After exercise: the overnight risk and the high that tempts you

The session ends, but its effect on blood sugar doesn't. This page explains how long the risk of going low lasts after exercise, the adjustments with the best evidence for the night that follows, and the single most dangerous moment in the whole picture: the high right after a hard workout.

The session ends. The risk doesn't.

This is why exercise after 4 p.m. so often becomes a problem at 2 a.m. The adjustments below are the published starting points; the exact amounts are for you and your team to set.

Drop the overnight basal by about 20%

The best-evidenced single move is a temporary 20% reduction in basal insulin for around six hours, starting at bedtime.

Cut the next meal's dose by about half

Pair it with a decent refuel — roughly 1 to 1.2 g of carbohydrate per kg of body weight, plus 20 to 30 g of protein.

A bedtime snack, if you're under 10

If your glucose is under 10 mmol/L at bedtime, have a snack with slow carbohydrate and no bolus. Add protein if you're under 7. But a snack alone does not cover the night — it needs the basal change too.

If you sleep alone, or have a history of difficult nights, set sensor alarms, or add a follower who can see your numbers remotely.

The most dangerous moment is the high after a hard session

Here is how it usually happens. You finish a tough workout, the number is up, and it feels wrong. So you correct. It's still up, so you correct again. Meanwhile your muscles are about to start pulling glucose out of the blood for the next several hours, and the insulin is stacking up.

Remember from the start of this section: hard, short efforts push blood sugar up through adrenaline and stress hormones. That rise is expected. What follows it — hours of increased insulin sensitivity — is what makes a stack of corrections risky.

This is as much for coaches and parents as it is for the person with type 1. The urge to "fix" a post-game number often comes from the people around them.