How To Prevent Altitude Sickness On The Everest Base Camp Trek

The Short Answer

Altitude sickness is the most common reason trekkers turn back before reaching Everest Base Camp, and it can affect anyone, whatever their age or fitness. The good news: it is largely preventable. You prevent it by climbing slowly, taking your acclimatization days seriously, drinking plenty of water and descending at the first sign of serious symptoms.

10 Golden Rules to Prevent Altitude Sickness on the Everest Base Camp Trek

1. Go up slowly. Above 3,000 m, raise your sleeping altitude by no more than about 300–500 m a night.
2. Never skip an acclimatization day. Use the rest days in Namche Bazaar and Dingboche, even if you feel strong.
3. Climb high, sleep low. Hike higher on rest days, then come back down to sleep.
4. Walk at a pace you could talk at. "Bistari, bistari" (slowly, slowly) is the best advice on the trail.
5. Drink 3–4 litres of water a day. Watch for clear, pale urine as a simple hydration check.
6. Eat well, even without an appetite. Carbohydrate-rich meals like dal bhat give your body steady fuel.
7. Avoid alcohol and sleeping pills. Both can slow your breathing at night and mask early symptoms.
8. Stay warm and rested. Cold and exhaustion make your body work harder at altitude.
9. Speak up early. Tell your guide about any headache, nausea or unusual tiredness straight away.
10. Never go higher with symptoms. If they worsen, descend. Descent is the most effective treatment.

What Is Altitude Sickness?

Altitude sickness happens when your body can't adjust quickly enough to the lower oxygen levels at high altitude. At Everest Base Camp (5,364 m), each breath contains only about half the oxygen available at sea level.

Given time, your body adapts: you breathe faster and deeper, your heart works harder and, over days and weeks, you produce more red blood cells. This process is called acclimatization. Altitude sickness develops when you climb faster than your body can acclimatize. It can affect anyone above about 2,500 m, and being young or fit gives you no protection.

Why the Everest Base Camp Trek Carries Real Altitude Risk

The Everest Base Camp Trek takes you from Kathmandu's comfortable 1,400 m to the thin air of Gorak Shep (5,160 m) in just over a week, and higher still on Kala Patthar (5,550 m). Here is how our 14-day itinerary manages that climb.

[embed: node/35bc2966-0268]

Three things make the trek a genuine altitude challenge:

• You start high. The flight to Lukla drops you at 2,860 m in about half an hour, with no gradual build-up.
• You spend several nights above 4,000 m. Dingboche, Lobuche and Gorak Shep are where most altitude problems appear.
• The final days are the highest. Base camp day and the Kala Patthar sunrise climb come when your body is already working hardest.

That's why the trek's two acclimatization days, in Namche Bazaar and Dingboche, are non-negotiable parts of a safe itinerary.

Know the Signs: AMS, HAPE and HACE

Altitude sickness comes in three forms. Recognizing them early is the single most important safety skill on the trek.

Condition	What it is	Key symptoms	How serious?
AMS (Acute Mountain Sickness)	The common, mild form	Headache plus nausea, loss of appetite, tiredness, dizziness or poor sleep	Common and manageable if you stop ascending
HAPE (High Altitude Pulmonary Edema)	Fluid in the lungs	Breathlessness at rest, persistent cough (sometimes with pink, frothy spit), chest tightness, extreme fatigue, gurgling breath	Life-threatening: descend immediately
HACE (High Altitude Cerebral Edema)	Swelling of the brain	Severe headache, confusion, unusual behaviour, loss of balance or coordination, drowsiness	Life-threatening: descend immediately

Most cases of AMS appear 6–24 hours after reaching a new altitude, often in the evening or overnight. HAPE and HACE usually follow untreated AMS, especially when trekkers keep climbing despite symptoms, though HAPE can sometimes appear without warning.

Normal at Altitude vs Warning Sign

Usually normal	Warning sign: tell your guide
Breathless when climbing, but recovering when you stop	Breathless while resting
Waking briefly at night or unusual breathing patterns while asleep	A headache that doesn't ease with rest, water or a painkiller
Needing to urinate more often	Nausea or vomiting
Slightly less appetite than usual	Unusual tiredness or reluctance to get out of bed
A dry "Khumbu cough" from cold, dry air	Stumbling, confusion or behaving out of character

The Heel-to-Toe Test

A simple check for HACE: walk a straight line placing the heel of one foot directly against the toes of the other, like a tightrope walker. If someone can't do this without wobbling or stepping off the line, especially after a few steps they could normally manage easily, treat it as an emergency and start descending.

Important: a trekker with altitude sickness may not notice their own symptoms or may play them down. Watch out for each other, and never leave someone with symptoms alone.

Prevention Step 1: Choose a Well-Paced Itinerary

The best protection against altitude sickness is decided before you take a single step: the pace of your itinerary. Mountain medicine experts recommend a few simple rules, and a good Everest Base Camp itinerary is built around them.

Gain Sleeping Altitude Slowly

Above 3,000 m, try not to raise your sleeping altitude by more than about 500 m a night. What matters most is where you sleep, not how high you walk during the day. On our itinerary, sleeping altitude rises by 430–540 m on most days above Namche, and by just 250 m on the night at Gorak Shep.

The one bigger jump is the climb from Phakding to Namche Bazaar (about 830 m). That's why the very next day is a rest day in Namche.

Take a Rest Day Every 3–4 Days

A rest day (or a day without gaining sleeping altitude) every 3–4 days, or roughly every 1,000 m of height gained, gives your body time to catch up. Our itinerary includes two:

Rest day	Sleep at	Acclimatization hike	Why it matters
Day 4	Namche Bazaar, 3,440 m	Everest View Hotel and Khumjung (~3,880 m)	Recovers from the big climb from Phakding and prepares you for 4,000 m
Day 7	Dingboche, 4,410 m	Nangkartshang viewpoint (~5,083 m)	Prepares you for nights at Lobuche and Gorak Shep

Climb High, Sleep Low

On rest days, don't stay in bed. Hike a few hundred metres higher, spend some time there, then return to sleep lower down. This gentle exposure to higher altitude helps your body adapt faster. Even an hour up the ridge above Dingboche makes a real difference.

Walk Slowly from Day One

The first few days feel easy, and that's when many trekkers rush. A slow, steady pace (one at which you could still hold a conversation) uses less oxygen and puts less strain on your body. On the trail, guides call it "bistari, bistari": slowly, slowly.

Add Extra Days if You Can

A longer itinerary is the simplest way to lower your risk further. Good options include:

• An extra night in Namche or Dingboche, especially if you have had altitude sickness before
• An extra night at Pheriche or Dingboche before heading higher, if you feel slow to adjust
• 1–2 buffer days at the end of the trip, so a delayed Lukla flight never pressures you to rush the trek

Shortcut itineraries that skip rest days, or fly straight into high villages, may save time but significantly raise the risk of altitude sickness.

Prevention Step 2: Daily Habits on the Trail

A good itinerary does most of the work, but your daily habits decide how well your body copes.

Drink Enough Water

At altitude, you lose much more water than usual through fast breathing in cold, dry air. Dehydration doesn't cause altitude sickness, but its symptoms (headache, fatigue, dizziness) look the same and make you feel much worse.

• Aim for 3–4 litres a day, sipped steadily rather than gulped at once
• Hot drinks count: ginger, lemon or garlic soup and herbal tea are trail favourites
• Check your urine: pale and clear is good, dark yellow means drink more
• Don't overdo it: much more than 4–5 litres a day brings no extra benefit

Eat Well, Especially Carbohydrates

Your body uses more energy at altitude, and carbohydrates need less oxygen to turn into energy than fats. Dal bhat, potatoes, rice, noodles, porridge and Tibetan bread are all ideal. Appetite often drops above 4,000 m, so eat small, regular meals and carry snacks.

Avoid Alcohol, Smoking and Sleeping Pills

Avoid	Why
Alcohol	Dehydrates you, slows breathing during sleep and can hide early symptoms
Smoking	Further reduces the oxygen your blood can carry
Sleeping pills and sedatives	Can slow your breathing at night, when oxygen levels are already lowest

Save the celebration beer for your return to Namche or Lukla.

Stay Warm and Rest Well

Cold makes your body burn more energy and work harder. Wear layers, keep your head and hands warm and change out of sweaty clothes as soon as you reach the teahouse. Go to bed early, and don't worry if you wake often or breathe unevenly at night: this is a normal part of adjusting.

Pace Your Effort

Use trekking poles, let your porter carry the heavy bag and take short, regular breaks. Arriving at the teahouse tired but not exhausted is the goal.

A Simple Daily Routine Above 3,000 m

Time	What to do
Morning	Check how you feel, drink a litre with breakfast and tell your guide about any headache or poor sleep
On the trail	Walk at a talking pace, sip water every 20–30 minutes and eat a snack every couple of hours
Arrival	Change into dry, warm layers, drink a hot drink and rest
Afternoon	Take a short walk higher than the village, then return (climb high, sleep low)
Evening	Eat a full meal, have a pulse and oxygen check with your guide and avoid alcohol
Night	Keep water in an insulated bottle by your bed, and use a pee bottle to avoid cold trips outside

Prevention Step 3: Medication and Oxygen Monitoring

Diamox (Acetazolamide)

Diamox is the most widely used medicine for preventing altitude sickness. It works by making your body breathe faster and deeper, which speeds up acclimatization. It's a prescription medicine, so speak to your doctor or a travel clinic before your trip.

Detail	What to know
How it's commonly used	For prevention, doctors often prescribe a low dose (commonly 125 mg twice a day), starting the day before you go high and continuing until you begin descending
Who it suits	Trekkers with a history of altitude sickness, or itineraries with fast altitude gain
Common side effects	Tingling in fingers and toes, needing to urinate more often, fizzy drinks tasting flat
Who should check first	Anyone with a sulfa drug allergy, kidney or liver problems, or who is pregnant
Trial run	Many doctors suggest trying a dose at home first to check for side effects

Diamox helps, but it is not a shortcut. It doesn't let you climb faster safely and won't stop symptoms if you ignore them. Always follow your doctor's advice on dose and timing.

Other medicines, such as dexamethasone and nifedipine, are used to treat serious altitude illness and should only be taken under medical guidance. Painkillers like paracetamol or ibuprofen can ease a mild headache, but if a headache returns or worsens, stop ascending.

Pulse Oximeter Checks

A pulse oximeter clips onto your finger and measures your blood oxygen level (SpO₂) and heart rate. Our guides check every trekker daily, and the readings help spot trends before symptoms become serious.

Altitude	Typical resting SpO₂ in acclimatizing trekkers (approximate)
Sea level	95–100%
Namche Bazaar, ~3,440 m	85–92%
Dingboche, ~4,410 m	80–88%
Gorak Shep, ~5,160 m	75–85%

Readings vary from person to person and with cold fingers or movement, so take them at rest and wait for the number to settle. A single low number is less important than a falling trend, or a low reading together with symptoms. How you feel always matters more than the number.

Altitude Sickness Myths vs Facts

Myth	Fact
"I'm very fit, so I won't get altitude sickness."	Fitness makes walking easier but gives no protection; fit trekkers often push too fast.
"Young people don't get it."	Altitude sickness affects all ages.
"A headache is normal, so I'll keep going."	A headache at altitude is AMS until proven otherwise. Rest, and don't go higher until it clears.
"Diamox means I can skip rest days."	Diamox supports acclimatization; it doesn't replace it.
"Drinking lots of water prevents altitude sickness."	Hydration helps you feel better, but only slow ascent truly prevents it.
"Garlic soup cures altitude sickness."	It's a tasty, warming way to stay hydrated, not a treatment.
"I've done treks before without problems, so I'm safe."	Your response can change from trip to trip. Every ascent deserves the same care.

Before You Go: Prepare Your Body and Your Kit

Know Your Risk Factors

Higher risk	Why
A previous history of altitude sickness	The strongest predictor of getting it again
Fast ascent or short itineraries	Less time for the body to adjust
Living at sea level	No existing adaptation to altitude
Heart or lung conditions, anaemia, sleep apnoea	Can reduce how well your body copes with low oxygen
Arriving exhausted or ill	A cold, stomach bug or jet lag adds strain in the first days

Get a Medical Check

See your doctor 6–8 weeks before departure, especially if you have any health conditions or take regular medication. It's also the right time to discuss Diamox, pack any prescriptions and ask about vaccinations.

Train for Endurance (It Helps, but Doesn't Protect)

Fitness doesn't prevent altitude sickness, but a fit body handles long trekking days with less strain, leaving more energy for adapting to altitude. Start 8–12 weeks before your trip with hill walks, stair climbing and back-to-back hiking days carrying a light pack.

Arrive Rested

If you can, arrive in Kathmandu a day early to recover from jet lag. Avoid late nights and heavy drinking before the Lukla flight, and start the trek well hydrated.

Pack for Altitude

• Pulse oximeter (optional; your guide carries one, but some trekkers like their own)
• Insulated water bottles (2 × 1 litre) so water doesn't freeze at Lobuche and Gorak Shep
• Water purification tablets or a filter to drink plenty without buying plastic bottles
• Electrolyte or rehydration sachets
• Warm layers: a down jacket, hat, gloves and a sleeping bag rated to about -15°C
• Buff or neck gaiter to warm the air you breathe and reduce the Khumbu cough
• Personal first-aid kit, including painkillers and any medication your doctor prescribes
• Snacks like energy bars, nuts and chocolate for when your appetite drops

Get the Right Insurance

Choose a travel policy that covers trekking up to 6,000 m and emergency helicopter evacuation. Many standard policies stop at 3,000–4,500 m, which isn't enough for Everest Base Camp or Kala Patthar.

What to Do if Symptoms Appear

Even with perfect preparation, some trekkers develop symptoms. Acting early turns a potential emergency into a minor delay.

Your Altitude Sickness Action Plan

Situation	What to do
Mild AMS (headache, mild nausea, tiredness)	Stop ascending. Rest at the same altitude, drink fluids, eat lightly and take a painkiller if needed. Continue only once symptoms have fully gone.
Symptoms not improving after 24 hours, or getting worse	Descend, ideally 300–1,000 m, until you feel better.
Signs of HAPE or HACE (breathless at rest, confusion, loss of balance)	Descend immediately, day or night, with someone accompanying you. Your guide arranges oxygen, medical help or helicopter evacuation.

The Three Golden Rules

1. If you feel unwell at altitude, assume it's altitude sickness until proven otherwise.
2. Never ascend with symptoms.
3. If you're getting worse, or showing serious signs, go down at once.

Medical Help on the Trail

• Himalayan Rescue Association (HRA) aid post, Pheriche (~4,240 m): staffed by volunteer doctors during the main trekking seasons, offering consultations and daily altitude awareness talks
• Clinics in Namche Bazaar and Lukla for lower-altitude care
• Supplemental oxygen and portable hyperbaric (Gamow) bags, used by trained teams to stabilize serious cases while descent or evacuation is arranged

Helicopter Evacuation

When descent on foot isn't safe or fast enough, a helicopter can reach most villages on the route, including Gorak Shep, Lobuche, Pheriche, Dingboche and Namche, and fly you to Lukla or a Kathmandu hospital. Helicopters fly only in daylight and good weather, so serious symptoms in the afternoon should be acted on right away, not left until morning.

Without insurance, a rescue flight often costs US$3,000–6,000 or more, which is why cover for helicopter evacuation is essential. Learn more about our helicopter services.

Turning back is never a failure. Base camp will still be there next season; your health comes first.

How Nepal Trip Services Keeps You Safe at Altitude

On our Everest Base Camp Trek, altitude safety is built into every day of the journey:

Safety measure	What it means for you
Acclimatization-first itinerary	Rest days in Namche Bazaar and Dingboche, with climb-high, sleep-low hikes
Experienced, licensed guides	Trained to spot early signs of AMS, HAPE and HACE and act quickly
Daily health checks	Oxygen and pulse readings with a pulse oximeter, plus a daily symptom check
Steady pacing	Small groups walking at a comfortable, talking pace
First-aid kit	Carried by your guide throughout the trek
Porter support	One porter for every two trekkers, so you carry only a light daypack
Emergency coordination	24/7 contact with your insurer and rescue providers for fast helicopter evacuation
Flexible plans	Extra acclimatization days or a slower pace can be added for anyone who needs them

With 16 years of experience in the Himalaya, our team's priority is simple: getting you to base camp safely and home again with the memories of a lifetime.

FAQs About Altitude Sickness on the Everest Base Camp Trek

1. How common is altitude sickness on the Everest Base Camp Trek?

Mild altitude sickness is common. Many trekkers get a headache or poor sleep at some point above 4,000 m. Serious altitude illness (HAPE or HACE) is much rarer, especially on well-paced itineraries with rest days.

2. At what altitude does altitude sickness start?

It can start above about 2,500 m. On the Everest trail, symptoms most often appear from Namche Bazaar (3,440 m) upwards, and especially in Dingboche, Lobuche and Gorak Shep.

3. Can a beginner trek to Everest Base Camp without getting altitude sickness?

Yes. Previous experience matters far less than pace. Beginners who follow a well-paced itinerary, take the rest days seriously, drink enough water and report symptoms early usually reach base camp safely.

4. Does fitness prevent altitude sickness?

No. Fitness makes the walking easier but doesn't protect you from altitude sickness. Very fit trekkers sometimes get sick because they walk too fast.

5. Should I take Diamox for the Everest Base Camp Trek?

Many trekkers do, especially those with a history of altitude sickness. It's a prescription medicine, so talk to your doctor about whether it suits you, the right dose and possible side effects.

6. How many acclimatization days does the Everest Base Camp Trek need?

A standard 14-day itinerary includes two: one in Namche Bazaar and one in Dingboche. Adding a third day is a sensible option if you've had altitude sickness before.

7. What is the most dangerous point for altitude sickness on the trek?

The highest nights, at Lobuche (4,910 m) and Gorak Shep (5,160 m), carry the greatest risk. This is why the acclimatization day in Dingboche, just before them, is so important.

8. Is a headache at altitude always altitude sickness?

Not always, but treat it as altitude sickness until proven otherwise. Rest, drink fluids and don't go higher. If it disappears with rest and water, you can usually continue with your guide's approval.

9. What oxygen level is normal at Everest Base Camp?

At around 5,000–5,200 m, resting oxygen readings of roughly 75–85% are typical for acclimatizing trekkers. Readings vary between people, so trends and symptoms matter more than one number.

10. Can I drink alcohol on the Everest Base Camp Trek?

It's best to avoid alcohol on the way up. It dehydrates you, affects your breathing at night and can hide early symptoms. Celebrate on the way down instead.

11. Does garlic soup really help with altitude sickness?

Garlic soup is a warming, hydrating trail tradition, but there's no strong evidence that it prevents or treats altitude sickness. Enjoy it for the fluids and comfort.

12. What happens if I get altitude sickness on the trek?

For mild symptoms, you rest at the same altitude until you feel better. If symptoms worsen, you descend. In serious cases, your guide arranges immediate descent, oxygen or a helicopter evacuation.

13. Will I be able to finish the trek if I get mild AMS?

Often, yes. Many trekkers with mild AMS recover after a rest day or a short descent and go on to reach base camp. This is why buffer days in your itinerary are so valuable.

14. Does travel insurance cover altitude sickness rescue?

Only if your policy covers trekking up to 6,000 m and includes emergency helicopter evacuation. Check the altitude limit carefully, as many standard policies stop well below this.

15. Is a guide important for preventing altitude sickness?

Yes. An experienced guide sets a safe pace, checks your oxygen levels, spots symptoms you may miss in yourself and knows exactly when and how to descend or call for help.

Trek to Everest Base Camp Safely with Nepal Trip Services

Altitude sickness is the biggest challenge on the trail to Everest, but it doesn't have to stop you. Climb slowly, respect your rest days, drink well, listen to your body and trust your guide, and you give yourself the best possible chance of standing at the foot of the world's highest mountain.

Our 14-day Everest Base Camp Trek is designed around safe acclimatization, with rest days in Namche and Dingboche, daily oxygen checks, licensed guides and full emergency support. Want a slower pace or extra rest days? We'll tailor the itinerary to you through our trip planner, or explore more routes on our Everest Region Treks page.

• WhatsApp / Viber: +977 982-8696557
• Email: info@nepaltripservices.com
• Office: Thamel, Kathmandu, Nepal
• Response time: usually within 0–2 hours