The best way to talk him into getting blood drawn is to tell him what kind of tests they are going to use the blood to perform.  And the best way to keep him calm during a blood draw is to have him watch the needle go into his arm and then discuss step by step how the blood is being transferred into the vial. 

Me, I'm a cringing mess when I get a blood draw.  My son, studying every step until they pulled the needle out.  (Then he almost fainted!) 

He was really upset to find out that he couldn't actually watch them perform the lab tests with his blood.  I promised to try to find some pictures online.  Wish me luck!

We also got to look at picture and 3-D forms of noses and lungs and such while we waited for the doctor to see us.  AND, DS met a man with an artifical leg- one of the old school kind with a tennis shoe stuck to a metal stick!  He was thrilled to see it and the man was so amused he took the thing off and showed DS how it attached to his knee.  The man says he lost his leg due to a poor diet complicating his diabetes, so now he tells everyone that he lost his legs because he didn't eat his fruits and vegetables.  He's hoping it will help others remember to eat healthy. 

So, that's science class for today.   You know, it's no wonder I have trouble cracking a school book some days.