Should patients with type 2 diabetes mellitus who are on oral agents monitor their blood glucose levels?

Published controlled clinical trials provide clear evidence that strict glycemic control reduces the risk of the development of microvascular and macrovascular complications in patients with type 1 and type 2 diabetes mellitus.^1-3 Self-monitoring of blood glucose (SMBG) is an underused but vital part of disease management in patients with diabetes.

From a clinical perspective, SMBG is recommended because it provides 1) real-time reliable blood glucose levels, 2) data to assess the effects of food with both preprandial and postprandial glucose concentrations, 3) quantified symptoms of hypoglycemia, and 4) timely adjustments of therapeutic regimens.⁴ SMBG provides immediate feedback on the effects of nutrition, activity, and stress. SMBG improves a patient’s problem-solving skills for preventing, detecting, and/ or treating blood glucose concentrations that are out of the targeted range. SMBG is a tool to support self-management and a useful guide to assist healthcare providers in assessing therapeutic effectiveness.

Determining blood glucose levels at different times throughout the day allows for the timely identification of hyperglycemia and hypoglycemia and provides valuable information when medication refinement or adjustment is necessary to improve glycemic control. Positive benefits of SMBG have been seen in patients with type 1⁵ and type 2⁶ diabetes mellitus who are receiving insulin. Because of this, there is much consideration being given to the usefulness of SMBG as an instrument in the self-management of patients with type 2 diabetes mellitus who are not treated with insulin.

Data on the effectiveness in SMBG in patients with type 2 diabetes mellitus who are not treated with insulin are still emerging. Most data have come from small cross-sectional studies rather than prospective longitudinal studies. Several newer observational studies have shown that SMBG is associated with improvement in hemoglobin A_1c (HbA_1c) values. Most other studies that have failed to show improvement in HbA_1c values have been small in size or failed to educate or encourage patients to take action based on the results.⁴

A recently published meta-analysis of randomized controlled trials suggests a positive benefit of SMBG in patients with type 2 diabetes mellitus who are not treated with insulin.⁷ Eight randomized controlled trials with a total of 1307 patients were involved in the analysis. The main outcome measure was the effect of SMBG on the difference in HbA_1c reduction between self-monitoring and non–self-monitoring groups. Overall, the effect of SMBG was a statistically significant decrease of 0.39% in HbA_1c compared with controls. Based on data from the UK Prospective Diabetes Study, this reduction in HbA_1c should reduce the risk of microvascular complications by ~14%.⁸ The authors demonstrated that when integrated with proper diabetes education, SMBG as an adjunct to diet, exercise, behavior modification, and medication may contribute to the improvement of glycemic control in patients with type 2 diabetes mellitus who are not receiving insulin. Due to various limitations identified in the studies included in the meta-analysis, these data should be interpreted with caution.

To provide a more clearly defined answer to this question, an adequately powered randomized controlled trial with sufficient follow-up to assess long-term effects should be conducted. Testing frequencies, cost-benefit, patient satisfaction, and quality of life should also be explored.

1. The Diabetes Control and Complications Trial Research Group. Effect of intensive diabetes management on macrovascular events and risk factors in the Diabetes Control and Complications Trial. Am J Cardiol. 1995;75:894-903.
2. The Writing Team for the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Research Group. Effect of intensive therapy on the macrovascular complications of type 1 diabetes mellitus. JAMA. 2002;287:2563-2569.
3. UK Prospective Diabetes Study Group. Tight blood pressure control and risk of macrovascular and microvascular complications in type 2 diabetes: UKPDS 38. BMJ. 1998;317:703-713.
4. Ipp E, Aquino RL, Christenson P. Point: Self-monitoring of blood glucose in type 2 diabetic patients not receiving insulin: the sanguine approach. Diabetes Care. 2005;28:1528-1530.
5. The Diabetes Control and Complications Trial Research Group. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. N Engl J Med. 1993;329:977-986.
6. Karter AJ, Ackerson LM, Darbinian JA, et al. Self-monitoring of blood glucose levels and glycemic control: the Northern California Kaiser Permanente Diabetes registry. Am J Med. 2001;111:1-9.
7. Sarol JN, Nicodemus NA, Tan KM, Grava MB. Self-monitoring of blood glucose as a part of a multi-component therapy among non-insulin requiring type 2 diabetes patients: a meta-analysis (1966-2004). Curr Med Res Opin. 2005;21:173-182.
8. Stratton IM, Adler AI, Neil HA, et al. Association of glycaemia with macrovascular and microvascular complications of type 2 diabetes (UKPDS 35): a prospective observational study. BMJ. 2000;321:405-412.