What Causes Tingling Sensation In Left Hand And Finger?

my blood glucose has been in teh 130 s for 4 years now, but my tryclyceides are perfect. My doctor feels walking 30 minutes a day will reduce this. I am having knee replacement surgery in a month,and hope to walk after I m recovered. But I also have a left hand and finger tingling sensation when the hand is up and while typeing at work. But when I bring it down to my side, it goes away. What is this?