings the weight back.
Semaglutide dosage calculator
Opens at 0.25 mg, from the doses reported for Semaglutide. Change any box to match your own vial. It works out where to pull the plunger to.
How much is in the vial?
Printed on the label, in milligrams
How much water did you add?
Bacteriostatic water, in millilitres
What dose are you taking?
The dose you already intend to use
Which syringe?
Barrel size, printed on the wrapper
Draw to
5 units
on a 0.5 mL insulin syringe (0.05 mL)
- Strength once mixed
- 5 mg/mL
- Doses in the vial
- 40
10 mg in 2 mL makes 5 mg/mL. A 0.25 mg dose is 0.05 mL of that, which is 5 units.
Want a rounder number? Adding 4 mL instead would put this dose at exactly 10 units, which is easier to draw accurately.
This is arithmetic, not advice. It converts a dose you already have into a mark on a syringe. It does not tell you what dose to take, and Semaglutide is not prescribed by us. Dosing belongs with a qualified clinician.
Semaglutide side effects: what people reported
The best-documented side-effect profile of any peptide here, because millions of people take it. Overwhelmingly digestive, and overwhelmingly during the step-up.
What most people notice
- Nausea, the most common reason people stop
- Constipation
- Diarrhoea
- Reflux and burping
- Food losing its appeal, sometimes including things you used to love
- Feeling full very quickly
Worth keeping an eye on
- Muscle loss alongside fat, especially without enough protein or any resistance training
- Hair shedding around month three or four, usually a response to rapid weight loss rather than the drug
- Gallstones when weight comes off quickly
- Facial changes people call Ozempic face, which is fat loss rather than anything the drug does to skin
Reasons to call someone
- Severe, persistent stomach pain radiating to the back
- Vision changes, particularly if you have diabetic eye disease and your blood sugar has dropped fast
Dose matters. Every dose increase tends to bring a few rough days. People who rush the ramp are the ones who quit.
Source: STEP and SUSTAIN trial programmes, plus years of prescribing data. This is a summary of published findings, not a complete safety profile and not medical advice. Semaglutide should only be considered with a qualified clinician who knows your history.
Your Genetics & Semaglutide
The genes involved in how Semaglutide works
Semaglutide works through the receptors these genes build, and the genes vary from person to person. Researchers have linked some of that variation to differences in how people respond. A DNA report tells you which versions you carry.
GLP1R · ••
The Ala316Thr variant affects GLP-1 receptor signaling efficiency. Thr316 carriers show altered receptor internalization kinetics, potentially requiring dose adjustment. This variant has been associated with differential weight loss response in clinical cohorts.
TCF7L2 · ••
The strongest common genetic risk factor for type 2 diabetes. T-allele carriers have impaired beta-cell insulin secretion. Semaglutide's glucose-dependent insulin release may partially compensate for this deficit, but glycemic response magnitude varies by genotype.
Beta-arrestin 1 mediates GLP-1 receptor internalization and desensitization after activation. Variants affecting ARRB1 expression influence how quickly receptors are recycled, potentially affecting sustained response to semaglutide over months of treatment.
PCSK1 · ••
Proprotein convertase 1 processes proglucagon into active GLP-1. Variants reducing PCSK1 activity lower endogenous GLP-1 production — these individuals may be particularly responsive to exogenous GLP-1R activation by semaglutide.
The dots after each gene are where your own result goes. Your report fills them in with the two letters you carry at that position.
Which variants do you carry?
Upload your DNA data, or get tested through our partner, to find out.
Commonly combined with
What Semaglutide is most often paired with, and why:

BPC-157
GI Protection StackModerate EvidenceBody Protection Compound 157
BPC-157 is the peptide people reach for when something will not heal. Tendons, ligaments, a gut that has been irritated by painkillers, an injury that has stalled. It is a short chain of amino acids copied from part of a protein your stomach already makes, and the animal research on it is unusually consistent for this category: across a lot of separate rat studies, injured tissue healed faster than it did without it. The gap is that this has largely not been repeated in people, and it is not an approved medicine, so nobody is checking what is in the vial you buy.
3
Gene variants
19+
Studies

AOD-9604
Body Composition StackEmerging EvidenceAdvanced Obesity Drug 9604 (hGH Fragment 177-191)
AOD-9604 is a fragment cut out of growth hormone, specifically the piece thought to handle fat burning, with the rest of the molecule left behind. The idea was elegant: get the fat-loss effect without the blood-sugar and growth effects of the whole hormone. It is also one of the very few peptides in this space that was put through a proper randomised human trial, which is the part vendors do not mention, because it did not beat the placebo. Development stopped there.
4
Gene variants
15+
Studies
Sourcing & access
Where to buy Semaglutide
Semaglutide is available through licensed telehealth and retail providers. We rank them by price, reviews and a credibility score — so you can find the cheapest source that's actually legitimate.
- Buy only from licensed providers that publish recent third-party purity tests (COAs).
- Compare the total cost — consultation, the compound, and shipping — not just the sticker price.
- Confirm the provider ships to your country and requires a genuine medical intake.
Before you buy: see whether your DNA actually responds to Semaglutide, and at what dose. Analyze my DNA — $99 →
Educational information only, not medical advice. Some outbound links are affiliate links (disclosed, at no extra cost to you). Most peptides are not FDA-approved — consult a qualified professional and check your local laws before purchasing.
Worth knowing before you consider Semaglutide
Interactions and situations where there is a specific reason to be careful. Where the honest answer is that nobody has studied something, it says so and says what that leaves open.
- Gut effects are common and are why most people stop
- Nausea, diarrhoea, constipation and vomiting are the most frequently reported problems, mostly mild to moderate and worst while the dose is being increased. In the two-year trial, 82% on semaglutide reported a gut side effect at some point, against 54% on placebo.
- Compounded semaglutide is not the trialled drug
- Every number here comes from the manufacturer's product. Compounded versions sold through telehealth have not been through these trials, and some use a different salt form that was never studied at all.
- Weight returns after stopping
- The trial that withdrew treatment saw weight regained. It is being studied as an ongoing treatment rather than a course you finish, and that has real cost implications worth knowing before starting.
The evidence behind Semaglutide
Along with tirzepatide, this is as good as evidence gets on this site: hundreds of randomised trials and an approved medicine rather than a research chemical. One trial below deserves singling out. SELECT enrolled 17,604 people and measured heart attacks and strokes rather than weight, which is the difference between a drug that changes a number and one shown to change what happens to you.
The literature, counted
Counted in PubMed on 3 August 2026 for semaglutide. Every figure links to the search that produced it, so you can re-run it. “Tagged human” is not the same as a human trial: that tag also covers work on human cells and reviews discussing people, which is why the trial count is given separately.
Studied in people
3 of 8The only kind that directly answers whether it works in humans.New England Journal of Medicine · 2023
HumanSemaglutide and Cardiovascular Outcomes in Obesity without Diabetes
Lincoff AM, Brown-Frandsen K, Colhoun HM, et al.
The most important trial of any compound on this site, because it measured events rather than weight. Among 17,604 people with existing heart disease and obesity but no diabetes, cardiovascular death, heart attack or stroke occurred in 6.5% on semaglutide against 8.0% on placebo, a 20% reduction in risk.
Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes — source for Semaglutide (opens in a new tab)Phase 3 · n=17,604 · mean 40 months
Read the paperNew England Journal of Medicine · 2021
HumanOnce-Weekly Semaglutide in Adults with Overweight or Obesity
Wilding JPH, Batterham RL, Calanna S, et al.
The trial behind the weight-loss approval, known as STEP 1. Average loss was 15.3 kg against 2.6 kg on placebo. Half the semaglutide group lost at least 15% of their body weight, against 5% on placebo.
Once-Weekly Semaglutide in Adults with Overweight or Obesity — source for Semaglutide (opens in a new tab)Phase 3 · 68 weeks
Read the paperNature Medicine · 2022
HumanTwo-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial
Garvey WT, Batterham RL, Bhatta M, et al.
Answers the obvious question about whether it lasts. At two years the semaglutide group was 15.2% lighter against 2.6% on placebo, so the effect held rather than fading. It also reports the honest side of that: 82% had a gut side effect at some point.
Two-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial — source for Semaglutide (opens in a new tab)Phase 3 · 104 weeks
Read the paper
Every source behind this page85 more
- Effect of Continued Weekly Subcutaneous Semaglutide vs Placebo on Weight Loss Maintenance in Adults With Overweight or Obesity: The STEP 4 Randomized Clinical TrialRubino D, Abrahamsson N, Davies M, et al. · JAMA · 2021 · Phase 3Human
- Effect of Weekly Subcutaneous Semaglutide vs Daily Liraglutide on Body Weight in Adults With Overweight or Obesity Without Diabetes: The STEP 8 Randomized Clinical TrialRubino DM, Greenway FL, Khalid U, et al. · JAMA · 2022 · Phase 3Human
- Oral semaglutide 50 mg taken once per day in adults with overweight or obesity (OASIS 1): a randomised, double-blind, placebo-controlled, phase 3 trialKnop FK, Aroda VR, do Vale RD, et al. · Lancet · 2023 · Phase 3Human
- Semaglutide in patients with overweight or obesity and chronic kidney disease without diabetes: a randomized double-blind placebo-controlled clinical trialApperloo EM, Tuttle KR, Pavo I, et al. · Nature Medicine · 2025 · Phase 3Human
- Tirzepatide as Compared with Semaglutide for the Treatment of ObesityAronne LJ, Horn DB, le Roux CW, et al. · New England Journal of Medicine · 2025 · Phase 3bHuman
Everything we cite for Semaglutide, including animal work and early research. Each link goes to the source itself, so you can judge it rather than take our word for it.
Last updated · literature counts verified against PubMed on
Frequently Asked Questions
Is semaglutide affected by CYP enzyme genetics?
No. Unlike most drugs, semaglutide is NOT metabolized by cytochrome P450 (CYP) enzymes. It is degraded by general proteolytic enzymes after albumin dissociation. This means CYP2D6, CYP3A4, and other pharmacogenomic CYP variants do not affect semaglutide levels or dosing — a major advantage for genetic predictability.
What genetics affect semaglutide response?
GLP1R variants (rs6923761) affect receptor sensitivity and weight loss magnitude. TCF7L2 (rs7903146) influences the glycemic improvement component. ARRB1 variants affect receptor recycling and long-term efficacy. These are receptor-level and pathway-level genetics rather than metabolism genetics.
How much weight loss can semaglutide produce?
The STEP clinical trials showed average weight loss of 15-17% of body weight over 68 weeks at the 2.4mg weekly dose. However, individual response varies significantly — from 5% to over 25% — driven partly by GLP1R receptor genetics and baseline metabolic status. A genetic report can help predict where you fall on this spectrum.
Learn more about Semaglutide
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In depthTirzepatide vs Retatrutide vs Semaglutide: Which GLP Agonist Wins by Genotype?
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Your next move
Two ways forward with Semaglutide.
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How does Semaglutide relate to your genes?
Your report scores Semaglutide against your receptor, pharmacogene and pathway variants and shows the genetic markers relevant to it, with commonly cited dosing information to review with a clinician.
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