Hypoglycemia or low blood glucose in the late evening causes a rebound effect in the body, leading to hyperglycemia or high blood glucose in the early morning.
This phenomenon, known as the Somogyi effect, is widely reported but remains controversial due to a lack of scientific evidence. It is reported more by people with type 1 diabetes than by people with type 2 diabetes.
What is the Somogyi effect?
The Somogyi effect may be similar to the dawn phenomenon.
Named after Michael Somogyi, a Hungarian-born researcher who first described it, the Somogyi effect is the body's defensive response to prolonged periods of low blood sugar. A dose of insulin before bed that is too high can be a cause.
When insulin reduces the amount of glucose in the blood by too much, it causes hypoglycemia. In turn, hypoglycemia makes the body stressed, triggering the release of the stress hormones epinephrine (adrenaline), cortisol, and growth hormone. The endocrine hormone glucagon is also released.
Glucagon triggers the liver to convert stores of glycogen into glucose, which can send blood glucose levels into a rebound high. The stress hormones keep the blood glucose levels raised by making the cells less responsive to insulin. This is known as insulin resistance.
The Somogyi effect is widely cited among doctors and people with diabetes, but there is little scientific evidence for the theory.
For example, one small study found that hyperglycemia upon waking is likely to be caused by not enough insulin before bed. Researchers also found that participants who appeared to have rebound hyperglycemia did not have higher levels of growth hormone, cortisol, or glucagon than others.
A 2007 study of 88 people with type 1 diabetes using continuous glucose monitoring, found that individuals who experienced hyperglycemia upon waking had not experienced hypoglycemia at nighttime. In other words, the Somogyi effect was not observed.
However, other studies cite the Somogyi effect as a common cause of morning time hyperglycemia in people with type 1 diabetes.
Somogyi effect versus dawn phenomenon
The dawn phenomenon, or "dawn effect," is similar to the Somogyi effect in that people experience hyperglycemia in the morning. But the reasons for the hyperglycemia differ.
The dawn effect results from a rise in early-morning blood sugar levels, which are triggered by declining levels of insulin, and an increase in growth hormones.
Testing blood sugar levels at 3.00 a.m. and again in the morning can help distinguish between the Somogyi effect and the dawn phenomenon. Blood sugar that is low at 3.00 a.m. indicates the Somogyi effect, while high or normal blood sugar at that time suggests the dawn phenomenon.
The Somogyi effect is considered less common than the dawn phenomenon. But some research indicates it is the most common cause of fasting hyperglycemia in people with type 1 diabetes.
Symptoms of the Somogyi effect may include blurred vision, confusion, and dizziness upon waking.
Symptoms of the Somogyi effect start with high blood glucose levels upon waking, which are unresponsive to increased insulin doses. Symptoms include:
- low blood glucose levels at 2.00 a.m. or 3.00 a.m.
- night sweats
- rapid heart rate
- waking with a headache
- blurred vision
- dry mouth
- increased appetite
The Somogyi effect is seen in people with diabetes who use insulin therapy to manage their condition. It is caused by:
- taking too much insulin
- not eating enough before bed
Both of these factors cause blood glucose levels to fall too low. The body then responds to this by releasing hormones to raise blood sugar levels. However, sometimes the sugar levels get too high, causing hyperglycemia.
People who have hyperglycemia in the morning without any other known cause may be experiencing the Somogyi effect. Also, morning-time hyperglycemia that resists treatment with increased insulin is also an indicator.
Diagnosing the Somogyi effect is relatively straightforward. It can be done by taking blood glucose readings over several nights.
People should check their blood sugar levels:
- before bed
- at 3.00 a.m.
- upon waking
Low blood glucose at 3.00 a.m., with a high blood glucose reading upon waking, indicates the Somogyi effect.
Diabetes UK advise that, due to the nature of nocturnal hypoglycemia, many people who experience it do not wake up during the night. Therefore, monitoring blood glucose during the night is especially important in diagnosing the Somogyi effect.
Frequent glucose monitoring
Frequent glucose monitoring using a continuous glucose monitoring (CGM) system may be especially helpful.
It can help confirm the diagnosis over time and check for other periods of hypoglycemia that can cause rebound hyperglycemia.
This continuous testing also helps in the management of hypoglycemic unawareness, a complication of diabetes linked to frequent episodes of hypoglycemia. It occurs when a decrease in blood sugar no longer causes the characteristic symptoms of low blood sugar levels, leaving the person unaware that their levels are low.
Treatment and prevention
Treatment, after consultation with a doctor, may include adjusting the dose and timing of insulin.
The only way to prevent the Somogyi effect is to avoid the development of hypoglycemia. Treatment of it should always be in consultation with a doctor.
Treatment options include:
- adjusting the timing of insulin administration
- lowering the dose of insulin taken before bed
- changing the type of insulin used
- eating a snack with evening insulin dosage
- taking into account lifestyle factors, such as stress and exercise
Doctors may recommend CGM for the long-term management of diabetes and the Somogyi effect. A CGM system can alert people to hypoglycemia or hyperglycemia through the use of alarms.
To ensure proper management of the Somogyi effect, a person's weight and levels of the red blood cell protein called hemoglobin A1C, which binds to glucose, may also be monitored over time.
If people need to increase their nightly insulin dose, the risk of the Somogyi effect increases. So, to check for the Somogyi effect, testing blood sugar levels at 3.00 a.m. may be necessary for the first few nights following the insulin increase. If the new dose is causing issues, a doctor may recommend increasing the dosage gradually so that the body can adjust.
If the Somogyi effect is properly identified and managed, the outlook is excellent.
It is vital that people who are experiencing the Somogyi effect discuss the issue with their doctor before making any changes to their insulin regimen. In addition to insulin management, diet, exercise, and other lifestyle factors can also affect the outlook for people with diabetes and the Somogyi effect.