Altitude Sickness · Colorado

Altitude sickness in Colorado

By Bidwell Cranage, APRN, FNP-C, Member, International Society of Travel Medicine · Clinically reviewed by Ashley Cranage, APRN, FNP-C · Reviewed June 18, 2026

Yes, altitude sickness is common in Colorado, mostly in the mountains rather than Denver. It usually starts above about 8,000 feet, and most Colorado ski towns sleep between 8,000 and 10,000 feet. Flatland visitors who fly in and go straight up are the ones who feel it. Acetazolamide (Diamox) can lower the risk, and because Colorado is one of our eligible states, you can be seen online whether you live here or are already in town.

It is the mountains, not the mile-high city

Denver sits at 5,280 feet and rarely causes trouble on its own. The problem is the drive up: many trips go from a Denver flight straight to a ski town two or three thousand feet higher the same afternoon. That fast gain is what triggers symptoms.

Place	Elevation	Altitude sickness risk
Leadville	~10,150 ft	High; the highest city in the US
Breckenridge	~9,600 ft	High
Vail	~8,150 ft	Moderate to high
Aspen	~7,900 ft	Moderate
Estes Park (gateway to Rocky Mountain NP)	~7,500 ft	Moderate
Denver	5,280 ft	Low; a good place to spend night one

Day hikes climb much higher still: Trail Ridge Road in Rocky Mountain National Park tops out near 12,000 feet, and Colorado has 53 ranked peaks above 14,000 feet, the fourteeners, all listed below. The higher you sleep and the faster you got there, the more likely you are to feel it.

Bidwell Cranage at the top of the Imperial Express lift at Breckenridge, Colorado, beside the 12,840 foot elevation sign — Breckenridge tops out at the Imperial Express, the highest chairlift in North America at 12,840 feet. Bidwell Cranage, Bidwell Health founder, on the mountain.

Every Colorado fourteener, by elevation

Colorado has 53 ranked fourteeners (peaks above 14,000 feet with at least 300 feet of prominence); some lists count 58 named summits over 14,000 feet. Every one is far above the roughly 8,000 feet where altitude sickness can start, so climbing or even day-hiking any of them from a lower base is a real altitude exposure. Here is the complete list, highest to lowest.

#	Peak	Elevation	Range
1	Mount Elbert	14,440 ft	Sawatch Range
2	Mount Massive	14,428 ft	Sawatch Range
3	Mount Harvard	14,421 ft	Sawatch Range
4	Blanca Peak	14,351 ft	Sangre de Cristo Range
5	La Plata Peak	14,343 ft	Sawatch Range
6	Uncompahgre Peak	14,321 ft	San Juan Mountains
7	Crestone Peak	14,300 ft	Sangre de Cristo Range
8	Mount Lincoln	14,293 ft	Mosquito Range
9	Castle Peak	14,279 ft	Elk Mountains
10	Grays Peak	14,278 ft	Front Range
11	Mount Antero	14,276 ft	Sawatch Range
12	Torreys Peak	14,275 ft	Front Range
13	Quandary Peak	14,271 ft	Mosquito Range
14	Mount Blue Sky (formerly Mount Evans)	14,271 ft	Front Range
15	Longs Peak	14,259 ft	Front Range
16	Mount Wilson	14,252 ft	San Juan Mountains
17	Mount Shavano	14,231 ft	Sawatch Range
18	Mount Princeton	14,204 ft	Sawatch Range
19	Mount Belford	14,203 ft	Sawatch Range
20	Crestone Needle	14,203 ft	Sangre de Cristo Range
21	Mount Yale	14,200 ft	Sawatch Range
22	Mount Bross	14,178 ft	Mosquito Range
23	Kit Carson Mountain	14,171 ft	Sangre de Cristo Range
24	Maroon Peak	14,163 ft	Elk Mountains
25	Tabeguache Peak	14,162 ft	Sawatch Range
26	Mount Oxford	14,160 ft	Sawatch Range
27	Mount Sneffels	14,158 ft	San Juan Mountains
28	Mount Democrat	14,155 ft	Mosquito Range
29	Capitol Peak	14,137 ft	Elk Mountains
30	Pikes Peak	14,115 ft	Front Range
31	Snowmass Mountain	14,099 ft	Elk Mountains
32	Windom Peak	14,093 ft	San Juan Mountains
33	Mount Eolus	14,090 ft	San Juan Mountains
34	Challenger Point	14,087 ft	Sangre de Cristo Range
35	Mount Columbia	14,077 ft	Sawatch Range
36	Missouri Mountain	14,074 ft	Sawatch Range
37	Humboldt Peak	14,070 ft	Sangre de Cristo Range
38	Mount Bierstadt	14,065 ft	Front Range
39	Sunlight Peak	14,065 ft	San Juan Mountains
40	Handies Peak	14,058 ft	San Juan Mountains
41	Culebra Peak	14,053 ft	Sangre de Cristo Range
42	Ellingwood Point	14,048 ft	Sangre de Cristo Range
43	Mount Lindsey	14,048 ft	Sangre de Cristo Range
44	Little Bear Peak	14,043 ft	Sangre de Cristo Range
45	Mount Sherman	14,043 ft	Mosquito Range
46	Redcloud Peak	14,041 ft	San Juan Mountains
47	Pyramid Peak	14,025 ft	Elk Mountains
48	Wilson Peak	14,023 ft	San Juan Mountains
49	San Luis Peak	14,022 ft	San Juan Mountains
50	Wetterhorn Peak	14,021 ft	San Juan Mountains
51	Mount of the Holy Cross	14,011 ft	Sawatch Range
52	Huron Peak	14,010 ft	Sawatch Range
53	Sunshine Peak	14,007 ft	San Juan Mountains

The Sawatch Range holds the most fourteeners, including the two highest, Mount Elbert and Mount Massive. The popular front-range climbs near Denver (Grays, Torreys, Bierstadt, Longs, Quandary) are the ones most flatland visitors attempt first, and they are exactly where a fast drive up from sea level meets thin air.

Bidwell Cranage on the summit of Mount Democrat, a Colorado fourteener, holding a summit sign

From the founder

That is me on the summit of Mount Democrat, one of Colorado's 14ers, and I have climbed several others and ridden Breckenridge. I have felt the Colorado version of altitude sickness doing it: the headache the first night, the breathlessness on the last pitch. Coming from sea level to a 14er trailhead in one morning is exactly the fast ascent that brings it on. This page exists because I have lived it, not just read the guideline.

Bidwell Cranage, Bidwell Health founder, on the summit of Mount Democrat (Colorado).

Who benefits most from Diamox in Colorado

You fly in from sea level and drive straight to a high town like Leadville or Breckenridge
You are sleeping above about 8,500 feet
You have had altitude sickness on a past mountain trip
You only have a few days and cannot spend the first one taking it easy lower down

If you can build in a night in Denver, go up gradually, hydrate, take the first day easy, and skip alcohol early, you may not need medication at all. Acetazolamide is for people who cannot acclimatize slowly or who know their body reacts badly to altitude.

When to head down or get help

Ordinary altitude sickness is a headache, nausea, tiredness, and bad sleep, and it usually eases as you adjust or come down a little. But confusion, trouble walking a straight line, breathlessness at rest, or a cough with frothy spit are signs of severe altitude illness (HACE or HAPE). Those are emergencies even in a US ski town: descend and get care right away. No medication replaces going lower.

Get acetazolamide for Colorado online

Bidwell Health can review you for acetazolamide online and send it to your pharmacy, when it is clinically appropriate. Colorado is one of our eligible states.

$45 flat visitNo videoNo subscriptionSent to your pharmacyYou pay the generic price, nothing added

A $45 asynchronous visit (no video, no membership), reviewed by a licensed nurse practitioner. If you live in Colorado or have already arrived, you can be seen here. If you are flying in from another eligible state, request it before you leave, because you start the medication the day before you go up to altitude.

FAQ

Do you get altitude sickness in Colorado?

Yes, often. Altitude sickness usually starts above about 8,000 feet, and most Colorado ski towns sleep between 8,000 and 10,000 feet. Visitors coming from sea level who go straight up to a mountain town are the ones who feel it most, with headache, nausea, and poor sleep in the first day or two.

Do I need Diamox for a Colorado ski trip?

Many flatland visitors benefit from it. Acetazolamide (Diamox) makes the most sense if you fly in from low elevation and go straight to a high town like Leadville or Breckenridge, if you have had altitude sickness before, or if you are sleeping above about 8,500 feet. If you can spend your first night in Denver and ease up, you may not need it.

Which Colorado towns are highest?

Leadville is the highest at about 10,150 feet, followed by Breckenridge near 9,600 feet. Vail, Estes Park, and Aspen sit roughly between 7,500 and 8,200 feet. Denver, the mile-high city, is 5,280 feet and rarely causes altitude sickness on its own; the mountains are where it happens.

How many fourteeners does Colorado have?

Colorado has 53 ranked fourteeners, peaks above 14,000 feet with at least 300 feet of prominence, and some lists count 58 named summits over 14,000 feet. Mount Elbert is the highest at 14,440 feet and Sunshine Peak is the lowest at 14,007 feet. Every one is well above the roughly 8,000 feet where altitude sickness can begin.

Can I get Diamox for Colorado online?

Yes. Colorado is one of our eligible states, so if you live in Colorado or are already here, a $45 asynchronous online visit works, no video and no subscription. If you are flying in from another eligible state, request acetazolamide before you leave, since you start it the day before you go up to altitude.

Start your $45 altitude visit ›

Clinically reviewed by Bidwell Cranage, APRN, FNP-C, AANP board-certified Family Nurse Practitioner and Member, International Society of Travel Medicine.
Last reviewed: June 18, 2026 · References: CDC Yellow Book (High-Altitude Travel and Altitude Illness); Wilderness Medical Society Acute Altitude Illness guidelines (2024).