Why Split-Dosing GLP-1s Might Work Better Than Once a Week
Okay, I've talked about split dosing in the past, but let's talk about it specifically for GLP-1s and get some community feedback here. Plus, we have a lot of new researchers in here that probably haven't been introduced to this concept, so it's worth bringing up again. Here's something that surprises a lot of people: the once-a-week dosing schedule for GLP-1s like semaglutide and tirzepatide wasn't designed to give you the best results. It was designed so the most people would actually stick with it. And there's a big difference. Let me break this down in the simplest way possible. First, What's a Half-Life? (The 60-Second Version) Think of a half-life like an hourglass. When you administer a peptide, the hourglass flips. The half-life is how long it takes for half of that peptide to leave your system. - Semaglutide has a half-life of roughly 5-7 days (≈160-168 hours) - Tirzepatide has a half-life of roughly 5 days (≈120 hours) - Retatrutide has a half-life of roughly 6 days (≈144 hours) So if you administer semaglutide on Monday, by the following Sunday, about half of it is still working. Sounds great, right? Well... sort of. Why Once a Week Creates a Roller Coaster Here's a common misconception: your levels don't spike on administration day. GLP-1 concentration actually takes time to build up in your system after each dose. But once those levels peak, they start to fall off over the course of seven days. And here's the bigger picture — it actually takes about four weeks of consistent dosing for the peptide to fully build up in your system and reach true steady-state titration. That's why the effects feel different in week one versus week four at the same dose. But even after you've reached steady state, the once-weekly pattern still creates a wave within each week: - After administration, Levels gradually rise over the first couple of days as the peptide absorbs and builds. - Mid-week: You hit your peak concentration. This is when effects are strongest — but also when side effects like nausea can be most noticeable. - Days 5-7: Levels are declining. This is when many people report the appetite suppression "wearing off," food noise creeping back in, and increased cravings toward the end of the week.