Hand numbness or tingling can stem from many causes, from minor things to serious health problems. Common ones are sleeping in an odd position, repetitive actions like typing, and vitamin B12 shortage. Electrolyte imbalances, diabetes (which can cause diabetic neuropathy), neck or spine issues, and autoimmune disorders can also be to blame. Poor blood flow, like in Raynaud’s phenomenon, and nerve compression from cysts or tumors are other possible factors. Infections like shingles or Lyme disease can mess with nerve function. Occasional tingling is usually no big deal, but if symptoms keep up, see a doctor to check for serious conditions.