Semaglutide
GLP-1 Receptor Agonist (Ozempic / Wegovy)
Semaglutide is an FDA-approved GLP-1 receptor agonist used for type 2 diabetes management (Ozempic) and chronic weight management (Wegovy). It mimics the naturally occurring GLP-1 hormone, slowing gastric emptying, reducing appetite, and improving insulin sensitivity. Administered as a once-weekly subcutaneous injection, semaglutide has demonstrated significant efficacy in large-scale clinical trials for both glycemic control and sustained weight loss.
Quick Reference
Mechanism of Action
Semaglutide is a modified analog of human GLP-1 (glucagon-like peptide-1) with 94% structural homology. Key modifications give it a dramatically extended half-life of approximately 7 days compared to native GLP-1's 2-minute half-life:
- Appetite regulation — acts on hypothalamic receptors to reduce hunger signaling and increase satiety
- Gastric emptying — slows the rate at which food leaves the stomach, prolonging fullness after meals
- Insulin secretion — enhances glucose-dependent insulin release from pancreatic beta cells
- Glucagon suppression — reduces glucagon secretion in a glucose-dependent manner, lowering hepatic glucose output
- Cardiovascular effects — reduces inflammation, improves endothelial function, and lowers blood pressure
Dosing & Titration Schedule
Semaglutide follows a gradual dose titration to minimize gastrointestinal side effects. Each dose level is maintained for at least 4 weeks before escalating. Titration speed may be adjusted based on tolerability.
Month 1 — Initiation
0.25 mg/week
Once weekly
Weeks 1–4
Starting dose for GI tolerance. This is not a therapeutic dose for weight loss — it is purely for acclimation. Nausea is most common during this phase.
Month 2 — First Escalation
0.5 mg/week
Once weekly
Weeks 5–8
First therapeutic dose level. Appetite suppression becomes noticeable. This is the typical maintenance dose for Ozempic in T2D management.
Month 3 — Second Escalation
1.0 mg/week
Once weekly
Weeks 9–12
Standard therapeutic dose for weight management. Significant appetite reduction and weight loss typically observed. Maximum dose for Ozempic.
Month 4 — Third Escalation (Wegovy)
1.7 mg/week
Once weekly
Weeks 13–16
Wegovy-specific dose tier. Continue titrating if weight loss goals are not met and the medication is well tolerated.
Month 5+ — Maintenance (Wegovy)
2.4 mg/week
Once weekly
Weeks 17+
Maximum approved dose for Wegovy. The target maintenance dose for chronic weight management. Most clinical trial data (STEP trials) is based on this dose level.
Titration tips
- Inject on the same day each week. If you need to change your injection day, ensure at least 48 hours between doses.
- If side effects are intolerable at a new dose, drop back to the previous dose for an additional 4 weeks before re-attempting.
- Eat slowly, stop at the first sign of fullness, and avoid high-fat meals — these significantly reduce nausea.
- Stay hydrated. Dehydration worsens nausea and constipation.
Injection Sites
Semaglutide is injected subcutaneously using the provided auto-injector pen. Approved injection sites:
- Abdomen — most common site. Inject at least 2 inches from the navel. Rotate within the area to prevent lipodystrophy
- Thigh (front) — inject into the outer/front area of the upper thigh. Avoid the inner thigh
- Upper arm — back of the upper arm. May require assistance for self-injection at this site
Rotate injection sites weekly. Do not inject into areas that are tender, bruised, red, or hard. The injection can be given at any time of day, with or without food.
Side Effects
Gastrointestinal side effects are the most common and typically diminish with continued use and proper titration. Incidence rates below are from the STEP clinical trial program at the 2.4 mg dose:
Nausea
Diarrhea
Vomiting
Constipation
Abdominal pain
Headache
Fatigue
Injection site reaction
Serious risks & boxed warning
- Thyroid C-cell tumors (boxed warning) — semaglutide caused thyroid C-cell tumors in rodents. Contraindicated in patients with a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2)
- Pancreatitis — rare but serious. Discontinue immediately if severe abdominal pain occurs
- Gallbladder disease — increased incidence of cholelithiasis (gallstones) with rapid weight loss
- Hypoglycemia — risk increases when combined with insulin or sulfonylureas
- Kidney injury — dehydration from GI side effects can impair renal function in susceptible individuals
Research Summary
Semaglutide has one of the most robust clinical evidence bases of any weight management therapy, with large-scale randomized controlled trials across multiple populations:
Participants lost an average of 14.9% of body weight (vs. 2.4% placebo) over 68 weeks at the 2.4 mg dose. One-third of participants lost over 20% of body weight.
Wilding et al., 2021, N Engl J Med
Combined with intensive behavioral therapy, participants achieved 16.0% mean body weight reduction over 68 weeks.
Wadden et al., 2021, JAMA
Continued treatment over 2 years maintained 15.2% body weight loss, demonstrating long-term sustainability when therapy is continued.
Garvey et al., 2022, Nat Med
In adults with overweight/obesity and established cardiovascular disease, semaglutide 2.4 mg reduced major adverse cardiovascular events (MACE) by 20% over a mean follow-up of 39.8 months.
Lincoff et al., 2023, N Engl J Med
Semaglutide 1.0 mg reduced HbA1c by 1.4 percentage points and demonstrated a 26% reduction in MACE events in patients with T2D at high cardiovascular risk.
Marso et al., 2016, N Engl J Med
In patients with T2D and chronic kidney disease, semaglutide reduced the risk of kidney disease progression by 24% and reduced major cardiovascular events.
Perkovic et al., 2024, N Engl J Med
All cited studies are peer-reviewed, randomized controlled trials published in major medical journals.
Storage & Handling
Brand pens (Ozempic / Wegovy)
- Before first use: refrigerate at 36–46°F (2–8°C). Do not freeze.
- After first use: store at room temperature (59–86°F / 15–30°C) or refrigerated for up to 56 days.
- Keep the pen cap on when not in use to protect from light.
- Discard the pen 56 days after first use, even if medication remains.
Compounded semaglutide
- Follow the compounding pharmacy's specific storage instructions, which may differ from brand products.
- Lyophilized (freeze-dried) vials should be refrigerated and reconstituted with bacteriostatic water before use.
- Once reconstituted, typically stable for 28–30 days refrigerated.
FAQ
What is the difference between Ozempic and Wegovy?
Both contain semaglutide. Ozempic is approved for type 2 diabetes (max 2.0 mg/week). Wegovy is approved for chronic weight management (max 2.4 mg/week) and cardiovascular risk reduction in adults with obesity. The titration schedules and pen configurations differ, but the active molecule is identical.
What about compounded semaglutide?
Compounded semaglutide is produced by 503A and 503B compounding pharmacies. It is typically supplied as a lyophilized powder requiring reconstitution or as a pre-mixed solution. Compounded versions are not FDA-approved and may vary in purity and potency. They are generally more affordable than brand products.
What if I miss a dose?
If fewer than 5 days have passed since the missed dose, take it as soon as possible. If 5 or more days have passed, skip the missed dose and take the next dose on the regularly scheduled day. Do not double up on doses.
Can I drink alcohol on semaglutide?
Alcohol is not contraindicated, but it can worsen nausea and GI side effects. It also adds empty calories and may impair judgment around food choices. Many users find their alcohol tolerance decreases significantly. Moderate or avoid alcohol, especially during titration.
Will I lose muscle mass?
Approximately 25-40% of weight lost on semaglutide is lean mass (muscle), which is consistent with weight loss from any method. To minimize muscle loss: maintain adequate protein intake (0.7-1.0 g per pound of body weight), engage in resistance training 2-4x per week, and avoid excessively rapid weight loss.
What happens when I stop taking semaglutide?
Clinical data (STEP 1 extension) shows that approximately two-thirds of lost weight is regained within one year of discontinuation. Appetite suppression effects wear off as the drug clears the system. Many clinicians recommend a structured maintenance plan, ongoing lifestyle modifications, or a reduced maintenance dose.
How long does it take to start working?
Appetite suppression is often noticeable within the first 1-2 weeks. Meaningful weight loss (5%+ of body weight) typically occurs by weeks 12-16. Maximum weight loss is usually seen at 60-68 weeks of treatment at the full dose.
What are the best injection sites?
The abdomen (at least 2 inches from the navel), front of the thigh, and back of the upper arm are all approved sites. Rotate injection sites weekly. The abdomen is the most commonly used and generally the easiest for self-injection.
Track your semaglutide protocol
Use our free calculator for reconstitution math, or explore other peptide and GLP-1 protocols.