The Mountain Towns That Send People to the ER Every Weekend
Breckenridge sits at 9,600 feet. Aspen is at 7,908. Telluride is at 8,750. Vail is at 8,150. The Eisenhower Tunnel on I-70 tops out at 11,013 feet — and most people drive through it without thinking twice.
Denver is at 5,280 feet. If you fly into Denver and drive straight to the mountains, you are gaining 3,000-5,000 feet of elevation before you sleep that night. Your blood’s oxygen-carrying capacity has not caught up. This is where the problems begin.
Altitude sickness (Acute Mountain Sickness, or AMS) sends hundreds of visitors to Colorado’s mountain clinics every ski season. Most cases are preventable. Almost all are survivable with proper response. A small number escalate to serious conditions — High Altitude Pulmonary Edema (HAPE) or High Altitude Cerebral Edema (HACE) — that require immediate descent and emergency care.
This guide exists to make sure none of that happens to you.
What Altitude Actually Does to Your Body
At sea level, each breath delivers oxygen at normal atmospheric pressure. At 9,000 feet, the same breath delivers about 70% of that oxygen. At 14,000 feet (Colorado’s higher peaks), it’s closer to 60%.
Your body responds by:
- Breathing faster and deeper
- Increasing heart rate
- Producing more red blood cells over days and weeks
- Redirecting blood flow to vital organs
The immediate problem is the gap between what your body needs and what it’s getting. This produces the classic AMS symptoms: headache, fatigue, nausea, loss of appetite, dizziness, and difficulty sleeping.
The serious problem — HAPE and HACE — happens when fluid accumulates in the lungs or brain. These are medical emergencies requiring immediate descent.
Who Gets It
Altitude sickness is not a fitness issue. Elite athletes get AMS. Young, healthy skiers get it. It is primarily a genetic predisposition combined with rate of ascent.
Higher risk factors:
- Flying directly to altitude from sea level (no gradual acclimatization)
- Ascending too quickly (driving from Denver to Breckenridge in the same day you land)
- History of AMS
- Dehydration
- Alcohol consumption (especially the night before or after ascent)
- Heavy exertion immediately after arrival
Lower risk does not mean no risk. People who’ve been fine at altitude before can get AMS on a subsequent trip. The mountain doesn’t remember your track record.
The Prevention Protocol
Acclimatize in Denver First
Denver at 5,280 feet is high enough to begin acclimatization. Spending one night in Denver before heading to mountain towns gives your body a partial adjustment before the next gain.
If your schedule is tight and you’re arriving the day before skiing, consider staying in Denver rather than going directly to Breckenridge that night.
Ascend Gradually
If possible, spend your first mountain night at lower elevation (Vail at 8,150 is lower than Breckenridge at 9,600). Don’t go straight to Telluride on night one.
The general guideline above 8,000 feet: don’t increase your sleeping elevation by more than 1,000 feet per night.
Hydrate Aggressively
You lose water faster at altitude through increased respiration. Start hydrating 24 hours before you go up. During your first 48 hours at altitude, aim for 3-4 liters of water per day. Avoid alcohol for the first 24 hours — it accelerates dehydration and suppresses the body’s natural acclimatization response.
Consider Diamox (Acetazolamide)
Diamox is a prescription medication that prevents and treats AMS by accelerating breathing rate, which increases blood oxygen saturation. It is genuinely effective.
How it works: Diamox makes your kidneys excrete bicarbonate, which makes your blood slightly more acidic, which triggers faster breathing. More breaths = more oxygen.
Dosing: 125-250mg twice daily, starting 24 hours before ascent, continuing for 48-72 hours at altitude. Requires a prescription — talk to your doctor before the trip.
Side effects: Increased urination, tingling in fingers and toes, carbonated drinks taste flat. These are minor and temporary.
Who should take it: Anyone who has had AMS before, anyone planning a rapid ascent, anyone with a history of mountain illness.
Take It Easy the First Day
“Take it easy” means genuinely easy — short walks, unpacking, eating well, not immediately hammering difficult runs or high-altitude hikes. Your first ski day should be lower runs at moderate effort, not charging expert terrain at 12,000 feet.
Most people arrive, feel fine, push hard the first day, and feel terrible by evening. The symptoms lag the exertion by several hours.
Symptoms: What to Watch For
Mild AMS (address immediately):
- Headache (especially at temples or back of head)
- Fatigue out of proportion to exertion
- Loss of appetite, nausea
- Dizziness
- Difficulty sleeping
Moderate AMS (do not ascend further, consider descent):
- Severe headache not relieved by ibuprofen
- Vomiting
- Significantly decreased coordination
- Shortness of breath at rest
Severe AMS / HAPE / HACE (medical emergency — descend immediately):
- Confusion, disorientation, or altered mental state
- Ataxia (inability to walk a straight line)
- Persistent cough producing pink or frothy sputum
- Cannot catch breath even at rest
- Loss of consciousness
The most important rule: If in doubt, go down. Descending even 1,000-2,000 feet can dramatically improve severe symptoms. Do not wait to see if symptoms improve at the same elevation when symptoms are severe.
Treatment: What to Do When It Hits
For mild AMS:
- Stop ascending — do not go higher
- Rest at current elevation
- Hydrate
- Ibuprofen (600-800mg) or aspirin for headache
- If symptoms worsen after 24 hours: descend
For moderate to severe AMS:
- Descend immediately — this is the most effective treatment
- Supplemental oxygen if available (many mountain clinics and resorts have it)
- Descend to where symptoms significantly improve, not just to the next lower town
Diamox at altitude: If you have symptoms and a prescription, Diamox can help stabilize mild to moderate AMS while you decide whether to descend. It is not a substitute for descent when symptoms are severe.
Medical Resources in Colorado Mountain Towns
Every major Colorado ski resort has medical facilities on the mountain:
Breckenridge: Breckenridge Medical Center (970-453-9000) in town; Summit Medical Center at the base area for on-mountain emergencies.
Vail: Vail Health (970-476-2451) with 24-hour emergency services. Well-equipped for altitude issues given the volume of cases.
Aspen: Aspen Valley Hospital (970-925-1120) — full emergency department.
Telluride: Telluride Medical Center (970-728-3848) — smaller but experienced with altitude cases.
Estes Park / Rocky Mountain National Park: Estes Park Health (970-586-2317).
If you’re in a situation where descent to a medical facility would help, go. Mountain town ERs see altitude sickness constantly — there’s no stigma, no embarrassment, just experienced staff who know exactly what to do.
The Practical Altitude Calendar
Day 1 in Colorado: Fly into Denver. Stay in Denver overnight. Drink water. No alcohol. Light activity.
Day 2: Drive to mountain town. Arrive before evening. Light activity only. Eat a real meal. Drink water. Sleep.
Day 3: First full mountain day. Start easy. Take breaks. Note any headache or nausea — these are warnings.
Day 4: Most people are substantially acclimatized. Energy improves. Appetite normalizes. You can push harder.
One week in: Your body has made meaningful adaptations. Red blood cell production has begun increasing. You are operating more efficiently at altitude.
The One Thing to Remember
Altitude sickness is not a sign of weakness, poor fitness, or bad luck. It is a predictable physiological response to rapid ascent. The people who get in trouble are the ones who ignore mild symptoms, push through, drink alcohol, and keep ascending. The people who have great mountain trips are the ones who drink water, take the first day easy, and descend if things get worse.
Colorado’s mountains are worth every precaution. A headache on day one is a small price for everything that follows.
Related: Breckenridge guide | Aspen guide | Telluride guide | Vail guide