High levels in the night

Did you retest? This happens to me quite a lot as I suffer disturbed sleep but it has never been as high as the teens.

Did you wake up in the middle of the night or was this a first-thing-in-the-morning reading?
I ask because the rise may be relatively recent and not through the night. I am referring to Dawn Phenomenon where our body releases glucose to give us the energy to get up in the morning. This is normal for everyone. Those with healthy pancreases release insulin to convert the glucose to energy.