How to Stay Hydrated on Every Run with Galaxy Watch Ultra2

Galaxy Watch Ultra2 may be best known for its rugged titanium build and dive-ready certifications, but one of its most practical additions for runners is hydration guidance you receive while you run, not after it.
Through Nutrition Alert, a new addition to the existing Sweat Loss feature, Galaxy Watch Ultra2 estimates fluid loss relative to your body weight and tells you when to drink and how much. Combined with dedicated Trail Run tracking, it helps you manage effort and hydration together, so a long climb in the heat doesn’t end your run early.
What is Nutrition Alert on Galaxy Watch Ultra2?
Nutrition Alert is a real-time hydration guidance feature on Galaxy Watch Ultra2. It builds on Sweat Loss, which estimates how much fluid you lose during exercise, and turns that estimate into direct guidance: when to drink, and how much.
The difference is timing. Sweat Loss tells you what happened during a session. Nutrition Alert tells you what to do about it while the session is still running, which is when the information changes the outcome.
How does Galaxy Watch Ultra2 measure hydration?
Galaxy Watch Ultra2 estimates sweat loss relative to your body weight, using continuous biometric data captured by Samsung’s BioActive sensor along with the intensity and duration of your activity. That estimate is what Nutrition Alert converts into hydration prompts during your run.
Because the guidance is scaled to body weight rather than a fixed average, two runners on the same trail can receive different recommendations.
How do I turn on Nutrition Alert?
Nutrition Alert is a Samsung Health feature on Galaxy Watch Ultra2, available across supported workout types rather than a single mode. To use it, open exercise settings and enable the Nutrition feature. Samsung showcases it most prominently within Trail Run, where sustained effort and heat make fluid loss hardest to judge, but the guidance is not limited to trail running.
What is Trail Run on Galaxy Watch Ultra2?
Trail Run is a dedicated tracking mode built for uneven outdoor terrain. It tracks detailed elevation, climbing progress and terrain impact, helping you pace yourself across a route and reduce injury risk on descents and technical ground.
Hydration guidance works alongside this. Elevation and terrain tell you how hard the route is working you, while Nutrition Alert tells you what that effort is costing you in fluid, so you can adjust both pace and hydration on the same run. Trail Run is available on Galaxy Watch Ultra2 only, and requires an Android phone with the Samsung Health app and a Samsung account.
What else on Galaxy Watch Ultra2 supports long outdoor runs?
Three things make all day tracking realistic. Galaxy Watch Ultra2 carries an 800 mAh battery, a 35% increase over the original Galaxy Watch Ultra, so a long route doesn’t become a battery decision. Its display reaches up to 5,000 nits, keeping hydration prompts and pace data readable in direct sunlight. And highly accurate dual frequency GPS, powered by the Snapdragon Wear Elite platform, keeps route and elevation data reliable on trails where signal is inconsistent.
Together with Trail Run and Nutrition Alert, these turn Galaxy Watch Ultra2 into a running companion that guides your effort in the moment, rather than reporting on it afterwards.