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Why do I have high blood glucose in the morning?

Why do I have high blood glucose in the morning?

Both the Somogyi effect and dawn phenomenon indicate a rise in blood sugar. But the reasons are different. We take a closer look

High blood glucose

The ‘dawn phenomenon’ and the ‘Somogyi effect’ are two possible reasons why people with diabetes have high blood glucose levels in the morning before breakfast. In the Somogyi phenomenon, low blood sugar in the middle of the night causes high blood sugar in the morning. While in the dawn phenomenon, there is a normal rise of blood sugar as a person’s body prepares to wake up, however, it does not have hypoglycemic episodes (blood glucose falling below normal to a potentially dangerous level) during the night. The level of glucose in the blood of a healthy person is between 70 and 130 mg/dl. If your blood sugar level is below 70, it indicates hypoglycaemia, and a reading above Somogyi 130 indicates hyperglycaemia.

A recent graphical observation report using Continuous Glucose Monitoring (CGM), which transmits glucose readings every one to 15 minutes, on a 35-year-old man from Vellore, Tamil Nadu, threw up a disturbing pattern. These fluctuations could have gone undetected in the traditional ‘before’ and ‘after’ fasting blood tests done at specific isolated intervals during the day if it weren’t for the CGM device. These undetected nocturnal variations in blood glucose levels have thrown light on the relevance of closely monitoring the Somogyi effect and the Dawn phenomenon responsible for silent glucose variations.

Continuous monitoring of blood glucose levels could be lifesaving for people with diabetes especially from nocturnal hypoglycemia, also classified as ‘dead in bed’ syndrome. Dr Nihal Thomas, professor and head of department of endocrinology at the Christian Medical College, Vellore, points out that six percent of all diabetes deaths are due to dead-in-bed syndrome. “The duration of nocturnal hypoglycaemia before a seizure is 2.25 to four hours. More than two episodes of hypoglycaemia per week can lead to a loss of counter-regulation and cause the loss of symptom awareness. Repeated hypoglycaemia may impact cognitive function and memory loss,” he says.

The perils of stealth blood glucose fluctuations

Thirty-five-year-old Rahul (name changed), an accountant, one of Dr Thomas’s case studies, who works as an accountant, had diabetes for ten years. The outcome of his closely monitored glucose levels helped Dr Thomas to unravel the complex ups and downs recorded in his glucose levels while sleeping, including moments when his glucose levels dipped to the level of 40 at 4 am, a point where he could even die or suffer brain damage.

Rahul used to have dinner at 10 pm and insulin before his sleep. A report collected from four different days shows that after he fell asleep, there was a significant dip in glucose levels, at an alarming level, around 4 am. He wasn’t aware of the dip in glucose levels; there were no symptoms, which is called Hypoglycemia Unawareness (HU). But before he woke up in the morning, fortunately, his sugar levels were seen rising again. This is called the Somogyi effect and it can happen during the daytime.

Dr Thomas points out that hypoglycaemia is prevented with the help of effective functioning of counter-regulatory hormones such as adrenaline, corticosteroids, growth hormone and glucagon.

Dangers of hypoglycaemia

Rahul’s glucose levels dipped to the level of 40 and were seen increasing before he woke up. If his body hadn’t produced hormones after 4 am, he would have probably become unconscious as the dip in glucose levels was being recorded from about 2 am, as per his CGM report.

Dr Thomas says there would be drastic impacts such as brain damage, memory loss, nightmares, headaches, cardiac arrest and even death while sleeping due to prolonged hypoglycaemia. Liver, kidney diseases and alcoholism are factors that aggravate it.

How to prevent hypoglycaemia

Changing the night routine is pivotal to controlling blood sugar. “Taking dinner with insulin at 10 pm and going to sleep is a common mistake that many Indians make, also because they come back home very late after work. We advise all diabetic patients to have dinner as early as possible, by 7.30 pm or 8 pm, with insulin. Two hours later, they should have a bedtime snack. This is very important,” says Dr Thomas.

Dawn phenomenon

If Rahul had insulin at 9 pm, the sugar would have started rising at dawn (5 am), as the insulin effect ends there. This is called the Dawn Phenomenon. To deal with this, doctors depend on long-acting insulins such as Glargine or advance the timing of the insulin to 10 pm.

“In the Somogyi effect, if you take a bedtime snack, you won’t go to hypoglycaemia. If the patient takes a bedtime snack, glucose levels will not dip below the level of 100,” says Dr Thomas. He says that doctors might not be aware of this in most cases. “If I hadn’t done this CGM on the accountant, I wouldn’t have known his glucose patterns. For people who can’t afford the CGM, a glucometer may be enough to check sugar at midnight and 3 am, once a week. It will help to find out if there is hypoglycaemia while sleeping. A glucometer is cheap even if it is not the best,” adds Dr Thomas.

Dr Vijay Viswanathan, head and chief diabetologist at M V Hospital for Diabetes and Prof M Viswanathan of Diabetes Research Centre in Chennai, who handles hundreds of diabetes patients in South India say that some people who take insulin injections at night have high fasting blood sugar levels. “In these people, there is a drop in blood sugar at night during sleep. But immediately, the body compensates by producing glucose which increases the fasting blood sugar,” he says.

A study, ‘Prevention and Management of Severe Hypoglycemia and Hypoglycemia Unawareness: Incorporating Sensor Technology’ published in Current Diabetes Report, on August 18, 2018, is about the purpose of sensor technology to aid in the detection and prevention of hypoglycaemia. The study notes that integration of CGM with continuous subcutaneous insulin infusion (CSII) therapy, a system known as sensor-augmented pump (SAP) therapy, very significantly reduces the occurrence of these conditions by providing real-time glucose readings/trends and automatically suspending insulin infusion when the glucose is low (LGS) or, even, before the glucose is low but is predicted to soon below (PLGS). The study concludes that the sensor technology (CGM) promises to continue to improve patients’ lives not only by attaining glycaemic control but also by reducing hypoglycaemia.

Insulin-induced insulin resistance

Dr Vijesh Vijayan, an internal medicine specialist at Smt. Sucheta Kriplani Hospital and Lady Hardinge Medical College, New Delhi, talks about the case of a 27-year-old man who was diagnosed with Type I Diabetes Mellitus. He has been taking insulin for the past 12 years. “He weighs 48 kg and gets ten units of insulin injected under the skin 30 minutes before each meal. Also, 30 minutes before breakfast and dinner, he takes 18 more units of insulin. His average blood glucose level over the past three months was 7.1 percent, which means he is doing a great job of managing his diabetes. But his fasting blood glucose levels over the past five days show that his glucose levels have gone up by 221, 198, 186, 200, and 196. When the HbA1c test is taken into account, the person in this case seems to be healthy. However, he has hypoglycemic episodes around midnight. And the high blood sugar he experiences in the early morning is a rebounding effect of the hypoglycaemic episodes he has previously experienced. This is a typical example of Somogyi,” says Dr Vijayan.

The causes of Dawn and Somogyi phenomenon include excess or ill-timed insulin, skipped meals and poor technique of insulin administration, and are attributed to insulin-induced insulin resistance, nocturnal growth hormone secretion, glucagon, adrenaline and cortisol response, says Dr Vijayan.

Dr Vijayan says the availability of continuous glucose monitors makes the diagnosis easier. This can be managed by adjusting the type and dose of insulin and refining the method of administration and meal timings. “Hypoglycemia is potentially avoidable, and the occurrence also reflects poor overall management of diabetes,” he says.

The falling glucose levels between 2 am and 4 am may be responsible for some of the symptoms of low blood sugar. These symptoms include night sweats, a rapid heart rate, waking up with a headache, blurred vision, confusion, dizziness, dry mouth, fatigue, increased appetite and thirst.


Nocturnal and pre-dawn blood sugar fluctuations could trigger serious health consequences, especially in elderly people with diabetes. It should be properly managed with strict lifestyle and healthy diet, specifically during dinner time. Somogyi effect is the sudden dip in blood sugar levels late in the night while sleeping. Dawn phenomenon happens when there is an increase in blood sugar levels during the early morning hours which is in fact a natural phenomenon. Strict and wise diabetes management is essential to ensure that either the Somogyi effect or the Dawn Phenomenon do not lead to serious health consequences. Here are some tips to manage your early morning blood glucose levels better:

1) Avoid eating carbohydrate rich food, especially snacks, at bedtime.

2) Do not skip meals and always try to have an early dinner.

3) Walk a bit after dinner. Do not overexert as it could trigger a blood sugar crash.

4) Workout every morning to burn off excess calories and blood glucose.

5) Always have a glucose monitoring device for regular updates on monitor blood sugar levels.



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