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Time in range to A1c
The A1c your CGM time in range predicts. Runs in your browser; nothing is sent anywhere.
Where the number comes from
Beck and colleagues (2019) compared CGM time in range with lab A1c in adults with type 1 from four clinical trials. On average, a time in range of 70% went with an A1c near 7%, and 50% with an A1c near 8%. A 10-point rise in time in range came with an A1c about 0.6 points lower.
The average hides a wide spread. At 70% time in range, the study's 95% range for one person runs from 5.6% to 8.3%. That is why the calculator shows a band under the number. Two people with the same time in range can have lab A1c results more than 2 points apart.
The formula
- A1c (%) = 10.31 − 0.048 × time in range (%), from the study's baseline data, 455 adults
- A1c (mmol/mol) = 10.93 × A1c (%) − 23.50, the NGSP to IFCC conversion
The study's table covers 20% to 90% time in range. Outside it the calculator still gives the formula's number, but no band.
Time in range to A1c chart
| Time in range | A1c | mmol/mol | 95% range, one person |
|---|---|---|---|
| 20% | 9.4% | 79 | 8.0–10.7% |
| 30% | 8.9% | 74 | 7.6–10.2% |
| 40% | 8.4% | 68 | 7.1–9.7% |
| 50% | 7.9% | 63 | 6.6–9.2% |
| 60% | 7.4% | 57 | 6.1–8.8% |
| 70% | 7.0% | 53 | 5.6–8.3% |
| 80% | 6.5% | 48 | 5.2–7.8% |
| 90% | 6.0% | 42 | 4.7–7.3% |
Rows from the study's baseline table (Beck et al., 2019). The 2019 consensus sets a time in range above 70% as the goal for most people with type 1. Glide's Insights tab shows time in range for the last 14 days beside GMI and GRI.