Altitude Sickness on Health TLDRLSS

Why Should You Keep Eating Candy at High Altitudes? Is Carbohydrate the 'Most Oxygen-Saving' Energy Source? How to Drink Water Without Cramping? Dehydration Actually Worsens Altitude Sickness! A Complete Guide to Precise Hydration!

Thu, 21 May 2026 21:30:00 +0800

When climbing, guides always tell you to suck on a candy or eat a chocolate bar. What is the science behind this?

At high altitudes, eating the right things is more important than eating well. Choosing the wrong food will make your body suffer more in a low-oxygen environment, while choosing the right food can help you last for several more hours.

Why Keep Eating Candy at High Altitudes? The Oxygen-Saving Science of Carbohydrates

You might think eating candy is just for “replenishing energy,” but in low-oxygen high-altitude environments, the significance of eating candy goes far beyond that.

For the human body to convert food into energy, it needs to consume oxygen. Comparing carbohydrates and fat, when consuming the same amount of oxygen, burning sugar generates 8% to 10% more energy than burning fat.

Energy Source	Characteristics	Oxygen Efficiency
Carbohydrates (Sugar)	Simple structure, high proportion of oxygen atoms	Oxygen Saver, quickly converted to energy with little oxygen
Fat	Complex structure, requires a lot of oxygen to decompose	High Oxygen Consumer, a slow remedy for an urgent need

At high altitudes, your body faces a “tight oxygen budget” every second.

Eating candy is like choosing the “oxygen-saving mode”.

Save precious oxygen for your brain and muscles, and you will naturally breathe easier.

This is why guides always tell you to suck on brown sugar, eat chocolate, or gummies.

Eating Candy Helps Red Blood Cells Release More Oxygen?

When the human body is in a high-altitude low-oxygen environment, red blood cells will absorb a large amount of glucose from the blood.

Red blood cells use this sugar to produce a molecule called 2,3-BPG. This molecule goes and binds with hemoglobin, forcing hemoglobin to “let go” and release the oxygen it holds to surrounding oxygen-deprived tissues and organs.

Replenishing enough sugar is like providing an endless supply of raw materials for red blood cells, speeding up oxygen release and utilization within the body.

Red blood cells release more oxygen the following steps:

Eat candy
Red blood cells absorb glucose
Produce 2,3-BPG
Increase oxygen release to surrounding oxygen-deprived tissues and organs

Eating Candy Can Make You Breathe Deeply Automatically?

Burning carbohydrates produces more carbon dioxide than burning fat.

After the concentration of carbon dioxide in the blood rises slightly, it triggers the respiratory center of the brain, which commands the lungs to spontaneously deepen and speed up breathing.

This deep breathing induced by eating candy actually allows you to unconsciously inhale more thin air from high altitudes, thereby increasing blood oxygen saturation.

What Foods to Eat at High Altitudes? Which Ones are Landmines?

Now that we know the benefits of carbohydrates, the next question is: how should we choose foods?

Trail Food: What to Eat While Hiking?

When climbing, the body is very short of oxygen, so you won’t have the energy to chew hard nuts or beef jerky.

Chewing itself consumes oxygen, and liquid or semi-liquid sugars are the best instant fuels.

Recommended Food	Reason
Energy Gel (Energy Drink)	Liquid, no chewing required, rapid absorption
Gummies, Brown Sugar Bars	High carb, easy to swallow
Raisins, Yogurt Bars	Small size, high calorie density

The core principle of trail food: high carb, easy to swallow, no long chewing required.

Meals: What to Eat at Camp?

Digestion at camp is slightly better than during movement, but gastrointestinal blood flow decreases at high altitudes, and digestion speed is still greatly reduced.

Recommended Food	Reason
Dehydrated Rice, Instant Noodles	Easy to digest, high calorie, dehydrated vegetables or egg drops can be added
Instant Mashed Potatoes	High carbohydrate content, virtually no chewing required

Why is Flatulence Easy at High Altitudes? Which Foods to Avoid at All Costs?

This is related to the physical law of Boyle's Law.

When atmospheric pressure drops, the volume of gas inside a closed container expands.

Your stomach and intestines originally contain gas; at high altitudes, these gases expand collectively.

In addition, when the body is hypoxic at high altitudes, it prioritizes sending blood to the brain and heart, reducing blood flow to the gastrointestinal tract and severely reducing digestive function.

Low air pressure + slow digestion = severe flatulence. Eating too full actually increases the cardiopulmonary burden.

High Altitude Diet Landmine List

Foods to Avoid	Reason
Beans (Red Beans, Soybeans)	Gas-producing food, worsens gastrointestinal flatulence
Carbonated Drinks (Cola, Beer)	A large amount of gas expands in low-pressure environments
Sweet Potatoes, Onions	Intestinal fermentation produces a large amount of gas
High-fat Foods	Digestion is highly oxygen-consuming, increasing the burden in hypoxic environments

How to Drink Water at High Altitudes? “Precise Hydration Method”

Many people “drink only when thirsty” when climbing, which is very dangerous on mountains.

High-altitude air is extremely dry, and combined with faster breathing, the body loses up to 1 to 2 liters of water per day just through breathing.

By the time you feel thirsty, your body is already dehydrated.

Hydration Formula: Small Amounts, Multiple Periods, Regularly

Timing	Water Intake	Principle
During Movement	Drink 50-100 ml (2-3 sips) every 15-20 minutes	Never chug 500 ml at once
Daily Total	`Weight(kg)` × `30ml` + `Climbing Hours` × `300ml`	60 kg climbing 6 hours = at least 3,600 ml

Water Temperature Matters: Refuse Ice Water

On dry and cold mountains, drinking ice water forces the body to consume precious calories to “heat” the water in the stomach to body temperature.

You must have a thermos in your backpack. Drinking warm water saves energy and prevents cold air from inducing airway spasms (high altitude cough).

Electrolyte Replenishment to Prevent Cramps

Drinking only pure water accelerates salt loss from the body; panting and sweating take away a lot of salt, and pure water will only make it worse.

Replenishment Method	Explanation
Add sports drink powder or effervescent tablets to the water bladder	Replenish lost sodium, potassium, magnesium
Suck on a salt candy regularly	Lowest cost, most effective for preventing thigh cramps

What is the Relationship Between Dehydration and Altitude Sickness?

This is the most easily overlooked yet most impactful link.

When the body is dehydrated, blood becomes thick. If blood is too thick, red blood cells flow slower, and the efficiency of carrying oxygen drops like an avalanche.

Dehydration not only makes you uncomfortable, it directly worsens altitude sickness, and can even cause your symptoms to be misdiagnosed as altitude sickness.

Chain Reaction of Dehydration	Result
Thick blood	Red blood cells flow slower
Reduced oxygen delivery efficiency	Increased tissue hypoxia
Headache, nausea, fatigue	Symptoms are almost identical to altitude sickness

Drinking plenty of water to keep blood thin allows red blood cells to flow smoothly like traffic on a highway, quickly delivering inhaled oxygen to the entire body.

Conscious and regular hydration is the simplest yet most easily overlooked step to prevent altitude sickness.

Reference

What Medicine Should I Take for High Altitude Illness? How to Use Diamox? Can Viagra Also Treat Altitude Sickness? A Complete Guide to Essential Climbing Medications and Emergency Procedures

Thu, 21 May 2026 18:30:00 +0800

One week before departure, you checked the gear checklist in your backpack three times, but you only have a vague understanding of those few pills in your medicine bag?

Taking them at the wrong time or using the wrong medication can be more dangerous than not bringing any at all.

Overview of Altitude Sickness Medications: Preventive vs. Treatment Drugs

Altitude sickness medications are divided into two main categories: Preventive and Treatment. Their roles are entirely different.

Function	Positioning	Timing of Use
Preventive Drugs	Accelerate the body’s adaptation to altitude	Start taking before departure
Treatment Drugs	Relieve symptoms that have already occurred	Use after symptoms appear

Preventive drugs are helping the body do its homework in advance, while treatment drugs are helping the body survive a crisis.

“Preventive drugs” and “treatment drugs” both cannot replace “descending,” which is the most fundamental solution.

Preventive Drug: Diamox (Acetazolamide / Diamox)

Diamox is currently the most widely used preventive medication for altitude sickness, and it is the only first-choice drug supported by sufficient research evidence.

Mechanism of Action

Diamox is a carbonic anhydrase inhibitor that acts on the kidneys:

Mechanism	Description
Inhibits carbonic anhydrase	Reduces the reabsorption of bicarbonate
Acidifies the blood	Stimulates the respiratory center
Deepens and accelerates breathing	Mimics the body’s acclimatization response at high altitudes

Simply put, Diamox allows your body to start adapting in advance, rather than scrambling only when oxygen is scarce.

Dosage and Administration

Item	Description
Dosage	For adults, 125 mg each time, once every 12 hours (250 mg daily)
Start Time	Start taking 1 day before departure
Duration	Continue taking until 2 to 3 days after arriving at the highest altitude, or when beginning to descend
Child Dosage	2.5 mg per kilogram of body weight, once every 12 hours

Common Side Effects

Side Effect	Description
Tingling in hands and feet	Most common, usually mild and tolerable
Frequent urination	Because the kidneys excrete more bicarbonate and water
Altered taste of carbonated beverages	Sodas and beers will taste weirdly metallic
Mild nausea	A small number of people may experience gastrointestinal discomfort

Contraindicated Groups

Contraindicated for those allergic to sulfonamide drugs
Those with severe renal or hepatic insufficiency
Patients with hypokalemia

It is recommended to try taking it once before departure to confirm that you do not have a severe allergic reaction to Diamox before bringing it up the mountain.

Alternative Preventive Drug: Dexamethasone

If you are allergic to sulfonamides and cannot use Diamox, Dexamethasone is an alternative option.

Item	Description
Type	Steroid (Glucocorticoid)
Dosage	4 mg every 6 hours
Action	Directly reduces brain swelling and inflammatory response
Limitation	Cannot be used long-term (steroid side effects) and does not accelerate altitude adaptation

Dexamethasone is “suppressing symptoms,” while Diamox is “accelerating adaptation.” Their mechanisms are completely different.

If Dexamethasone is used as a preventive, once you stop taking it, the body may experience rebound altitude sickness symptoms because it only temporarily masks the problem.

Medications for Treating High Altitude Cerebral Edema (HACE)

High Altitude Cerebral Edema is one of the most critical types of altitude sickness and can be fatal within 24 hours.

Drug	Dosage	Action
Dexamethasone	First dose 8 mg, then 4 mg every 6 hours	Rapidly reduces brain swelling, takes effect within hours

The role of Dexamethasone in treating HACE is “to buy time for descent,” temporarily restoring the patient’s consciousness and physical mobility.

Works better when paired with a Portable Altitude Chamber (PAC) or bottled oxygen

But the most important thing is still to descend immediately.

Medications for Treating High Altitude Pulmonary Edema (HAPE)

The fatality rate of High Altitude Pulmonary Edema is the highest among the three types of altitude sickness, and the core issue is excessively high pulmonary artery pressure.

Drug	Dosage	Action
Nifedipine (Adalat OROS)	30 mg every 8 hours (extended-release form)	Lowers pulmonary artery pressure, improves lung blood flow
Tadalafil (Cialis)	10 mg every 12 hours	Phosphodiesterase type 5 inhibitor (PDE5i), lowers pulmonary artery pressure
Sildenafil (Viagra)	50 mg every 8 hours	Also a PDE5i, lowers pressure by dilating pulmonary blood vessels

Yes, Viagra is indeed one of the medications used to treat High Altitude Pulmonary Edema.

It was originally developed for the purpose of lowering pulmonary artery pressure, and was only later discovered to have another more widely known “side effect” besides treating altitude sickness.

So if you see Viagra in a climbing medicine bag, don’t laugh; it could be a critical, life-saving drug.

Recommended Climbing Medicine Bag Checklist

Drug	Purpose	Carrying Suggestion
Diamox 125mg	Altitude sickness prevention	Prepare according to the number of itinerary days, start 1 day before departure
Dexamethasone 4mg	HACE emergency treatment	Carry at least 10 pills
Nifedipine 30mg ER	HAPE emergency treatment	Carry at least 6 pills
Panadol	Headache relief	Caffeine-free version is preferred
Anti-nausea drug	Nausea and vomiting	Such as Ondansetron

All medications must be obtained after physician evaluation before departure; do not purchase them on your own or use others’ medications.

It is recommended to visit a Travel Medicine Clinic for consultation.

Non-Drug Equipment: Oxygen and Altitude Chambers

Equipment	Description	Effect
Bottled Oxygen	Directly increases inhaled oxygen concentration	Maintains for a few hours, suitable for emergencies
Portable Altitude Chamber (PAC)	Manually pressurized sealed bag	Mimics a descent of 1,500 to 2,000 meters in altitude
Fingertip Pulse Oximeter	Monitors oxygen saturation (SpO₂)	Normal value is above 95%, below 90% at high altitude requires alertness

The process of using a Portable Altitude Chamber (PAC):

Place the patient inside the bag
Pressurize continuously with a foot pump
Maintain for 1 to 2 hours
The effect is roughly equivalent to descending 1,500 to 2,000 meters

The pressure bag is a lifesaver for buying time, but it cannot replace descent. Symptoms will return after the pressure treatment ends.

Emergency Situation Handling Flowchart

When a teammate or you experience severe altitude sickness symptoms, handle them in the following order:

Step 1: Assess Severity

Assessment Item	Mild	Severe (Requires Immediate Action)
Headache	Mild, relieved by pain relievers	Severe, pain relievers ineffective
Gait	Normal	Unsteady walking (Sign of cerebral edema)
Breathing	Slightly short of breath during activity	Short of breath even at rest (Sign of pulmonary edema)
Consciousness	Clear	Confused, lethargic, slow response

Step 2: Handling Mild Symptoms

Stop ascending
Rest and observe at the same altitude
Replenish water and keep warm
Take pain relievers to alleviate headache
If no improvement within 24 hours → proceed to Step 3

Step 3: Emergency Handling of Moderate to Severe Symptoms

Descend immediately by at least 500 to 1,000 meters
Give oxygen (if available)
Use a PAC (if immediate descent is impossible)
Cerebral edema → give Dexamethasone
Pulmonary edema → give Nifedipine
Do not let the patient act alone; at least one teammate must accompany them

Step 4: Follow-up Care

If symptoms improve after descending, continuous observation for 24 to 48 hours is still required
After symptoms disappear completely, consider resuming a slow ascent
Patients who have experienced HACE or HAPE are recommended to seek medical attention after descending

On the mountain, it is better to retreat one time too many than one time too few.

Travel Medicine Clinic: The Most Important Stop Before Departure

Almost all major hospitals in Taiwan have travel medicine clinics. Clinic services include:

Assessing your personal medical history and altitude sickness risk
Prescribing preventive medications based on itinerary altitude and days
Teaching you to recognize symptoms and emergency handling procedures
Providing vaccination recommendations (applicable to overseas trips)

Spending an afternoon at the clinic gains you peace of mind for the entire trip. This is the most worthwhile pre-trip investment.

Reference

Debunking 7 High Altitude Illness Myths: Can Oxygen Injection Keep You Climbing? Does Being Fit Prevent AMS? Everything You Need to Know to Prevent and Handle High Altitude Illness

Thu, 21 May 2026 17:30:00 +0800

“I run marathons, so altitude sickness shouldn’t affect me, right?”

In fact, high altitude illness will not spare you just because you exercise regularly.

Myth #1: Being Fit Prevents Altitude Sickness

Altitude sickness has nothing to do with fitness; it relates to how fast your body adapts to low oxygen.

The air oxygen content above 2,500 meters is only about 75% of sea level, and it drops to less than 55% at 5,000 meters.

Faced with such an environment, the body needs time to trigger a series of adaptation mechanisms:

Adaptation Mechanism	Purpose
Deeper and faster breathing	Increase air intake
Faster heart rate	Accelerate blood circulation
Increased red blood cells	Improve oxygen-carrying capacity

These adjustment speeds vary from person to person, depending on your genes and your physical state on the day, and have no direct relation to how many kilometers you usually run.

Fit people are actually more prone to make a mistake: climbing too fast.

Because their muscles do not feel tired, they ignore that other systems of the body are lacking oxygen.

Myth #2: Being Fine Last Time Means Being Fine This Time

The occurrence of altitude sickness is not constant; every climb’s conditions and physical states are different.

There are too many variables affecting altitude acclimatization:

Variable	Influence
Ascent Speed	For the same mountain, chartered vehicle direct ascent vs. three days of slow hiking leads to completely different results
Sleep Quality	Insomnia the night before or staying up late the previous week will reduce adaptation capacity
Physical Condition	Unrecovered cold or gastrointestinal discomfort means the immune system is already consuming resources
Water Intake	Dehydration will worsen the symptoms of altitude sickness
Alcohol	Even in small amounts, it will suppress the respiratory center

Being fine last time might just mean the conditions were all just right that time.

Every time you go up a mountain, prepare as if it were your first time.

Myth #3: Taking a Painkiller Will Fix the Headache

Painkillers only suppress the alarm; they do not disarm the danger.

When a headache occurs above 2,500 meters, the first reaction should be:

This could be altitude sickness
Stop ascending further
Observe for other symptoms (nausea, dizziness, insomnia)

Taking painkillers can temporarily relieve discomfort, but if the root cause is cerebral vasodilation caused by hypoxia, painkillers will only make you falsely assume you are fine and keep climbing, leading to a sudden outbreak at higher altitudes.

The rule for handling headaches on mountains: “Unless you can prove it is due to other causes, always treat it as altitude sickness first.”

Myth #4: Inhaling Oxygen Lets You Keep Climbing

Oxygen is an emergency rescue tool, not a cure.

Using oxygen (bottled oxygen or portable hyperbaric chamber) at high altitudes is equivalent to “temporarily returning you to a lower altitude”:

Oxygen Equipment	Effect	Limitation
Bottled Oxygen	Directly supplements inhaled oxygen concentration	Limited capacity, usually only lasts for a few hours
Portable Hyperbaric Chamber (PAC)	Simulates a drop in air pressure of 1,500 to 2,000 meters	Lasts about 1 to 2 hours per use, requires manual pressurization

The function of both oxygen and medication is to “buy time to descend,” not “to let you keep climbing up.”

Once the oxygen supply is removed, the body returns to the same hypoxic environment. If you do not descend, symptoms will keep recurring or even worsen.

Myth #5: Walking Slowly Prevents Altitude Sickness

Ascent speed is the key factor affecting altitude sickness.

The critical indicator for altitude sickness prevention is “the net gain in sleeping altitude per day,” not your walking speed.

Scenario	Risk
Riding a car for 3 hours directly to 3,400 meters	High risk, the body has absolutely no time to adapt
Hiking for 2 days from 2,000 meters to 3,400 meters	Lower risk, the body has time to adjust gradually
Climbing from 3,000 meters to 4,200 meters within a day, but sleeping back at 3,000 meters	Well controlled, aligns with the “climb high, sleep low” principle

Many Baiyue itineraries, to fit holidays, are designed to go directly from the trailhead (approx. 2,000 meters) to a cabin above 3,000 meters for overnight stay in one day.

This kind of itinerary design itself is a breeding ground for altitude sickness.

If the itinerary cannot be changed, at least do the following:

Consult a travel medicine clinic before departure and carry preventive medications.

Myth #6: Only Children and the Elderly Get Altitude Sickness Easily

Age is not a deciding factor.

Group	Actual Situation
Young Adults	The incidence is not lower than the elderly, and they are more likely to ignore symptoms due to overconfidence
Children	Because they cannot express discomfort accurately, they are more prone to delayed discovery
Women	Some studies show slightly higher AMS incidence in women, but the difference is not significant
Long-term High-Altitude Residents	Returning to high altitude after a stay at sea level, they can still experience altitude sickness

Everyone is equal in the face of altitude sickness. The only difference is whether you are prepared.

Myth #7: Taking Altitude Sickness Pills Guarantees Safety

Fact: Medication is a support tool, not a magic cure.

The most common preventive medication, Diamox (Acetazolamide), works by speeding up the body’s acclimatization process, prompting your kidneys to excrete bicarbonate, which acidifies the blood and stimulates the respiratory center to deepen breathing.

But it has several major limitations:

Limitation	Description
Not suitable for everyone	Contraindicated for people with sulfa drug allergies
Has side effects	Numbness in hands and feet, frequent urination, altered taste for carbonated drinks
Cannot replace acclimatization	Even after taking it, you still need to control the ascent speed
Needs to be taken in advance	Usually starts 1 day before departure, continued until 2 days after arriving at the highest altitude

Medication is like a seatbelt; it can save lives at key moments, but it doesn’t mean you can drive with your eyes closed.

Altitude Sickness Risk Assessment for Different Routes

The following compiles the risk levels of common high-altitude routes in Taiwan and overseas:

Taiwan Baiyue

Route	Maximum Altitude	Risk Level	Suggestion
Hehuanshan Main Peak	3,417 meters	Moderate	Start from Cingjing, adapt midway
Yushan Main Peak	3,952 meters	Moderate-High	Acclimatize before staying overnight at Paiyun Lodge (3,402 meters)
Jiaming Lake	3,310 meters	Moderate	Two-day itinerary has high risk; three-day itinerary is recommended
Qilai Main & North Peaks	3,560 meters	Moderate-High	High risk if ascending directly to Chenggong Cabin on day one

Overseas Routes

Route	Maximum Altitude	Risk Level	Suggestion
Mount Fuji, Japan	3,776 meters	Moderate	Strongly recommended to stay overnight at the 7th or 8th station
Nepal EBC	5,364 meters	High	Standard itinerary takes about 12 to 14 days, including multiple acclimatization days
Lhasa, Tibet	3,650 meters	Moderate-High	Flying direct has extremely high risk; taking the train to Tibet is recommended
Cusco, South America	3,400 meters	Moderate-High	Can stay in a lower-altitude city for 1 to 2 days first
Mount Kilimanjaro	5,895 meters	Extremely High	Choose a route of at least 6 days or more

What You Can Do Before Departure

Preparation Item	Description
Travel Medicine Clinic	Inform the doctor of destination altitude, itinerary days, ascent speed, and discuss preventive meds
Physical Training	While it doesn’t prevent altitude sickness, good fitness can reduce extra physical burden
Study the Route	Understand daily altitude changes and mark potential risk zones
Prepare Gear	Oximeter (fingertip), headache pills, warm clothing
Inform Teammates	Let teammates know your physical condition and past history of altitude sickness

The best attitude toward climbing: “Keep awe for the mountains, keep honesty to your body.”