Causes of high blood sugar levels

Updated February 21, 2017

Blood sugar or glucose levels rise when the body is unable to process the amount of glucose consumed. There are several reasons this may occur. In those with diabetes, the body may not produce enough insulin to adequately process glucose or the body may process glucose inefficiently. The patient may require medication and alter her lifestyle to maintain adequate control.


Carbohydrates convert to glucose (sugar) in the bloodstream and serve as the body's main source of fuel. Consuming large amounts of carbohydrates causes a rise in blood sugar levels, even if the food does not contain sugar. In healthy individuals who do not have diabetes, the body produces sufficient insulin to process the sugar and convert it to an energy source for the body. Rises in blood sugar are only temporary and will return to normal in a short period.


For those with diabetes, the body does not produce sufficient insulin to convert the sugar to usable energy, and the rise in blood sugar does not return to normal on its own. Medication may be necessary to control the sugar level. Exercise also affects the processing of glucose and assists in returning sugar levels to within the normal range. Regular exercise assists in maintaining normal blood glucose levels.


Many mistakenly believe that those with diabetes or high blood sugar can eat anything they wish as long as it does not contain refined sugar. Although refined sugar causes a quick rise in blood sugar levels, other carbohydrates found in fruits, vegetables, pasta, bread, rice and grains also cause blood sugar to rise. People with diabetes must watch the total number of carbohydrates consumed, not just the amount of sugar consumed.


Blood glucose monitors provide a quick check of blood sugar levels. The patient generally pricks the finger with a lancet and places the drop of blood on a test strip inserted into the glucose monitor. Within seconds, the monitor produces a digital reading of the glucose level. Testing the glucose level before eating and testing again an hour after eating gives a picture of how the food affects blood glucose levels. Using this method, an individual can quickly assess which foods cause the blood sugar level to rise and alter his diet accordingly. Following the same procedure before and after exercise shows how effectively the exercise lowers high glucose levels.


Repeated high readings that do not return to normal within a few hours may indicate hypoglycaemia or high blood sugar. Contact your doctor for a thorough evaluation.

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About the Author

Nannette Richford is an avid gardener, teacher and nature enthusiast with more than four years' experience in online writing. Richford holds a Bachelor of Science in secondary education from the University of Maine Orono and certifications in teaching 7-12 English, K-8 General Elementary and Birth to age 5.