Ask an Endo: Morning Fasting Numbers

Blog, Wellness

Question: Can taking Glipizide and Metformin later in the evening help with morning fasting numbers instead of taking it in morning. I can’t seem to get fasting number down?


Dr. Richard Jackson: The short answer is that it probably won’t make much difference. High fasting glucose numbers are a common concern for people with diabetes and can sometimes be a sign that the glucose control is deteriorating. Importantly, it is the A1C that most accurately tells you whether your glucose control is changing. If your A1C is in your target range, but your morning fasting glucose results seem high, you can be reassured that the morning glucoses are not high long enough or often enough to affect your overall glucose control, which is measured by the A1C. You don’t need to change anything and can keep taking your medications at whatever time is most convenient.

However, if your A1C is higher than your target, the high fasting glucoses can provide helpful information. So, the next question to ask is, what is your blood glucose at bedtime?  Check before you go to bed, at least four hours or more after eating a meal or snack. And then when you wake up the next morning, check again. Here’s what we need to look at: how does your bedtime blood glucose compare to your morning blood glucose?

If your number at night is the same or higher than your morning number, then lowering your blood glucose at bedtime will probably lower your morning numbers also.  Here are a few suggestions on how to do that:

♦ Change what you eat at night—you might try eating less food overall or eating fewer carbs

♦ Get a little exercise in the evening—even a short walk after dinner can help lower your blood glucose.

♦ Talk to your doctor about changing your medications– starting a GLP-1 medication or taking fast-acting insulin at supper are both good options.

Now, if your morning blood glucose is higher than your bedtime blood glucose, here are two things that may help:

♦ Make sure that you’re not eating a large bedtime snack.  This can cause your blood glucose to rise while you’re asleep.

♦ Talk to your doctor about starting long-acting insulin.  This can counterbalance some of the hormonal changes that happen in the early morning called the dawn phenomenon. These hormonal changes work together to get your metabolism ready for the day, and they can sometimes result in high morning blood sugar numbers for people with diabetes.

If you’re already on insulin though… we need to do one last blood glucose check to make sure that the high in the morning isn’t a rebound from low blood glucose during the night.  To test this, you’ll need to wake up around four hours after you go to sleep to test your blood glucose to make sure that it’s not low. I know this is a pain and will disrupt your sleep, but it will help you and your doctor get to the bottom of whether going too low might be causing your morning highs. You don’t need to do this regularly– only when you need to make sure that you’re not going low during the night.

So now you know how to be a diabetes detective and figure out what’s causing morning highs… here are the questions to ask:

♦ Is my A1c at my target?

♦ If not, what’s my blood glucose at bedtime?

♦ Is it higher or lower than my blood glucose the following morning?

Use these numbers to work with your doctor to figure out what the right approach is to get your A1c to target… remember, it’s your A1c and not your individual glucose numbers that tell you how you’re doing to manage your diabetes.

To answer your specific question, practical experience shows us that changing the timing of glipizide or metformin is seldom helpful when it comes to lowering morning numbers or A1c. Their effects are not that tied in to the timing of the dose. If your A1C has been in your target range while taking your medications at a particular time, and then at some later time the A1C rises, changing the timing of your medications is unlikely to be helpful. Instead, you will need to address areas of possible improvement in your food or physical activity, increase a medication dose, or add a new one.

Dr. Richard Jackson is an Endocrinologist who worked for more than 30 years with the Joslin Diabetes Center in Boston, MA.