A time-series forecasting extension for pydexcom using Google's TimesFM. Readings from the previous 24 hours are captured from the Dexcom Share API service and fed into the model to create a forecast of blood glucose values for the next hour.
All modelling and forecasting is performed locally on your device. The only external connections made are with:
- Dexcom Share API: fetching CGM readings following the
pydexcomapproach.- HuggingFace: one-time download of the forecasting model weights on the first run.
- Ensure that you have also installed the
pydexcompackage and enabled the Share service within your Dexcom G7 / G6 / G5 / G4 mobile app.
pip install pydexcom forecose
- Initialise
pydexcomwith your Dexcom credentials (below shows the simplist route, refer to pydexcom for further instruction).
>>> from pydexcom import Dexcom
>>> dexcom = Dexcom(username="username", password="password")- Generate a prediction. By default, the
DexcomForecastclass predicts the upcoming hour (the next 12 readings) to prevent overextending the forecast. Set custom prediction lengths by adjusting thehorizonargument.
>>> from forecose import DexcomForecast
>>> predictions = DexcomForecast(horizon=12).get_forecast(dexcom)
>>> print(predictions)
timestamp predicted_glucose q10 q25 q50 q75 q90
0 2026-06-30 11:56:43.332500+01:00 156.0 156.0 147.0 155.0 159.0 162.0
1 2026-06-30 12:01:43.332000+01:00 159.0 159.0 142.0 156.0 165.0 169.0
2 2026-06-30 12:06:43.331500+01:00 160.0 159.0 137.0 156.0 169.0 176.0
3 2026-06-30 12:11:43.331000+01:00 160.0 161.0 132.0 155.0 172.0 180.0
4 2026-06-30 12:16:43.330500+01:00 162.0 161.0 128.0 156.0 176.0 185.0
5 2026-06-30 12:21:43.330000+01:00 162.0 162.0 125.0 155.0 177.0 188.0
6 2026-06-30 12:26:43.329500+01:00 163.0 164.0 120.0 155.0 180.0 192.0
7 2026-06-30 12:31:43.329000+01:00 162.0 162.0 116.0 153.0 181.0 194.0
8 2026-06-30 12:36:43.328500+01:00 162.0 162.0 113.0 152.0 183.0 197.0
9 2026-06-30 12:41:43.328000+01:00 161.0 161.0 109.0 151.0 183.0 197.0
10 2026-06-30 12:46:43.327500+01:00 162.0 162.0 107.0 151.0 186.0 201.0
11 2026-06-30 12:51:43.327000+01:00 161.0 160.0 104.0 149.0 186.0 201.0
>>> print(predictions.mmol_l)
timestamp predicted_glucose q10 q25 q50 q75 q90
0 2026-06-30 11:56:43.332500+01:00 8.7 8.7 8.2 8.6 8.8 9.0
1 2026-06-30 12:01:43.332000+01:00 8.8 8.8 7.9 8.7 9.2 9.4
2 2026-06-30 12:06:43.331500+01:00 8.9 8.8 7.6 8.7 9.4 9.8
3 2026-06-30 12:11:43.331000+01:00 8.9 8.9 7.3 8.6 9.5 10.0
4 2026-06-30 12:16:43.330500+01:00 9.0 8.9 7.1 8.7 9.8 10.3
5 2026-06-30 12:21:43.330000+01:00 9.0 9.0 6.9 8.6 9.8 10.4
6 2026-06-30 12:26:43.329500+01:00 9.0 9.1 6.7 8.6 10.0 10.7
7 2026-06-30 12:31:43.329000+01:00 9.0 9.0 6.4 8.5 10.0 10.8
8 2026-06-30 12:36:43.328500+01:00 9.0 9.0 6.3 8.4 10.2 10.9
9 2026-06-30 12:41:43.328000+01:00 8.9 8.9 6.0 8.4 10.2 10.9
10 2026-06-30 12:46:43.327500+01:00 9.0 9.0 5.9 8.4 10.3 11.2
11 2026-06-30 12:51:43.327000+01:00 8.9 8.9 5.8 8.3 10.3 11.2predicted-glucose: The average trajectory of your blood sugar forecast (smoothed, centred baseline of the confidence bands).q10toq90: The range of confidence bands provide a realistic upper and lower estimate boundaries, showing the full probability distribution of predicted glucose values.
To account for key events (e.g., insulin administration or carbohydrate (carbs) intake) that act on blood glucose values without distorting the underlying TimesFM probability distribution, you can apply a deterministic overlay to your baseline forecast.
Drawing on mathematical frameworks utilised in closed-loop Artifical Pancreas systems and the Hovorka/Bergman meal submodels, event impacts are computed as a second-order linear delay process. Here, event unit rates (e.g., the absorption of insulin or carbs) are translated into a physiological curve that begins slowly, reaches a peak, and then gradually decays over time.
By default, forecose updates the forecast predictions using standard clinical baselines (a 55-minute peak for insulin, and a 40-minute peak for carbs):
>>> carb_predictions = predictions.add_event(type="carbs", units=30, minutes_ago=0)
>>> print(carb_predictions.mmol_l)
timestamp predicted_glucose q10 q25 q50 q75 q90
0 2026-06-30 11:56:43.332500+01:00 8.7 8.7 8.2 8.7 8.9 9.0
1 2026-06-30 12:01:43.332000+01:00 9.0 9.0 8.0 8.8 9.3 9.5
2 2026-06-30 12:06:43.331500+01:00 9.3 9.2 8.0 9.0 9.8 10.2
3 2026-06-30 12:11:43.331000+01:00 9.5 9.5 7.9 9.2 10.2 10.6
4 2026-06-30 12:16:43.330500+01:00 9.9 9.8 8.0 9.5 10.7 11.2
5 2026-06-30 12:21:43.330000+01:00 10.2 10.2 8.1 9.8 11.0 11.6
6 2026-06-30 12:26:43.329500+01:00 10.5 10.5 8.1 10.0 11.4 12.1
7 2026-06-30 12:31:43.329000+01:00 10.8 10.8 8.2 10.3 11.8 12.5
8 2026-06-30 12:36:43.328500+01:00 11.0 11.0 8.3 10.5 12.2 13.0
9 2026-06-30 12:41:43.328000+01:00 11.3 11.3 8.4 10.8 12.5 13.3
10 2026-06-30 12:46:43.327500+01:00 11.7 11.7 8.6 11.0 13.0 13.8
11 2026-06-30 12:51:43.327000+01:00 11.9 11.8 8.7 11.2 13.3 14.1
>>> insulin_predictions = predictions.add_event(type="insulin", units=5, minutes_ago=0)
>>> print(insulin_predictions.mmol_l)
timestamp predicted_glucose q10 q25 q50 q75 q90
0 2026-06-30 11:56:43.332500+01:00 8.6 8.6 8.1 8.5 8.8 8.9
1 2026-06-30 12:01:43.332000+01:00 8.7 8.7 7.7 8.5 9.0 9.2
2 2026-06-30 12:06:43.331500+01:00 8.5 8.5 7.3 8.3 9.0 9.4
3 2026-06-30 12:11:43.331000+01:00 8.3 8.4 6.8 8.0 9.0 9.4
4 2026-06-30 12:16:43.330500+01:00 8.2 8.1 6.3 7.8 8.9 9.4
5 2026-06-30 12:21:43.330000+01:00 7.8 7.8 5.8 7.4 8.7 9.3
6 2026-06-30 12:26:43.329500+01:00 7.5 7.6 5.2 7.1 8.5 9.2
7 2026-06-30 12:31:43.329000+01:00 7.2 7.2 4.6 6.7 8.2 8.9
8 2026-06-30 12:36:43.328500+01:00 6.8 6.8 4.1 6.2 7.9 8.7
9 2026-06-30 12:41:43.328000+01:00 6.4 6.4 3.5 5.8 7.6 8.4
10 2026-06-30 12:46:43.327500+01:00 6.0 6.0 3.0 5.4 7.4 8.2
11 2026-06-30 12:51:43.327000+01:00 5.6 5.6 2.4 4.9 7.0 7.8Sensitivity to insulin (ISF) and carbohydrates (CSF) is set at 40 mg/dL per 1U and 4 mg/dL per gram, respectively. These values are placeholders meant to represent reasonable values and should be adjusted through the add_event method using the tau and sensitivity parameters. In future, I hope to develop a method for calculating estimate values from historic data.
>>> insensitive_insulin_predictions = predictions.add_event(type="insulin", units=5, minutes_ago=0, sensitivity=20.0)
>>> print(insensitive_insulin_predictions.mmol_l)
timestamp predicted_glucose q10 q25 q50 q75 q90
0 2026-06-30 11:56:43.332500+01:00 8.7 8.7 8.2 8.6 8.8 9.0
1 2026-06-30 12:01:43.332000+01:00 8.8 8.8 7.8 8.6 9.1 9.3
2 2026-06-30 12:06:43.331500+01:00 8.7 8.7 7.4 8.5 9.2 9.6
3 2026-06-30 12:11:43.331000+01:00 8.6 8.7 7.0 8.3 9.3 9.7
4 2026-06-30 12:16:43.330500+01:00 8.5 8.5 6.7 8.2 9.3 9.8
5 2026-06-30 12:21:43.330000+01:00 8.4 8.4 6.4 8.0 9.3 9.9
6 2026-06-30 12:26:43.329500+01:00 8.3 8.4 5.9 7.9 9.3 9.9
7 2026-06-30 12:31:43.329000+01:00 8.0 8.0 5.5 7.5 9.1 9.8
8 2026-06-30 12:36:43.328500+01:00 7.9 7.9 5.2 7.3 9.0 9.8
9 2026-06-30 12:41:43.328000+01:00 7.7 7.7 4.8 7.1 8.9 9.7
10 2026-06-30 12:46:43.327500+01:00 7.5 7.5 4.5 6.9 8.9 9.7
11 2026-06-30 12:51:43.327000+01:00 7.3 7.2 4.1 6.6 8.7 9.5