Assess understanding of how CGM data differ from SMBG data
STEP 1 — Gather Information
Collect device model, wear time, frequency of data review, recent SMBG log, and ask the patient to describe what they see on the CGM screen (numeric value, trend arrows) and what they do with fingerstick results.
STEP 2 — Rule In / Rule Out
Determine if the patient correctly states that CGM measures interstitial glucose with a physiological lag (≈5‑15 min) and displays direction/trend arrows, whereas SMBG provides an instantaneous capillary glucose at a single point in time. If yes, rule in understanding; if not, rule out.
STEP 3 — Classify or Stratify
Classify understanding into: (A) Full – explains lag, trend arrows, and uses trend data for insulin decisions; (B) Partial – knows CGM gives a number but confuses with SMBG or misses lag/trend; (C) None – believes CGM and SMBG are identical or does not know what trend arrows mean. Assign the patient to the appropriate tier.
STEP 4 — Decide
Based on tier: (A) Reinforce and advance to trend‑based dosing strategies; (B) Provide focused teaching on lag, trend interpretation, and calibration requirements; (C) Initiate basic CGM education covering device components, difference from SMBG, and need for confirmatory fingersticks.
Clinical Guardrails / Mimics / Pitfalls
Do not assume that wearing CGM equates to understanding; avoid relying solely on self‑report without probing trend interpretation; do not let patients adjust insulin based solely on CGM without confirmatory SMBG if the device requires calibration; watch for alarm fatigue that may cause patients to ignore trend alerts.
Concrete Clinical Example
A 58‑year‑old with type 1 diabetes wearing a Dexcom G6 reports seeing “120 with an upward arrow.” When asked what the arrow means, they say “My sugar is going up.” They note a fingerstick might differ due to lag and plan to check a fingerstick before dosing if the arrow is steep. This shows partial‑to‑full understanding; the clinician reinforces trend‑based dosing and confirms the calibration schedule.
Source: Diabetes Technology—Continuous Subcutaneous Insulin Infusion Therapy and Continuous Glucose Monitoring in Adults: An Endocrine Society Clinical Practice Guideline, Endocrine Society, 2016, doi:10.1210/jc.2016-2534