Semaglutide
A once-weekly GLP-1 receptor agonist. Approved in the US as Ozempic for type 2 diabetes and Wegovy for weight management.
- lost 15% or more of their body weight (placebo: 4.9%)
- 50.5%
- lower risk of heart attack, stroke or cardiovascular death in SELECT
- 20%
lost 15% or more of their body weight (placebo: 4.9%)[1]
lower risk of heart attack, stroke or cardiovascular death in SELECT[2]
5 sources, every claim linked. PepDose sells no peptides and takes no vendor money.
01 · What it is
What is Semaglutide?
Semaglutide is a long-acting version of the gut hormone GLP-1, made by Novo Nordisk. The injectable forms are Ozempic (type 2 diabetes) and Wegovy (chronic weight management, 2.4 mg once weekly).
Semaglutide sold as a research powder is not the approved medicine and has no FDA quality checks.
Illustration. A peptide is a short chain of amino acids.
02 · How it works
How does Semaglutide work?
It mimics GLP-1, a hormone released after meals. That slows stomach emptying, reduces appetite, and helps the pancreas release insulin when blood sugar is high.
Tap a drug to compare. Each extra receptor adds another hormone signal. More receptors does not by itself mean safer or better.
03 · Research
What does the research on Semaglutide show?
−14.9%
Weight change at 68 weeks on 2.4 mg in STEP 1 (1,961 adults with overweight or obesity, no diabetes, with lifestyle support). Placebo: −2.4%.[1]
In STEP 1, adults with overweight or obesity lost an average of 14.9% of their body weight over 68 weeks on semaglutide 2.4 mg weekly, versus 2.4% on placebo. In SELECT, the same dose cut the risk of heart attack, stroke or cardiovascular death by 20% in people with heart disease.
STEP 1: weight change at 68 weeks[1]
Phase 3 · 1,961 adults with overweight or obesity, no diabetes, with lifestyle support
STEP 1: lost 15% or more of body weight[1]
% of people at 68 weeks
SELECT: heart attack, stroke or cardiovascular death[2]
% of people over about 40 months · 17,604 adults with heart disease, no diabetes
- In SURMOUNT-5 (751 adults with obesity, no diabetes, 72 weeks), a head-to-head trial at the highest tolerated doses, average weight change was −13.7% on semaglutide versus −20.2% on tirzepatide. The trial was open-label and funded by Eli Lilly.[4]
All findings, in words
- In STEP 1 (1,961 adults with overweight or obesity, no diabetes, 68 weeks), weight changed by −14.9% on semaglutide 2.4 mg weekly versus −2.4% on placebo, alongside lifestyle support.[1]
- In the same trial, half of the people on semaglutide (50.5%) lost 15% or more of their body weight, versus 4.9% on placebo.[1]
- In SELECT (17,604 adults with heart disease and overweight or obesity, no diabetes), semaglutide 2.4 mg cut the risk of heart attack, stroke or cardiovascular death by 20% over about 40 months.[2]
- In SURMOUNT-5 (751 adults with obesity, no diabetes, 72 weeks), a head-to-head trial at the highest tolerated doses, average weight change was −13.7% on semaglutide versus −20.2% on tirzepatide. The trial was open-label and funded by Eli Lilly.[4]
04 · Side effects
What are the side effects of Semaglutide?
Nausea and diarrhea are the most common side effects of semaglutide. In STEP 1 they were usually mild to moderate and eased over time, and 4.5% of people stopped because of stomach side effects, versus 0.8% on placebo. In the longer SELECT trial, 16.6% stopped because of side effects of any kind.
- Placebo
- 2.4 mg
Stomach side effects (STEP 1)
Any side effect (SELECT)
- Nausea and diarrhea were the most common side effects. They were usually mild to moderate, temporary, and eased over time.[1]
Commonly listed reasons to avoid it
- Personal or family history of medullary thyroid carcinoma or MEN 2
- History of pancreatitis, or pregnancy and breastfeeding
Approved
05 · Legal and regulatory status
Is Semaglutide FDA-approved?
Yes. Semaglutide is FDA-approved as Ozempic for type 2 diabetes and as Wegovy for chronic weight management (approved June 2021, 2.4 mg once weekly). Both are made by Novo Nordisk. Semaglutide sold as a research powder is not the approved medicine and has no FDA quality checks.
- FDA-approved. Wegovy was approved for chronic weight management in June 2021, and Ozempic is approved for type 2 diabetes.[3]
06 · Mixing and units
How do you mix Semaglutide and read the units?
Units on a U-100 syringe = dose (mg) ÷ concentration (mg/mL) × 100. For example, a 2 mg vial mixed with 1 mL of bacteriostatic water is 2 mg/mL, so 10 units hold 0.2 mg. Pick your vial and water below; the maths is the same for any brand of Semaglutide.
- 1 Peptide vial
- 2 Bacteriostatic water
- 3 U-100 syringe
- 4 Alcohol swabs
Vial size
Water added
- Semaglutide in the vial
- 2 mg
- Water added
- 1 mL
- Strength
- 2 mg/mL
- 1 unit holds
- 20 mcg
Where the doses used in studies land on a 1 mL (100 unit) syringe
Shown to help you read the units, not as advice.
- 0.25 mg (starting step)12.5 units
- 0.5 mg25 units
- 1 mg50 units
- 1.7 mg85 units
- 2.4 mg (STEP 1, SELECT)over 100 units
Over 100 units means more than one full 1 mL syringe at this strength. Less water makes each unit stronger.
STEP 1 and SELECT used 2.4 mg once weekly. The Wegovy label reaches it in 4-week steps: 0.25, 0.5, 1 and 1.7 mg, then 2.4 mg from week 17. Shown to help you read the units, not as advice.[1,2,5]
- Step 1
Clean
Wipe the vial stopper with an alcohol swab and let it dry.
- Step 2
Add water
Let the bacteriostatic water run slowly down the inside wall of the vial.
- Step 3
Swirl
Swirl or roll gently until clear. Don't shake.
- Step 4
Label and chill
Write the date and strength (mg/mL) on the vial and keep it in the fridge.
The full Semaglutide protocol
- Week-by-week schedule and titration
- What to track and when
- Stacking notes and timing
- Dose tracker with injection-site rotation
- Every study explained in detail
- Step-by-step start guide
07 · Questions
Common questions about Semaglutide
How many units is 0.25 mg of semaglutide?
In a 5 mg vial mixed with 2 mL (2.5 mg/mL), 0.25 mg is 10 units on a U-100 syringe. In a 2 mg vial with 1 mL (2 mg/mL), it is 12.5 units.
Semaglutide units to mg: how do I convert?
Units ÷ 100 gives millilitres; millilitres × concentration (mg/mL) gives milligrams. The units-to-mg converter does this and prints a full chart for your vial.
Is compounded or research semaglutide the same as Ozempic?
Same molecule on paper, but not the same product. Ozempic and Wegovy are made under FDA oversight. Research powders have no such checks, so purity and dose accuracy are unknown.
How much weight do people lose on semaglutide?
In STEP 1, a 68-week trial in 1,961 adults with overweight or obesity, average weight change was −14.9% on semaglutide 2.4 mg weekly versus −2.4% on placebo, alongside lifestyle support. About half (50.5%) lost 15% or more of their body weight.
Does semaglutide lower heart risk?
In SELECT, a trial of 17,604 adults with heart disease and overweight or obesity but no diabetes, semaglutide 2.4 mg cut the risk of heart attack, stroke or cardiovascular death by 20% over about 40 months.
Semaglutide vs tirzepatide: which leads to more weight loss?
Tirzepatide, in the one head-to-head obesity trial. In SURMOUNT-5 (751 adults, 72 weeks, highest tolerated doses), average weight change was −20.2% on tirzepatide versus −13.7% on semaglutide. The trial was open-label and funded by tirzepatide's maker, Eli Lilly.
How is the semaglutide dose increased?
The Wegovy label steps up every 4 weeks: 0.25, 0.5, 1 and 1.7 mg, then 2.4 mg from week 17. That is what the label and trials describe, shown here to help you read the units, not as advice.
Sources
- 1.Once-weekly semaglutide in adults with overweight or obesity (STEP 1)
Wilding JPH et al. N Engl J Med 2021;384:989-1002 · Human trial - 2.Semaglutide and cardiovascular outcomes in obesity without diabetes (SELECT)
Lincoff AM et al. N Engl J Med 2023;389:2221-2232 · Human trial - 3.Wegovy approval letter
FDA. Wegovy (semaglutide) NDA 215256 approval letter, June 2021 · FDA - 4.Tirzepatide as compared with semaglutide for the treatment of obesity (SURMOUNT-5)
Aronne LJ et al. N Engl J Med 2025;393:26-36 · Human trial - 5.Wegovy label
FDA. Wegovy (semaglutide) prescribing information, 2025 · FDA