The concern is real, but it’s not instant the minute you start dosing Reta.
Reta doesn’t have its own official label yet, so everyone is borrowing from tirzepatide (Mounjaro/Zepbound). After a single 5mg Tirz dose they saw roughly a 20% drop in overall exposure to the pill hormones and a much bigger drop in peak levels, plus a several-hour delay. That’s why the official advice on Mounjaro is: switch to a non-oral method, or add a barrier for 4 weeks after you start and 4 weeks after every dose increase.
Semaglutide studies generally didn’t show a meaningful drop. Tirzepatide did. Reta’s gastric emptying delay looks more like tirzepatide than Ozempic, so treating it like Mounjaro is the conservative play.
Couple of other things to consider: 1) If you vomit or have bad diarrhea soon after taking the pill, that can dump it before it absorbs. 2) Weight loss / better insulin sensitivity can bring ovulation back if you were irregular. So fertility can go up at the same time absorption gets less predictable.
On a stable tiny maintenance dose (as you proclaim) the emptying effect usually eases off compared with week 1 and each titration bump. So the risk is probably lower than that scary day-1 tirz study. I'm not saying it's zero however.
You don’t have to get an IUD. Anything that doesn’t go through your stomach is fine: copper IUD, Depo shot, patch, or ring. IUD/implant are just the “set it and forget it” options with the lowest typical-use failure rates.
Lastly, this is not medical advice — run it by your own doctor.
