Why Blood Sugar Is Higher In The AM

Patient Expert
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It seems terribly illogical. After waking up but before eating or exercising, our blood sugar is higher than before we went to bed. When those of us who have diabetes start to check our blood sugar, we get this big surprise, and naturally concerns us. What can we do about it?

What is the dawn phenomenon?

When our blood sugar starts to rise about 4 a.m., this can be the dawn phenomenon, according to the “Diabetes Dictionary.” This is actually normal. Even people who don’t have diabetes have it to give us enough fuel in anticipation of our needs after we get up. But when we have diabetes and insulin resistance, our blood sugar can rise more. Because our hormones stimulate the release of sugar from our liver, we get higher blood sugar levels.

How can I tell if I have the dawn phenomenon?

The best way to see if you have it is to use a meter to check your blood sugar at bedtime and then again when you get up. If it’s higher then, you probably have the dawn phenomenon.

Could my level be high for other reasons?

Yes. If you take insulin injections, it could be that the effect of insulin you took is wearing off, as I wrote at “Taming the Dawn Phenomenon.” Your blood sugar will rise if you didn’t take enough to keep your insulin level up through the night.

Could something else be raising my blood sugar?

Yes. There is another possibility, although it is much less likely. Formerly called the Somogyi effect, it is a rebound from a low blood glucose level in the middle of the night. The best way to see if that is what you have is to use a continuous glucose monitor. But you can also find out if this is what is happening by checking to see if your blood glucose is low at about 2 or 3 a.m.

What else could be causing my dawn phenomenon?

The first thing to consider is what we ate the previous day. Part of the problem could be eating too much carbohydrate, particularly at bedtime. Carbohydrate is the only food group that will raise our sugar level.

But people tell me to eat or drink something before bed

One study found that uncooked cornstarch at bedtime seemed to reduce high blood sugar in the morning. A different study suggest that drinking a bit of wine at dinner helps. The book, Stop the Rollercoaster: How to Take Charge of Your Blood Sugars in Diabetes, says that eating green apples -- like Granny Smith’s, not unripe ones -- helps.

Other people think I should drink vinegar. Does this make sense?

Maybe. Several studies show that vinegar can reduce our blood glucose levels, and lots of people use vinegar to manage their dawn phenomenon. But if you try this, be aware that pure vinegar is too strong to take straight. Some people take a few tablets and others dilute the vinegar with water when they drink it. And it doesn’t work for everyone.

Or should I take long-acting insulin at bedtime?

This could be a good idea. A study suggests that taking one of the basal insulins, Lantus or Levemir, at bedtime “abolishes the dawn phenomenon.” I reviewed a preliminary version of this study here at “The Dawn Phenomenon: A Diabetes Puzzle Solved,” and the final version is now available at “Thirty Years of Research on the Dawn Phenomenon.”