Glucose monitoring in diabetes

Red Flags

Recurrent or severe hypoglycaemia (≥1 episode <54 mg/dL or any requiring assistance) — escalate to CGM; reassess insulin or sulfonylurea doses^[1]
Hypoglycaemia unawareness (no symptoms below 70 mg/dL) — strict avoidance of further hypoglycaemia for 2–3 weeks; CGM essential^[1]
DKA or HHS history despite reportedly good adherence — CGM uncovers nocturnal patterns, missed insulin, and misalignment of food and dosing^[1]
Pregnancy with T1DM or insulin-treated T2DM — CGM with time-in-range >70% target reduces large-for-gestational-age infants^[1]

First-line treatment

Interventions

Structured fingerstick SMBG^[1]
T1DM: 4–10 tests/day. T2DM on insulin: pre-meal and bedtime. T2DM on oral therapy: paired pre-/post-prandial during structured education only — routine SMBG without structured use does not improve outcomes
Continuous glucose monitoring (CGM)^[1]
Real-time CGM (Dexcom G7, Libre 3) or intermittently scanned (FreeStyle Libre 2) — all T1DM; insulin-treated T2DM with frequent hypoglycaemia or HbA1c persistently above target; pregnancy
Hybrid closed-loop (automated insulin delivery) systems^[1]
T1DM with frequent hypoglycaemia or wide glucose variability; specialist initiation; significantly reduces hypoglycaemia and improves TIR
Structured CGM data interpretation^[1]
Ambulatory glucose profile (AGP) review with patient at every visit — identify post-prandial spikes, dawn phenomenon, nocturnal hypoglycaemia; adjust regimen accordingly
Targets per population^[1]
General adults: HbA1c <7%, TIR ≥70%. Older or frail: HbA1c <8%, TIR ≥50%. Pregnancy: HbA1c <6.5%, TIR (63–140 mg/dL) ≥70%

Safety-net

Calibrate CGM as per device instructions; trust validated devices but verify with fingerstick if symptoms don't match the reading^[1]
If hypoglycaemia symptoms occur — eat 15g rapid-acting carbohydrate, recheck in 15 min, repeat as needed; severe (loss of consciousness) needs glucagon or A&E^[1]
Sick-day rules: check glucose more frequently when ill; ketone testing if T1DM with glucose >250^[1]

Referral criteria

Recurrent severe hypoglycaemia or hypoglycaemia unawarenessDiabetes specialist for CGM and possible hybrid closed-loop^[1]
Pregnancy with insulin-treated diabetesJoint diabetes-obstetric care with CGM^[1]
T1DM not on CGMDiabetes specialist for CGM initiation^[1]
T2DM with persistent above-target HbA1c despite multiple agentsDiabetes specialist; consider CGM diagnostically^[1]

Clinical summary

Self-monitoring strategies for diabetes — fingerstick blood glucose, continuous glucose monitoring (CGM), and HbA1c surveillance with structured interpretation.

References

1.RSSDI Expert Consensus for Optimal Glucose Monitoring in Diabetes (2024); ADA Standards of Care 2026 (2024)