Do your blood sugars rise early every morning, for no apparent reason? You may be experiencing “dawn phenomenon.” It’s frustrating, but it’s common, and this article will help you with a few strategies for preventing those glucose spikes.

There are several possible causes of a high blood sugar level in the morning:

1. Dawn phenomenon. This occurs when your body releases a surge of hormones overnight, which then triggers your liver to dump sugar into your blood. This is an entirely natural process, but people with diabetes cannot properly secrete or utilize insulin to counteract the blood sugar rise.
2. Reactive hyperglycemia, also called the Somogyi effect. This is distinct from dawn phenomenon. It happens when low blood sugar in the middle of the night triggers your liver to dump sugar into your blood in an attempt to stabilize your blood sugar.
3. Finally, your blood sugar may simply rise overnight for less complex reasons. Perhaps your basal insulin dosage isn’t set quite right, or a late-night meal took hours to cause a glucose spike.

Why Are My Blood Sugars High in the Morning?

Here’s a simple plan for diagnosing the source of high blood sugars in the morning.

1. Test your blood sugar before you sleep.
2. Test your blood sugar in the middle of the night.
3. Test your blood sugar first thing in the morning.

It takes a little bit of effort, but you probably only need to do it a few times to diagnose the issue.

To diagnose either dawn phenomenon or Somogyi effect, experts recommend checking blood sugar levels for several nights, specifically between 3 a.m and 5 a.m.

Compare these three glucose values and find the pattern:

• If your blood sugar stayed steady overnight, but rose in the morning, you are likely experiencing dawn phenomenon.
• If your blood sugar rose steadily throughout the night, your morning glucose highs may be the result of your diet choices (for example, a carbohydrate-heavy bedtime snack), or a sign that you may want to adjust your insulin and glucose-lowering medication regimen.
• If your blood sugar dipped low in the middle of the night, you may be experiencing Somogyi effect.

The best option is to use a continuous glucose monitoring system (CGM). This will give you an entire night’s worth of blood sugar values, making it easy to identify what direction your blood sugar moved while you slept, without having to set an alarm in the middle of the night.

If you think you’ll have a tough time having insurance approve the use of a CGM (especially if you have type 2 diabetes), talk to your healthcare provider about the use of a CGM on loan. Only a few days of data will teach you a lot. Visit our learning page on CGM to learn all about this vital technology.

How to Fix High Blood Sugars in the Morning

The Dawn Phenomenon

More than half of people with diabetes (including both types 1 and 2) are thought to experience dawn phenomenon, and it can lead to significant increases in A1C.

The dawn phenomenon begins when your body secretes a surge of hormones, including growth hormone, cortisol, adrenaline, and glucagon. These hormones start working very early each morning around the same time to prepare your body to wake. Basically, your body is starting the engine, releasing some fuel, and prepping to go for the day.

These hormones trigger the conversion of the liver’s glycogen stores into glucose, which is then dumped into the blood in a process called glycogenolysis.

Source: The University of California, San Francisco

This general process occurs in all humans regardless of whether they have diabetes. In people without diabetes, the body’s natural insulin response prevents the blood sugars from rising. In people with diabetes, though, the body is unable to produce a healthy insulin response, and therefore blood glucose levels spike up.

The Mayo Clinic suggests several strategies you can try to combat the effects of dawn phenomenon:

• Use an insulin pump to administer extra insulin during early-morning hours.
• Avoid carbohydrates at bedtime.
• Adjust your dose of medication or insulin. (If you take a long-acting insulin such as Lantus, be aware it doesn’t last a full 24 hours. This means you may want to try taking it at night or splitting the dose by taking half in the morning and the other half 12 hours later.)
• Switch to a different glucose-lowering medication.
• Adjust the time when you take your medication or insulin from dinnertime to bedtime.

Dawn phenomenon also contributes to early morning insulin resistance. You may want to limit carbohydrates during the hour or two after you wake up. Insulin-users may need to have a higher insulin-to-carb ratio and take more insulin in the morning than during other parts of the day.

Some patients probably don’t need to be too concerned about dawn phenomenon. If most of your night is spent with normal blood sugars, and you experience a small, temporary increase in the morning, there is likely little to worry about. For those that are otherwise usually in their target blood sugar range, the morning increase is often less than they experience during a typical meal, and even more short-lived.

High Blood Sugars from the Night Before

If you are experiencing high blood sugar in the morning as a result of elevated blood sugar from the night before, there are several things you could try:

• Eat fewer carbohydrates during the evening hours.
• Add evening exercise like an after-dinner walk.
• In consultation with your doctor, increase blood sugar lowering medication or insulin.

Reactive Hypoglycemia (Somogyi Effect)

This is also known as rebound hypoglycemia, or the Somogyi effect. It is less common than dawn phenomenon.

If your blood sugar goes too low overnight, it may explain elevated morning blood sugar levels. Your body essentially goes into panic mode and attempts to save you by secreting counter-regulatory hormones like glucagon and epinephrine (adrenaline), which then trigger the liver to change its reserves of glycogen into glucose. In short, your body senses a low and dumps as much sugar as it can into the blood in an attempt to get enough fuel to function.

Here are some things you could try to reduce this occurrence:

• Eat a carbohydrate snack before bed.
• Reduce blood sugar-lowering medication or insulin in the evening.
• Reduce your long-acting insulin dose.
• Change your exercise schedule from afternoon or evening to morning.

Make sure you don’t ignore reactive hypoglycemia. It’s a sign that your blood sugar is approaching dangerous levels overnight.

Over time, your body’s response to low blood sugar levels may change due to hormone changes, leaving your body unable to warn you of low blood sugar symptoms and unable to trigger the liver into dumping sugar into your blood. Also, if other low blood sugar episodes have occurred earlier the same night or excess exercise has taken place, the liver may have already depleted its reserves of glycogen and may not be able to secrete glucose and raise your blood sugar.

Summary

If your blood sugar is high in the morning, it’s important to figure out why. Use a CGM, or an alarm clock and a blood sugar meter, to examine your overnight blood glucose for trends and figure out what’s happening.