I qualified as a nurse - Registered Nurse Mental Handicap - RNMH - here in the UK in 1989.
Many of those I cared for needed regular blood tests. Esp those prescribed lithium and other anti-convulsants so that the drug regime was within therapeutic limits.
There is, for example, a patient called John. He needs a blood test. He comes into a room with a person he has never met, to be subjected to something he is unfamilar with and, unsurprisngly, get agitated and refuses.
This happened again and again and again.
We, as a group of nurses say "Hey, let us do the blood sampling, we know the person, we can time it right, we know this person"
This idea was opposed 100% because DOCTORS KNOW BEST.