Levels which are significantly above or below this range are problematic and can in some cases be dangerous. A level of <3.8 mmol/L (<70 mg/dL) is usually described as a hypoglycemic attack (low blood sugar). Most diabetics know when they're going to "go hypo" and usually are able to eat some food or drink something sweet to raise levels. A patient who is hyperglycemic (high glucose) can also become temporarily hypoglycemic, under certain conditions (e.g. not eating regularly, or after strenuous exercise, followed by fatigue).
Levels greater than 13-15 mmol/L (230-270 mg/dL) are considered high, and should be monitored closely to ensure that they reduce rather than continue to remain high. The patient is advised to seek urgent medical attention as soon as possible if blood sugar levels continue to rise after 2-3 tests. High blood sugar levels are known as hyperglycemia, which is not as easy to detect as hypoglycemia and usually happens over a period of days rather than hours or minutes. If left untreated, this can result in diabetic coma and death.
Prolonged and elevated levels of glucose in the blood, which is left unchecked and untreated, will, over time, result in serious diabetic complications and sometimes even death. It is therefore highly important that a diabetic patient checks their blood levels either daily or every few days to see what levels they are achieving over a given period of time. There is also computer software for the PC which is available from blood testing manufacturers which can display results and trends over time. Type 1 patients will have to check on a more regular daily basis due to insulin therapy, which is a fine art to master.
A history of blood sugar level results is especially useful for the diabetic to present to their doctor or physician in the monitoring and control of the disease. Failure to maintain a strict regimen of testing can accelerate symptoms of the condition, and it is therefore imperative that any diabetic patient strictly monitor their glucose levels regularly.