Pressure briefly starves nerves of blood supply; moving restores it within minutes.
The NHS says pins and needles happens when blood supply to the nerves is cut off, typically from sitting or sleeping on the body part, and stops within a few minutes of taking the weight off. That is the whole story for the everyday version. It becomes a GP question when it is constant, recurrent without a pressure cause, mapped to a specific area, or accompanied by weakness or other symptoms, since persistent pins and needles can come from trapped nerves, diabetes, B12 deficiency, or some medicines.
What to do
Common questions
Why do I get pins and needles?
The everyday version is simple plumbing. The NHS explains that pins and needles, that prickling, tingling, or numb feeling, happens when the blood supply to nerves is cut off, usually because you are sitting or sleeping on that body part, and it stops within a few minutes of taking the pressure off. Crossed legs, a dead arm from sleeping on it, and feet falling asleep on the floor are all this. You do not need to do anything except move and let the blood flow back. The patterns that change the answer: pins and needles that is constant, keeps coming back without a pressure explanation, follows a specific map (one hand, both feet in a stocking pattern, or running down one leg), or arrives with weakness, back pain, or vision changes. The NHS says to see a GP if you constantly have pins and needles or it keeps returning, because the persistent version can come from trapped nerves, sciatica, diabetes, vitamin B12 deficiency, some medicines, or conditions like carpal tunnel syndrome. None of those are diagnosed from a single tingly evening, so the rule of thumb is: pressure plus minutes equals normal; unexplained plus persistent equals get it checked.