Self-monitoring blood glucose concentrations

General principles

Blood glucose concentration monitoring is a vital aspect of care for adults with type 1 diabetes. Regular and frequent self-monitoring of blood glucose concentrations (SMBG) is associated with an improved glycaemic profile and a lower incidence of acute complications. Information from SMBG is used by the patient and their health professionals to:

  • adjust insulin dosage
  • identify and guide treatment of hyperglycaemia and hypoglycaemia
  • assess the effect of food, exercise and other factors (eg medications) on blood glucose concentrations
  • monitor blood glucose during illness or times of change (eg lifestyle change)
  • show the benefits of optimal dietary intake and physical activity
  • check any abnormal or unexpected glucose results from a CGM or flash glucose monitor (eg results that do not match a patient’s symptoms).

For SMBG to be of clinical benefit, patients must understand when and why they are checking, and what the blood glucose concentration results mean. Clinician input is required to interpret data and adjust treatment accordingly.

SMBG is usually performed by pricking the finger and applying the resulting capillary blood to a glucose strip, which is read by a blood glucose meter. The patient’s SMBG technique should be reviewed at least once a year.

Patients with type 1 diabetes should perform SMBG at least 4 to 6 times each day, usually before and/or after main meals, before exercise, when hypoglycaemia is suspected, and before critical activities such as driving. Blood glucose monitors have varying abilities to record, store and download data, and may be able to calculate parameters related to blood glucose concentrations such as bolus insulin doses.

More frequent SMBG is required in the following situations:

  • during periods of illness
  • after treatment of hypoglycaemia
  • during times of increased activity
  • when the insulin regimen has been changed
  • when planning pregnancy, and during pregnancy.

For information about glycaemic targets, see Glycaemic targets for adults with type 1 diabetes.

Other considerations

Even with optimal use, capillary (finger-prick) blood glucose concentration checking is less accurate than laboratory testing of venous blood, especially when blood glucose concentrations are low. Symptoms are the primary diagnostic indicator of hypoglycaemia.

Capillary blood glucose concentration results may be falsely elevated in patients on peritoneal dialysis because some glucose meters do not distinguish between glucose and the icodextrins contained in some peritoneal dialysis fluids (eg Extraneal). Patients on peritoneal dialysis should see the meter’s product information, or ask a credentialled diabetes educator, to check whether the meter distinguishes between icodextrins and glucose.

Capillary blood glucose concentration checking is not a substitute for laboratory venous blood glucose testing for the diagnosis of diabetes.