What causes hands and feet to tingle?

Many possibilities: Tingling in the hands and feet at the same time can occur with hyperventilation (can be mild enough that you cannot tell you are hyperventilating; occurs with anxiety), & peripheral neuropathy (nerve disease). Peripheral neuropathy has many possible causes including diabetes & autoimmune diseases (eg lupus). Could be 2 different things at once; e.g. Carpal tunnel syndrome and arthritis of spine.

Tingling hands/feet: Many things can cause hands and feet to tingle, ranging from early nerve damage (e.G diabetes or thyroid or medication side-effects or alcohol) to chronic hyperventilation syndrome (almost always unconsciously). An accurate history and careful examination are required to determine the cause, and then determine the best treatment(s).