All of us have had the “my leg / hand has fallen asleep” experience. This “sleeping” experience mostly occurs if you cut off blood supply to a particular body part by applying pressure for a long time. That is the reason why you have numbness and tingling in your hand if you sleep on it for long. This numbness and tingling is absolutely normal and goes away within minutes, but if you have a similar experience at random, the reason could be a medical condition. Paresthesia, also known as numbness and tingling of the hands and legs, has multiple causes, but some of this can be controlled with physiotherapy.
There are multiple causes for the tingling sensation and numbness felt in the hands and fingers. The most common cause is carpal tunnel syndrome, a type of nerve compression. Repeated motion in an unnatural position which puts abnormal stress on your hand causes microscopic tears. These tears in ligaments and muscles later swell up and later cause nerve compression. The ulnar nerve which passes through our hand and forearm can get trapped during accidents or falls and cause numbness. There are various other causes like diabetes, alcoholism, poor circulation and more.