What is High Altitude?

hiking on rocks and mountains
  • High Altitude is from 8,000 to 13,000 feet. This is common hiking elevation in western U.S.
  • Very High Altitude is 13,000 to 18,000 feet. Some hiking, mostly in high Rocky Mountains.
  • Extremely High Altitude is over 18,000 feet. Special breathing gear required.

Air is made up of nitrogen, oxygen, and argon with traces of other stuff in it. Nitrogen is about 78%, oxygen is 21%, and argon is 1% - those percentages stay constant no matter what the elevation.
Air pressure becomes less as you climb up a mountain, and less air pressure means less oxygen to breath. High altitude hiking is when you trek at an elevation that may affect your body. Some people are affected as low as 7000 feet. Let's take a minute to explain a bit about air pressure and available oxygen.

If you put your arms out and turn around, you've made a circle that is about 5 feet wide. Imagine that circle being a column of air going from the ground up, up, up to the edge of the atmosphere. From where you're standing, there are thousands and thousands of feet of air above you in your column. All the nitrogen, oxygen, and argon above you is pushing down on the air around you. The height of that column of air determines the air pressure where you are and that air pressure determines how densely the gas particles are packed together.

hiking at high elevations     oxygen for hiking

The higher you climb, the less air there is above you in the column, so the lower the air pressure and the less dense the gas. Every 1000 feet you climb, you lose about 3% of the available oxygen because there is less gas packed into your column of air. At 12,000 feet, every breath you take brings in only 2/3 the amount of oxygen that you would suck in at sea level.

Another important thing to keep in mind is that air temperature drops about 3.5 degrees for every 1000 feet of elevation gain. A nice 75 degree day at 5,000 feet will be more like 60 degrees at 10,000 feet.

Hiking at High Altitudes

hiking at high elevations As you expand your hiking adventures, you'll probably be driven to hike up higher and higher mountains. At some point, it becomes mountaineering, but there are many peaks over 14,000 feet that have trails all the way to the top. Colorado has many 14,000+ peaks that people make a goal of summiting.

As you climb ever higher, you need to understand the added risks and problems with higher altitudes. You will find yourself needing to breathe deeper and more often to keep enough oxygen circulating to your muscles. Every breath has less oxygen, so you need more breaths. There are more special preparations for higher altitude hiking:

  • Slower Pace - If you are not expecting the lack of oxygen, you will find yourself needing frequent rest stops to recover. But, by slowing your pace as you gain elevation, you will keep your body working without overexerting.
  • Even Rhythm - Maintaining a breathing/stepping rhythm is even more important at higher elevations than lower down. It will help keep you from overexerting yourself.
  • Deep Breathing - when you first notice any breathlessness, start thinking about your breathing. Take deeper breaths and smaller steps until you have a sustainable pace again. On steeper sections, deliberately placing each foot and taking a breath may be the way to go.
  • Sunscreen is critical because the sun is more powerful higher up. Snow, light-colored rocks, cool temperature, and no shade above treeline also contribute to easy sun burns.
  • Sunglasses will help prevent squinting and headaches. Snowblindness and sunburned eyelids are real problems. Use side guards on your glasses for more protection.
  • Extra Clothes - long sleeves, long pants, hats, and gloves to protect from the sun, wind, and cold. Weather can change in a heartbeat, easily dropping more than 30 degrees in 1/2 hour or less.
Ignoring the risks of hiking at higher elevations will ruin your day. If you're lucky, you'll just be wiped out, but there's a good chance you can get yourself in deep trouble.

Altitude Sickness

mountain hiking Everyone needs to breathe more when they are at altitude. But, some people become sick when they hike too high. It just happens.
The biggest problem with hikers is that they want to reach their goal and may not accept that they need to stop when problems occur. Being honest enough to stop and possibly turn back can be a very difficult step to take.
There are many factors that come into play when altitude sickness hits, but taking some steps will help minimize your risk:
  • Acclimatize - The biggest contributor to altitude sickness is climbing too fast. That means the person in good shape has a good chance of getting sick since he tends to push harder and hike faster. People that reside at lower elevations will experience a greater change at lower heights. To acclimatize:
    • Rest and relax for 2 hours for every 1000 feet the trailhead is above your normal elevation. For example, if you live in Iowa at 1,000 feet and plan to hike in Wyoming at 9,000 feet, you should arrive in the afternoon and start your hike in the morning after sleeping a night to acclimatize.
    • Climb slowly and steadily.
    • Check how you are feeling every hour. Nausea, lack of hunger or thirst, headache, dizziness, difficult breathing, lack of coordination are all warning signs.
    • On multi-day hikes, sleep no more than 1500 feet higher than the previous night. You can climb higher during the day, but come down to sleep.
  • Expect It - just because you went to 14,000 feet last summer does not mean your hike to 12,000 feet will not affect you next weekend. Any height over 8,000 feet should make you be on the alert. Every hike is a new experience and by being on the lookout for symptoms, you will catch problems early on.
  • Hydrate - drinking more water helps reduce the symptoms. Drink even if you do not feel thirsty.
  • Reduce Exertion - the harder you push your body, the greater your risk of getting symptoms.
  • Eat Well - eat a high carbohydrate menu, and don't forget to drink water.

AMS - Acute Mountain Sickness

acute mountain sickness About 75% of people that hike over 10,000 feet will experience some mild AMS symptoms. Hikers can continue on with mild symptoms, but if they do not subside or they get worse, then corrective action is required. The problem with AMS is that its symptoms are similar to other common hiking problems such as dehydration, fatigue, and eating bad food.
Ignoring these symptoms can result in extreme situations, possibly death. Ordered from most severe to least:
  • Disorientation - confusion, hallucinations, irrational behavior can all be caused by edema, which is swelling of tissue and can be caused by higher elevation.
  • Loss of Coordination - someone stumbling or dropping their water bottle should be signals. If you suspect someone may be experiencing this, test them:
    • Have him walk heel-to-toe in a straight line.
    • Have him stand straight with feet together and arms at sides and then close his eyes. He should be able to balance for at least 15 seconds.
  • Lassitude - similar to exhaustion, just being tired out. After eating and drinking water and resting, exhaustion should go away. If it does not get better, do not go on and keep resting. There will be no energy to eat, talk, or do anything as the situation worsens.
  • Headache - there are many causes for a headache, from bright sun to altitude sickness. If a headache does not go away after food, water, and rest, then suspect altitude sickness.
  • Nausea - upset stomach and loss of appetite.

HAPE - High Altitude Pulmonary Edema

mountain hike High Altitude Pulmonary Edema is excess fluid in the lungs which further reduces oxygen exchange from air to your body. The level of oxygen diminishes which can lead to impaired thinking and ultimately death. HAPE symptoms include shortness of breath while at rest, feeling of tightness in the chest, weakness, feeling of suffocating, persistent cough, and fatigue. The person may also cough up watery fluid.

HACE - High Altitude Cerebral Edema

High Altitude Cerebral Edema is excess fluid in the brain which puts pressure on the brain. This usually develops over a few days but is a life-threatening situation. Disorientation and weird behavior will lead to unconsciousness most likely followed by death if nothing is done.

Treating Altitude Sickness

The important thing to do is stay alert and catch early symptoms fast. The longer symptoms develop, the more drastic the response will need to be. Assuming you catch the symptoms early, follow these steps - but if the symptoms are advanced, decide between the last couple steps:
  • Rest - take a break and take in some fluids and food. Take aspirin for headache. Do not be in a hurry and plan to break for an hour to give the symptoms a chance to recede.
  • Medicate - Diamox is an altitude medication that may help.
  • Descend - Drop at least 1,500 feet down the mountain and rest.
  • Halt - Stop the hike and descend completely off the mountain.
  • 9-1-1 - Call for medical services. If the victim can hike, start descending immediately, not in the morning or after supper, now! Otherwise, wait for evacuation.

 Feb 16, 2012 - greg dowler
Great info. What do you suggest to tell what your elevation limits are before starting the hike. I had asthma as a kid and sometimes when I get sick and want to accompany my son on BSA Philmont hike but am concerned about the lighter air and my limitations. What can I do to prepare for the elevation differences. It goes from 5k ft to 12k ft.
Feb 16, 2012 - Hiking Dude
Greg - You can't know how your body will react to lessened oxygen density at elevation.

To prepare before going, you should work your lungs and muscles through extended aerobic activity.  The better your body gets at acquiring and using oxygen, the better it will perform at higher elevations.  Start exercising 3 months or more before.  Hiking is great prep for hiking.

A good thing about Philmont treks is that you are given ample time to acclimate.  First night at Basecamp at 6400, 2nd night around 7000 or 7500, and then working up to higher campsites.  I believe the highest campsite is around 10,500 on Phillips.
When you get your annual BSA physical, be sure and ask your doctor for his advice about your hope of exerting yourself at altitude - he may have suggestions or tell you not to do it.

Oct 29, 2012 - Affan
i have asthma problem as well.. but i feel great at hight.. just come back from a lake at 14000 feet in himalaya Pakistan.. and i feel awesome there..
May 18, 2013 - Lee Drapela
Awesome info. We are fixing to go to Kandersteg, Switzerland for are trip for the summer and I got pick to look up this topic for my group "how to prevent altitude sickness , tips to diminish it,and how to treat if you get it" because we are going to do a lot of hiking up there this summer. Glad that I find this website and I am going to present it to my group Sunday May 19th,2013.  
May 29, 2013 - shawn yoder
Planning on hiking Pikes Peak next summer. It has been several years since I have hiked over 5000 feet. I live in Indiana so most hikes are not very high. How is it best to train my body so that when I hike high elevation it doesn't whoop me? Thanks.
Jun 11, 2013 - Deanna
Why is it that I do MUCH better to keep at a steady pace on the incline than I do if I stop and take breaks?  The difference is significant or I wouldn't bother posting this question.  Starting back up each time is horrid for me.   Any info would be appreciated.  
Jun 13, 2013 - Hiking Dude
@Deanna - Me too!  Once the muscles stop moving, it's hard to get them started.  Maintaining a steady, moderate pace keeps the muscles warm, lose, and active.  I try to keep moving until I reach a vista, natural stopping point, or the top - even if it is just a very slow plod up the hill.
Jun 21, 2013 - rick michot
I'm looking for a hiking area, preferably in New Mexico or Colorado, where I can hike at no more than 5000 ft elevation and high temperature less  than 80 degrees in July...any ideas?
Jun 21, 2013 - Hiking Dude
Rick - There is no such place.   Any location under 5000 feet is too far east and south to be cool enough.  Any place cool enough is cool because it is at a higher elevation.
See media.maps.com/magellan/Images/newmexicousrah.gif and media.maps.com/magellan/Images/coloradousrah.gif

Jul 01, 2013 - david browne
@shawn - I have been mountaineering in the Sierra for 40 years, and climbed many peaks over 13 or 14000.  Other than general fitness and being acclimated, there is not much you can do to improve high elevation performance.  It is all about how your body processes lower oxygen levels, and it varies greatly from person to person without regard to fitness.  When I introduce people to high climbing, that is one of the things I really watch closely because until you have done it, you cannot predict it.  Sleeping at altitude before climbing is the best way to acclimate and get best performance.  Follow the suggestions in this article, which are all very valid and part of standard mountaineering lore.
Jul 07, 2013 - Charles Johnson
My son and friends are planning a summit trip to Mt Fuji end of this month.  Your site has been a great source for information.  Will keep you posted on his progress
Sep 09, 2013 - conor
Where can I hike in the US where I would need O's
Sep 17, 2013 - hi
i love hiking. but the highest iv ever gone is 500meters and i struggle to breath then.
Oct 19, 2013 - Catherine Wagner
I have a family member who went hunting elk high on a mountain in Colorado.  He became very ill and almost died after coming down the mountain.  In fact, he was on his way home when he became very ill.  The ambulance attendant was able to save him.  When he became stable, he was moved to a larger hospital in Denver because no doctor identify what was the cause of his near death situation.  His new doctor suggested that it was most likely altitude sickness.  Can a person get this violently ill after coming off the mountain several hours before the onset of the attack?

Oct 23, 2013 - Hiking Dude
@Catherine - Well, from your description, the answer to your question is "Yes".  If a doctor diagnosed the cause, I'm certainly not one to say he is incorrect.  I would be more interested in finding out what to do to prevent it from happening again.
Nov 01, 2013 - irfan
plz any body tell me...
How many degree of elevation are there from sea level,so that we can call it mountain.
my number is 03364307740.You can tell me at it.
Nov 01, 2013 - Hiking Dude
@irfan - There is no minimum height nor steepness required to call a high point a "mountain".  Check out en.wikipedia.org/wiki/Mountain for some details, or look up Mount Wycheproof which is supposedly the lowest mountain in the world.
Dec 30, 2013 - Steve
I realize this is an older article, but it appears to still be in discussion. So....

Ummm, I find this article interesting and informative, but am confused by something.

Several times you advise to drink more water ("Hydrate - drinking more water helps reduce the symptoms. Drink even if you do not feel thirsty.", et al). Yet, excessive water intake can also cause symptoms similar to high-altitude sickness through dilution of electrolytes. And, edema is a condition that can be exacerbated by excessive fluid intake.

How can a person determine when dehydration is the real cause of their symptoms, without misdiagnosing the problem and contributing to their severity through excessive fluid intake?
Jun 02, 2014 - Patricia Cameron

I am an EMT who recently started hiking 14ers here in Colorado, where I live.  It is almost impossible to get too many fluids in these circumstances.  1.) You body requires a higher amount and so you drinking more is for these needs.  2.) It takes a LOT of water to create an electrolyte imbalance.  If it still really concerns you, you can bring along ONE athletic drink (sugar will makes things worse) or you can try the salt pills in some outdoor stores such as REI.  You can recognize electrolyte imbalances by severe cramps in the muscles, like your thighs and your calves.  Popping these before strenuous activity (with plenty of water) and another if muscle pain occurs (with plenty of water) should do you well.  
Jun 02, 2014 - Hiking Dude
@Steve - Simplest way to check on dehydration is comparing the person's water bottle with others to see if he's been drinking.  And, ask when he last urinated and what the color was - darker urine indicates more water is needed.

@Patricia - Salt tablets are rarely a recommended way to balance the sodium levels in the body.  It's better to snack on food throughout the hike since that stimulates thirst, provides energy, and reduces the chances of taking in too much unneeded salt.
Jun 20, 2014 - Chao
I m 48yrs old and had hypertension.
I managed to stabilize the systolic and diastolic to an acceptable level,would you recommend for me to make a climb to an elevation of 14000ft?
Jun 21, 2014 - Hiking Dude
@Chao - No, the only thing I would recommend is that you ask a doctor about medical conditions and what activities would be safe.  I'm a hiker, not a doctor!
Jul 10, 2014 - gary b jorgensen
HELP ! PLEASE advise of a recommended oxygen concentrator to allow me to camp at 13,000 ft and accend to 14,500-15,000. I really need  smallest weight available equipment. I am 73 years old, in fair shape and have COPD/ sleep apnea. This hunt is the top of my bucket list but my bride is not a happy camper. You "big boys and/or gals" that have knowledge of my requirements will be in my gratitude to offer your input. I will have limited access in camp (13,000 ft) to generator power until around 10:00 PM and have 12 volt access until climb (stalk) is required. PLEASE,PLEASE suggest an oxygen concentrator that fits my needs without being burdensome weight wise. Going to Tajikistan so must take all survival equipmemnt with me. Thanks, in advance, for ANY help you may provide. Gary B Jorgensen
Jul 11, 2014 - Hiking Dude
@Gary - If you google for "portable oxygen concentrator" there are 300,000 results with a huge range of weights, features, and costs.
You should ask a doctor for recommendations.  Maybe someone else can go out on a limb with a recommendation, but I'm a hiker, not a doctor!
Jul 18, 2014 - Dan
I was wondering if you or anyone has climbed  Mauna Kea in Hawaii?  My first time hiking anything this high.  I am in good shape , been doing high interval training since January. Any advice on this particular hike and what to pack? Thanks
Jul 20, 2014 - Hiking Dude
@Dan - Not me.  But, at 13,800 feet, it's certainly high enough for you to experience altitude sickness.  Looks to me like water will be a concern and absolutely no protection from weather above treeline.  Good luck - sounds like an adventure!
Jul 30, 2014 - daniel
Thanks Hiking Dude. making my backpack list at this very moment.  It will for sure be an adventure, planning on bringing a ton of water and some good hearty snacks. I will keep you posted on how it goes.

Nov 14, 2014 - Kendra Kirby
I have been trying to find information on descending and acclimation your body. I'm not a climber but think there is a spiritual/psychological parallel when coming off a very powerful "mountaintop" experience.  Any tips on what to do as you transition back into the groundatabase (i.e. real life,for my purposes). Thanks.
Nov 15, 2014 - Hiking Dude
@Kendra - There is no physical need to acclimate when descending from a high elevation hike.  As far as "spiritual" - well that's really up to the individual.
Many long-distance hikers that are out on the trail for months do have concerns about re-entering society, but I know of none that purposely plan for that event.  
Jan 17, 2015 - Jacki
What happened to me?  Hiked Pikes Peak a couple of years ago for my Bucket List.  When we reached the top, I was fine until I sat down in the booth to eat.  My jaw sort of 'locked up', my hands curled and I basically had a hard time moving anything.  Had to have help to walk to the Cog train for the ride down and even after back down and home, it took a couple of hours until I was back to normal.  Assuming it was some sort of altitude sickness, of course, but it doesn't seem to match any of the altitude sickness descriptions.  I can hike the Manitou Incline with no problems like that. Must have been something about not enough oxygen getting to my muscles. More careful now when I hike.  Never want that to happen ever again.  Way too scarey.
Mar 05, 2015 - Jane
We will be hiking the Salkantay Trail (Machu Picchu) in a few months.  We live at sea level.  Will 4 days at almost 11,000 feet in Cusco be sufficient for acclimatization?
Mar 05, 2015 - Hiking Dude
@Jane - There no absolute answer to "How much acclimatization is needed?"  Some people are barely effected while others get hit hard, and the same person may be effected differently on different trips.
But, going from 0ft to 11,000ft all at once is an awful big jump.  A day at 8K, then 9K, then 10K, then 11K would be a better plan, but I don't suppose you can do that.
I would just relax the first day at 11K, then a few short walks the 2nd day to see how it goes.  If all is well, then I'd use day 3 and 4 to walk around with packs.
Sounds like a terrific trek!
Mar 24, 2015 - Debra
@Jane - We will also be hiking the Salkantay in a few months and we also live at sea level. You might want to consider a night or two in the Sacred Valley first, if you can, instead of four nights in Cusco. The towns are lower, so it would provide a bit of gradual acclimatization. Several also have Inca ruins. We, for example, are flying into Cusco but then going immediately to Ollaytantambo for our first night and day. It's a little higher than 9K. So, 24 hours or so isn't a lot but I figured it was better than leaping from sea level to 11,200 feet. I'm no expert, of course, but this was a suggestion in a guidebook and I thought it was a good one. Have a great time - see you on the trail!! :)
Apr 01, 2015 - Bernard
Good day Hiking Dude.
Please give your best opinion.
I'm early 60,s, can run 5kms fairly well, of average fitness level, not too good at cardio, but will do required training for Mt. Kilimanjaro over 8 month period. What are my odds of reaching 19,000 ft in 6 days? (no special breathing equipment)
From what I read above,...I am a little skeptical!?!?
Apr 05, 2015 - Jessica
How much is the maximum one should hike per day? I will be hikinh in Apolobamba and the people I will be following will be going 1000m per day for the first 3-4 days. I was told that I shouldn't go up more than 300m for the first days.
Apr 06, 2015 - Hiking Dude
@Bernard - It looks like that is the standard climb length offered by guide services.  Sounds like you are preparing well before and understand it will be a challenge - so I'd say your odds are very good.

@Jessica - It's a good idea to gain altitude slowly so you acclimate to the air and generally 1000-1500 feet per day reduces the probability of problems.  Someone gaining 1000m per day for 4 days just gained 12000feet - that's a lot.

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