Major causes of tingling and numbness in hands include diseases such as diabetes, toxic exposure, bacterial and viral infections, traumatic injuries or repetitive stress injuries. The tingling and numbness may also be as result of poor sitting or sleeping position, such as sleeping on the arm, explains WebMD.
Numbness and tingling is a form of nerve damage, but it is often nothing to worry about. Lack of certain vitamins in the body such as vitamin E, vitamin B-1, niacin, vitamin B-12 and vitamin B-6 also cause tingling and numbness in both hands and feet, states WebMD. Approximately 20 percent of tingling and numbness cases are caused by diabetes, and this is one of the key initial symptoms of that condition. Other than diabetes, other systemic diseases that may cause tingling and numbness in the hands include liver diseases, cancers and benign tumors, connective tissues disorders, hormonal imbalances, amyloidosis, and kidney disorders.
Certain medications may also cause tingling and numbness, including chemotherapy used in lung cancer patients and some antibiotic drugs, according to WebMD. Exposure to toxins such as heavy metals, including mercury, arsenic and thallium, may also cause tingling and numbness. Finally, Charcot-Marie-Tooth diseases are inheritable diseases that can cause tingling.