Continuous Glucose
& Glycemic Variability
Reference for every metric GlucoDex computes from a continuous glucose monitor (CGM) trace — definitions, formulas, target ranges, and the evidence base behind each. The headline figures are the international CGM-consensus metrics; on them GlucoDex layers the established variability and risk indices, a few emerging patterns, and cross-node fusion composites. Companion to the trace; not a substitute for clinical evaluation or your diabetes care team. All values and ranges here are in mg/dL — the CGM-consensus unit GlucoDex computes and exports in; the dashboard adds an optional mg/dL ⇄ mmol/L display switch (display-only, compute stays mg/dL).
The mean of all valid sensor readings — the level around which everything else varies, and the input to GMI.
| Mean (mg/dL) | Approx. control |
|---|---|
| < 140 | Near-normal average |
| 140–180 | Elevated |
| > 180 | High — review with clinician |
Absolute glucose variability. Read alongside CV (consensus prefers CV because SD scales with the mean).
Average absolute rate of change per hour — how briskly glucose moves between samples.
Share of the reporting period with valid sensor data. Consensus guidance wants ≥70% over 14 days for the metrics to be representative.
| % Active | Confidence |
|---|---|
| ≥ 70% | Representative (consensus) |
| 50–70% | Partial — interpret with care |
| < 50% | Insufficient |
Total days of active sensor wear in the analysis. Some indices (ADRR, MODD) require at least two days; the consensus AGP window is 14 days.
| Days | Adequacy |
|---|---|
| ≥ 14 | Full consensus window |
| 3–14 | Partial window |
| < 3 | Too short for inter-day indices |
Minutes of suspected nocturnal compression (lying on the sensor), held out of the time-below-range accounting so a false low does not inflate hypoglycemia. A genuine sharp insulin hypo (sustained sub-70, gradual descent + Somogyi rebound) is now disambiguated from a positional artifact and survives into the nocturnal-hypo count; only a near-vertical, single-cell drop-and-recover is flagged here.
A direct data-quality confidence multiplier reflecting coverage, gaps and flagged artifact.
Count of detected nocturnal sub-70 mg/dL episodes — the most clinically consequential lows, and an input to the hypo↔QTc fusion signal.
| Episodes | Read |
|---|---|
| 0 | None detected |
| 1–2 | Occasional — review |
| ≥ 3 | Recurrent — discuss with clinician |
Number of slope-detected glucose excursions exceeding one SD — the raw count feeding MAGE.
The primary CGM target: percentage of time glucose sits in 70–180 mg/dL. Each 5-point gain in TIR is clinically meaningful; the consensus goal for most adults is >70%.
| TIR | Read |
|---|---|
| > 70% | At target (consensus) |
| 50–70% | Below target |
| < 50% | Well below target |
An estimated HbA1c-equivalent computed from mean glucose. A modelled estimate that can differ from a lab HbA1c by ±0.3% or more — see GMI vs Lab.
| GMI | Read |
|---|---|
| < 6.5% | At/near target |
| 6.5–7.5% | Above target |
| > 7.5% | High — review |
The ADAG study’s mean-glucose-to-A1c regression — an alternative estimate to GMI using a different coefficient set.
| eA1c | Read |
|---|---|
| < 6.5% | At/near target |
| 6.5–7.5% | Above target |
| > 7.5% | High |
Glucose variability normalised to the mean — the consensus stability metric. Above 36%, hypoglycemia risk rises sharply.
| CV | Read |
|---|---|
| < 36% | Stable (consensus) |
| ≥ 36% | Unstable — elevated hypo risk |
Total time below 70 mg/dL — overall hypoglycemia exposure (TBR level 1 + 2 combined).
| Time Below | Read |
|---|---|
| < 4% | At target (consensus) |
| 4–10% | Above target |
| > 10% | High hypo exposure |
Total time above 180 mg/dL — overall hyperglycemia exposure (TAR level 1 + 2 combined).
| Time Above | Read |
|---|---|
| < 25% | At target (consensus) |
| 25–50% | Above target |
| > 50% | High hyper exposure |
Time in the tighter 70–140 mg/dL band — a more demanding target introduced in the 2023 trial-metrics consensus, relevant for near-normal glycemia goals.
| TITR | Read |
|---|---|
| > 50% | Strong tight control |
| 30–50% | Moderate |
| < 30% | Limited tight control |
Time in 54–69 mg/dL — level-1 hypoglycemia.
| TBR 54–69 | Read |
|---|---|
| < 4% | At target |
| ≥ 4% | Above target |
Time below 54 mg/dL — clinically significant level-2 hypoglycemia.
| TBR <54 | Read |
|---|---|
| < 1% | At target |
| ≥ 1% | Above target — act |
Time in 181–250 mg/dL — level-1 hyperglycemia.
Time above 250 mg/dL — level-2 hyperglycemia.
| TAR >250 | Read |
|---|---|
| < 5% | At target |
| ≥ 5% | Above target |
Average size of glucose swings exceeding one SD — the classic variability index, sensitive to large meal/treatment excursions.
Average absolute difference between glucose at the same clock time on consecutive days — day-to-day reproducibility. Needs ≥2 days.
SD of the differences between readings a fixed interval apart (commonly 1, 2 or 4 h) — intra-day variability at a chosen timescale.
A single index combining mean level and variability into one number.
| J-index | Read |
|---|---|
| < 20 | Good control |
| 20–40 | Fair |
| > 40 | Poor |
A risk score weighting each reading by its log-scaled deviation from euglycemia — penalises both highs and lows.
A symmetric daily risk index capturing both hypo- and hyperglycemic excursions equally. Needs ≥2 days of data.
| ADRR | Risk |
|---|---|
| < 20 | Low |
| 20–40 | Moderate |
| > 40 | High |
A risk-weighted measure of hypoglycemia exposure — emphasises how far and how often glucose drops low.
| LBGI | Hypo risk |
|---|---|
| < 1.1 | Minimal |
| 1.1–2.5 | Low–moderate |
| > 2.5 | Moderate–high |
A risk-weighted measure of hyperglycemia exposure — the upper-range counterpart of LBGI.
| HBGI | Hyper risk |
|---|---|
| < 4.5 | Low |
| 4.5–9 | Moderate |
| > 9 | High |
Variability as the extra path-length the glucose trace travels versus a flat line — a geometric variability measure that captures both amplitude and frequency.
The pre-breakfast glucose rise from the 03–06h nadir — a circadian counter-regulatory pattern that can drive morning highs.
| Dawn rise | Read |
|---|---|
| < 20 mg/dL | Minimal |
| 20–40 mg/dL | Moderate |
| > 40 mg/dL | Marked dawn effect |
The rate-corrected QT interval imported from ECGDex when available — paired with nocturnal hypoglycemia to flag the hypo↔QTc pattern below.
| QTc (ms) | Read |
|---|---|
| < 450 | Normal |
| 450–480 | Borderline |
| > 480 | Prolonged |
A 0–100 stability headline blending time-in-range, CV and hypoglycemia exposure.
A directional insulin-resistance risk band from glycemic level/variability and autonomic inputs.
A composite autonomic-risk signal combining ECGDex overnight slope, surges and coupling with glycemic context.
A composite variability index blending CV, MAGE and the dawn rise — a single fusion input for the Integrator.
A directional composite flagging the coincidence of nocturnal hypoglycemia and prolonged QTc — the “dead-in-bed” risk pattern. A screening signal, not a diagnosis.
The gap between GMI and a lab HbA1c when one is entered. GMI reflects recent mean glucose; lab A1c reflects red-cell glycation over months — a delta is expected, not an error.
Sensor mean glucose versus the estimated average glucose implied by a lab A1c — a sensor-calibration sanity check.
Validation refers to the underlying metric’s validation in published literature/consensus, and does not imply validation of the GlucoDex implementation against a gold-standard laboratory dataset.
| Metric Category | Status | Basis |
|---|---|---|
| TIR / TITR / TBR / TAR / CV targets | ● Consensus | International CGM consensus; Battelino 2019 / 2023 |
| GMI · Estimated A1c | ● Literature-based | Bergenstal 2018; Nathan/ADAG 2008 |
| Mean / SD / MAG / coverage | ● Direct measurement | Raw sensor statistics |
| MAGE · MODD · CONGA · J-index | ● Literature-based | Service 1970; McDonnell 2005; Wójcicki 1995 |
| GRADE · ADRR · LBGI · HBGI | ● Literature-based | Hill 2007; Kovatchev 2006 |
| GVP · Dawn phenomenon | ◐ Emerging | Published but less standardized / device-dependent |
| QTc (fusion) | ● Literature-based | Bazett rate correction, computed by ECGDex |
| Stability · IR-risk · Autonomic · Hypo↔QTc · GMI-vs-lab | ○ Experimental composite | GlucoDex / fusion internal algorithms; no independent validation |
| Tier | Meaning | Examples |
|---|---|---|
| Core | Consensus-supported, universally interpretable | TIR, GMI, CV, Time Below/Above |
| Advanced | Published support, less common in routine review | TITR, MAGE, LBGI/HBGI, dawn rise |
| Research | Exploratory / emerging / composites — interpret with caution | GRADE, ADRR, fusion composites |
| Metric / Formula | Primary Citation | Category |
|---|---|---|
| TIR / TBR / TAR / CV targets | Battelino 2019 (consensus) | Consensus |
| TITR (tight range) | Battelino 2023 (trial metrics) | Consensus |
| GMI = 3.31 + 0.02392·mean | Bergenstal 2018 | Index |
| eA1c = (mean+46.7)/28.7 | Nathan / ADAG 2008 | Index |
| MAGE | Service 1970 | Variability |
| CONGA | McDonnell 2005 | Variability |
| J-index = 0.001·(mean+SD)² | Wójcicki 1995 | Variability |
| GRADE | Hill 2007 | Risk |
| ADRR / LBGI / HBGI | Kovatchev 2006 | Risk |
| QTc (Bazett) | ECGDex (cross-node) | Fusion |
| Stability / IR-risk / Autonomic / Hypo↔QTc | GlucoDex internal — no external source | Internal |
| Formula | Source / Author | Year | Reference |
|---|---|---|---|
| GMI = 3.31 + 0.02392·mean | Bergenstal RM et al. | 2018 | Diabetes Care. 41(11):2275–80 |
| eA1c = (mean+46.7)/28.7 | Nathan DM et al. (ADAG) | 2008 | Diabetes Care. 31(8):1473–8 |
| TIR/TBR/TAR/CV targets | Battelino T et al. | 2019 | Diabetes Care. 42(8):1593–1603 |
| TITR 70–140 | Battelino T et al. | 2023 | Lancet Diabetes Endocrinol. 11(1):42–57 |
| MAGE | Service FJ et al. | 1970 | Diabetes. 19(9):644–55 |
| CONGA | McDonnell CM et al. | 2005 | Diabetes Technol Ther. 7(2):253–63 |
| J-index = 0.001·(mean+SD)² | Wójcicki JM | 1995 | Horm Metab Res. 27(1):41–2 |
| GRADE | Hill NR et al. | 2007 | Diabet Med. 24(7):753–8 |
| ADRR / LBGI / HBGI | Kovatchev BP et al. | 2006 | Diabetes Care. 29(11):2433–8 |
- Interstitial glucose lags blood glucose by ~5–15 min
- Factory-calibrated sensors carry a MARD error band (~8–10%)
- Compression (lying on the sensor) can create false nocturnal lows
- Metrics need ≥70% coverage over 14 days to be representative
- GMI / eA1c are models of mean glucose, not lab HbA1c
- Lab A1c reflects months of red-cell glycation; GMI reflects ~14 days
- A GMI–lab delta is expected, not an error
- Anaemia / haemoglobinopathy can shift lab A1c independent of glucose
- Stability / IR-risk / Autonomic / Hypo↔QTc are internal composites
- Fusion values depend on ECGDex being present and time-aligned
- Variability bands (GVP, MAGE) are relative, not universal cut-points
- Not FDA cleared or CE marked as a medical device
- Not for diagnosis or self-directed insulin/medication dosing
- Personal, research, and wellness use only
- Discuss medication and dosing changes with your care team
| Method / Metric | Primary Citation | Category |
|---|---|---|
| TIR / TBR / TAR / CV targets (consensus) | Battelino T, Danne T, Bergenstal RM, et al. Clinical targets for continuous glucose monitoring data interpretation: recommendations from the international consensus on time in range. Diabetes Care. 2019;42(8):1593–1603. doi: 10.2337/dci19-0028 | Consensus |
| TITR (tight range) & trial metrics | Battelino T, Alexander CM, Amiel SA, et al. Continuous glucose monitoring and metrics for clinical trials: an international consensus statement. Lancet Diabetes Endocrinol. 2023;11(1):42–57. doi: 10.1016/S2213-8587(22)00319-9 | Consensus |
| GMI | Bergenstal RM, Beck RW, Close KL, et al. Glucose Management Indicator (GMI): a new term for estimating A1C from CGM. Diabetes Care. 2018;41(11):2275–2280. doi: 10.2337/dc18-1581 | Index |
| Estimated A1c (ADAG) | Nathan DM, Kuenen J, Borg R, et al. Translating the A1C assay into estimated average glucose values. Diabetes Care. 2008;31(8):1473–8. doi: 10.2337/dc08-0545 | Index |
| MAGE | Service FJ, Molnar GD, Rosevear JW, et al. Mean amplitude of glycemic excursions, a measure of diabetic instability. Diabetes. 1970;19(9):644–55. doi: 10.2337/diab.19.9.644 | Variability |
| CONGA | McDonnell CM, Donath SM, Vidmar SI, et al. A novel approach to continuous glucose analysis utilizing glycemic variation. Diabetes Technol Ther. 2005;7(2):253–63. doi: 10.1089/dia.2005.7.253 | Variability |
| J-index | Wójcicki JM. “J”-index. A new proposition of the assessment of current glucose control in diabetic patients. Horm Metab Res. 1995;27(1):41–2. doi: 10.1055/s-2007-979906 | Variability |
| GRADE | Hill NR, Hindmarsh PC, Stevens RJ, et al. A method for assessing quality of control from glucose profiles. Diabet Med. 2007;24(7):753–8. doi: 10.1111/j.1464-5491.2007.02119.x | Risk |
| ADRR / LBGI / HBGI | Kovatchev BP, Otto E, Cox D, et al. Evaluation of a new measure of blood glucose variability in diabetes. Diabetes Care. 2006;29(11):2433–8. doi: 10.2337/dc06-1085 | Risk |
| QTc (rate-corrected QT) | Imported from ECGDex (Bazett rate correction) — see the ECGDex reference guide. | Fusion |
| Stability / IR-risk / Autonomic / Hypo↔QTc | GlucoDex internal composites — no external source. Directional only. | Internal |
Implementation · Validation · UI/UX
Literature synthesis · Reference formatting
Planicka M. GlucoDex: Continuous Glucose Analysis Node. Version 1.0.0. 2026.