One question I am often asked: I don’t eat at bedtime so why does my blood sugar go up overnight? Many patients with Type 2 Diabetes notice that their sugar goes up overnight.
There is one main reason for this overnight rise in glucose.
Before answering I first must stress that I am speaking about a rise in blood sugar level from bedtime to the next morning in people with Type 2 Diabetes.
You would have to test your sugar at bedtime, at least 4 hours after the evening meal to check this out.
Some people just check before meals and not at bedtime.
A high bedtime reading could be caused by a large supper and could carry over to the morning.
So let’s say you check your sugar at bedtime, around 4 hours after supper, and you get a reading of 130 mg/dl. And you find the next morning your sugar is 170.
And you might find this 40 point rise much of the time.
Why does the sugar go up overnight?
Well we need to understand what brings the blood sugar up in general.
I discussed this in a post last year on how insulin should be used.
Blood sugar increases come in two ways:
from the food you eat and from what the liver makes.
Let’s focus on the liver.
If you don’t eat for a day or two or more, your sugar does not go to zero. Right?
Correct! That is correct even if you have not fasted this long. Why is it true?
Because your liver makes sugar. And in people with Type 2 Diabetes, the liver makes too much sugar. This excessive liver production of sugar causes the glucose to rise even without eating.
Extra insulin would take care of this overproduction of glucose by the liver. But people who have Type 2 Diabetes have inadequate action of insulin on the liver.
Another hormone from the pancreas called glucagon causes the liver to make excessive glucose. And in the morning, other hormones may contribute to a rise in glucose in the morning. Those hormones are growth hormone and cortisol.
People without diabetes simply make more insulin to prevent a glucose rise in the morning. That extra insulin counteracts the other hormones that would tend to increase the glucose. But people with Type 2 Diabetes may not be able to make extra insulin and their liver does not respond to insulin normally.
In treating people with Type 2 Diabetes, it may difficult to prevent the glucose from going up overnight.
Regular exercise, weight loss, metformin and other agents including insulin may be necessary to control this glucose rise overnight.
Now here’s a final strange observation. Occasionally I see people who think that by eating carbs at bedtime, their morning sugar is actually better in the morning than if they do not eat! And they often have evidence to support that.
Now these are patients who are not getting hypoglycemic overnight and rebounding up.
Although I do not understand the mechanism for this apparent benefit on morning sugars in these people, I do know that eating more makes you gain more weight and that’s not good for people with Type 2 Diabetes. So eating at night is not the best answer for them, even if they note that it might help the morning glucose readings.
For the vast majority of people with Type 2 Diabetes, there is no mystery as to why the sugar goes up overnight. The answer is in the liver. And we can take care of it!