Self-Monitoring of Blood Glucose

SMBG is an effective way to evaluate short-term glycemic control. It helps patients and physicians assess the affect of food, medications, stress, and activity on blood glucose levels. The frequency of checking depends on the type of medical therapy, risk for hypoglycemia, and need for short-term adjustment of therapy.

For patients with type 1 diabetes mellitus (T1DM) and insulin-dependent type 2 diabetes (T2DM) patients, clinical trials have demonstrated that SMBG plays a role in effective glycemic control because it helps to refine and adjust insulin doses by monitoring for and preventing asymptomatic hypoglycemia and preprandial and postprandial hyperglycemia.^2,4–5,7 The current American Diabetes Association (ADA) guidelines recommend that T1DM patients self-monitor their glucose at least three times per day. Those who use basal–bolus regimens should self-monitor before each meal and at bedtime (four times daily). Initially some patients require more frequent monitoring, including both preprandial and postprandial readings. Patients with gestational diabetes who are taking insulin should monitor their blood glucose three or more times daily. Patients should be educated on how to use real-time blood glucose values to adjust their food intake and medical therapy.

It is commonly recommended that T2DM patients who use insulin self-monitor their blood glucose levels, but the evidence to support the effectiveness of this practice is inconclusive. Initial studies showed that SMBG in T2DM patients results in reduction in HbA_1c, but the inclusion of health-improving behavior such as diet and exercise in many of the analyses made it difficult to assess the degree of contribution of SMBG alone.^2,9 Follow-up studies that attempted to correct for this found there was not a significant improvement in glycemic control after 12 months.⁸

It is important to establish individual goals with patients regarding target blood glucose measurements. The ADA recommends preprandial blood glucose levels in nonpregnant adults to be 70 to 130 mg/dL and less than 180 mg/dL for peak postprandial levels.^10,12 The ADA’s goals for gestational diabetes is preprandial blood glucose 95 mg/dL or less and either 1 hour postprandial glucose no more than 140 mg/dL or 2 hours postprandial no more than120 mg/dL. For pregnant women with preexisting T1DM or T2DM, goals are preprandial, bedtime, and overnight glucose levels of 60 to 99 mg/dL and peak postprandial levels between 100 and 129 mg/dL.¹² The American Association of Clinical Endocrinologists (AACE) recommends in nonpregnant adults a fasting blood glucose level lower than 110 mg/dL and a 2-hour postprandial level lower than 140 mg/dL.¹¹

Hemoglobin A_1c

HbA_1c measures nonreversible glycosylation of the hemoglobin molecule, which is directly related to blood glucose concentrations. It reflects a mean of the patient’s blood glucose values over a 2- to 3-month period and can be used as a predictor of a patient’s risk of microvascular complications.¹³ Periodic testing is recommended in all patients with diabetes. The frequency of testing depends on the clinical situation and the patient’s treatment regimen. The ADA recommends that patients with stable glycemic control be tested at least twice a year. Quarterly testing is suggested for those with a recent change in therapy or not meeting glycemic goals.¹²

HbA_1c testing does have some limitations. HbA_1c is influenced by rapid red blood cell turnover and blood loss; therefore, anemia and hemoglobinopathies can result in inaccurate values. Physicians should consider these conditions when there is a discrepancy between HbA_1c and SMBG values. Episodes of hypoglycemia and hyperglycemia cannot be determined with HbA_1c values alone. Table 1, adapted from the ADA’s 2009 Executive Summary on diabetes management, demonstrates that correlation between HbA_1c and average blood glucose values.

Table 1 Correlation between HbA_1c and Average Blood Glucose Values

Traditionally it has been recommended that therapy be adjusted to maintain HbA_1c values near or less than 7% in nonpregnant adults. This target has been shown to reduce microvascular complications. For patients with T1DM or T2DM who become pregnant, the goal is less than 6.0%.¹² The AACE recommended an HbA_1c of less than 6.5% in nonpregnant adults.¹¹ The ADA recommends that selected patients, especially those with a long life expectancy and little comorbidity, adopt glycemic targets close to normal, providing the target can be achieved without significant hypoglycemia.¹²

Insulin Sensitizers

Insulin Secretagogues

Insulin secretagogues stimulate secretion of insulin from the pancreas, thereby decreasing hepatic glucose production and enhancing glucose uptake by muscles and fat.

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