Semaglutide is the most-prescribed GLP-1 receptor agonist in the world, and probably the most-talked-about drug of the decade. If you've heard about Ozempic, Wegovy, or "the weight-loss shot," you've heard about semaglutide.
This guide is the orientation we wish we'd had — what semaglutide actually is, who it's for, how to dose it, what side effects to expect, and how compounded versions compare to the brand pens. Every section links to a deeper-dive question if you want to keep going.
What semaglutide actually is
Semaglutide is a synthetic peptide that mimics GLP-1 (glucagon-like peptide-1), a hormone your gut releases after you eat. Natural GLP-1:
- Tells the pancreas to release insulin
- Slows how fast food leaves your stomach
- Signals fullness to your brain
Natural GLP-1 only sticks around for a few minutes. Semaglutide is engineered to last about a week — which is why it's a once-weekly injection rather than something you'd take with every meal.
It binds to the same receptors as natural GLP-1, but the prolonged signaling is what produces the appetite suppression and weight loss most people associate with the drug.
The brand-name landscape
Semaglutide is sold under three brand names, all manufactured by Novo Nordisk:
| Brand | Form | FDA-approved use | Dose range |
|---|---|---|---|
| Ozempic | Weekly injection (pen) | Type 2 diabetes | 0.25 → 2 mg |
| Wegovy | Weekly injection (pen) | Chronic weight management | 0.25 → 2.4 mg |
| Rybelsus | Daily oral tablet | Type 2 diabetes | 3, 7, or 14 mg |
The active drug is identical across Ozempic and Wegovy — the difference is the approved indication and the dose ceiling. Rybelsus is the same molecule in oral form, but with much lower bioavailability (only about 1% of an oral dose is absorbed), which is why the milligram numbers look so much higher.
For deeper coverage, see our cluster pages on Ozempic vs Wegovy and switching between brands.
Compounded semaglutide
Because semaglutide has been on the FDA shortage list for stretches of 2022–2025, 503A and 503B compounding pharmacies have been allowed to produce their own versions. Compounded semaglutide:
- Comes as a vial of dry powder you reconstitute with bacteriostatic water
- Costs roughly $200–400/month vs. $1,000+ for brand pens (without insurance)
- Is dosed in milligrams, identical to the brand strengths
The trade-off: less standardization, more user responsibility (drawing your own dose, sterile technique), and ongoing regulatory uncertainty as Novo Nordisk pushes back on compounders. Our is compounded semaglutide safe? cluster goes deeper on what to look for.
How semaglutide is dosed
Semaglutide is titrated — you start at a sub-therapeutic dose and ramp up every 4 weeks. The slow ramp lets your gut adjust to the slower digestion, which dramatically reduces nausea.
Standard Wegovy titration (weight loss):
| Weeks | Weekly dose |
|---|---|
| 1–4 | 0.25 mg |
| 5–8 | 0.5 mg |
| 9–12 | 1.0 mg |
| 13–16 | 1.7 mg |
| 17+ | 2.4 mg (maintenance) |
Ozempic titration (T2D) stops at 1.0 mg or 2.0 mg depending on your provider's plan.
You inject once per week, on the same day each week, into the abdomen, thigh, or upper arm. Rotate sites with each injection to avoid lipohypertrophy.
For the full breakdown including what to do if a step is too aggressive, see semaglutide dosing schedule. For compounded users doing reconstitution math, our calculator handles the conversion from mg to syringe units.
Side effects: what to actually expect
The vast majority of semaglutide side effects are gastrointestinal:
- Nausea (most common, especially the week after a dose increase)
- Constipation or sometimes diarrhea
- Reflux / heartburn
- Fatigue in the first few weeks
- Decreased appetite — usually the desired effect, occasionally too aggressive
Less common but worth knowing:
- Pancreatitis (rare; signs are severe abdominal pain radiating to the back)
- Gallbladder issues (gallstones occur at a slightly elevated rate, especially with rapid weight loss)
- Thyroid C-cell tumors (signal in animal studies, not confirmed in humans; black-box warning regardless)
- Hair loss (associated with rapid weight loss in general, not semaglutide specifically)
We have a full pillar on GLP-1 side effects and how to manage them — every common complaint, why it happens, and the playbook that works for most people.
Realistic results
The headline trial number from STEP-1 (semaglutide at 2.4 mg for weight management) was 14.9% mean body weight loss at 68 weeks. Real-world results are typically a bit lower because trial participants get more support, but here's what to expect:
- Month 1: Appetite drops noticeably; 2–4 lbs lost
- Month 3: 5–8% body weight typically gone
- Month 6: 10–12% loss is common at the full maintenance dose
- Month 12+: 14–18% loss typical for adherent users
For diabetes, the numbers are different — what matters is HbA1c reduction (typically 1.5–2.0 percentage points over 6 months).
The trajectory is rarely linear. Plateaus are normal. Stopping the drug typically results in significant weight regain within 12 months — see our stopping semaglutide cluster for what the data says.
Common questions
Can I drink alcohol on semaglutide?
Pharmacologically, yes — there's no dangerous interaction. Practically: nausea + alcohol is rough, and many users report alcohol simply stops being interesting. Many drinkers use less or quit altogether without willpower. See semaglutide and alcohol for more.
What if I miss a dose?
If it's been less than 5 days, take it as soon as you remember. If more than 5 days, skip it and resume next week — don't double up. Missed dose details here.
Can I switch from semaglutide to tirzepatide?
Yes, and it's increasingly common. The switch usually involves a one-week gap and starting tirzepatide at 2.5 mg. See our tirzepatide guide for what to expect.
Who semaglutide is right for
Semaglutide is most often prescribed for adults with:
- Type 2 diabetes that's not well-controlled on metformin alone
- BMI ≥ 30
- BMI ≥ 27 with a weight-related comorbidity (hypertension, sleep apnea, prediabetes, dyslipidemia)
It's not recommended in pregnancy, in people with a personal or family history of medullary thyroid carcinoma or MEN-2, or in people with active pancreatitis. As always, that conversation belongs with your clinician.
Where to go next
The questions below are the most-searched semaglutide questions on the internet. Each is its own page with a focused answer.