Blood sugar is a term used to describe the amount of sugar that is freely available in the bloodstream. In normal instances your blood sugar ranges between 70 and 110 mg/dL when you are fasting and in the mid to low 100s mg/dL in random testing, according to Virginia Mason Medical Center. If you have diabetes, you may experience high levels of blood sugar at night or in the morning even if your disease is otherwise well-controlled.
Insulin
Insulin is a hormone produced by the pancreas that helps glucose pass from the bloodstream into the cells of the body where it is used for energy. Without insulin, or when your body doesn't use insulin well, you have too much glucose in your bloodstream that can cause damage to your nerves and vascular system. Control of your blood sugar is important in order to reduce the long-term side effects of diabetes, even when your blood sugar only spikes for a short time in the early morning or in the evening.
The Dawn Phenomenon
The "dawn phenomenon" or "dawn effect" is the term used to describe why your blood sugar may be higher in the morning hours, according to the Cleveland Clinic. It is the result of natural hormonal fluctuations your body experiences through the night. Between midnight and 3 a.m., you have very little need for insulin when you should be sleeping most soundly. Between 3 a.m. and 8 a.m., your body begins to get ready for the day by releasing hormones that increase insulin resistance and stored glucose in preparation for the day. These events result in an increase in blood sugar in the morning hours.
The Somogyi Effect
Another reason you can experience higher levels of blood sugar in the morning is from the Somogyi effect, or rebound hyperglycemia. According to an article by Theresa Garnero, nurse practitioner and certified diabetic educator, this is a pattern of undetected low blood sugar values that are followed by high blood sugar levels, usually over 200 mg/dL. When your body is experiencing low blood sugar, it releases hormones to release stored glucose, causing your blood sugar to swing in the opposite direction and resulting in high blood sugar.
Circadian Rhythms
In a study published in the Dec. 7, 2008, issue of "Nature Genetics," researchers collaborating from four different countries reported a mutation in a gene that controls the actions of melatonin. Melatonin regulates the internal clock that develops sleeping and eating patterns in response to light. Researchers discovered that this impaired pattern of sleep can result in high blood sugar levels.
High Blood Sugar at Night
Control of your blood sugar is a balancing act between the foods you eat, the exercise you get and the insulin you take. When even one of those factors is not in balance, it can make your blood sugar levels higher than normal, especially in the evening hours when you are likely to be less active. Increases in blood sugar levels at night can also be caused by not taking the right amount of medication when needed, not following your meal plan, not getting enough exercise, having an illness or taking other medications that affect how your diabetes medication works.
References
- Virginia Mason Medical Center: What Are Normal Blood Glucose Levels?
- Cleveland Clinic: What Causes High Blood Sugar Levels in the Morning?
- DLife; Somogyi Effect vs. Dawn Phenomenon; Theresa Garnero, APRN, MSN, CDE; April 2011
- ScienceDaily; Body Clock Linked to Diabetes and High Blood Sugar in New Genome-wide Study; December 2008
- KidsHealth: Causes of High Blood Sugar Levels
- "Nature Genetics"; A Variant Near MTNR1B Is Associated With Increased Fasting Plasma Glucose Levels and Type 2 Diabetes Risk; N. Bouatia-Naji, et al.; December 2008
