T1D Sleep Stages Explained: Why You're Exhausted After 7 Hours of Sleep
You slept seven hours. By any reasonable measure, that should be enough. You woke up feeling like you slept four. You weren't imagining it. This episode breaks down sleep stages, light sleep, deep sleep, REM, and explains exactly where...
The episode, word for word
This episode is going to be one of those episodes where I tell you something and you think "that can't be right" and then you look back at your own data and you go "oh no."
I'm preparing you for that feeling now so it lands a little softer.
Your Tuesday 8pm HIIT class? It has opinions about your 3am blood sugar. And honestly it seems a little defensive about it, but the data is pretty clear.
My name is Neil Greathouse, and this is Your Best T1D Year.
All right. Exercise and sleep. And specifically: the timing of exercise and what it does to your overnight glucose and your sleep quality.
I want to say upfront: exercise is good. You know exercise is good. I am not about to tell you to stop exercising. What I'm going to tell you is that WHEN you exercise might matter more than you thought, and that "late evening workout" might be quietly working against you at 3am.
OK. So. Here's what the research shows.
Afternoon exercise, generally in the window from about noon to 6pm, is associated with better sleep quality and better glucose stability overnight. Your body temperature, your cortisol rhythm, your cardiovascular system, all of these are at a point in the afternoon that translates well to exercise and then naturally winds down as you move toward sleep.
Evening exercise, especially high-intensity stuff in the 7 to 9pm range, does a few things your sleep would prefer it didn't.
First, it raises your core body temperature. Remember what we talked about in the bedroom environment episode? Your body needs to drop its core temperature to go into deep sleep. If you just did forty-five minutes of cardio at 8pm, your core temperature is elevated. And it's going to stay elevated for a couple of hours. Which means when you try to go to sleep at 10:30, you're fighting physics. Your body is still warm. Deep sleep would like your body to not be warm.
Second, intense exercise releases cortisol. Which is fine, cortisol is what helps drive the effort. But cortisol at 8pm is cortisol that's still in your system at 10 or 11pm. Which, as we discussed on Friday, is not great for blood sugar and is not great for falling asleep.
Third, and this is the one that's specific to T1D: post-exercise glucose patterns.
The glucose response to exercise in T1D people is... the word I'd use is "specific." In a polite way. High-intensity exercise can initially raise blood sugar. Then, in the hours after, it can create a drop as your muscles are restocking glycogen. That drop can happen at 2 or 3am. Which fires an alarm. Which disrupts your sleep. Which, you know by now, affects your insulin sensitivity the next day.
I spent twenty years exercising at whatever time was available and wondering why my overnight numbers were all over the place on workout days. I thought it was the food. I thought it was the site. I blamed every variable except the one that was a spinning bike at 8pm.
One note: I know that a lot of people exercise in the evening because that's when they can. Work, kids, life, the general chaos of existing, sometimes 8pm is what you've got. I'm not here to add guilt to your workout. What I am here to say is: if you're exercising late and seeing patterns in your overnight numbers that you can't explain, this might be part of the story. And if you have any flexibility in your schedule, even shifting from 8pm to 5pm occasionally is worth experimenting with.
Your body has opinions about when you move it. It's not unreasonable. It's just inconvenient.
What time was your last workout?
That's it. Just write it down. And then note your overnight CGM pattern from that night. Did anything look different? More variability? A drop in the early morning hours?
You don't need to change your schedule yet. Just look for the correlation in your own data first.
To the person who's been doing all the right things, exercise and consistency and effort, and still getting overnight numbers that don't cooperate.
The effort is right. The timing might be worth a look.
That's not failure. That's refinement. That's T1D management doing what T1D management does, which is requiring you to pay attention to variables that most people never have to think about.
You're not doing a bad job. You're doing a difficult job. I'm proud of you for adjusting.
Type 1 diabetes is relentless, but managing it doesn't have to be. New episodes every Monday, Wednesday, and Friday. You're not doing a bad job, you're doing a difficult job. Nobody remembers easy.
This is the script as read on the mic, lightly tidied for reading. Education, not medical advice. Talk to your care team before you change anything about your insulin.