The drop that
lands hours later.

You finished the workout. You ate. You felt fine.

And then, somewhere between dinner and dawn, your blood sugar quietly slid downward.

This is the part of exercise physiology most apps don't model. Hard training depletes muscle glycogen. To refill it, your muscles keep pulling glucose from your bloodstream long after the workout ended — and insulin sensitivity stays elevated for a day or more. For people on insulin, that combination is a setup for a late-onset drop. For everyone else with a CGM, it's the kind of pattern that explains why some nights feel ragged for no apparent reason.

Body Insights reads your workout data and your CGM together and surfaces the window where a delayed dip is most likely. You get the heads-up before sleep, not after.

For people living with type 1 diabetes, this is not a new conversation. Endocrinologists have been counseling patients about late-onset hypoglycemia after exercise for decades, and most athletes with T1D have built their own informal version of this read — checking glucose before bed, eating a slow-carb snack on heavy training nights, setting an alarm for the small hours after a hard ride. The point of this feature isn't to replace any of that. It's to give the pattern a name on the screen, so the decision is grounded in what your CGM is actually drawing, not in what you remember from last Tuesday.

Evening workouts hide the problem.

If you train in the morning, a late-onset dip lands during a workday — close to food, easy to catch. If you train at night, it lands during sleep. You're not awake to notice the trend, you're not eating, and the same physiological drift that would be obvious at noon becomes a quiet line on a chart you only see in the morning.

Fasted workouts compound it. So does hitting the higher heart-rate zones for any sustained stretch. None of this is dangerous on its own — it's just useful to know which sessions tilt the balance, and which ones don't.

This is what we mean by "the watch already knows." Your Apple Watch recorded the workout. Your CGM recorded the descent. The work is in putting those two streams in the same sentence.

Why hypoglycemia after exercise is delayed.

Three physiological things happen at once and they don't peak together.

Glycogen replenishment — muscle cells pull glucose out of the bloodstream to refill the stores they spent during the workout. The deeper the spend, the longer the refill runs.

Enhanced insulin sensitivity — exercise raises insulin sensitivity for a long stretch after the session ends. For people on exogenous insulin, the same dose works harder than it did the day before.

Persistent GLUT4 activity — the glucose transporters that exercise pulls to the cell surface stay active long after you've cooled down, continuing to move glucose out of the blood and into muscle.

Layered together, these processes are the reason a late-onset dip can land far enough after the workout that nothing in the immediate post-session feels off. The clinical literature has tracked this window for decades — it's why post-exercise late-onset hypoglycemia has its own name and its own management protocols. Body Insights doesn't invent that physiology. We just read it on your own CGM and your own training.

The other piece worth naming is individual variability. The same workout, on two different days, can produce two different overnight curves — depending on what you ate before, how slept you were, whether you were already running a bit warm with a low-grade infection, and a dozen other inputs. A single model can't capture that. A pattern read across weeks of your own data can. The longer Body Insights watches your sessions and your overnight traces, the more it learns the shape of your delayed dip — which workouts produce it, which ones don't, and which evenings are the ones to keep something on the nightstand.