FLOWBIO: A Sweat Sensor That Measures Sodium Live
Hydration in triathlon is still a guessing game. Most of us have no idea exactly how much fluid and sodium we lose through sweat, so we go on generic advice and then fade in the heat, cramp, and lose watts in the final kilometres of the bike leg. FLOWBIO promises to turn that guesswork into data. It is a sensor that analyses your sweat during training and tells you what you are actually losing.
What it actually measures
FLOWBIO measures two things: fluid loss rate and sodium loss. The sensor captures sweat through a tiny channel, using the pressure your own sweat glands generate, and there is no needle involved. That is the key difference from the now-discontinued Supersapiens, which pierced the skin. The light module (about 10g) clips onto a chest strap, and the reading updates every few seconds.
The data lands in the FLOWBIO app, where the in-house AHi engine (Advanced Hydration Intelligence) combines it with intensity and ambient temperature and outputs a specific plan: how much to drink, when, and why. You go from “I hope I took in enough electrolytes” to knowing how much sodium you will lose over a 70.3 at 30°C (86°F).
Does it work: the hard numbers
The manufacturer has not hidden behind marketing and published an independent, peer-reviewed validation in the journal Frontiers in Physiology (2025). The study compared the sensor against lab reference methods: body weighing for fluid loss, and flame photometry plus an L’Aqua Twin analyser for sodium. The team was led by David Bandiera, with Yannis Pitsiladis among the co-authors, and the work was carried out at the University of Rome Foro Italico and at CREPS Montpellier.
On accuracy: in lab conditions FLOWBIO claims 90% accuracy. In the field, it drops to up to 83% for sodium (a difference of up to 180mg, about six times less than a pinch of salt) and 73% for fluids (a difference of up to 250ml). That is not laboratory perfection, but for an amateur planning a drinking strategy for a long race, it is a step up from generic tables.
Device compatibility and battery
This is the freshest news. A live data feed to Wahoo head units launches in late June 2026, putting sweat loss straight on your bike computer screen mid-ride. A live view on Garmin watches and head units is in internal testing and is due to reach beta later in the summer. Long term, FLOWBIO is built to work with Garmin, Wahoo, COROS and Zwift.
Battery life is a strong point: over 100 hours of use, charged over USB-C. The sensor is reusable, with no disposable inserts and no extra subscription; you pay once.
| Spec | FLOWBIO |
|---|---|
| Measures | Fluid and sodium loss from sweat |
| Mount | Chest strap, about 10g |
| Needle | None, sweat collected through a channel |
| Battery | 100+ hours, USB-C |
| Connectivity | Garmin, Wahoo, COROS, Zwift |
| Live data (Wahoo) | Late June 2026 |
| Live data (Garmin) | Beta later in summer 2026 |
Price, and who it is for
International pricing runs about £295 to £379, or $399. That puts it firmly in “serious gadget” territory, not an impulse buy. But if you race 70.3 and full IRONMAN distance, fight the heat, or cramp regularly, a personalised sodium strategy can be worth more than another pair of aero socks.
It is not for someone running 40-minute sessions in cool weather with no gut issues. Hydration only becomes critical at long efforts and in the heat, and that is where FLOWBIO earns its place.