Breathing cold and very dry air may also irritate and dry the mucous membranes of the upper respiratory tract. This weakens their natural protective function and increases susceptibility to infections.

To reduce this effect, it is recommended to breathe through a buff, face covering, or a dedicated mask, which helps humidify the inhaled air.

WHY DEHYDRATION IS COMMON IN THE MOUNTAINS

During acclimatization, the body produces more urine than at sea level. This is a natural physiological process: the body eliminates excess alkaline substances produced as a result of faster breathing.

In practice, this means:

➤ more frequent urination during the day

➤ waking up at night to urinate

➤ increased loss of body fluids

Additional fluid loss occurs through:

➤ breathing dry mountain air

➤ sweating during physical activity

At an altitude of around 4000 m (13,100 ft), even during moderate walking, breathing alone may cause a loss of:

➤ about one glass of water per hour

➤ approximately 1 liter during 5 hours of walking

Without drinking several liters of fluids per day (minimum about 4 liters), dehydration is almost inevitable.

SYMPTOMS OF DEHYDRATION

Typical symptoms include:

➤ headache

➤ fatigue

➤ intense thirst

To prevent dehydration, it is recommended to drink water with electrolytes.

A useful indicator of hydration is urine color.

If you produce large amounts of light-colored urine about four times per day, it usually means your body is well hydrated and acclimatization is progressing properly.

HYDRATION AND BLOOD AT ALTITUDE

At high altitude the body produces more red blood cells in order to transport limited oxygen more efficiently.

However, this also has a downside: the blood becomes thicker and more viscous.

Proper hydration helps counteract this effect.

A simple rule is:

drink enough so that the marks you leave in the snow are light or almost invisible rather than dark yellow.

HYDRATION SYSTEM DURING CLIMBING

One practical way to prevent dehydration is to use a 2-liter hydration bladder worn in the backpack (e.g., Camelbak).

Why is it effective?

➤ it is lighter than a thermos

➤ it allows you to carry more fluid

➤ it enables drinking without stopping or removing the backpack

Many climbers notice that:

➤ hydration bladders are usually emptied completely

➤ thermoses often return from the climb half full, because people do not want to stop and take them out of the backpack.

PREPARING WATER IN CAMP

One of the main daily tasks during high-altitude expeditions—apart from climbing—is making water, which means melting snow or ice.

After reaching camp it is worth first:

➤ collecting snow or ice

➤ storing it in bags (for example sleeping-bag sacks or garbage bags)

The melted water is usually used for:

➤ drinking after the climb

➤ preparing food

➤ preparing water for breakfast and the next day’s climbing

Evening is the best time to do this, because mornings in the mountains are usually very time-limited.

PREVENTING WATER FROM FREEZING IN A HYDRATION SYSTEM

The best solution is to wear the hydration bladder under your jacket, and only then put the backpack on top.

This way:

➤ the initially hot liquid warms your back

➤ later body heat keeps the water from freezing

➤ the drinking tube runs close to the body and stays warm

Important rule:

After each sip, blow air back through the tube to push the remaining water into the bladder.

If water stays in the tube, it may freeze quickly.

When the tube is empty, you will hear a distinct bubbling sound in the bladder on your back.

NIGHTTIME URINATION

During expeditions it is useful to bring a large pee bottle for use inside the tent at night.

For women, devices that allow urination while standing—such as Shewee—can be very helpful.

For older men, frequent nighttime urination may also be related to prostate enlargement, so it is advisable to consult a urologist before an expedition.

SAFE DRINKING WATER IN THE MOUNTAINS

Before an expedition you should plan how you will disinfect water.

In many mountain regions:

➤ access to clean water may be limited

➤ bottled water may not always be available

The safest methods include:

➤ boiling water to a rolling boil

➤ using portable water filters

➤ using chemical disinfectants

One option is iodine solution.

If you are not allergic to iodine, do not have thyroid disease, and are not pregnant, you can use:

➤ 5 drops of 2% iodine solution per 1 liter of water

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WANT TO LEARN MORE?

If you want to better prepare your health for trekking or a high-altitude expeditions, check out the expanded guide in the ebook "High-Altitude Medicine for Trekkers and Climbers" >>

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Gain practical skills for handling emergencies in the mountains through our online training "High-Altitude First Aid" >> - prepared for those planning trips to high altitudes.

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For a detailed list of what to include in your expedition medical kit and step-by-step instructions for assembling your personal first aid set, see the ebook "High-Altitude Expedition Medical Kit Guide" >>

PLANNING A TREK OR A HIGH-ALTITUDE EXPEDITION?

If you would like to check whether your health condition allows you to safely participate in a trek or high-altitude expedition, consider booking a medical consultation >> or using a telemedical expedition package >>

This allows you to assess potential health risks in advance, prepare properly fot altitude, and increase your safety during the expedition.

07 March 2026

The company was established in 2004. The goal of MedEverest is education in the field of mountain medicine and the dangers of high altitudes. I deal with all medical aspects of staying at high altitude. I organize medical support for trekking and high-altitude expeditions.

Specialist Medical Practice Medeverest Robert Szymczak based in Gdańsk (80-360), at ul. Bolesława Krzywoustego 19F, NIP: 5841943576, REGON: 220148318.

Also checkStore regulations >> Implementation: ColinMedia.eu >>