Semaglutide
FDA APPROVEDGLP-1 receptor agonist | Weight loss & diabetes
By the INFOPEPTIDOS editorial team · content based on scientific literature.
Updated: August 2026 · Based on the STEP and SUSTAIN trials.
Key points
- What it is: GLP-1 receptor agonist (marketed as Ozempic and Wegovy).
- Main use: weight loss and type 2 diabetes.
- Typical dose: 0.25 → 2.4 mg weekly, subcutaneous injection, with gradual escalation.
- Key result: ~15% weight loss in the STEP trials.
- Common effects: nausea, diarrhea and constipation (dose-dependent).
- Comparison: mono-agonist; less potent than tirzepatide (dual) and retatrutide (triple).
- Status: FDA-approved for weight (Wegovy) and diabetes (Ozempic).
Technical data: Molecular formula C187H291N45O59 · Molecular weight 4114 g/mol. Source: PubChem.
Overview
What is Semaglutide?
Semaglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist approved by the FDA for type 2 diabetes and chronic weight management. It is sold as Ozempic, Wegovy and Rybelsus. In clinical trials with more than 17,000 participants, it showed significant weight loss (an average 15-20% body-weight reduction) through appetite suppression, slower gastric emptying and glucose control.
Key benefits
FDA-approved treatment with proven efficacy for weight loss (15-20% on average) and diabetes control. Convenient weekly dosing, with proven cardiovascular benefits and extensive safety data from large clinical trials.
Mechanism of action
Subcutaneous semaglutide mimics native GLP-1, binding to GLP-1 receptors to stimulate glucose-dependent insulin secretion, suppress glucagon, slow gastric emptying and reduce appetite through hypothalamic pathways. Its 7-day half-life allows weekly dosing.
Quick start guide
Dosing protocol (weekly titration)
| Phase | Weeks | Weekly dose | Goal |
|---|---|---|---|
| Start | 1–4 | 0.25 mg | Adaptation; minimizes nausea |
| Titration 1 | 5–8 | 0.5 mg | Gradual increase |
| Titration 2 | 9–12 | 1.0 mg | Progressive increase |
| Titration 3 | 13–16 | 1.7 mg | Approaching target dose |
| Maintenance | 17+ | 2.4 mg (max.) | Maintenance dose (Wegovy) |
Subcutaneous route, once a week, increasing the dose every 4 weeks. The exact dose must be set by a healthcare professional.
Reconstitution: units in the syringe
Example with a 5 mg vial + 2 ml of bacteriostatic water → a 2.5 mg/ml solution. On a U-100 insulin syringe (100 units = 1 ml):
| Dose | Volume | Units (U-100) |
|---|---|---|
| 0.25 mg | 0.10 ml | 10 U |
| 0.5 mg | 0.20 ml | 20 U |
| 1 mg | 0.40 ml | 40 U |
| 1.7 mg | 0.68 ml | 68 U |
| 2.4 mg | 0.96 ml | 96 U |
Is your vial or water different? Calculate the exact units below.
🧮 Calculate your exact syringe dose →Retatrutide vs Tirzepatide vs Semaglutide
| Semaglutide | Tirzepatide | Retatrutide | |
|---|---|---|---|
| Receptors | GLP-1 | GLP-1 + GIP | GLP-1 + GIP + glucagon |
| Type | Mono | Dual | Triple |
| Weight loss (max. in trials) | ~15% | ~21–22% | ~24–28% |
| Frequency | 1×/week | 1×/week | 1×/week |
| FDA status | Approved | Approved | Investigational |
⚠️ Who should NOT use it
- Personal or family history of medullary thyroid carcinoma or MEN 2 syndrome.
- History of pancreatitis.
- Pregnancy or breastfeeding.
- Always under the supervision of a healthcare professional.
What to expect
- Week 1-4: mild appetite reduction, possible nausea during the initial dose.
- Month 2-3: noticeable weight loss (5-10% typical), greater satiety.
- Month 4-6: continued weight loss (10-15% common), stable glucose levels.
- Month 6 onward: possible weight-loss plateau, focus on maintenance.
- Diabetes benefits: blood sugar improvements within 1-2 weeks.
- Long term: sustained benefits with continued use.
Side effects & safety
- FDA-approved medication with extensive safety data from trials of 17,000+ participants.
- Start low and titrate slowly to minimize gastrointestinal side effects.
- Most common side effects: nausea, diarrhea, vomiting, constipation, stomach pain, headache, fatigue, dizziness, bloating, belching, gas, heartburn and upset stomach.
- Hair loss and changes in skin sensations have been reported.
- Contraindicated with a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).
- May cause thyroid tumors including cancer — tell your provider about neck lumps, hoarseness, or trouble swallowing or breathing.
- May cause gallbladder problems including gallstones — some may require surgery.
- May increase resting heart rate — tell your provider if you feel your heart racing or pounding for several minutes.
- Increased risk of low blood sugar (hypoglycemia) when combined with insulin or sulfonylureas.
- Dehydration from gastrointestinal side effects may lead to kidney problems — stay well hydrated.
- Tell all healthcare providers you take this medication before any surgery or procedure with anesthesia, due to aspiration risk.
- Stop use 2 months before a planned pregnancy — may harm an unborn baby.
- Not recommended during pregnancy or breastfeeding.
- Severe allergic reaction: rash, itching, swelling of the face, lips or throat, or difficulty breathing.
- Severe, persistent abdominal pain that may radiate to the back (possible pancreatitis).
- Persistent vomiting or diarrhea with signs of dehydration.
- Lump or swelling in the neck, hoarseness or difficulty swallowing.
- Pain in the upper right abdomen or yellowing of the skin (possible gallbladder problem).
- Symptoms of severe hypoglycemia: confusion, sweating, tremors or fainting.
- Vision changes or worsening of diabetic retinopathy.
- If you are pregnant or plan to be within the next 2 months.
Frequently asked questions
What is Semaglutide?
Semaglutide is a GLP-1 receptor agonist approved by the FDA for type 2 diabetes and chronic weight management. It is sold as Ozempic, Wegovy and Rybelsus.
What is Semaglutide used for?
It is used for weight loss and to control blood glucose in type 2 diabetes.
How does Semaglutide work?
It mimics the GLP-1 hormone: it stimulates glucose-dependent insulin secretion, slows gastric emptying and reduces appetite through brain pathways.
How long does Semaglutide take to work?
Appetite reduction is usually noticeable within 1-2 weeks, significant weight loss within several weeks and full effects within a few months.
What is the usual Semaglutide dose?
It starts at 0.25 mg weekly and is increased progressively up to the target dose (up to 2.4 mg). The schedule is set by a professional.
How is Semaglutide administered?
By subcutaneous injection once a week (abdomen, thigh or arm). There is also a daily oral version.
How much weight can you lose with Semaglutide?
In clinical trials, an average reduction of 15-20% of body weight was observed, though it varies by person.
How is Semaglutide stored?
Refrigerated between 2 and 8 °C. See the storage guide for details.
What are the side effects of Semaglutide?
The most common are digestive: nausea, diarrhea, constipation and stomach discomfort, especially when increasing the dose.
What is the difference between Semaglutide and Tirzepatide?
Semaglutide acts on a single receptor (GLP-1), while tirzepatide acts on two (GIP and GLP-1), with greater average weight loss.
Is Semaglutide approved?
Yes, it is approved by the FDA for both type 2 diabetes and weight management.
Who should not use Semaglutide?
It is contraindicated in people with a history of medullary thyroid carcinoma or MEN 2 syndrome, and during pregnancy.
Research areas
- Weight loss
- Type 2 diabetes control
- Appetite reduction
- Cardiovascular health
- Blood glucose control
Related peptides
- Tirzepatide — Dual GIP/GLP-1 agonist, with greater average weight loss.
- Retatrutide — Triple GLP-1/GIP/glucagon agonist in advanced research.
- AOD-9604 — hGH fragment researched for fat loss.
Related articles
Related topics
- Semaglutide for weight loss
- Semaglutide and diabetes
- Semaglutide dose
- Semaglutide side effects
- Semaglutide vs Tirzepatide
- Semaglutide Ozempic and Wegovy
Summary
What it is: GLP-1 receptor agonist (Ozempic, Wegovy, Rybelsus).
How it is researched: Weekly subcutaneous injection or oral; 0.25 to 2.4 mg.
Key features: Reduces appetite and glucose; average 15-20% loss. FDA-approved.
Related peptides: Tirzepatide, Retatrutide and AOD-9604.
References
- Tan HC et al. (2022). Efficacy and Safety of Semaglutide for Weight Loss in Obesity Without Diabetes: A Systematic Review and Meta-Analysis. J ASEAN Fed Endocr Soc. PubMed · DOI
- Rodriguez PJ et al. (2024). Semaglutide vs Tirzepatide for Weight Loss in Adults With Overweight or Obesity. JAMA Intern Med. PubMed · DOI
- Rubino D et al. (2021). Effect of Continued Weekly Subcutaneous Semaglutide vs Placebo on Weight Loss Maintenance in Adults With Overweight or Obesity: The STEP 4 Randomized Clinical Trial. JAMA. PubMed · DOI
- Ryan DH et al. (2024). Long-term weight loss effects of semaglutide in obesity without diabetes in the SELECT trial. Nat Med. PubMed · DOI
Studies compiled from PubMed for informational purposes; many are preclinical or research-stage and do not constitute medical advice.