01/02/2026
How reliable are CGMs for detecting hypos?
Continuous Glucose Monitors (CGMs) are brilliant for trends and early warnings - but they don’t always reflect your exact blood glucose in that moment.
CGMs are around 90% accurate overall, but less accurate when glucose is changing fast.
CGMs measure glucose in interstitial fluid, NOT blood.
So when glucose is dropping fast, there can be a lag of around 5–10 minutes.
That means you may feel hypo symptoms, while your CGM still looks “okay”.
👉 when your symptoms don’t match the CGM readings, a finger-prick can provide a real-time BGL.
👉 check the CGM trend arrows to see how fast your BGL is falling. The number + the direction + how you feel tells the full story.
🏵️Tip #1: catch hypos early
Set your low alert higher than hypo range, around 4.2 - 4.5mmol/L (81 mg/dL) to allow time to act early with long-acting carb, and prevent the drop.
🏵️Tip #2: trust your finger-prick
For the most accurate reading:
✳ use a well-maintained, in-date glucometer
✳ wash your hands with soap and water and dry them thoroughly before testing
Residue on fingers or an old meter can skew results, especially during hypos.
👉 The bottom line:
✳ CGMs guide you.
✳ Finger-pricks confirm real-time levels.
✳ Early alerts + the right carbs can stop a hypo before it fully lands.
see more about hypos 👉 hypoduo.com