Check Your Nails: If yours are yellow, brittle, or thick, see a podiatrist. According to New York City podiatrist Krista Archer, DPM, all are signs of – forgive us for mentioning it – fungus. Your doctor can prescribe medicine to penetrate the nail plate and clear up the offending condition, but you’ll still have to wait for the nail to grow out (typically six months to a year). So it’s better to start treatment sooner rather than later.