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. Your muscles refill glycogen after the workout. They keep pulling glucose from your blood to do it. Insulin sensitivity also 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 warned patients about late-onset hypoglycemia after exercise for decades. Many athletes with T1D already make a manual version of this read. They check glucose before bed. Some eat a slow-carb snack after heavy training. Others set an overnight alarm 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 are not awake to notice the trend, and you are not eating. A drift that would be clear at noon becomes a quiet line. You may only see it on the chart 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. The effect lasts long after the session ends. For people on exogenous insulin, the same dose works harder than it did the day before.

Persistent GLUT4 activity. Exercise pulls these glucose transporters to the cell surface. They stay active long after you cool down. They keep moving glucose from the blood into muscle.

Together, these processes can delay the drop. You may feel fine right after the workout. Clinical research has tracked this window for decades. Post-exercise late-onset hypoglycemia has its own name and 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 can produce different overnight curves on different days. Your earlier meal and sleep can change the response. A low-grade infection can change it too. Many other inputs also matter. A single model can't capture that. A pattern read across weeks of your own data can. Body Insights learns from your sessions and overnight traces over time. It finds which workouts produce your delayed dip and which do not. It also shows which evenings may call for keeping something on the nightstand.