What semaglutide is
Semaglutide is a GLP-1 receptor agonist. It copies GLP-1, a hormone your gut releases after you eat, but lasts much longer, so a single injection works for a full week.
How it works
- In the brain: it acts on appetite centers, so you feel full sooner and think about food less. Many people describe quieter "food noise."
- In the stomach: it slows how quickly food leaves your stomach, so meals keep you satisfied longer.
- In the pancreas: it helps release insulin when blood sugar rises, which is why it was first used for type 2 diabetes.
A short history
Semaglutide was approved in 2017 for type 2 diabetes (as Ozempic). Patients lost meaningful weight, which led to the STEP trials and FDA approval for chronic weight management in 2021 (as Wegovy). In 2024, the FDA also approved it to lower the risk of heart attack and stroke in adults with heart disease and overweight, based on the SELECT trial.
What the research shows
- Weight loss: in STEP 1, adults taking 2.4 mg weekly lost an average of 14.9% of their body weight over 68 weeks, compared with 2.4% on placebo.
- Heart health: in SELECT, semaglutide lowered the risk of major heart events by 20% in adults with heart disease and overweight.
- After stopping: in the STEP 1 extension, people regained about two-thirds of the weight they'd lost within a year of stopping. Semaglutide works best as a long-term treatment.
What to expect
- Weeks 1 to 4: the starting dose lets your body adjust. Many people notice less appetite even now.
- Months 2 to 4: doses step up and weight loss becomes steadier. Stomach side effects are most likely in the days after an increase.
- Months 4 and beyond: you reach your maintenance dose. Weight loss continues more gradually and usually levels off after about a year.
How dosing works
Compounded semaglutide is often prepared at 2.5 mg/mL with vitamin B6. Doses start low and step up about every four weeks.
Compounded semaglutide is often prepared at 2.5 mg/mL with vitamin B6 (pyridoxine) 10 mg/mL, for each patient under a prescription. Doses are measured with a standard U-100 insulin syringe.
| Vial size | Strength | Semaglutide per vial | Vitamin B6 per vial |
|---|---|---|---|
| 2 mL | 2.5 mg/mL | 5 mg | 20 mg |
| 4 mL | 2.5 mg/mL | 10 mg | 40 mg |
Typical dose schedule
- 0.25 mgWeeks 1–410 units
- 0.5 mgWeeks 5–820 units
- 1 mgWeeks 9–1240 units
- 1.7 mgWeeks 13–1668 units
- 2.4 mgWeek 17 on96 units
Increase only as directed by your prescriber.
See every dose and how long a vial lasts
| Weekly dose | Amount | Syringe | 2 mL vial lasts | 4 mL vial lasts |
|---|---|---|---|---|
| 0.25 mg | 0.10 mL | 10 units | 20 wks | 40 wks |
| 0.5 mg | 0.20 mL | 20 units | 10 wks | 20 wks |
| 0.75 mg | 0.30 mL | 30 units | 6 wks | 13 wks |
| 1 mg | 0.40 mL | 40 units | 5 wks | 10 wks |
| 1.25 mg | 0.50 mL | 50 units | 4 wks | 8 wks |
| 1.5 mg | 0.60 mL | 60 units | 3 wks | 6 wks |
| 1.75 mg | 0.70 mL | 70 units | ~2.9 wks | ~5.7 wks |
| 2 mg | 0.80 mL | 80 units | 2.5 wks | 5 wks |
| 2.4 mg | 0.96 mL | 96 units | ~2.1 wks | ~4.2 wks |
Approximate supply, once weekly. Your prescriber sets your dose and any custom schedule.
Tips for success
- Eat protein at every meal and add strength training to protect muscle.
- Eat slowly and stop when you first feel full.
- Drink water through the day.
- Take your injection on the same day each week.
- Tell your provider about side effects instead of pushing through them.
See the side-effect guide for more.
Sources
- Wilding JPH, et al. Once-weekly semaglutide in adults with overweight or obesity (STEP 1). New England Journal of Medicine, 2021.
- Lincoff AM, et al. Semaglutide and cardiovascular outcomes in obesity without diabetes (SELECT). New England Journal of Medicine, 2023.
- Wilding JPH, et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide (STEP 1 extension). Diabetes, Obesity and Metabolism, 2022.
