Semaglutide

What semaglutide is

GLP-1 — glucagon-like peptide-1 — is a hormone released by the gut after eating. It stimulates insulin release when blood glucose is high, suppresses glucagon, slows the rate at which the stomach empties, and acts on brain regions involved in appetite. Natural GLP-1 is broken down within minutes.

Semaglutide is a modified analogue engineered to resist that breakdown and to bind albumin in the blood, extending its presence from minutes to days. That extended half-life is what makes once-weekly injection possible, and it is the single most important pharmacological fact about the drug for anyone keeping a record: a missed or shifted injection does not have an immediate effect, which makes memory an unreliable substitute for a log.

GLP-1 receptor agonist

A drug that binds and activates the receptor for the natural hormone GLP-1. 'Agonist' means it switches the receptor on, in contrast to an antagonist which blocks it.

Ozempic, Wegovy and Rybelsus

The same molecule reaches patients as three distinct products. They are not substitutes for one another, and a record that says only "semaglutide" has lost information that matters.

Because the products differ in strength and presentation, switching between them is a prescribing decision with its own instructions. In a log, always record the product name as printed on the pen or box, not the ingredient alone.

What the pen label tells you

Injectable semaglutide is supplied in a pre-filled pen. Two numbers on the packaging get confused constantly:

• The pen's total contents — how much drug is in the cartridge overall.
• The amount delivered per administration — what the dial or the fixed setting delivers each time.

These are different figures, and the second is the one your record needs. A pen that contains several administrations does not mean each administration is the contents figure.

If you want to understand why volume-based conversions do not transfer to pens, see pens versus vials.

Keeping a useful record

Semaglutide is a case where a personal log earns its keep, because the things a prescriber asks about at a review are exactly the things nobody remembers accurately.

• Product name and strength as printed, plus the pen or lot identifier.
• Date and time of each injection. With a weekly medication, drift accumulates invisibly — a log makes the actual interval visible.
• Injection site, rotated and recorded. See injection site rotation.
• Titration changes with the date they were instructed and by whom. A dose change is an event worth timestamping.
• Side effects with timestamps, since the pattern relative to injection day is often what the clinician is trying to establish. See logging side effects.
• Missed or late injections marked as such, never deleted. A gap is information.

PepCycle records all of this on a weekly schedule with drift-aware reminders, and exports the history so a review appointment can begin with a timeline rather than a guess.

Compounded and unapproved semaglutide

During periods of shortage, compounded semaglutide became widely available in the US, and semaglutide is also sold by research-chemical suppliers as a lyophilised powder. Neither is the approved product, and both differ from it in ways that matter to a record.

• Compounded preparations come from a pharmacy with its own labelling, concentration and beyond-use date — all of which must be recorded from that label.
• Salt forms such as semaglutide sodium or semaglutide acetate are not the approved active ingredient, and the FDA has stated they are different substances.
• Once shortages are resolved, the legal basis for compounding a drug changes. Rules here have shifted repeatedly.

See compounded GLP-1 medications for what to record when a product does not come with manufacturer labelling.