Why do fingers go numb while you are laying on your back?

Fingers going numb while lying on your back is commonly caused by compression of the ulnar nerve, which is also known as the "funny bone" nerve. This nerve runs along the inner side of your arm and elbow, and it supplies sensation to your ring and pinky fingers, as well as the inner part of your palm.

When you lie on your back with your arms extended, your body weight can put pressure on the ulnar nerve where it passes through the elbow joint. This pressure can temporarily block the nerve's function, leading to numbness and tingling sensations in your fingers.

The numbness usually resolves once you change your position and relieve the pressure on the nerve. If you experience persistent numbness or tingling in your fingers, it's important to consult a healthcare professional to rule out any underlying medical conditions.