Blood sugar can be checked by patients at home. This is called SMBG (self-monitoring blood glucose) or in the laboratory. Small portable hand held battery operated devices are in common use. The accuracy has about 10% variability as compared to laboratory testing.
All cases of Type I Diabetes mellitus should frequently check blood sugars. This should be done multiple times daily in most cases as fluctuations are more common in Type I DM
- by those on multiple insulin injections daily,
- while adjusting insulin doses,
- when hypoglycemia is suspected,
- before exercise /games etc
- before driving.
- During travel
It is required less frequently in Type II Diabetes. It is checked for patients on insulin and those having hypoglycemic episodes. Once a week check may be enough for most patients. Those who are on a tight control of sugars require more frequent checks.
It is also recommended during treatment of hypoglycemia to ensure that blood levels of glucose have improved and remain improved.
Time of Testing :
For type II cases and those suspected to have hypoglycemia often, morning and before dinner levels are useful. However, treatment should not be delayed in serious hypoglycemia suspicions as delay in correcting glucose levels may cause permanent injury to some organs especially nervous system.
Venous or capillary blood is used for measurement of blood sugar. It can be measured in plasma or serum. Capillary and plasma levels are 10% lower and higher compared to venous and serum levels due to glucose utilization by tissues and RBCs.
Glucometers use strips impregnated with glucose oxidase. Most show plasma glucose rather than whole blood levels.
Calibration is required before using a fresh set of strips.
Best results are obtained if a lancet is used for puncture of the skin. Blood should come out easily rather than being squeezed from the fingertip. Sides of terminal digits should be used as punctures in front areas would be painful when hands are used. Hands should be washed and dried before a sample is taken.
Higher values may not be measured precisely and are often shown as High levels.
Test strips should be fresh and manufacturers guidelines should be adhered to.
Units of Measurement :
Old methods report sugar level in mg/deciliter while the newer methods are in mmol/liter. To convert from mg/dl to mmol /l the former values are divided by 18.
HbA1C or glycated Hb measures level over previous 12 weeks or so. The test, however, should be done in a fasting stage and is a good guide for overall diabetic control.