A: Many different issues, some of them serious, can cause tingling in the extremities, but most are very treatable. You should work with your GP to figure out what’s going on in your case, but I can share some of the conditions that cause tingling. Tingling on just one side can signal a problem with the brain or spinal cord, possibly caused by a stroke, though that’s usually accompanied by other symptoms, such as numbness, weakness, or difficulty finding words. Multiple sclerosis is another possibility, but it typically begins with blurry vision. A more common reason would be sleeping in an awkward position that compresses the nerves in the arms or legs. If only the hands tingle, a likely cause is carpal tunnel syndrome (here’s what you need to know about carpal tunnel); if there’s a rash too, the problem might be a viral infection. When tingling occurs in many different areas, there’s a good chance that it’s caused by diabetes. So even if you haven’t been diagnosed previously, the symptom is something you should flag for your doctor. Another common cause is a vitamin deficiency, particularly of B12. There’s little national data on this, but we almost always find low B12 levels in the patients we test, particularly women over age 40. Found primarily in meat, fish, and dairy, B12 is critical to brain and nerve health. Your doctor can perform a blood test to check your level, explain how to get more of the vitamin in your diet, and recommend a supplement, if necessary. I suggest keeping a journal to log the days and times you notice the symptoms. You may discover that you experience the tingly sensation when you’re resting on your back or after you’ve been drinking alcohol. Keeping a journal is a great way to see if there are any recurring triggers and may help lead your doctor to a proper diagnosis. SANJAY GUPTA, MD, is chief medical correspondent for CNN and a practicing neurosurgeon at Emory Clinic in Atlanta. Send your questions to askdrgupta@prevention.com. More from Prevention: Do You Have AVItamin B12 Deficiency?  Sanjay Gupta, MD, is chief medical correspondent for CNN and a practicing neurosurgeon at Emory Clinic in Atlanta.