Even under normal conditions, blood sugar levels vary throughout the day, but a sudden rise in blood sugar can be alarming. Stress or illness may cause blood sugar levels to rise suddenly. If you have diabetes, a sudden rise may involve diet or medication. Knowing the cause can help you better manage blood sugar and improve overall health.
About High Blood Sugar
Normal blood sugar measures 70 to 99 milligrams per deciliter after fasting, or less than 140 milligrams per deciliter two hours after eating. High blood sugar occurs when your body either doesn't make enough insulin or can't properly use the insulin it does make, and is most often associated with diabetes. A fasting blood sugar of 126 milligrams per deciliter or a random blood sugar reading of 200 milligrams per deciliter indicates high blood sugar. Frequent urination, increased thirst, weight loss or fatigue are signs that your blood sugar levels may be high. If left uncontrolled, high blood sugar leads to ketoacidosis, also referred to as a diabetic coma, which is when your body breaks down fat into ketones for fuel and the ketones build up in the blood.
Diet and Blood Sugar
If you have diabetes, a sudden rise in blood sugar may be related to your diet. When you eat carbohydrate foods, which include starches, fruit, milk and sweets, your body breaks them down into sugar. If you're eating too many carbs at a meal, your blood sugars may rise rapidly. Or if you're eating carbs that digest quickly, referred to as high-glycemic foods, you may see a sudden rise in blood sugar. High blood sugar levels after eating a meal or snack is called postprandial hyperglycemia.
Surge in Hormones
Between the hours of 4 and 5 a.m., most people, whether they have diabetes or not, have a surge in hormones called the "dawn phenomenon." People with diabetes also experience an increase in blood sugar during this time because their body is producing glucagon -- a hormone that raises blood sugar -- but their insulin is not able to compensate for the rise in blood sugar, leading to even higher levels. Eating an early dinner or exercising after you eat may help prevent the sudden rise in blood sugar related to the "dawn phenomenon."
How to Improve High Blood Sugar
The American Diabetes Association recommends exercise to help lower blood sugar. If your blood sugar is greater than 240 milligrams per deciliter, you should check your urine for ketones before you exercise, says the ADA. Exercising with ketones in your urine increases blood sugar, in which case you shouldn't exercise. Making changes to your diet may also help lower blood sugars. If you're eating too many high-glycemic foods, such as white bread or white rice, you can swap them out for low-glycemic foods, such as whole-wheat bread and brown rice. Decreasing portions, especially if you're eating large amounts of carbohydrate-containing foods, may also help bring your blood sugars back under control.
- Virginia Mason: What Are Normal Blood Glucose Levels?
- American Diabetes Association: Hyperglycemia
- Diabetes Self-Management: Strike the Spike
- Harvard School of Public Health: Carbohydrates and Blood Sugar
- American Diabetes Association: Carbohydrate Counting
- American Diabetes Association: Dawn Phenomenon
- Harvard Medical School: Glycemic Index and Glycemic Load for 100+ Foods