Why do we get pins and needles?

Sitting on a leg or sleeping on an arm compresses nerves and the blood vessels that supply them with oxygen. The squeezed nerves stop sending normal signals, so the limb feels numb or as if it has fallen asleep. When you move and the pressure lifts, blood flow returns and the nerves start firing again, but erratically at first. The brain interprets these chaotic signals as tingling, prickling or buzzing, which usually fades within a minute or two. Frequent pins and needles without an obvious cause can be linked to conditions such as diabetes or vitamin B12 deficiency.