Do you average blood sugars for diabetes management?

Blood Glucose Management: Averaging vs. Individual Readings

Blood glucose values should not be averaged for diabetes management decisions—instead, use individual readings to guide specific insulin dose adjustments, with particular attention to patterns of fasting, pre-meal, and post-meal values. 1, 2

Why Individual Readings Matter Over Averages

The evidence strongly supports using discrete glucose measurements rather than averaged values for several critical reasons:

• Insulin dosing algorithms require specific glucose values at defined time points (fasting, pre-meal, bedtime) to make safe and effective adjustments, not averaged numbers 3
• Pattern recognition from individual readings identifies when and where glycemic control fails, which averaging obscures—for example, fasting hyperglycemia suggests inadequate basal insulin, while post-meal spikes indicate insufficient prandial coverage 1, 2
• Hypoglycemia detection depends on identifying individual low values (<70 mg/dL), which can be masked when averaged with higher readings 1

The Clinical Framework for Using Individual Glucose Readings

In Hospitalized Patients

• Initiate insulin therapy when blood glucose exceeds 180 mg/dL on two separate measurements, not when an average crosses this threshold 1, 2
• Target individual glucose readings between 140-180 mg/dL for most critically ill and non-critically ill patients 1, 2
• Reassess the insulin regimen when any single blood glucose falls below 100 mg/dL, as this predicts hypoglycemia within 24 hours 2
• Modify treatment immediately when blood glucose drops below 70 mg/dL, unless easily explained by missed meals 2

In Outpatient Settings

• Pre-meal glucose targets of 80-130 mg/dL guide basal insulin adjustments, while post-meal peaks <180 mg/dL inform prandial insulin needs 1
• Patients on intensive insulin regimens should check glucose 6-10 times daily at specific time points: before meals and snacks, at bedtime, occasionally postprandially, before exercise, when suspecting hypoglycemia, and after treating low blood glucose 1
• Software algorithms that adjust insulin dosing every 1-4 weeks based on individual glucose readings (not averages) achieved glycemic targets in >88% of patients with type 2 diabetes 3

Common Pitfalls When Averaging Blood Sugars

Averaging masks critical hypoglycemia: A patient with readings of 50,180,200, and 190 mg/dL has an average of 155 mg/dL (appearing acceptable), but the 50 mg/dL reading represents dangerous hypoglycemia requiring immediate intervention 1

Averaging obscures timing patterns: Consistently elevated fasting glucose (indicating inadequate basal insulin) averaged with normal daytime values may appear acceptable, delaying necessary basal insulin dose increases 1, 2

Treatment decisions require specificity: Basal insulin doses are adjusted based on fasting glucose readings, while prandial insulin is titrated to pre-meal and post-meal values—averaging these together provides no actionable information 1, 2

The Role of HbA1c vs. Individual Glucose Readings

• HbA1c reflects average glucose over 2-3 months but should not replace individual glucose monitoring for day-to-day management decisions 1
• HbA1c targets of <7% for most patients translate to specific glucose targets, but achieving this requires adjusting insulin based on individual readings, not averaged daily values 1
• Racial and ethnic differences affect the HbA1c-glucose relationship, making individual glucose readings even more critical for treatment decisions in diverse populations 1

Practical Algorithm for Using Individual Readings

For hospitalized patients 2:

• Check glucose before meals and at bedtime (minimum 4 times daily)
• If any reading >180 mg/dL on two occasions → initiate insulin
• If any reading <100 mg/dL → reduce insulin doses
• If any reading <70 mg/dL → modify regimen immediately

For outpatient intensive insulin users 1:

• Fasting glucose guides basal insulin adjustments
• Pre-meal glucose guides prandial insulin doses
• Post-meal glucose (1-2 hours after eating) identifies inadequate meal coverage
• Bedtime glucose prevents nocturnal hypoglycemia

Frequency of adjustments matters: Insulin dosing adjusted every 1-4 weeks based on individual glucose patterns (not averages) achieved target HbA1c <7% in 88% of patients without excessive hypoglycemia 3