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Self-monitoring of blood glucose in management of adults with diabetes mellitus

David K McCulloch, MD
Section Editor
Irl B Hirsch, MD
Deputy Editor
Jean E Mulder, MD


All patients with diabetes mellitus who use insulin and some patients who take other glucose-lowering medications that can cause hypoglycemia should measure their blood glucose concentrations to help maintain safe, target-driven glucose control. The effectiveness of self-monitoring in patients with type 2 diabetes who do not use hypoglycemic agents is less certain.

In addition to self-monitoring of blood glucose (SMBG), periodic measurement of glycated hemoglobin (A1C) is the accepted means of estimating chronic glycemic control. Several practical points about SMBG will be reviewed here, including the accuracy of glucose meters and glucose test strips, the accuracy of the operator, the efficacy and reliability of continuous glucose monitoring (CGM) systems, and how to use the glucose information that is obtained. The use of A1C measurements to estimate mean blood glucose is reviewed elsewhere. (See "Estimation of blood glucose control in diabetes mellitus".)


Self-monitoring of blood glucose (SMBG) usually requires intermittent capillary blood sampling and the use of a glucose meter, with different frequencies of testing indicated for type 1 and type 2 diabetes. Devices to sample the glucose continuously from interstitial fluid are also available, with ongoing development in progress. Most continuous glucose monitoring (CGM) devices still require some SMBG testing for calibration and to double-check high and low CGM values. (See 'Continuous glucose monitoring' below.)

Indications — Based upon the results of randomized trials, we suggest SMBG in patients who take medications that can cause hypoglycemia and that need to be adjusted based on ambient glucose levels.

Type 1 diabetes — SMBG is an integral part of intensive therapy aimed at achieving near-normal glycemia in type 1 diabetes, which is widely accepted as recommended therapy owing to its benefits. Ideally, testing at home should be done four to seven times daily (before and 90 to 120 minutes after meals, before bedtime, and, occasionally for safety, at 3 AM). Additionally, it is useful to test blood glucose levels before, during, and after exercise. Patients with hypoglycemia unawareness may need to test more frequently, particularly prior to driving or operating any machinery, watching small children, and other activities where compromise of cognitive function may be dangerous.

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Literature review current through: Nov 2017. | This topic last updated: Nov 17, 2017.
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