In people with Type 1 diabetes, exercises sometimes lower blood sugar to the extent beneficial for the overall treatment of type 1 diabetes. Sometimes, exercise increases blood sugar levels; it can even rise to the point of hyperglycemia.
Among non-diabetic people, exercise lowers blood glucose. Still, in most cases, it will not cause abnormally low blood sugar levels (Hypoglycaemia), but in rare instances, exercises can cause hypoglycaemia among relatively healthy people.
In non-diabetic people, low blood sugar induced by exercise is relatively easy to manage, but it is far more challenging in people with Type 1 diabetes.
However, low blood sugar (hypoglycaemia) during exercise in people with Type 1 diabetes is a relatively mild problem compared with post-exercise hypoglycaemia, which may happen from 3 to 12 hours after exercising.
The most dangerous post-exercise hypoglycaemia happens during night sleep (night-time hypoglycaemia or nocturnal hypoglycaemia). Night-time hypoglycaemia (or nocturnal hypoglycaemia) can be fatal. Actually, night-time hypoglycaemia has been considered to be responsible for a large proportion of sudden deaths in young T1DM patients.
In order to understand why exercises cause low blood sugar (hypoglycaemia) in some people with diabetes and in some people without diabetes, it is essential to understand why exercises induce weight loss in some people; in some people, it doesn't have any effect on weight loss, and in some people, it even causes further weight gain. Understanding post-exercise weight loss is essential to understanding and preventing post-exercise hypoglycaemia, including night-time hypoglycaemia.
The problem is that post-exercise weight loss is attributed to an elevated breathing rate for some time after exercising (post-exercise oxygen consumption), which is wrong. Plenty of factors prove that post-exercise weight loss cannot be due to an elevated breathing rate for some time after exercising.
Before any discussion about the cause of post-exercise hypoglycaemia and post-exercise hyperglycaemia, it is essential to understand what really causes post-exercise weight loss.
I have explained the underlying mechanism of post-exercise weight loss in my book "Mechanical Stimulation Low-Grade Inflammation Weight Gain: Muscles Upward Lifting Activity Weight Loss".