Nix Hydration Biosensor review – a revolutionary tool for endurance athletes

Studies have shown that up to 87% of endurance athletes become physically impaired during their workouts and competitions due to dehydration, despite ample access to fluids. Considering the rate at which we lose fluids and electrolytes varies significantly from one person to another, this should not be surprising.

That is why the release of the Nix Hydration Biosensor has the potential to be a revolutionary tool for endurance athletes. Read on to watch/read our full review.

Nix Hydration Biosensor review – Video

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What is Nix?

The Nix Hydration Biosensor is the first biosensor to analyze sweat and provide endurance athletes with personalized hydration data in real time.

With a pod worn on the upper arm, Nix continuously measures sweat throughout your workout or race and sends personalized notifications to your phone or watch in real-time to tell you when, what, and how much to drink, thus eliminating any guess work on how to stay optimally hydrated.

The Nix Hydration Biosensor currently costs $129 USD which comes with:

  • 1 Pod
  • 1 Case (that also works as a charger)
  • 1 USB to USB C cable
  • 4 Patches

The pod attaches to the adhesive patches which contain the sensors are single use only. After going through the included patches, refill packs (of four) can be purchased for $25 USD.

How it works

Using the Nix Hydration Biosensor is fairly simple and straightforward. First, you’ll need to setup your workout on the Nix app; currently the options include indoor and outdoor running, as well as indoor and outdoor cycling.

Then, once you have a patch adhered to your bicep, you can attach and snap the Pod onto it. The Pod connects and sends the real-time data to your phone via bluetooth.

From here, you can specify what sort of drink you will be rehydrating with. There are lots of options already preloaded onto the app, but you can create a custom drink should you need to. Nix analyzes both your water loss and electrolyte loss, so it can give better recommendations if it knows exactly what sort of drink you are replenishing with.

Here you can also set up notifications if you would like. You can choose to be reminded on a set time cadence, or after a certain amount of water loss.

Once you start the workout, it can take up to 25 minutes for enough sweat to reach the pod before your data will begin to appear. You can see this data on your phone, on an Apple Watch, or most Garmin watches/bike computers.

Nix says it will expand this to more platforms like Strava, Wahoo, TrainingPeaks, Zwift, Suunto, and others soon.

What I liked

Hydration is so crucial for endurance performance, and while other devices give estimates on fluid loss, they are highly generalized. Since sweat rates are so different from one person to the next, I was excited to finally get more personalized data, and Nix absolutely delivered.

I took Nix on a 90-minute run and was able to see both my fluid loss and electrolyte loss per hour. Additionally, Nix was able to analyze my sweat to show me what my electrolyte loss was per ounce, so I could make better choices about which drink to best hydrate with during workouts.

Now sweat rates will typically vary a lot depending on how the temperature and humidity, and so Nix takes the local weather and gives you a Nix score from 0-100 (the more hot and dry weather earning a higher score). The more you use Nix, the more it creates a “sweat-profile” for you so you can get a better understanding of how you will need to hydrate under different conditions.

Knowing more about my personal rate of fluid and electrolyte loss will absolutely help me prepare my hydration strategy for future long workouts and races.

Another bonus with Nix is the battery life and data storage. The battery life of the Pod is around 24 hours, and it can store the data locally if you don’t keep your phone on you. I know this because when my phone died half way through my 90-minute run, I was worried I wouldn’t be able to get all the data. But when I charged my phone later, I was pleasantly surprised to see all of my data from Nix from the entire session.

What I didn’t like

The biggest issue currently with Nix is its watch integrations. In order to see your data and get notifications on the Apple Watch, you have to have the Nix app running during your workout. This is fine, but because of the way the Apple Watch works, you cannot run another workout app at simultaneously.

This Nix watch app is very basic with only your heart rate, distance, and current pace being displayed. This means in order to use Nix, you’ll need to forgo data like Power, Ground Contact Time, or even be able to take splits on your watch.

The app on the Garmin works in a similar way. To get the Nix data, you will need to install and use the Nix app. Again, you will be limited in the data you see and will not be able to use your regular running data, nor will you be able to set up navigation.

Of course, you could not use the Nix app on your watch, and just keep it on the phone. This is what I chose to do, but it is not really that ideal as I typically keep my phone packed away in a pouch (if I bring it at all).

Nix is a brand new device, so I can understand the current limitations. But hopefully they can improve the app on the Apple Watch, and make it so that you add the Nix info to your regular run configuration on Garmin watches.

Other uses

Nix says the biosensor is only designed to be used for endurance activities, but I was still curious if I could use it during the day to analyze my hydration outside of workouts. Though after trying for several hours, Nix was not able to give me any data (I guess typing doesn’t work up enough of a sweat).


Despite the current less-than-stellar watch integrations, I think the Nix Hydration Biosensor is still a game-changer for endurance athletes. Being able to easily see and understand your personalized fluid and electrolyte loss, as well as electrolyte composition is a huge advantage!

Buy Nix Hydration Biosensor here

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