Altitude sickness, also known as acute mountain sickness (AMS), is a condition that can affect people rapidly ascending to high altitudes above 2,500 meters (8,200 feet). It is caused by low air pressure and lower oxygen levels at higher elevations. Drinking plenty of water can help prevent and alleviate altitude sickness symptoms.
What causes altitude sickness?
At higher altitudes, the air pressure is lower, meaning each breath contains fewer oxygen molecules. This is called hypobaric hypoxia. The body needs time to adapt to this reduction in available oxygen. When ascending too quickly, the body cannot adjust fast enough, resulting in altitude sickness.
Specifically, hypobaric hypoxia causes the following physiological effects:
- Cerebral edema – Excess fluid buildup in the brain due to increased capillary pressure
- Pulmonary edema – Fluid accumulation in the lungs
- Increased cerebral blood flow – More blood pumped to the brain to increase oxygen delivery
- Increased heart rate and blood pressure – Higher workload for the circulatory system
These changes trigger the symptoms of altitude sickness like headaches, nausea, fatigue, and shortness of breath. The higher and faster someone ascends, the more likely they are to develop altitude illness.
How does drinking water help?
Staying well hydrated by drinking plenty of water can reduce the symptoms and risks of altitude sickness for several reasons:
Prevents dehydration and headaches
Dehydration is a common side effect at higher altitudes due to increased breathing and water loss. Headaches are one of the first and most common acute mountain sickness symptoms. Drinking adequate water prevents dehydration and helps minimize headache pain.
Improves blood circulation
Blood becomes thicker at high altitudes. Well-hydrated blood circulates easier and transports oxygen more effectively. Drinking water improves blood flow to the brain and other organs.
Increases oxygen saturation
One study found subjects who drank at least 16 oz. of water in the hour before ascending to around 3,500 meters increased arterial oxygen saturation compared to dehydrated subjects.
Prevents HAPE and HACE complications
If left untreated, acute mountain sickness can progress to life-threatening conditions like high-altitude pulmonary edema (HAPE) and high-altitude cerebral edema (HACE). Staying hydrated helps prevent these dangerous complications.
Reduces effects of diuretics
Diamox (acetazolamide) is sometimes prescribed to help the body adjust to altitude changes. It works by increasing the rate of breathing. However, it has a common side effect of increased urination which can lead to dehydration. Drinking extra water counteracts this diuretic effect.
Improves sleep
Altitude often disrupts normal sleep patterns and quality. Well-hydrated individuals report improved sleep at altitude, which allows the body and brain to better recover and acclimate.
Helps treat mild symptoms
Drinking water may also provide mild relief for early altitude sickness symptoms like fatigue, dizziness, and nausea before they worsen.
How much water should you drink?
To prevent and treat altitude sickness, health experts often recommend doubling or tripling normal daily water intake. The exact amount to drink will vary between individuals based on weight, activity levels and environmental conditions. Some general hydration guidelines include:
- 12-16 oz (350-450 ml) every hour during active ascent
- 48-64 oz (1.4-1.9 liters) per day at altitude
- More water before, during, and after physical activities
- Sip frequently instead of drinking large amounts at once
Urine color is a simple way to gauge hydration. Pale or clear urine indicates adequate hydration, while dark yellow urine usually signals dehydration.
High altitude hydration tips
Here are some additional tips for staying hydrated and preventing altitude dehydration:
- Avoid alcohol and caffeine – These have diuretic effects.
- Eat hydrating foods – Fruits, vegetables, broth soups.
- Monitor for overhydration – Drinking too much can cause hyponatremia.
- Descend if symptoms persist – Fluids alone won’t treat severe altitude illness.
- Use a reusable water bottle – Make drinking water easy and eco-friendly.
- Flavor water for taste – Add slices of fruit, vegetables, or low-sugar drink mixes.
The bottom line
Drinking adequate water is a simple yet highly effective way to prevent and alleviate altitude sickness symptoms. Staying well hydrated improves oxygen circulation, blood flow to the brain, altitude acclimatization and sleep quality. Most people require at least double their normal water intake to stay hydrated in high altitude environments. Pay close attention to hydration levels when ascending to altitude.