The Somogyi effect is one of many possible causes of high blood sugar (hyperglycemia) in the morning in people with diabetes. It may happen due to an episode of low blood sugar overnight.
The Somogyi (so-MOH-gyee) effect happens when a low blood sugar (hypoglycemia) episode overnight leads to high blood sugar (hyperglycemia) in the morning due to a surge of hormones. It can affect people with diabetes who take insulin.
The effect was named after the doctor who first wrote about it in the 1930s — Dr. Michael Somogyi. Healthcare providers sometimes call it “rebound hyperglycemia.”
Researchers consider the Somogyi effect a theory, meaning it’s not considered to be a fact, but there’s scientific evidence that supports it. While healthcare providers once thought of the effect as a likely cause of morning high blood sugar, more recent studies involving continuous glucose monitoring (CGM) have disputed the Somogyi effect.
The Somogyi effect is one of multiple possible causes of high blood sugar in the morning, including:
The Somogyi effect and dawn phenomenon are both phenomena that can cause people with diabetes to have high blood sugar in the morning.
The Somogyi effect also involves a surge of hormones, but it’s due to a low blood sugar episode overnight. Dawn phenomenon doesn’t happen because of low blood sugar.
Dawn phenomenon is also a much more common cause of high blood sugar in the morning than the Somogyi effect.
The main sign of the Somogyi effect is high blood sugar in the morning when you wake up. You may find you have high blood sugar with a glucometer reading and/or through your continuous glucose monitoring (CGM) device when you wake up.
Depending on how elevated your blood sugar is, you may have the following symptoms when you wake up:
The theory of the Somogyi effect states that if your blood sugar drops too low in the middle of the night while you’re sleeping due to injected insulin, your body will release hormones in an attempt to “rescue” you from the low blood sugar.
These hormones include:
They increase your blood sugar by triggering your liver to release stored glucose in larger amounts than usual. This glucose release increases your blood sugar (glucose). If you have diabetes, your pancreas doesn’t produce any or enough insulin to correct the increase. This means your blood sugar remains high.
If you don’t have diabetes, your body naturally regulates your blood sugar to keep it in range. This is why the Somogyi effect doesn’t affect people who don’t have diabetes.
The Somogyi effect isn’t a common cause of high blood sugar in the morning, so it may be difficult to detect. Also, recent studies have found that the Somogyi effect may not be a cause of high blood sugar in the morning. So it may be hard or impossible for a healthcare provider to “diagnose” it.
Talk to the healthcare provider who helps you manage diabetes if you frequently have high blood sugar in the morning. They’ll assess your blood sugar readings to determine the cause. The most effective way to do this is with continuous glucose monitoring (CGM).
If you don’t use a CGM device, your provider may ask you to manually check your blood sugar more frequently, such as:
They may also ask you to keep notes of what kinds of food you eat for dinner and how much and what kind of exercise you do in the evening, if applicable.
This information can help them determine the cause of the morning high blood sugar levels.
Once you and your healthcare provider determine how your blood sugar levels are behaving throughout the night, they’ll advise you about the changes you can make to try to prevent morning high blood sugar levels. Several factors affect your blood sugar, and every person is unique. Because of this, preventing and treating high blood sugar levels in the morning will be different for everyone.
Options your provider may suggest include:
Regardless of whether the Somogyi effect is actually a cause of high morning blood sugar, it highlights two complications that people with diabetes should try to prevent:
Consistently high blood sugar leads to an increase in A1C levels and your Time in Range (TIR). An A1C test measures the average amount of glucose (sugar) in your blood over the past three months. Your TIR is the average percent of time per day that your glucose level is in the target range.
The higher your A1C and TIR levels, the more risk you have for developing complications, especially if they’re consistently high over several years. Diabetes complications include:
Studies show that people with diabetes may be able to reduce the risk of diabetes complications by consistently keeping their A1C levels below 7%.
As high morning blood sugar levels can be a persistent issue, not addressing or treating them can lead to consistently high blood sugar for at least a few hours every day. This can increase your risk of diabetes complications over time.
For most people with diabetes, low blood sugar (hypoglycemia) is when your blood sugar is below 70 mg/dL (milligrams per deciliter).
Most people experience symptoms of low blood sugar, such as:
However, if you experience low blood sugar while you’re sleeping, it may take longer for you to notice symptoms and wake up. This can be dangerous, and severe hypoglycemia can be life-threatening. Symptoms of overnight lows may be slightly different and include:
When you have any low blood sugar symptoms, it’s important to check your blood sugar to see if your levels are low (and how low they are). This will guide how you treat the low blood sugar. You need to consume fast-acting carbohydrates (sugar), like a banana or apple juice, to treat hypoglycemia.
If you’re experiencing frequent low blood sugar episodes overnight, be sure to talk to your healthcare provider. Together, you’ll adjust your diabetes management plan to prevent future episodes.
If you have consistently high blood sugar in the morning, it’s important to talk to the healthcare provider who helps you manage diabetes. They can assess your blood sugar readings to see if the Somogyi effect or something else is the culprit and recommend treatment options.
A note from Cleveland Clinic
Experiencing high morning blood sugar can be frustrating and annoying. There’s no single way to anticipate and manage morning highs, so it may take time to find the best strategy for you. Your healthcare provider can help you determine the best plan of action. Don’t hesitate to reach out to them for help. Taking action now can help you avoid short-term and long-term complications.
Last reviewed by a Cleveland Clinic medical professional on 01/31/2023.
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