I have never used thumbs or index fingers. For other fingers I don’t do the center part, just the sides.
When at doctors and they do in office A1C, I do my own lancet (multiclix or fastclix). That was after they once pricked center of index finger before I realized it. Ouch !! Never again.
I can squeeze pretty much any of my fingers hard enough and I’ll get one to bleed enough for a test. Now that’s progress
You can get blood out of any part of the fingers and palms as well. There’s a lot of “real estate” with the hands but tips just get used the most.
I’ve been checking probably 5-15 times a day since I was one year old (I’m 31 now), less during times when I haven’t been able to afford enough strips. The only time I’ve had an issue is if the lancet device is set to a really low number, or if I am barely pressing down. Sometimes they come with a lid that seems to be for “regular fingers,” and a lid that would be for someone like me with callouses. I wonder if there is an oil or cream you could use before bed if there are painful little marks everywhere? This reminds me, I should go change my lancet, it’s been a few years. Ha ha.