Diabetics should monitor their blood glucose levels closely, but non-diabetics also should be aware of the thresholds that may indicate hyperglycaemia, hypoglycaemia and diabetes.
Blood glucose levels are measured by simple blood tests, either after fasting and/or as part of an oral glucose tolerance test (OGTT). According to the American Diabetes Association, the normal fasting blood glucose target is 70 to 100 mg/dl. After a meal, the target can be as high as 180. Readings between 100 and 126 (after fasting) could indicate a pre-diabetic condition.
A blood glucose test measures the amount of glucose in the blood and is helpful in diagnosing diabetes, as well as hyperglycaemia and hypoglycaemia. The OGTT is a fasting glucose screening, followed by several blood tests over a period of several hours. The patient drinks a glucose solution that tests the system. Readings under 140 during the OGTT are considered normal. Readings between 140 and 200 may indicate impaired glucose tolerance, or pre-diabetes. A reading greater than 200 may indicate diabetes.
When taking a glucose tolerance test, fasting is considered to be an eight- to 10-hour period without food or drink.
A blood glucose screening is helpful in diagnosing diabetes, but it is also used when hyperglycaemia or hypoglycaemia is suspected. Symptoms of hyperglycaemia include fatigue, increased thirst and urination, blurred vision and infections that are slow to heal. Warning signs of hypoglycaemia may include anxiety, confusion, sweating, hunger and blurred vision.
Pregnant women are typically screened for gestational diabetes with a basic glucose tolerance test. A level of less than 140 is considered normal, while a reading of 140 or greater is abnormal and may require further testing, such as the OGTT.
The fasting OGTT during pregnancy is usually read over three hours. The target level for the first test is 95, followed by 180 one hour after the glucose load, 155 two hours after the glucose load and 140 three hours after the glucose load.
Some medications (particularly steroids, antidepressants, hormones and diuretics) can affect blood glucose levels.