5 Hydration Mistakes Hikers Make (And How to Avoid Them)

A long hike can challenge your body in ways that are easy to underestimate. Heat, elevation, exertion, sweat and limited access to water can all affect how much fluid you need. But hydration is not simply a matter of carrying as much water as possible.

In fact, drinking too little and drinking too much can both create problems. Understanding your individual needs can help you stay comfortable, focused and safer on the trail.

1. Drinking Too Much Water

One of the biggest hydration mistakes hikers make is assuming that more water is always better. Excessive water consumption can dilute the sodium concentration in your blood, potentially causing exercise-associated hyponatremia, a potentially life-threatening condition.

A case report in Wilderness & Environmental Medicine described a Grand Canyon hiker who consumed more than 7.5 litres of water during each of two hiking days. He subsequently developed severe hyponatremia, rhabdomyolysis and acute kidney injury.

The lesson is simple: don't force yourself to drink enormous quantities just because you're hiking in hot weather. Instead, pay attention to thirst and the conditions around you.

2. Following a One-Size-Fits-All Hydration Rule

There is no universal amount of fluid that every hiker should drink per hour. Your sweat rate can vary considerably depending on body size, fitness, temperature, humidity, pace and elevation.

Research published in Nutrients found substantial individual variation in sweat and sodium losses. The researchers found that a personalized hydration strategy based on individual fluid and sodium losses improved fluid balance and exercise performance in hot conditions.

For hikers, that means your hydration plan should be based on your own experience rather than someone else's bottle or backpack. Pay attention to how your body responds during training hikes and different weather conditions.

3. Ignoring Electrolytes on Long, Hot Hikes

Water is important, but prolonged sweating also means losing electrolytes, particularly sodium. This becomes more relevant during lengthy hikes in hot conditions when sweating can continue for several hours.

That doesn't mean every short walk requires an electrolyte drink. However, on longer or particularly demanding outings, consider how much you're sweating and whether your food and fluids provide adequate sodium.

A pilot study in Biology examined hydration and electrolyte balance during ultra-trail events and highlighted the complex relationship between fluid intake, electrolyte balance and physiological stress during prolonged endurance activity.

4. Waiting Until You Feel Terrible to Drink

The opposite mistake is starting a challenging hike without a hydration plan and waiting until you're exhausted, dizzy or extremely thirsty before thinking about fluids.

Dr. Stacy Sims, an exercise physiologist and nutrition scientist whose research focuses extensively on hydration, thermoregulation and athletic performance, emphasizes that individual hydration needs vary. She writes, “Everyone is individual, so your fluid needs may be very different from those of your teammates or training partners.”

Before heading out, check the weather, distance, elevation gain and availability of reliable water sources. Carry enough for the planned route, with an appropriate margin for unexpected delays.

5. Treating Hydration as Separate From Overall Trail Preparation

Hydration does not exist in isolation. Your food intake, pacing, heat exposure, fitness level and recovery all influence how your body handles a demanding hike.

Research published in the Journal of Applied Physiology examined hypohydration during the 100-mile Western States Endurance Run and found that lower hydration status was associated with greater acute changes in urinary biomarkers related to kidney injury.

A separate study in the same journal examined the physiological and thermoregulatory responses of an elite mountain-ultramarathon athlete during the 2025 Western States 100. The research provides a useful reminder that hydration is part of a much broader system involving fluid balance, heat regulation, nutrition and endurance performance.

For everyday hikers, the takeaway is not to copy an elite athlete's exact strategy. Instead, use the principles to plan appropriately for your own ability, environment and route.

What Do the Experts Recommend?

Dr. Susan Yeargin, an exercise scientist and athletic trainer who researches thermoregulation and hydration, has emphasized that individual fluid requirements differ because people can sweat at very different rates. Her advice is particularly relevant to hikers because environmental conditions can change rapidly during outdoor activity.

For practical preparation, think beyond simply filling a bottle. Your hiking water bottle should be easy to access while walking, while a hiking hydration pack can make frequent drinking more convenient without requiring you to stop.

On longer routes, hikers should also consider whether their hiking hydration backpack has enough capacity for the conditions, distance and availability of refill points.

Hydrate Smarter, Not Harder

Good hydration is about balance, not simply drinking as much as possible. Avoiding these five mistakes means understanding your individual needs, planning for the environment and paying attention to how your body responds.

Before your next hike, consider your route, weather, duration, sweat rate and water availability. A thoughtful approach to hydration can help you enjoy the trail while reducing the risk of both dehydration and overhydration.