Type 2 Diabetes Guide

Why Blood Sugar is Highest in the Morning & How to Prevent It

Many diabetics struggle with achieving good glycemic control. Some people struggle in particular with fasting blood glucose levels, the reading taken first thing in the morning before consuming any calories. Naturally, it would seem that blood sugar should be lowest in the morning because you haven't had anything to eat in so long. That's why it can be so confusing when .

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Reasons Why Fasting Blood Sugar Can Be High

  • The Dawn Phenomenon. In the hours just after going to bed - typically midnight to around 3:00am - our bodies don't need a lot of insulin. Medications taken before bedtime will cause a drop in blood sugar during this time.

    But as our bodies begin to get ready for a new day, they release stored glucose as well as hormones like cortisol and growth hormones. These hormones counteract the effects of insulin - they cause a rise in blood sugar levels instead of dropping them. The combination of the release of stored glucose, the release of hormones, and the bedtime dose of insulin wearing off results in a rise in blood sugar levels.

    So when you wake up in the morning, your blood sugar is high. Most people don't realize this is happening and only find out when they wake up and take a blood sugar reading.

  • Rebound Hyperglycemia (The Somogyi Effect). Rebound hyperglycemia is caused by poor diabetes management, rather than natural changes in the body during sleep (like the Dawn Phenomenon).

    High morning blood sugar can be caused by taking too large a dose of insulin at bedtime, for example, or eating too small of a bedtime snack. This causes blood sugar levels to drop too low, triggering your body to release hormones to counteract it and bring blood sugar levels back up.

    Another way high blood sugar can happen is if the bedtime insulin dose is too small. Without sufficient insulin, blood sugar levels will remain high.

Figuring Out the Cause

Before figuring out what can be done about high blood sugar in the morning, you need to know what's causing t. Your doctor may ask you to check your blood sugar early, typically between 2:00am and 3:00am, for several nights in a row. If there is a consistently a low reading, then it's likely rebound . If the readings are consistently normal or high, then it's more likely to be the Dawn Phenomenon.

Trying to Achieve a Normal Fasting Blood Glucose

Discuss with your doctor how to manage high morning blood sugar. Options can include:

  • Changing what you eat or how much you eat at your bedtime snack. If you're not currently eating at night, you may need to have a little. If you are currently eating carbohydrates, protein and/or fat may be needed instead. You may need to eat a little more to prevent your blood sugar from dipping too low overnight while you fast.

  • Aim for a lower blood glucose reading before bedtime. That might mean you need to adjust what you eat for dinner, such as having fewer carbohydrates or eating a smaller meal.

  • Adjust the time you take your bedtime insulin, adjust the dosage, or change the type of insulin you're taking. The morning insulin dose may also need adjusting.

  • Exercise in the evening. is a great regulator of blood sugar levels, and the effects can last for hours after you stop.

Be sure to keep good records of your blood sugar readings, along with notes about diet, exercise, medication, etc. so that you can see what's working and what is not. Your doctor or diabetes educator can advise you on what changes to make to your to try to prevent the issue where blood sugar is highest in the morning. It can take some experimentation and time but it can usually be resolved.



The information on this website is based on our own research and personal experience, and is not a substitute for medical advice. Questions about your health and individual situation should be directed to your doctor.