What Semaglutide is
Semaglutide is a GLP-1 receptor agonist, FDA approved as Ozempic for type 2 diabetes (maximum 2.0 mg weekly) and Wegovy for weight management (maximum 2.4 mg weekly). With a half-life of about one week it is dosed once weekly, and a missed dose barely dents the steady-state level.
The doses in the table are the Wegovy escalation steps, the schedule most compounded semaglutide protocols mirror.
What we do not know
- Weight regain after discontinuation is documented rather than unknown: trial extensions show most lost weight returns. What is unknown is whether any dosing strategy prevents it.
- Long-term effects past the roughly four-year cardiovascular outcome trials are unpublished.
- The muscle-loss question is unresolved; body-composition substudies are small relative to the main trials.
Reconstitution math
Concentration is everything: the same 5 mg vial gives a different draw for every amount of bacteriostatic water you add. The table uses the common 2 mL setup for each vial size, which puts every unit on a U-100 insulin syringe at 25 mcg for the default vial. Dashes mark draws too small to measure or larger than the syringe.
| Vial | BAC water | Concentration | 0.25 mg | 0.5 mg | 1 mg | 1.7 mg | 2.4 mg |
|---|---|---|---|---|---|---|---|
| 2 mg | 2 mL | 1 mg/mL | 25 u | 50 u | 100 u | - | - |
| 5 mg | 2 mL | 2.5 mg/mL | 10 u | 20 u | 40 u | 68 u | 96 u |
| 10 mg | 2 mL | 5 mg/mL | 5 u | 10 u | 20 u | 34 u | 48 u |
| 15 mg | 2 mL | 7.5 mg/mL | 3.3 u | 6.7 u | 13.3 u | 22.7 u | 32 u |
Dosing and protocol
Wegovy titration: 0.25 to 2.4 mg weekly, four weeks per step.
The 0.25 and 0.5 mg starting steps are small: on a 5 mg vial with 2 mL of water they come to 10 and 20 units on an insulin syringe. If your draws land under 5 units, add more water rather than eyeballing a 2-unit draw; the reverse calculator solves for the volume that puts your dose on a clean mark.
Pharmacokinetics
Semaglutide has published human pharmacokinetics: peak roughly 1 to 3 days after a subcutaneous dose. The curves below are normalized one-compartment models built from the cited half-life, the same math the Planner uses. They show shape and timing, not absolute blood levels.
How it is thought to work
A GLP-1 receptor agonist, structurally modified so albumin binding extends its half-life to about a week. It increases glucose-dependent insulin secretion, suppresses glucagon, slows gastric emptying, and acts centrally on appetite. It is the most thoroughly trialed compound on this site.
What the evidence supports
This table grades how well each outcome has been studied in humans, not how well Semaglutide works. A strong grade means the question was asked properly, and the answer may still have been negative. Nothing here is inherited from a drug class, a close analog, or the parent molecule of a fragment.
| Outcome | Strongest published evidence |
|---|---|
| Cardiovascular event reduction | Human RCT |
| Chronic kidney disease progression | Human RCT |
| Glycemic control in type 2 diabetes | Human RCT |
| MASH / liver histology | Human RCT |
| Weight loss | Human RCT |
Storage and handling
Lyophilized vials keep best cold, dark, and dry; refrigeration is the community default and freezing lyophilized powder is common for long holds. After reconstitution, refrigerate at 2 to 8 C, do not freeze the solution, and date the vial. Bacteriostatic water's preservative keeps multi-dose use practical for about 28 days by USP convention, though our 120-day stability study found the preservative itself outlasts that window.
Novo Nordisk labels the pens for refrigeration with defined in-use windows (up to 56 days for Ozempic). The same refrigerate-after-mixing rule applies to reconstituted vials.
Got a certificate of analysis with your vial? Run it through our COA Reader: it reads the report in plain English, checks purity and mass against the label claim, and links the testing lab’s own verification page. Our guide to reading a COA explains what the numbers do and do not tell you.
Sources
- Wegovy prescribing information (Novo Nordisk, 2023)Prescribing information
- Hall et al., Clinical pharmacokinetics of semaglutide: a systematic review, Drug Des Devel Ther 2024PMID 38952487 · DOI
- Wilding et al., Once-weekly semaglutide in overweight or obesity (STEP 1), NEJM 2021PMID 33567185 · DOI