Why are my CGM readings unusually high?

Food and drink
High-carbohydrate meals, sugary drinks, alcohol, or late-night eating can all push glucose higher than expected.

Stress, illness, or poor sleep
Physical or emotional stress, infection, inflammation, or sleep disruption can increase stress hormones (like cortisol), which raise glucose levels.

Dehydration
Being under-hydrated can lead to higher interstitial glucose readings.

Medications and supplements
Some medications (such as steroids) and supplements can increase glucose levels.

Morning hormone response (dawn phenomenon)
Glucose may rise in the early morning due to normal hormonal changes, even without food.

Lag time
There is typically a 5–10 minute delay between blood glucose and CGM readings. This is most noticeable after meals, exercise, or during rapid glucose changes.

Early sensor behaviour
In the first 24 hours after applying a new sensor, readings may be less stable while the sensor settles. This usually improves on its own.

Compression effects
Pressure on the sensor (for example, sleeping on it) can temporarily affect readings. When pressure is removed, readings may briefly appear higher.

Heat exposure
Saunas, steam rooms, hot baths, or prolonged sun exposure can affect sensor performance and lead to unreliable readings.

Extreme cold
Very cold environments can slow glucose movement in interstitial fluid, creating discrepancies.

Interfering substances
High doses of vitamin C, some painkillers, and certain medications can falsely elevate CGM readings.

Don’t match how you feel

Change very rapidly

Remain unusually high without an obvious reason