You're outside on a hot, summer day. Even though you're sitting, you start to feel nauseous and disoriented. Could it be heatstroke?You're outside on a hot, summer day. Even though you're sitting, you start to feel nauseous and disoriented. Could it be heatstroke? Heatstroke occurs when your body loses control of its temperature system. It's the most serious form of heat injury, and it can damage your brain and internal organs. In some cases, it's deadly. Heatstroke can affect people of all ages, even people who are healthy and haven't had a heat injury in the past. Dr. Julian E. Bailes, Jr., chats with Dr. Roizen about the red flags you should look out for, plus what you should do if you think you or a loved one is in danger. Bonus! 6 Surprising Signs of Dementia