It's common to notice differences between blood sugar sensor and finger prick glucometer readings. This can be disconcerting, but these variations are normal and expected.

This happens because your sensor doesn’t actually measure blood sugar levels. Rather, it measures the glucose that continuously seeps from blood vessels into interstitial fluid (a thin layer of fluid that surrounds the cells of the tissue just below the skin).

The amount of glucose in your interstitial fluid is a very close proxy of what’s happening in your bloodstream. However, it tends to be delayed by 5-15 minutes – the time it takes the glucose to leak into the interstitial space.

These differences can stack up, especially when your blood sugar levels are rising or falling in the hours after eating.

For this reason, we recommend that you don’t directly compare readings between your sensor and glucometer. Instead, we recommend that you focus more on the shape of the curves you see rather than the absolute numbers.