Dear 100 Hour Board,
I went to donate blood for the first time today, and when checking my iron levels the guy mentioned that if the levels were too low on the first hand, they could check the other hand and possibly get a different result. Why is that?
You ever heard that tired cliché "ruled the world with an iron fist?"
Well, that must be your other one.
It's not because the blood in each of your hands is different. It's because those point-of-care machines are squirrelly and sometimes give erroneous results for a variety of reasons. So if the machine gives an unexpected result, they'll just repeat the test. Picking a different hand for the second stick as opposed to a different finger on the same hand is just voodoo.