started actually tagging cycle phase in my logs back in february, mostly because I was tired of looking at a CGM line going up in the back half of my cycle and not knowing if it was the dose, the food, or hormones. so here’s four months of it. baseline first. I’m T2D, dx A1c was 8.4, now sitting at 5.6. CGM 14-day average runs around 102. the thing I kept seeing was a glucose creep in the luteal window, post-ovulation, estrogen falling and progesterone climbing. NOT mid-cycle. I see people tag this as mid-cycle constantly and it drives me a little nuts because the ovulation window is a different hormonal picture and it muddies the data for anyone trying to chart it. at 7.5mg the luteal bump on my 14-day average ran about 10 mg/dL over my follicular baseline. consistent enough across two cycles that I stopped writing it off as noise. titrated up and over the next two cycles it narrowed to roughly 5-6 mg/dL. still present. not flat. that directional shift is the part I find interesting, it reads like the higher dose is offsetting some of the luteal insulin resistance but not erasing it. here’s where I want to be honest about the limits. this is n=1, and it’s a single dose change. I can’t tell you the bump narrows proportionally with dose because I only have the one step to look at. could be a ceiling effect, could be the months smoothing out something else in my life. the literature on cycle-phase glucose variation in T2D women on GLP-1s is thin to nonexistent that I could find, so I’m not pretending this maps onto anything published. the other confound I can’t fully close: my training volume wasn’t constant across these four months. DEXA at month 9 showed about 2.1 lb lean loss while I was lifting the whole time, just not at enough volume-load to matter, and resistance work moves luteal insulin sensitivity on its own. so I’m logging volume-load now, not a yes/no on whether I trained, because the binary tells me nothing comparable week to week. the monthly trend summary is the thing I actually screenshot to bring to my endo, because the per-cycle pattern doesn’t show up in any single day’s read, you have to see the rollup. my fasting glucose, for what it’s worth, was flat-ish this whole time. it’s a useless number for catching this. the luteal signal only lives in the postprandial spread. anyone else tagging cycle phase against CGM on tirz, did your luteal delta narrow with dose or hold steady?
the cycle-phase precision is the right hill to plant on, luteal vs mid-cycle is a real hormonal distinction and people flatten it constantly, so that part of your post is doing honest work. where i’d push is the read you hang on the narrowing: “the higher dose is offsetting some of the luteal insulin resistance.” that’s one mechanism, but it’s not the only one that moves a postprandial spread, and it’s competing with a confound you can’t see in your own data. tirz’s gastric emptying delay deepens as you titrate up. a higher dose flattens postprandial excursions across the board, not selectively in the luteal window, just by slowing how fast glucose hits the blood. you said it yourself, “the luteal signal only lives in the postprandial spread.” that’s exactly the signal a deeper emptying delay compresses. so the 10 going to 5-6 could be the higher dose flattening every postprandial harder, follicular and luteal alike, and the delta narrowing as a side effect of that compression rather than the drug specifically chipping at luteal insulin resistance. those two stories predict the same number on a single dose step. the way you’d actually separate them is whether your follicular baseline postprandials also got tighter at the higher dose. if both phases compressed and the gap shrank, that points at emptying. if follicular held and only luteal moved, that’s closer to the insulin-resistance read you’re reaching for. you may already have that in your rollups. and yeah, the training volume thing stacks right on top, since resistance work moves luteal insulin sensitivity on its own and your volume-load wasn’t constant, so you’ve got at least two confounds riding the same direction as the dose. logging volume-load instead of a yes/no is the right move, that binary really does tell you nothing comparable week to week. n=1 on one dose step just can’t carry the attribution cleanly yet, which you mostly already granted.
“both phases compressed and the gap shrank, that points at emptying” is the right test and I actually have most of that in the rollups, so fair hit. the part I’d push back on is that it’s not fully separable from my data either, because I was reading the delta off the 14-day average, not a standardized postprandial AUC on a fixed meal. the 14-day average folds in whatever I ate, and luteal cravings shifted my carb load on their own, so a chunk of that follicular-vs-luteal gap is meal composition, not just hormones or emptying. when I pull the follicular postprandials at the higher dose they did tighten, but not as hard as luteal did, which leans toward your emptying read doing real work without closing the insulin-resistance piece. honestly the clean version of this is a standardized test meal in each phase at each dose, and I don’t have the discipline to eat the same breakfast on command for four months. the monthly rollup is what catches the pattern at all, single days are useless here. so yeah, two confounds riding the dose, granted.
Four months of phase-tagged CGM is genuinely more than most consultants will ever see on this, so well done for sticking with it through the volume-load mess. The dimension I’d toss in, since nobody’s raised it: progesterone slows gastric emptying on its own in the luteal window, independent of anything tirz is doing.
So you’ve potentially got two emptying effects stacking in the back half of the cycle, the hormonal one and the receptor one, pulling in the same direction on your postprandials while the insulin-resistance piece pushes the other way. That muddies the “higher dose offsetting luteal IR” read a bit, because part of what flattens your luteal postprandials at the higher dose could be the drug’s emptying delay riding on top of progesterone’s, not the IR moving at all. Worth tagging luteal sleep quality too if you log it, since core temp climbs in that window and a wrecked night nudges fasting insulin on its own.
edit: realized I said that wrong