This is a genuine question, which so far I've been unable to find an answer to.
Some time ago when my wife was pregnant, she seemed to be constantly needing to have samples taken for various tests etc. My wife is very petite, and it was an enduring problem for them to find a suitable vein to take the sample.
On one such occasion, after having watched my wife endure jab after jab from the nurse trying to find a vein that was big enough, I asked...
"Is it possible to take the sample from a different place, like her ankles?"
The veins on the ankles are larger, and more prominent, and it seemed a perfectly logical choice to me.
The nurse gave me an almost horrified look as she quickly answered "No!". She didn't give any kind of reason as to why this was not possible. It was almost like she was embarrassed that I'd even asked such an (apparently) absurd question.
So my question is, is there some actual reason why the ankles are not a suitable location? Some thoughts I've had...
Perhaps it effects the quality of the sample. I figured blood was blood, but I could be wrong.
Perhaps it could cause extra bleeding afterwards. This certainly seems like it could be possible, but should be easy enough to manage, by applying the cotton bud more firmly, keeping the patient lying down for longer etc.
Perhaps it's more painful? I can't imagine why though, I'm fairly sure that ankles are no more sensitive than wrists.