It depends on the person.
For some, 53 is too low, because they can only reach that number through many hypos, for others below 40 is fine because they can reach that hba1c without many hypos.
Things have changed now so many people are using CGM. With a T1 who takes a fingerprick 4 times a day it makes sense to assume lots of hypos are happening.
But if they use a CGM you get an overview of what's happening all day, no more hidden nighttime hypos and such.
The last serious hypo I had was about 16 years ago
It's not only about the serious hypos with symptoms, it's also about going below 4 without noticing. Someone who only feels symptoms at 2.5 can be having hypos all the time without even knowing, if they rely on fingerpricks.
Not safe or healthy.
But if you notice your hypos at around 4, it's fine to have a low hba1c.
Mine is below 40, and my endo is happy with that, but if I didn't have the Libre I'd definitely be higher, for safety reasons! With the Libre I'm happy to be hovering in the higher 4's and lower 5's, because I know I'll notice if it starts dropping and I can prevent going below 4.
But if i saw a 4.8 on a fingerprick being out and about, and I'd have to wait hours before testing again, I wouldn't feel safe, and I'd likely nudge it up a little as a precaution.
)
