The little dude kept saying he felt low so they kept checking.
Way to go!
First and foremost trust a child that says they don't feel right, there are long term implications of that trust as significant as the short term implications of a low. Kids need to know that we respect what they feel. Hopefully they see that and since we respect them they should respect them selfs too.
Meters are lagging indicators I don't know how or why blood drops rapidly but there are plenty of folks who've see it. Maybe it is because blood takes time to move around, I don't know. We have seen rapid changes, and I will not discount that it happens. This is one of the issues that makes people worry about CGM as the fluid they test is even more of a lag than blood.
Some insulins are less predictable than others. NPH can be great one day and hit like a ton of bricks the next. So who knows maybe this was one of NPH's little tricks.
But that why lags happen or how meters work isn't really what it is all about. The big issue is trust and respect. If the kids says they feel low, check. If the meter says something other than what the kids feels keep trusting the child.
Washing fingers and retesting is good sound practice, so is respecting what the child if feeling and saying well maybe you are feeling what happening before the meter shows it and we should keep an eye on it.
Things change. Sometimes they change fast. You want to be sitting back, with grey hair, saying they change, meaning grow up, so fast, what shouldn't change is valuing what kids feel.
I think it was some genius like Plato, Aristotle or Einstein who said YDMV - LOL -
Sometimes what varies is how fast it varies.
Care, respect, love aren't diabetes, they don't vary.
Oh and keep the tabs and glucagon handy.