Question from Aurora, Illinois, USA:

My seven year old daughter with type 1 diabetes is on an insulin pump. Two nights ago, she was 153 mg/dl [8.5 mmol/L] at 8 p.m. I tested her again before I went to sleep at 11:00 p.m. and she was 342 mg/dl [19 mmol/L]. I corrected her, tested at 2:00 a.m. and she was 420 [23.3 mmol/L]. Since the correction did not work, I changed her infusion site thinking it wasn’t working and corrected her again. She awoke at 231 mg/dl [12.8 mmol/L] and went to school. All day yesterday, she was running lower than she usually does, but not below 70 mg/dl [3.9 mmol/L].

This morning, I gave her the same breakfast she has every morning, at the same time and sent her to school. The nurse called saying she was 39 mg/dl [2.2 mmol/L] before lunch, the first low she has had since starting school. Since she has the same breakfast at the same time every morning before school, the only explanation I could think of was absorption.

Could it be possible that the insulin from the “bad infusion site” (that I thought was not working and therefore thought she was not getting) could still absorb slowly into her system, during and for 24 hours from the time I changed the site? Can this cause “insulin stacking,” a term I think I’ve heard when extra insulin builds up in the body?

I told the nurse at her school that I would try to find an explanation so that we don’t have to worry so much.