Why are drops of blood (for tests and the like) usually taken from the finger/hands?

Is this just a standardised way of doing it, or is there some advantage to pricking the finger?

Convenient and easy-to-reach?

Yep. Also the skin is relatively thin, with plenty of blood just below the surface, unlike, say, the belly, where my wife just got a shot and didn’t bleed at all.

You may or may not already know this, but in the olden days when you went to the Red Cross to donate blood, they pricked the earlobe for the iron test, not the fingertip.

"No, nurse, I said to prick his finger!"

Never gets old.

At least for testing blood sugar (for diabetics), testing blood from your fingertip is more accurate than when taken from other places (such as the arm or thigh), especially if your blood sugar is rapidly changing (such as after eating or exercising).

Except if you try to do it on the fingertip of the wrong hand of someone playing a string instrument.

Don’t forget that there are lots of nerves there, so pricking a fingertip will make sure that it hurts more.

Wait, you mean that is not the goal of medical care?

To elaborate on what kenobi 65 said - diabetics take blood from the fingers because fingertips have a higher concentration of actual blood. You can test from other spots, but you end up with interstitial fluid, not blood, and you don’t get as accurate of a reading.