SemaglutideDosing & Reconstitution Calculator

Semaglutide (Ozempic, Wegovy) — GLP-1 Dosing with Side Effects

Semaglutide activates one of the hormones your body releases after a meal — GLP-1 — at full native strength. It's the most established incretin drug and the only one with proven cardiovascular outcomes against placebo.³

• Appetite control — GLP-1 (1× native). GLP-1 is the hormone your gut releases after a meal to tell your brain "you're full." Semaglutide hits this receptor at full native strength — matching the peak satiety signal your body produces after a large meal, sustained continuously on a weekly schedule. The mechanism and the side-effect profile are inseparable: the strongest appetite suppression in the incretin class comes with the highest GI burden at comparable doses.

Semaglutide's defining edge isn't weight loss — it's cardiovascular outcomes. The SELECT trial (17,604 participants, median 40 months) showed a 20% reduction in major adverse cardiovascular events versus placebo in adults with obesity and established cardiovascular disease, without requiring diabetes.³ This is superiority data against placebo. Neither tirzepatide nor retatrutide has an equivalent readout. If your primary goal is cardiovascular risk reduction rather than weight loss, sema is the evidence-led choice.

The second organ-outcome readout landed in 2025: ESSENCE tested sema 2.4mg against placebo for histologic MASH resolution and reported 62.9% resolution without worsening fibrosis versus 34.1% on placebo.⁹ That's a distinct endpoint from MRI hepatic fat content — MASH resolution is the histologic inflammation-plus-ballooning pattern that defines the disease. Between SELECT on the cardiovascular arm and ESSENCE on the hepatic arm, sema is the GLP-1 with the deepest organ-outcome evidence base beyond weight loss.

On weight loss: STEP-1 (non-diabetic obesity, 68 weeks) produced ~15% average weight loss at 2.4mg weekly.¹ SURMOUNT-5 head-to-head showed 13.7% on sema vs 20.2% on tirz at maximum doses² — 47% less weight loss than tirzepatide in non-diabetic obesity. Body composition also runs weaker: sema's fat-to-lean loss ratio is ~60:40, versus tirz's ~75:25 at comparable total loss.⁵ The trade-off is direct: sema gives you CV outcome data; tirz gives you a better-quality pound.

The dose question below has three variables: total weekly dose, your primary goal (weight loss, CV risk reduction, or post-loss maintenance), and whether you're on a compounded vial or a pre-filled pen. Semaglutide is FDA-approved as Ozempic (T2D), Wegovy (obesity), and Rybelsus (oral T2D) — the ranges below come from labeled titration schedules plus clinical practice for low-dose maintenance.

Semaglutide Dosing Math — Why the GI Load Runs Highest

Receptor affinity values from primary trial sources, normalized against the body's own hormone at each receptor.

Sema is the only pure GLP-1 agonist among active incretin drugs, and its GLP-1 affinity is the highest of the three — dialed to full native strength. Tirzepatide at 0.2× native and retatrutide at 0.4× native were designed with softer GLP-1 signals precisely because the full GLP-1 signal drives GI side effects.

The dose implication: semaglutide's side-effect profile scales directly with GLP-1 receptor occupancy. There's no GIP-driven fat-cell thermogenesis to compensate and no glucagon-driven energy expenditure to offset the deficit. What you get is pure GLP-1 effect — strongest in the class for appetite suppression, gastric slowing, and cardiovascular outcomes. What you pay is the highest nausea incidence in the class at equipotent weight-loss doses.

The semaglutide deep dive covers the full trial cohorts, SELECT cardiovascular data, and the body-composition analysis.

Figuring out the right Sema dose for you

Three inputs shape the dose decision: what you're trying to do with the drug, what your baseline tolerates, and how your body responds in the first few weeks.

Before you start, check these

A baseline panel before your first injection makes every subsequent dose decision defensible. Without it, a shift in GI symptoms or lipids at week 12 can't be distinguished from a drug effect.

• Fasting glucose, HbA1c, fasting insulin — the metabolic starting point. If diabetes risk is part of the picture, these also frame whether sema is the right GLP-1 choice vs tirzepatide.
• Lipid panel — sema improves triglycerides, shifts the ApoB / non-HDL profile, and is associated with the SELECT CV outcome. Baseline matters for tracking the secondary metabolic effects.
• Gallbladder history — sema carries the highest gallbladder risk in the class (2.6× cholelithiasis odds vs placebo), amplified by rapid weight loss. Flag any prior cholecystitis or known gallstones before starting.
• Cardiovascular history — if CV risk reduction is the primary goal, document baseline BP, resting HR, and any prior MACE events. SELECT enrolled adults with established CV disease; your physiology matches that trial population if you have prior events.
• Medullary thyroid carcinoma or MEN2 history — hard contraindication across the GLP-1 class (rodent thyroid tumor signal; no confirmed human cases, but the label warning is firm).
• Pancreatitis history — class warning across GLP-1s. Prior acute pancreatitis is a relative contraindication; history of heavy alcohol use raises the risk during titration.

Finding your effective Sema dose: 0.25mg titration steps

The labeled Wegovy ladder ramps over 16–20 weeks. Hold each step for at least 4 weeks.

The step-duration rule is pharmacokinetic. Sema's half-life is roughly 7 days⁷ — the longest in the class — so plasma concentration at a new dose step takes about 2 half-lives (12–16 days) to stabilize. A GI response to dose N can arrive after you've already moved to dose N+1, and the next step loads on top of an unresolved reaction.

Discontinuation happens during titration, not at maintenance. The 4.3% GI-adverse-event discontinuation rate in STEP-1 (vs 0.7% placebo) clusters almost entirely in the escalation phase.¹ Over 95% of participants who tolerated the titration continued to week 68.

Stopping rule during the climb: if nausea, vomiting, or GI distress from the previous step hasn't resolved, extend the step duration — do not layer. If gallbladder symptoms appear (right-upper-quadrant pain, especially post-meal), hold at current dose and evaluate before increasing.

Typical Sema dose ranges, based on goals and needs

The best dose is the lowest that keeps appetite controlled, weight trending as desired, and side effects manageable. For weight loss alone, many users land at 1.0mg and stay there. If the reason you started sema is cardiovascular protection — prior MI, prior stroke, symptomatic peripheral artery disease, or an established ASCVD risk profile with BMI ≥27 — 2.4mg is the dose SELECT's 20% MACE reduction was tested at. Dropping below that is extrapolation for the cardiac arm; the CV evidence lives at 2.4mg.

What to track during the initial start phase

• Weight and waist circumference — weekly, same conditions (morning, fasted, post-void). Waist trend is the cleaner signal for visceral-fat response.
• Fasting glucose, HbA1c, fasting insulin — quarterly. Sema's glycemic effect is strongest in the class.
• Lipid panel — quarterly.
• Liver enzymes — quarterly; more often if MASLD is in the picture (sema reduces liver fat ~30%, less than tirz or reta).
• Blood pressure and resting heart rate — monthly during titration. Unlike retatrutide, sema does not raise resting HR, but CV monitoring still matters for users with established disease.
• Gallbladder symptoms — ongoing. Right-upper-quadrant pain after fatty meals is the typical presentation.

Sema at 0.25–0.5mg: the post-loss maintenance case

After the active weight-loss phase, many clinicians keep patients on 0.25–0.5mg weekly indefinitely — below any step on the labeled Wegovy titration ladder. This is off-label relative to the Wegovy protocol but established clinical practice.

The case for low-dose maintenance starts with what happens when you stop. Wilding 2022 STEP-1 extension showed two-thirds regain of weight lost within 52 weeks of discontinuation.⁶ STEP-4 (Rubino 2021) showed that continued full-dose 2.4mg treatment prevents regain.⁴ Real-world practice supports lower doses as a middle path: enough GLP-1 occupancy to hold the appetite-regulation effect, without the GI burden and nausea that come with the full titration dose long-term.

At 0.25–0.5mg weekly, three things shift that make this the maintenance band rather than a scaled-down weight-loss dose:

• Food-noise stays muted, but capacity returns. The between-meal snacking drive that predicts regain stays down. What comes back is the ability to eat a full meal when you want to — the appetite flatness of 2.4mg is gone, and meals stop feeling like a chore.
• GI load drops to near-zero. Nausea, vomiting, and the titration-phase burden that pushes most sema drop-outs out during escalation are already behind you. At the reduced GLP-1 occupancy, the gut settles — most maintainers report no active GI effects at all.
• Glycemic and lipid benefits attenuate but don't vanish. Fasting insulin, triglycerides, and the ApoB / non-HDL shifts persist at reduced magnitude. SELECT's 20% MACE reduction was tested at 2.4mg, though — if cardiovascular protection was your primary reason for starting, dropping to 0.25–0.5mg is extrapolation for the cardiac arm specifically.

Weight holds at this dose when the rest of the stack is there — resistance training and ≥1.6 g/kg protein doing the work the drug isn't. Without that stack, regain is still possible at low dose: not back to baseline, but drift.

This is semaglutide as a maintenance tool — keeping what active treatment achieved. It's a different mechanism pitch than tirzepatide's GIP-saturation case or retatrutide's sub-therapeutic metabolic-health case, because sema lacks GIP and glucagon. The logic is not "keep firing the fat-selective mechanism" — it's "keep enough GLP-1 occupancy to prevent the appetite rebound that drives regain."

How often should you take semaglutide? Weekly is the right default

Semaglutide's 7-day half-life⁷ produces the smoothest peak-trough curve in the incretin class. Tirzepatide (~5 days) and retatrutide (~6 days) have shorter half-lives and sharper weekly variance — splitting their weekly dose into twice-weekly or q3d injections reduces peak concentration. With sema, the natural weekly curve is already smooth, and splitting offers less marginal benefit.

The practical recommendation: start weekly. Split only if nausea or vomiting at each injection is limiting your ability to titrate. Most sema users never need to split — the 7-day half-life does the smoothing work on its own.

The GLP-1 Dosing Optimizer calculates the exact per-injection dose and plasma curve for any frequency.

Reconstituting semaglutide with BAC water

Every compounded sema vial is a fixed amount of peptide sitting at the bottom as a dry cake. Bacteriostatic water is what turns it into a solution you can draw and inject. The volume of water sets the concentration (mg per mL), and that concentration sets how far you pull the plunger for a given dose. More water means lower concentration and a larger, easier-to-read draw. Less water means higher concentration and a smaller injection volume. The total milligrams in the vial don't change — water is a measurement choice, not a potency factor.

New to reconstitution? The PeptideFox reconstitution guide walks through the full process — sterile technique, storage, troubleshooting — with images. Start there if this is your first vial.

How to reconstitute semaglutide

The mechanics are simple but they matter. Rough handling denatures the peptide. Bad technique contaminates the whole vial.

1. Wipe both stoppers (peptide vial and BAC water vial) with an alcohol swab.
2. Calculate the amount of BAC water needed — use an amount that allows for easy dosing.
3. Draw the BAC water into a sterile syringe.
4. Angle the needle so water runs down the inside wall of the peptide vial — not directly onto the cake.
5. Swirl gently. Do not shake. Mechanical agitation denatures peptides. A slow rocking motion dissolves the cake in 1–2 minutes.
6. Refrigerate at 2–8°C between draws. Never freeze reconstituted sema — freeze-thaw cycles damage the peptide structure.
7. Discard if the solution turns cloudy, discolored, or shows visible particles.
8. Use a fresh syringe and wipe the stopper with alcohol at every draw.

Reconstituted semaglutide is stable 4–8 weeks at 2–8°C (36–46°F). Longer than retatrutide or tirzepatide, which is part of why sema dosing is more forgiving on vial-size choice.

Where the vials come from

Semaglutide comes in two forms:

FDA-approved pre-filled pens — Ozempic (T2D), Wegovy (obesity), and Rybelsus (oral T2D). Novo Nordisk dispenses these as single-dose pens at fixed strengths. No reconstitution required. Costs $900–1,700/month without insurance.

Compounded vials — prepared by 503A or 503B pharmacies as a lyophilized powder requiring reconstitution. Costs $200–500/month. Compounding availability has tightened post-shortage; remaining supply runs through 503B outsourcing facilities under stricter federal oversight than 503A pharmacies. Ask your supplier for a certificate of analysis before your first order.

The two are the same molecule in different regulatory lanes. Compounded vials are a different regulatory category with different quality oversight, not a different drug.

Choosing the right vial size

Match vial size to your weekly dose and the 4–8 week reconstituted stability window. At 0.25–0.5mg maintenance: 2mg or 3mg vial. At 1mg weekly: 5mg vial (lasts 5 weeks). At 1.7–2.4mg: 10mg, 15mg, or 20mg vial. The 30mg vial only makes sense at 2.4mg weekly, and even then it covers ~12 weeks — past the stability window, so plan to split into a second sterile vial at week 6–8.

Related Topics

• Semaglutide Deep Dive — mechanism, trial data, CV outcomes, body composition
• GLP-1 Dosing Optimizer — interactive frequency calculator with plasma curves
• Full Reconstitution Calculator — all peptides, cocktails, custom BAC volumes
• GLP-1 Muscle Preservation — protect lean mass during weight loss
• Tirzepatide Dosing — the dual-agonist alternative
• Retatrutide Dosing — the investigational triple-agonist

References

¹ Wilding JPH, Batterham RL, et al. "Once-weekly semaglutide in adults with overweight or obesity." N Engl J Med. 2021. STEP 1 (NEJM 2021) — ~15% average weight loss at 2.4mg over 68 weeks.

² Aronne LJ, et al. "Tirzepatide versus semaglutide for obesity." N Engl J Med. 2024. SURMOUNT-5 — head-to-head, 20.2% on tirz vs 13.7% on sema.

³ Lincoff AM, Brown-Frandsen K, et al. "Semaglutide and cardiovascular outcomes in obesity without diabetes." N Engl J Med. 2023. SELECT (NEJM 2023) — 20% reduction in major adverse cardiovascular events vs placebo.

⁴ Rubino D, et al. STEP-4: effect of continued weekly semaglutide vs placebo on weight maintenance. JAMA. 2021. DOI 10.1001/jama.2021.3224

⁵ STEP-1 DXA body-composition substudy — ~60:40 fat-to-lean ratio in non-diabetic obesity. PMC8089287

⁶ Wilding JPH, et al. STEP-1 extension: weight trajectory 1 year after withdrawal of semaglutide. Diabetes Obes Metab. 2022. DOI 10.1111/dom.14725 — two-thirds regain at 52 weeks.

⁷ Dhillon S. "Semaglutide: a review in type 2 diabetes and obesity." Drugs. 2021. PMID 33296025 — ~7-day half-life; longest in the incretin class.

⁸ GLP-1 receptor agonists and gallbladder/biliary disease risk (meta-analysis). JAMA Intern Med — 2.6× cholelithiasis odds on semaglutide vs placebo; highest biliary risk in the incretin class.

⁹ Newsome PN, et al. Semaglutide in Patients with Metabolic Dysfunction-Associated Steatohepatitis. NEJM 2025. ESSENCE (PMID 40305708) — Phase 3 histologic-outcome trial; MASH resolution 62.9% on sema 2.4mg vs 34.1% placebo at 72 weeks.