What pharmacokinetics describes
Pharmacokinetics — PK for short — is the study of what your body does to a drug over time. It tracks four basic things: absorption (how the drug gets into your bloodstream), distribution (where it travels), metabolism (how it’s broken down), and elimination (how it’s cleared out). Together these determine how much drug is actually present, and for how long — which is what dictates the dose and how often you take it. If mechanism is what a drug does to you, pharmacokinetics is the timeline of what you do to it.
Why it matters if you’re on a GLP-1
Pharmacokinetics is arguably the reason modern GLP-1s exist in their current form. Natural GLP-1 is cleared from the blood within a couple of minutes — far too fast to be a practical medication. Drugs like semaglutide are deliberately engineered to slow that clearance, giving them a long half-life so a single injection keeps working for roughly a week. That extended timeline is also why these medications are eased in gradually through titration rather than started at full strength. The GLP-1 overview covers how this plays out across the class.
What to keep in mind
A closely linked idea is bioavailability — the fraction of a dose that actually reaches your bloodstream — which is a big part of why injected and oral versions are dosed so differently. Exact PK figures vary by drug and by person, and prescribing information lays out the specifics for each medication. This is background for understanding why your schedule looks the way it does; the actual dose and timing are set by your prescriber.