Routine self-monitoring of blood glucose

Clinical question

What are the pros and cons of routine self-monitoring of blood glucose (SMBG) for patients with type 2 diabetes (T2D) who do not use insulin?

Evidence

• Recent meta-analyses^1–3 examined routine SMBG in patients with T2D who do not use insulin.

  • -Largest analysis had 26 studies with 5373 patients.¹
  • -With SMBG, HbA_1c levels improved 0.21% to 0.31%.^1–3
• Only 3 of the trials that compared SMBG with no SMBG were of high quality.¹

  • -A 6-month trial (DINAMIC study)⁴ found

    • —SMBG improved HbA_1c by 0.25% (P = .0097) and
    • —no difference in weight, fasting glucose, or gliclazide dose.
  • -Two 12-month trials (DiGEM⁵ and ESMON⁶) found no difference in HbA_1c levels, drug initiation, or weight.

• Self-monitoring of blood glucose has not been shown to attain a minimum clinically important difference in HbA_1c (≥ 0.5%)⁷ in any meta-analysis or high-quality trial.

Context

• Important harms of routine SMBG include worsening of depression scores,^6,8 reduced quality of life,^8,9 and poor value for dollar^9,10; in patients with T2D who do not use insulin, there is also little to no clinical value.

  • -This evidence does not apply to patients with T2D who use insulin, patients with T1D, or pregnant patients with gestational diabetes.
• Reasons for nonroutine blood glucose testing include

  • -having symptoms of hypoglycemia or feeling unwell, as these symptoms often do not correlate well with actual blood sugar levels,¹¹
  • -seeing the effects of changes to medication, diet, or lifestyle behaviour on sugar status, and
  • -nonroutine circumstances (eg, driving).

Bottom line

Routine SMBG in patients with T2D who do not use insulin has no clinical benefits, is not cost-effective, and reduces the quality of life.

Implementation

The burden of SMBG should be minimized to the amount necessary to inform decision making. For patients with T2D who use only oral medications, routine SMBG rarely leads to changes in management, so discouraging this might benefit patients. Reactive SMBG (eg, in response to symptoms or specific circumstances) remains appropriate. Patients taking medications that can cause hypoglycemia require education on recognizing and managing these symptoms. The National Diabetes Information Clearinghouse website has handouts available (http://diabetes.niddk.nih.gov/dm/pubs/hypoglycemia/index.aspx).

Tools for Practice articles in Canadian Family Physician are adapted from articles published twice monthly on the Alberta College of Family Physicians (ACFP) website, summarizing medical evidence with a focus on topical issues and practice-modifying information. The ACFP summaries and the series in Canadian Family Physician are coordinated by Dr G. Michael Allan, and the summaries are co-authored by at least 1 practising family physician. Feedback is welcome and can be sent to toolsforpractice@cfpc.ca. Archived articles are available on the ACFP website: www.acfp.ca.