Semaglutide
A weekly shot that quiets appetite; the best-proven weight peptide here. The job is keeping the muscle while the fat comes off.
What it is
Semaglutide is the once-a-week shot for someone with real weight to lose who has tried the diet-and-willpower route and keeps losing to hunger. It turns the hunger down and slows the stomach so you feel full on less, and unlike nearly everything else on this site it has been tested on tens of thousands of people and is an approved medicine.
Who it is really for: adults carrying 30, 50, 80 extra pounds, people with prediabetes or type 2 diabetes, and people whose eating is driven by 'food noise', the constant background pull toward the next snack, which this drug is unusually good at silencing. It is not for ten vanity pounds; the muscle cost described below is a bad trade for a small result. It is also not for anyone who has had pancreatitis or a family history of medullary thyroid cancer.
What you will notice, and when: the hunger drop starts within days of the first shot. You stop finishing plates, lose interest in evening snacks, and feel full halfway through a normal meal. Weight follows at roughly one to two pounds a week once you reach a working dose, with most of the loss landing in the first six to nine months and a plateau after that. In the big STEP 1 trial people lost about 15 percent of their body weight at 68 weeks on the full dose. Good looks like a quieter relationship with food; it will not change what you eat, only how much, and when you stop, appetite returns and most people regain unless something else changed.
How people run it: one subQ shot a week, same day each week, any time, with or without food, rotated between belly, thigh and upper arm. You start at 0.5 mg (pharmacy pens start at 0.25 mg) and hold each step for at least four weeks before going up: 0.5, then 1, then 1.7, then 2.5 mg if you need it. Many people never need the top. The first mistake is stepping up on schedule instead of on need, chasing the max dose when 1 mg was already working; the second is under-eating protein. Semaglutide only removes appetite; it does not tell your body which tissue to burn, and in a deep deficit the body takes muscle, its biggest calorie burner. Eat protein first at every meal, close to a gram per pound of goal weight, and lift something heavy twice a week. Hydrate and get fiber, because constipation is the complaint that outlasts the nausea.
The honest evidence read: this is in a different league from the research peptides here. Large randomized trials (the STEP program for weight, SUSTAIN for diabetes) and a cardiovascular outcomes trial (SELECT) showing about a 20 percent cut in major heart events in people with obesity and heart disease. That is as proven as a drug gets. The real caveat is also from the trials: in the STEP 1 body-composition substudy, roughly 40 percent of the weight lost was lean mass. Think of your metabolism as a campfire: lose that much muscle and semaglutide leaves you with smoldering ashes, still warm, but put a log on and it will not catch.
When it is not worth it, and what to use instead: if you have modest weight to lose and want to keep eating like an athlete, retatrutide is our pick, with much milder appetite suppression and a real metabolic-rate effect; if you want stronger weight loss from an approved drug, tirzepatide beats semaglutide head to head; if semaglutide stalls, adding cagrilintide is where the trials are heading. Semaglutide is the right choice when you want the most proven option, prescribed, with the longest safety record, and you are prepared to do the protein and lifting that keep the loss from being half muscle.
What people use it for
Weight loss
Most evidenceThe STEP trials randomized thousands of adults; on 2.4 mg weekly, average loss was about 15 percent of body weight at 68 weeks against about 2 percent on placebo. That is approval-grade evidence and the reason it is the benchmark every newer weight drug is measured against. In practice, expect the loss to front-load into the first nine months and then flatten.
Blood sugar and diabetes
Most evidenceSemaglutide was a diabetes drug first; the SUSTAIN trials showed large, durable drops in A1c in type 2 diabetes, which is why it was approved for that years before weight. If you are prediabetic, the blood sugar effect arrives alongside the weight effect and is part of why doctors reach for it.
Heart protection
Most evidenceThe SELECT trial followed more than 17,000 people with obesity and existing heart disease and found about a 20 percent reduction in major cardiovascular events on semaglutide. That moved it from a weight drug to a heart drug in many clinicians' minds. It applies to people who already have heart disease; the benefit in healthy people is assumed, not shown.
Muscle loss while losing weight
Some evidenceIn the STEP 1 body-composition substudy, roughly 40 percent of the weight lost was lean mass. That is similar to what any large diet-driven deficit does, but semaglutide makes a large deficit easy, so the risk is real: people end up lighter, weaker and flat. Protein near a gram per pound of goal weight and resistance training two or three times a week are the fix, and they are not optional.
How it works
Where Semaglutide sits in the class
- Large human trials support meaningful weight loss and blood-sugar control
- FDA approved (Ozempic, Wegovy), the most established GLP-1 drug
- Nausea and other digestive upset are common and usually ease over time
- Best results come from gradual dose increases under medical guidance
How people use it
Safety, in brief
Things people sometimes notice
- Nausea for a few days after each step up, worst on the first dose at a new level, usually gone within a month at a stable dose
- Constipation, which outlasts the nausea and needs water and fiber, or loose stools for some
- Feeling full after very little, sometimes to the point of skipping meals, which is where muscle loss starts
- Tiredness in the first weeks, often from eating too little, and sulfur burps or reflux for some
The full picture — stop signs and who should talk to a doctor first — is on the dosing guide.
Sources
The labels and studies behind this page. Each link opens the original on PubMed, DailyMed or ClinicalTrials.gov.
- Wegovy (semaglutide) prescribing information
- Once-Weekly Semaglutide in Adults with Overweight or Obesity
- Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes
- Efficacy and safety of once-weekly semaglutide monotherapy versus placebo in patients with type 2 diabetes (SUSTAIN 1): a double-blind, randomised, placebo-controlled, parallel-group, multinational, multicentre phase 3a trial