9 Reasons Why You Can't Concentrate You walk into a restaurant to meet a friend and remember you were supposed to meet somewhere else. You leave your boss's office and, quick as that, forget the deadline she gave you for a new project. You had your keys in your hand, you were just holding them, and now they're gone -- again. What's going on? Here, nine possibilities for why your mind is wandering, and expert advice on how to get your concentration back. 1. Your numbers are low . Fuzzy mindedness could signal a vitamin or hormone deficiency, especially if you're also feeling unusually tired. For example, hypothyroidism -- too-low levels of thyroid hormone -- could be to blame, says Robert Orford, MD, consultant at the Mayo Clinic's Preventive Medicine Division in Scottsdale, AZ. "If there's a deficiency in thyroid hormone, metabolism slows, which reduces blood flow and cellular function in various parts of the brain," Dr. Orford says. B-12 deficien...