The revolutionary once-weekly GLP-1 medication that helps your body feel full faster and longer, leading to significant weight loss while also protecting your heart—FDA approved and backed by some of the largest clinical trials in obesity medicine history.
Written by Michael Carroll — Owner, Director of Research · Reviewed by the Peptide Initiative Research Team · Editorial standards
Subcutaneous
Route
3 recommended
Sites
Once weekly
Frequency
Preparation
Pre-filled semaglutide pen (Ozempic or Wegovy)—no mixing required
Pen needles (usually provided or prescribed separately)
Alcohol swabs for injection site cleaning
Sharps container for safe needle disposal
Pro tip
Prepare all supplies on a clean surface before you begin. Having everything ready makes the process smoother and more sterile.
Mixing
Example calculation
Semaglutide comes in pre-filled, pre-measured pens. For Wegovy: Starter pens contain set doses (0.25mg, 0.5mg, etc.) that you select. For Ozempic: The pen dial lets you select your dose (0.25mg, 0.5mg, 1mg, or 2mg). No calculations needed—the pen does the measuring for you.
Dose calculation
Simply dial your prescribed dose on the pen. For example, if prescribed 0.5mg weekly, turn the dose selector to 0.5mg and inject. The pen window shows your selected dose. One pen typically contains multiple doses depending on your prescription.
Location
Site 01
Abdomen
Pinch the skin 2 inches from navel. Avoid the area directly around the belly button. Rotate between left and right sides.
Site 02
Outer Thigh
Middle third of the outer thigh. Keep at least 4 inches above the knee and below the hip. Alternate legs each injection.
Site 03
Upper Arm
Back or outer area of the upper arm. This site may require assistance from another person for proper technique.
Rotate between 3 sites to prevent tissue buildup and ensure consistent absorption.
Pro tip
Rotate your injection sites with each dose to prevent lipohypertrophy (buildup of fatty tissue). Keep a simple log of where you last injected.
Step by step
Remove pen cap and attach a new needle—never reuse needles
Clean injection site with alcohol swab and let it air dry
If using a new pen, prime it according to package instructions
Dial your prescribed dose on the pen
Pinch skin at injection site and insert needle straight in (90-degree angle)
Press and hold the dose button until the dose counter shows 0
Keep the button pressed and count slowly to 6 before removing needle
Remove needle, dispose in sharps container, and replace pen cap
Pro tip
This peptide uses subcutaneous injection (into the fatty tissue just under the skin)—quick, relatively painless, and can be self-administered at home. Inject at a 45-90 degree angle into pinched skin. Aspirate before injecting to ensure you haven't hit a blood vessel.
Timing
Optimal timing
Best time
Choose any day of the week that works for your schedule and stick with it. Many people prefer Sunday or Monday to make it easy to remember. Take it at roughly the same time each week, though the exact hour doesn't matter much due to the long half-life [5][7].
With food?
Semaglutide injections can be taken with or without food—it doesn't affect absorption. However, because the medication slows stomach emptying, eating smaller meals will help reduce nausea. The oral version (Rybelsus) MUST be taken on an empty stomach with a small amount of water.
Stacking notes
Semaglutide is typically used as a standalone weight management therapy. If using with other diabetes medications, especially insulin or sulfonylureas, doses of those medications may need to be reduced to prevent low blood sugar. Always coordinate with your healthcare provider [5][7].
Sample daily schedule
Same day each week (e.g., every Sunday morning)
As prescribed (0.25mg to 2.4mg depending on phase) injection
Site: Rotate between abdomen, thigh, and arm weekly
Pick a day you'll remember. Many people choose a weekend day so they can rest if they experience nausea. The injection takes less than 30 seconds once you get the hang of it. If you miss a dose by less than 5 days, take it as soon as you remember. If more than 5 days late, skip that dose and take the next one on your regular day.
Dosing tiers
Dose
0.25 mg
Frequency
Once weekly
Duration
4 weeks
This is the starter dose to help your body adjust. It does not lower blood sugar much on its own, so it is only used for the first 4 weeks before stepping up [5].
Dose
0.5-1 mg
Frequency
Once weekly
Duration
At least 4 weeks at each step
After the starter month, the dose goes up to 0.5 mg, and can rise to 1 mg if more blood sugar control is needed. Wait at least 4 weeks before each increase [5].
Dose
2-2.4 mg
Frequency
Once weekly
Duration
Ongoing/maintenance
The highest weekly doses. 2 mg is the maximum for diabetes (Ozempic) [5]; up to 2.4 mg is used for weight management (Wegovy) after a slower titration.
Dose
3 mg
Frequency
Once daily
Duration
30 days
The pill form (Rybelsus) starts at 3 mg each morning for 30 days. Like the starter shot, this dose is for getting started and does not control blood sugar by itself. Take on an empty stomach with a small sip of water, 30 minutes before food or other pills [6].
Dose
7 mg
Frequency
Once daily
Duration
30+ days
After the first 30 days, the dose increases to 7 mg once daily. This is the first dose that actively lowers blood sugar [6].
Dose
14 mg
Frequency
Once daily
Duration
Ongoing/maintenance
The highest pill dose, used if more blood sugar control is needed after at least 30 days at 7 mg [6].
Preservation
Before mixing
Store new, unopened pens in the refrigerator at 36-46°F (2-8°C). Do not freeze—freezing destroys the medication. Keep in original carton to protect from light. If needed, unopened pens can be stored at room temperature (up to 86°F/30°C) for up to 28 days before first use.
After mixing
After first use, pens can be stored in the refrigerator or at room temperature up to 86°F (30°C). Use within 56 days of first injection. Always replace the pen cap after use to protect from light. Never store with needle attached.
Shelf life after mixing
56 days after first use
Signs of degradation
Discard the vial immediately if you notice any of these:
Solution appears cloudy, discolored, or contains particles (should be clear and colorless)
Pen has been frozen or exposed to temperatures above 86°F (30°C) for extended periods
Solution looks yellow or has changed color
Pen is damaged or the dose selector doesn't click properly
Important
When to stop
Severe or persistent nausea and vomiting that prevents adequate nutrition despite dose adjustments
Signs of pancreatitis—severe abdominal pain radiating to the back
Allergic reaction—rash, itching, swelling, difficulty breathing
Signs of thyroid tumors—neck lump, hoarseness, trouble swallowing
Pregnancy or planning to become pregnant (stop at least 2 months before conception)
Severe kidney problems or dehydration from GI symptoms
Your healthcare provider recommends discontinuation
Semaglutide is a prescription medication that should only be started, adjusted, or stopped under medical supervision. This information is educational and does not replace professional medical advice. Stopping suddenly is generally safe, but discuss any changes with your healthcare provider.
Clean technique checklist
Wash hands thoroughly with soap and water before handling supplies
Swab vial tops and injection site with alcohol and let dry
Never touch the needle tip or allow it to contact non-sterile surfaces
Use a new syringe and needle for each injection
Dispose of used sharps in a proper sharps container
Store reconstituted peptides according to the storage instructions above
Published research
Wilding JPH, Batterham RL, Calanna S, et al. · 2021
This landmark trial proved semaglutide's effectiveness for weight loss. Participants lost an average of 14.9% of their body weight over 68 weeks (about 33 pounds), compared to just 2.4% with placebo. Over half lost more than 15% of their body weight—results previously only seen with surgery.
Lincoff AM, Brown-Frandsen K, Colhoun HM, et al. · 2023
This massive trial of 17,604 people proved semaglutide reduces heart attacks, strokes, and cardiovascular death by 20% in people with obesity and heart disease—even without diabetes. This was the first time a weight loss medication showed direct cardiovascular benefits.
Weiskirchen R, Lonardo A · 2025
This comprehensive review traced semaglutide's development from laboratory discovery to clinical breakthrough, documenting its expanding role beyond diabetes into obesity treatment and metabolic liver disease—cementing its status as a transformative therapy.
Mondoh A, Crotty M, le Roux CW · 2025
Head-to-head comparisons show both medications are highly effective, with tirzepatide producing somewhat greater weight loss in some studies. However, semaglutide has more long-term safety data and the SELECT cardiovascular outcomes trial supporting its use.
Novo Nordisk / U.S. FDA · 2025
Subcutaneous semaglutide is started at 0.25 mg once weekly for 4 weeks, then increased to 0.5 mg, then 1 mg, then up to a maximum of 2 mg once weekly, with at least 4 weeks between increases.
Novo Nordisk / U.S. FDA · 2024
Oral semaglutide is started at 3 mg once daily for 30 days (initiation dose, not effective for glucose control), then increased to 7 mg once daily, and may be increased to a maximum of 14 mg once daily. Taken on an empty stomach with up to 4 oz water, 30 minutes before food or other medicines.
Novo Nordisk / U.S. FDA · 2024
US label for semaglutide 2.4 mg for chronic weight management and cardiovascular risk reduction. Carries the boxed warning for rodent thyroid C-cell tumors and contraindication in personal or family history of MTC or MEN 2. Indicated at BMI 30 or greater, or 27 or greater with at least one weight-related comorbidity. Titration is 0.25 mg weekly for 4 weeks then escalation every 4 weeks to a 2.4 mg maintenance dose, explicitly 'to minimize gastrointestinal adverse reactions.' Adverse reactions in 2,116 adults: nausea 44%, diarrhea 30%, vomiting 24%, constipation 24%, abdominal pain 20%, hair loss 3%. Cholelithiasis 1.6% and cholecystitis 0.6% versus 0.7% and 0.2% on placebo; acute pancreatitis adjudicated in 4 patients (0.2 per 100 patient-years). Semaglutide is 94% homologous to human GLP-1, modified at position 8 against DPP-4 degradation and acylated at lysine 26 with a C18 fatty di-acid via a hydrophilic spacer; albumin binding exceeds 99% and the elimination half-life is approximately 1 week. It delays gastric emptying, lowers calorie intake, and loses more fat mass than lean mass. Dose may be given any time of day with or without food; concomitant insulin or insulin secretagogue may require dose reduction.
Davies M, Færch L, Jeppesen OK, et al. · 2021
In 1,210 adults with overweight or obesity and type 2 diabetes, semaglutide 2.4 mg once weekly reduced body weight by 9.6% at 68 weeks versus 3.4% with placebo, and 68.8% versus 28.5% achieved at least 5% weight loss. Gastrointestinal adverse events, mostly mild to moderate, occurred in 63.5% of the 2.4 mg group.
Wadden TA, Bailey TS, Billings LK, et al. · 2021
In 611 adults with overweight or obesity, semaglutide 2.4 mg weekly plus intensive behavioral therapy reduced body weight by 16.0% at 68 weeks versus 5.7% with placebo; 55.8% versus 13.2% lost at least 15% of baseline weight.
Rubino D, Abrahamsson N, Davies M, et al. · 2021
After a 20-week run-in to semaglutide 2.4 mg, 803 adults were randomised to continue or switch to placebo. Continuing semaglutide produced a further 7.9% weight loss over 48 weeks while switching to placebo produced a 6.9% regain, a difference of 14.8 percentage points.
Wilding JPH, Batterham RL, Davies M, et al. · 2022
One year after semaglutide 2.4 mg and lifestyle intervention were withdrawn, participants had regained 11.6 of the 17.3 percentage points of weight they had lost, about two-thirds of the prior weight loss, and cardiometabolic improvements reverted toward baseline.
Lau J, Bloch P, Schäffer L, et al. · 2015
Semaglutide carries two amino acid substitutions relative to human GLP-1 (Aib at position 8 and Arg at position 34) and is derivatised at lysine 26 with a fatty di-acid linked through a spacer. The Aib8 substitution secures stability against metabolic degradation and the acylation raises albumin affinity, which is the protraction mechanism behind once-weekly dosing.
Secher A, Jelsing J, Baquero AF, et al. · 2014
In the arcuate nucleus, a GLP-1 analogue was internalised in neurons expressing proopiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART). Electrophysiology showed GLP-1 directly stimulates POMC/CART neurons and indirectly inhibits neurotransmission in neuropeptide Y (NPY) and agouti-related peptide (AgRP) neurons via GABA-dependent signalling.
Bjerre Knudsen L, Madsen LW, Andersen S, et al. · 2010
The GLP-1 receptor was localised to rodent thyroid C-cells, where agonists stimulated calcitonin release and C-cell hyperplasia. Humans and cynomolgus monkeys had low GLP-1 receptor expression in thyroid C-cells and no calcitonin release or adenylate cyclase activation in response to GLP-1 receptor agonists, delineating a species-specific difference in the thyroid.
Pasternak B, Wintzell V, Hviid A, et al. · 2024
Across 145,410 GLP-1 receptor agonist users and 291,667 DPP-4 inhibitor users in Denmark, Norway and Sweden, GLP-1 receptor agonist use was not associated with increased thyroid cancer risk (hazard ratio 0.93, 95% CI 0.66 to 1.31) over a mean 3.9 years of follow-up; the hazard ratio for medullary thyroid cancer was 1.19 (0.37 to 3.86).
Sodhi M, Rezaeianzadeh R, Kezouh A, Etminan M · 2023
In a population-based cohort of patients using GLP-1 receptor agonists for weight loss, the incidence of pancreatitis with semaglutide was 4.6 per 1000 person-years, versus 7.9 for liraglutide and 1.0 for bupropion-naltrexone. Biliary disease was 11.7 and gastroparesis 9.1 per 1000 person-years with semaglutide.
Burke OM, Sa B, Alvarez Cespedes D, Tosti A · 2025
Hair loss in the form of telogen effluvium has been observed with GLP-1 receptor agonists and is potentially linked to the rapid weight loss these drugs produce rather than to a direct drug effect on the follicle.
Eisa N, Barood O · 2026
Across 20 randomised trials and 15,782 participants, lean mass made up 25% to 39% of total weight lost with incretin agonists: 35.2% for semaglutide, 25.4% for tirzepatide and 26.8% for liraglutide. Lifestyle intervention alone was comparable at 26.2%, while lifestyle plus resistance training was the most favourable at 17.5%.
Hendershot CS, Bremmer MP, Paladino MB, et al. · 2025
In a 9-week phase 2 randomised trial in 48 adults with alcohol use disorder, low-dose semaglutide reduced laboratory alcohol self-administration, drinks per drinking day and weekly alcohol craving relative to placebo, and predicted greater reductions in heavy drinking over time.
Wharton S, Freitas P, Hjelmesæth J, et al. · 2025
A 7.2 mg once-weekly maintenance dose of subcutaneous semaglutide was tested against 2.4 mg and placebo in 1,407 adults with obesity over 72 weeks, producing 18.7% weight loss versus 15.6% with 2.4 mg and 3.9% with placebo. Gastrointestinal adverse events and dysaesthesia were more frequent at 7.2 mg.
Pratley RE, Crowley MJ, Gislum M, et al. · 2021
Across PIONEER 3-5, 7 and 8 (2,836 patients), semaglutide lowered HbA1c by 1.0 to 1.5 percentage points and body weight by 2.2 to 5.0 kg regardless of which background glucose-lowering medications patients were taking, and total daily insulin dose decreased in patients receiving semaglutide.
Verma S, Bhatta M, Davies M, et al. · 2022
Semaglutide 2.4 mg reduced serum C-reactive protein at week 68 versus placebo by 44% in STEP 1, 39% in STEP 2 and 48% in STEP 3, irrespective of baseline BMI, body weight or glycaemic status. Reductions tracked with weight loss, waist circumference, fasting glucose, fasting insulin and HOMA-IR, and more semaglutide-treated participants moved into a lower CRP-defined cardiovascular risk category, suggesting an anti-inflammatory role in obesity.