Semaglutide Dosage and Reconstitution Calculator
GLP-1 receptor agonist approved as Ozempic (type 2 diabetes), Wegovy (weight management, cardiovascular risk, MASH) and Rybelsus (oral).
Written by Kashif Khan, who builds and maintains this site and is not a clinician. Every figure links to its primary source.
FDA-approved
Approved 5 December 2017 as Ozempic, 4 June 2021 as Wegovy, and 20 September 2019 as oral Rybelsus. Wegovy added cardiovascular risk reduction in March 2024, MASH in August 2025, and a 7.2 mg high dose in March 2026. All approved injections are ready-to-use solutions, not powders. The FDA declared the semaglutide shortage resolved on 21 February 2025.
Key facts
- Molecular weight
- 4,113.58 Da31 amino acids, 94% homologous to human GLP-1, with an Aib substitution at position 8 and a C18 fatty di-acid on Lys26. The residue count comes from the literature; the label states the homology figure.
- Half-life
- About 1 week; steady state after 4–5 weeks, and it stays in circulation about 5–7 weeks after the last dose
- Also sold as
- Ozempic, Wegovy, Rybelsus
Approved titration schedule — Wegovy (weight management)
One escalation every 4 weeks. If a dose is not tolerated, the label says to consider delaying escalation by 4 weeks rather than pushing on.
Source: WEGOVY (semaglutide) injection and tablets — FDA prescribing information
How good is the evidence?
Extensively evidenced across diabetes, obesity, cardiovascular and liver indications, with multiple FDA approvals and published outcome trials.
Missing a dose: Ozempic and Wegovy do not agree
The two semaglutide labels answer this differently, and the difference is not cosmetic. Ozempic: administer the missed dose as soon as possible within 5 days; if more than 5 days have passed, skip it and resume on the regularly scheduled day. Wegovy publishes no 5-day rule at all — its instruction addresses two or more consecutive missed doses, and says to resume as scheduled or, if needed, to reinitiate and follow the dose-escalation schedule again, because coming back at the maintenance dose is what brings the gastrointestinal reactions back with it.
Tirzepatide's window is shorter again at 4 days, and liraglutide's daily schedule resets entirely after 3. Four drugs' worth of advice circulates online as though it were one rule; it is four rules, each tied to one label.
Storage: 56 days, 28 days, and which one is yours
Ozempic before first use lives in the refrigerator at 2°C to 8°C. After the first use, the pen may be kept for 56 days either at controlled room temperature, 15°C to 30°C (59°F to 86°F), or back in the refrigerator. Wegovy is a single-dose pen and the figure is different: stored from 2°C to 8°C, and if needed, prior to cap removal, from 8°C to 30°C for up to 28 days.
Both numbers describe a specific manufactured presentation, not the molecule. Neither is a statement about a compounded semaglutide vial, for which no equivalent stability testing has been published — and the 28-day figure people most often quote in that context is not this one at all, but the USP limit on a punctured bacteriostatic water bottle.
Why Ozempic contains a preservative and Wegovy does not
Each 1 mL of Ozempic contains disodium phosphate dihydrate 1.42 mg, propylene glycol 14 mg, phenol 5.5 mg and water for injections. Each 1 mL of Wegovy contains disodium phosphate dihydrate 1.42 mg, sodium chloride 8.25 mg and water for injection, with hydrochloric acid or sodium hydroxide added to adjust pH.
Phenol is the difference, and it is there for a structural reason: the Ozempic pen is multi-dose and gets punctured repeatedly over weeks, while the Wegovy pen is single-dose and is entered once. That is precisely the decision you make when you choose bacteriostatic water over sterile water for injection. The preservative is not there for the drug's benefit — it is there because of how many times the rubber will be pierced.
Adverse reactions, and where the useful numbers are
Semaglutide carries a boxed warning for the risk of thyroid C-cell tumours, with contraindications in personal or family history of medullary thyroid carcinoma and in multiple endocrine neoplasia syndrome type 2.
The incidence tables are more informative than the summaries built from them, mainly because they publish a placebo column: 47% of placebo patients in the weight-management trials reported a gastrointestinal adverse reaction, which reframes a large part of what gets attributed to the drug. The dose-by-dose figures — including dysesthesia at 0% on placebo, 6% at 2.4 mg and 22% at 7.2 mg — are reproduced in full in the side-effects guide rather than summarised here, because a summary of an incidence table is the thing that loses the information.
Common questions
Sources
Every number on this page comes from one of the documents below. Where no reliable source exists, the page says so instead of filling the gap.
- FDA labelFDA / DailyMed· 2026-05OZEMPIC (semaglutide) injection — FDA prescribing information
- FDA labelFDA· 2026-03WEGOVY (semaglutide) injection and tablets — FDA prescribing information
- FDA labelFDA / DailyMed· 2026WEGOVY — current FDA Structured Product Label (FlexTouch and prefilled syringes)
- FDA labelFDA / DailyMedRYBELSUS / OZEMPIC (semaglutide) tablets — FDA prescribing information
- Published studyReviews in Endocrine and Metabolic Disorders· 2022Mahapatra MK et al. Semaglutide, a GLP-1 receptor agonist — structure and cardiovascular benefits
- RegulatorFDA· 2026-09-01FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss
- FDA labelFDA / DailyMed· 2026-08ZEPBOUND (tirzepatide) injection — FDA prescribing information
- FDA labelFDA / DailyMedSAXENDA (liraglutide) injection — FDA prescribing information
- GuidelineUnited States Pharmacopeia· 2023USP General Chapter <797> Pharmaceutical Compounding — Sterile Preparations (2023 revision)
- FDA labelFDA / DailyMedBacteriostatic Water for Injection, USP — FDA prescribing information (NDA 018802)
- FDA labelFDA / DailyMedSterile Water for Injection, USP — FDA prescribing information
- Published studyeClinicalMedicine· 2022-09-29Chin YH et al. The placebo response rate and nocebo events in obesity pharmacological trials — a systematic review and meta-analysis