Apple Develops Innovative Hydration Sensor for the Apple Watch


Apple has developed a first-of-its-kind hydration sensor designed for the Apple Watch, a company patent filing has revealed. Apple’s hydration sensor takes the form of non-invasive electrodes that are placed against the skin, which it describes as a “reliable and elegant” solution. The sensor works by measuring the electrical properties of the Apple Watch wearer’s sweat.

The electrical properties, such as electrical conductance, can represent a concentration of electrolytes in the perspiration, which in turn represents a hydration level of the user.

For example, a high level of electrical conductance of the perspiration can indicate a high concentration of electrolytes and a low level of hydration. By further example, a low level of electrical conductance of the perspiration can indicate a low concentration of electrolytes and a high level of hydration.

Apple says that its hydration tracking system can be performed “non-invasively, repeatedly, accurately, automatically, and with minimal user intervention.” According to the patent, hydration data may be used to provide feedback to the user, particularly during activity such as workouts, and encourage better management of water intake, and in turn, overall health. The filing outlines why hydration is a valuable health metric:

“A user’s hydration level has significant impacts on the health of a user. Dehydration can impair performance and is associated with several deleterious health consequences, including hear strokes. Overdrinking can result in hyponatremia, fatigue, confusion, coma and even death.”


This is an extremely important finding for any competitive brands to acknowledge. This is both an important scientific exploration of hydration detection through a miniscule amount of perspiration but also given Apple’s monopolistic business standing, even a rumor such as this is something to make note of. The patent makes note that electrical conductance measured through sweat can alert user of a high proportion of electrolytes to hydration indicating dehydration. This method does not mention the use of heat but just the intake of sweat particles through the watch itself that also monitors heartbeat and many other health notes.


Charlton, H. (2021, August 17). Apple develops innovative hydration sensor for the Apple Watch. MacRumors. Retrieved August 23, 2022, from