Hydration is always important, but when running an ultra-marathon, or performing any endurance event for that matter, the importance of proper hydration increases drastically. The side effects that accompany dehydration are nothing to take lightly. I have been fortunate enough to receive great advice regarding hydration during endurance events and I wanted to pass along some of the knowledge I have received. 1. “If you’re thirsty, it’s too late.” This may be the best advice I have ever been given. From experience I can personally attest that this rule is accurate. Hydration for a race needs to start before the race even begins. If you start the race behind on fluids it can be very difficult to catch up. 2. Make a point to hydrate and refill at every aid station, even the first. Don’t blow through the aid stations, even though you may not feel thirsty and may think you don’t need to stop, you do. For example, when you first start your race you may not feel thirsty and you may want to run through the first station, but doing so may compromise your hydration level miles down the road. 3. If you’re not passing liquids regularly, you likely are not hydrated enough. This advice is not as explicit, as it’s more of a guideline than a rule. Some runners may have hydration down to a science and may not need to stop as frequently as others, but nonetheless, it’s a great rule of thumb. Even though every endurance athlete has been coached and told over and over again to hydrate, mistakes happen, and dehydration is always a possibility. But by following these simple preventative measures, dehydration is less of a risk.