Liquid IV hydration is a popular way to stay hydrated, but it's important to know the potential side effects before using it. The most common side effect of Liquid IV is nausea, which can be caused by the high sugar content in the drink. Other potential side effects include vomiting, diarrhea, and headaches. If you experience any of these symptoms after drinking Liquid IV, it's important to stop using the product and see a doctor.