Sea Level to High Altitude

Contrary to popular belief, you don’t have to be climbing Mt. Everest to start feeling altitude sickness; symptoms can start as low as 6,000 feet.  All of the various types of altitude illnesses are basically caused by a lack of oxygen and your body’s response to this stress.   The main cause is going too high, too fast without acclimating to the low oxygen level.    In Denver, which is the “mile high” city, there is 17% less oxygen in the air than at sea level.  At 8,000 feet, there is 25% less and at 14,000 feet about 40% less oxygen than at sea level.

Even if you are in excellent physical condition, this really has no bearing on how you will acclimate to high altitude.   It is very difficult to predict who will develop symptoms.   It doesn’t matter if you are young or old, fit or overweight, male or female.      People have been dealing with altitude sickness for as long as they have been climbing mountains so thankfully there are many remedies.    Your best defense is to understand and treat the symptoms so your trip will be a whole lot safer and enjoyable.

What is happening? 

Your body is an amazingly adaptable machine, so when you ascend to a higher altitude, your body is working hard to make the necessary adjustments.    First of all, your body starts to breath faster which works well to keep your oxygen level up initially.    To keep your body in balance, your kidneys produce more urine.   Over the next 4-7 days, your body will adapt to the altitude by adjusting your breathing rate and kidney function.   Your body will increase the amount of red cells in your blood in an effort to carry more oxygen to your system.    All forms of mountain sickness can be prevented by gradual ascent.   If you give your body time to make the necessary adjustments, you should have no problems.

But, if you happen to be on a tight schedule, and you do not have the luxury of gradually acclimating, then you are more likely to have some problems.   In fact, about 25% of unacclimated people will develop some symptoms of altitude sickness at 6,000 feet.    As elevation increases, so does the risk of illness.   If a person were dropped on the top of Mount Everest (29,000 feet) without giving the body time to acclimatize, he or she would die within five minutes.   This is why gradually acclimating is so important.

Rock Climbers, Eldorado Canyon State Park, Boulder, Colorado

Three levels of altitude sickness:

1.  Acute Mountain Sickness (AMS) is the most common and typically least severe form.   Most people compare the symptoms to having a bad hangover or flu.    Symptoms include headaches, nausea, dizziness, poor appetite, fatigue, shortness of breath with exertion, and tightness of chest.    Physical activity increases the speed in which these symptoms appear.     Symptoms usually take between a half hour and two hours to set in.    It is important to recognize these early symptoms and act appropriately to prevent more serious forms of altitude sickness.    

2.  High Altitude Pulmonary Edema (HAPE) is more dangerous.  Low oxygen levels can damage blood vessels in the lungs and cause them to leak fluid.  Symptoms include a dry, raspy cough, vomiting, headache that is not relieved by Tylenol or aspirin, severe trouble breathing even at rest, balance and coordination problems.   If these symptoms occur, get to lower altitude as quickly as possible!   Most authorities recommend a drop of about 1,000 – 1,500 feet or until symptoms resolve.   Typically, 1-2 nights at the lower elevation will allow your body to adjust and then you can gradually move to higher elevation.

3.  High Altitude Cerebral Edema (HACE) is the most severe and frequently fatal form of altitude sickness.   It is the result of swelling of brain tissue from fluid.   Symptoms include mental impairment, confusion, loss of coordination/balance, disorientation, loss of memory, hallucinations, turning blue, irrational behavior, and coma.   Severe HACE can be fatal so immediate descent and seeking medical attention is required.

So, if you are planning a trip to high altitude, here are some preventative measures:

1.  Drink large amounts of water!   At the very minimum, a liter of water every 4 hours of inactivity and a liter every 2 hours of physical activity.  The goal is to give your body more opportunity to expel the excess lactic acid in your system.   A rhyme to remember:  Before you hit the trail, best your urine be pale.

2.  Avoid alcohol or sleeping pills.   All these slow the body’s adjustment to elevation.

3.  Get rest when you arrive.  If you are coming straight from sea level, spend at least 24 hours being completely lazy with plenty of sleep and no strenuous activity.    If possible, opt to drive rather than fly – the longer trip will give your body time to acclimate.

4.  Maintain your iron level, which helps with oxygen delivery.  Take supplements or eat iron-rich foods, like red meat and greens.

5.  Increase carbohydrate intake (pasta, rice, pancakes) to 70% of total calories.  This means reducing fat intake.

6.  Acclimatize gradually.   Spend time gradually building up in altitude.  For example, start at a mild hike that ranges from 5,000 to 6,000 feet.    And after a few days, go a little higher.

7.  Medication.    If you are on a tight schedule and will be moving quickly to an altitude greater than 6,000 feet, Diamox (Acetazolamide) is an effective medication used to help a person acclimatize faster.   Your physician can prescribe this for you before you leave on your trip.  You generally need to take it for about 2 days prior to your trip to prevent altitude sickness.  It causes your kidneys to excrete bicarbonate, a form of carbon dioxide, which slightly acidifies the blood and helps you breathe deeper and increase blood oxygen levels.  This is an artificial acclimation so once the drug runs out, your true acclimation must occur.   If you take it when symptoms strike, expect to wait 24 hours or more before they subside.   Diamox (Acetazolamide) does not treat HACE or HAPE, so if AMS symptoms persist or worsen, you must descend to a lower elevation.  Side effects include numbness of the extremities and sun sensitivity.

Alternatively, another medication is Dexamethasone which treats symptoms of AMS, HAPE, and HACE.   It is a powerful steroid that decreases brain swelling and stabilize the leaky blood vessels, but does not speed acclimatization.  It’s also an immunosuppressant, so it’s not safe for long-term use.   Consult your physician before your trip to see which medication is best for your situation.

When you are on the trail:

1.  Drink Water!   Altitude accelerates dehydration, which compounds AMS symptoms; avoid alcohol, reduce caffeine intake.

2.  Ascend gradually.  Since there is less oxygen, you must reduce your need for it.  Find a pace that works for you and the faster hikers should slow their pace to accommodate you.   Be sure to rest when you’re tired, even if you feel as if you haven’t done enough to need a rest.   If you have never been above 4,000 feet, schedule in lots of rests on your trail.

3.  Treat symptoms appropriately.  Treat a headache with aspirin which will open blood vessels and encourage more blood flow.    If you can’t take aspirin, take an ibuprofen.  For nausea, ginger candies, extracts or capsules are great in helping with stomach problems.  Or you can try Tums.  Eating carbohydrates may also help combat fatigue.  Pack some trail mix, GORP (good old raisins and peanuts), hard candies, gummy bears, whatever you like.   M&Ms have saved my butt many times. 

4.  Keep an eye on other people you are with.    As AMS sets in cognitive abilities drop, that means that they may not have the presence of mind to notice they are getting AMS.

5.  Get off the mountain.   If you or someone in your party develops severe trouble breathing, severe headache and fatigue or are disoriented, descend immediately and seek medical attention.   Symptoms can worsen rapidly and lead to a more serious situation.  All but the most severe symptoms of altitude sickness will resolve all by themselves after descending from altitude, dropping just 1,500 feet is usually enough to recover.

6.  “Climb High, Sleep Low”    If you are tackling high peaks of 14,000, and plan to camp overnight, follow the “climb high, sleep low” rule, as bedtime is when breathing difficulties and many other symptoms are at their worst.   If you want to get to the top of a high mountain without experiencing the dilemmas of HAPE or HACE, you must sleep only 1,000 feet higher than the previous night.

Please note: The information above is merely a summary of what I have learned.  I am not a medical doctor, so please consult your physician to receive reliable information before traveling to high elevations.

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6 Responses to Sea Level to High Altitude

  1. Tonja Pizzo

    I recently relocated from (Houston) TX to (Denver) CO and suffered a some altitude issues. I bought a bottle of liquid chlorophyll that I use before and after elevated hikes or even if I’m driving to elevated destinations. It seems to help.

  2. Mickey

    i have moved from a elevation of about 700′ to Pueblo, Co of about 4700′ and my blood pressure has risen dramatically. The staff in medical at work say in 2 months I should be acclimated. I’ve heard many people say it can take a lot longer. What can help my situation?

    • thetrailgirl

      Hi Mickey, when I moved here from Dallas, it was hard to breathe. My daughter’s blood pressure was also high at first, she had an exam for school and the doctors were sort of freaking out about how high it was. It takes time to acclimate for sure. Drink lots of water, maybe add some electrolytes before you go exercise. Stay super hydrated is my advice and be patient. Your body is so wise, and it just needs time to adjust.

  3. Johnny Raven

    I just saw your article about altitude sickness, and I really like what I saw, you cover all the important things and explain what the body is dealing with … you are so correct, our body is amazing and can do so much, if only we listen to what our body is telling us.

    I also have a Facebook “note” that discusses altitude sickness, something I have known about since my first trip to Colorado (13,000+ feet) in 1955.

    Now I mostly hike the High Sierra to several 14,000+ peaks, and never get altitude sickness. 🙂

    My FB note is at:

  4. Timothy

    This is the the best information I’ve found on acclimating to altitude from sea level. Thank you! I’m preparing for the Mt. Evans Hill Climb this year and have never been above 5,000 ft. I plan on getting to CO a week in advance. I know longer acclimation is ideal, but will a week be helpful at all? Your advice to slowly acclimatize is very helpful. Great recipes too! Cheers.

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