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Tech & Wearables

Basic Review: Nix Hydration Biosensor

A connected, real-time hydration sensor sounds like a game changer for triathletes, but how well does the new tech work?

Review Rating


The non-invasive Nix Hydration Biosensor allows athletes to see their fluid and electrolyte loss in real time and receive suggestions for improving their nutrition plan based on personalized results. Think: needle-free Supersapiens (or Levels) for hydration.


Non-invasive (no needles)
Real-time results
Recommendations for improving fueling


Skin patches are single-use
Metrics are a bit vague
Not waterproof



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The Nix Hydration Biosensor takes every “sweat patch” and kicks them to the curb. The Hydration Biosensor is a wearable connective device that gives real time personalized sweat and hydration data to the athlete. The sensor itself is non-invasive (rejoice, needle-phobic athletes!) and is easy to use thanks to its stick-on skin patch.

The Hydration Biosensor provides data on fluid loss, electrolyte loss, and sweat composition during the time the sensor is worn. The data is of use to athletes of all levels; elite athletes can benefit from the specific numbers and hone their nutrition plan, while more recreational athletes can develop a baseline for their sweat rate and make a more accurate hydration plan during longer workouts.

Want even more details on the Nix Hydration Biosensor? Check out our in-depth review here.

The Good: Nix Hydration Biosensor

The first good thing to call out about the Nix Hydration Biosensor is that it is non-invasive—meaning it does not use needles or skin pricks to achieve its data. For those triathletes who have cringed at the idea of continuous blood glucose monitors inserting a tiny needle into the skin or lactic acid readers pricking a finger, the worst part of the Hydration Biosensor is that it may pull out some arm hairs upon removal.

Simply stick on a skin patch, attach the sensor to the patch, and start a bike or run via the Nix Biosensor app and you’re good to go.

The Nix Biosensor app gives athletes the option to choose from a variety of pre-programmed hydration mixes—Skratch, Maurten, GU, Gnarly, and more—to better assist with the biosensor’s ability to understand the electrolyte concoction you’ll be using to replenish fluids and electrolytes during the workout—thus improving the app’s data and personalized suggestions.

While cycling or running, the Hydration Biosensor analyzes the amount of fluid and electrolytes you are losing as well as the composition of your sweat and notifies you as to how much fluid you should intake and when via the Nix Biosensor app. You can also see the total amount of fluid and electrolytes lost in real time in the app, which is great for benchmarking throughout a session.

Post-workout, you can analyze how much fluid and electrolytes were lost and dive into sweat composition. The Nix app provides graphs comparing a variety of popular electrolyte drink mixes which allows athletes to make educated choices about their liquid fueling based on the data from the Hydration Biosensor and the makeup of common sports drink options.

The Hydration Biosensor can also currently sync with Garmin and Apple Health, allowing you to see your fluid loss and electrolyte loss right from your Garmin or Apple device. Nix says they plan on having more integrations (Zwift and TrainingPeaks, to name a couple) later this year.

RELATED: Dehydration Makes That Effort Feel Harder

The OK: Nix Hydration Biosensor

While the barrier to entry for using the Hydration Biosensor is low and the data it provides is accurate and timely, the top drawback of the Hydration Biosensor is that it is best used for intentional benchmarking than for all of your workouts. This is because the skin patches are single use and cost $25 for a four-pack. The sensor starter kit comes with an initial four-pack of skin patches, but if the average triathlete has, say, 10 training sessions per week, you’d already be on pack number three before the seven day mark.

Secondly, the Hydration Biosensor cannot be submerged in water. While we don’t often think of swimming as particularly dehydrating, it can exhaust our hydration reserves quite a bit. To truly appeal to triathletes as being worth the investment, it would be ideal for the sensor to be able to capture data across all three disciplines—although obviously the two most sweat-intensive are cycling and running.

RELATED: Yes You Can Get Dehydrated While Swimming

The post-workout data is easy enough to understand—fluid loss, electrolyte loss, and sweat composition—but the home-page sensor metrics are confusing at first. For example, the “Nix Index” takes a minute to understand, it’s not a “hydration score” as it may first appear, it’s a “sweat score.” The lower your score, generally, the better, because it implies you are not currently sweating as much, compared to how much you could be sweating. More precisely, Nix defines the Index as “a measure of your thermoregulatory potential in the current environmental conditions, from 1-100.” In real-world terms, if your Index is at 90, your rate is in the 90th percentile of your own sweat range.

“Solar Load” is another data point that seems confusing and is not defined within the app. It’s likely this data point is trying to correlate how sunny it is with how much you may or may not be sweating given the current weather, but an actual definition would be helpful.


The Nix Hydration Biosensor is quickly proving itself to be one of the best options on the market for athletes to accurately measure their fluid and electrolyte loss and understand their sweat composition from home.

The data is available in real time and syncs with Garmin and Apple Health, meaning athletes can view their fluid and electrolyte loss from their Garmin or Apple smart device during a workout.

Unfortunately, the Hydration Biosensor does not yet have the ability to be submerged in water, meaning it is not suitable for swimming. Although cycling and running tend to be the two activities in which triathletes sweat the most, it is a deterrent that the sensor can’t accommodate all three disciplines of triathlon.

The sensor’s skin patches are also single use and sit at $25 for a pack of four, meaning it’s inadvisable to use the Hydration Biosensor during every workout unless you have tons of cash to burn.

The Nix Hydration Biosensor is yet another overall beneficial development in at-home sports science testing for athletes, and even as an early version, it’s useful. If you have struggled with fueling and hydration in the past, the Nix Hydration Biosensor may be one way to get more granular and data-backed on a nutrition plan for upcoming races or long training sessions.

RELATED: Ask Stacy: Why is Hydration So Important for Triathletes?

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