Altitude sickness - Causes, Treatment & When to See a Doctor

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What is Altitude sickness?

Altitude sickness, also called acute mountain sickness (AMS), is a collection of symptoms that can develop when a person ascends to a high elevation too quickly for the body to adjust. The condition typically occurs above 2,500 meters (8,200 feet) but can affect some individuals at lower altitudes, especially if they have pre‑existing cardiopulmonary disease, are dehydrated, or have been awake for a long period.

When the atmosphere is thin, the amount of oxygen that reaches the bloodstream drops (a state called hypoxia). The brain and other vital organs respond with a cascade of physiological changes—hyperventilation, increased heart rate, and fluid shifts—that can cause the uncomfortable and sometimes dangerous symptoms of altitude sickness.

Most cases are mild and resolve with rest and proper acclimatization, but severe forms such as high‑altitude cerebral edema (HACE) or high‑altitude pulmonary edema (HAPE) can be life‑threatening and require immediate medical care.

Common Causes

Altitude sickness is not caused by a single factor; rather, it results from a combination of environmental and personal variables that affect how quickly the body adapts to reduced oxygen levels.

• Rapid ascent – climbing more than 300–500 m (1,000–1,600 ft) per day above 2,500 m.
• Insufficient acclimatization – skipping rest days or “climb high, sleep low” strategies.
• Physical exertion at altitude – hiking, skiing, or running before the body has adjusted.
• Dehydration – low fluid intake or excessive diuretic use (e.g., caffeine, alcohol).
• Pre‑existing respiratory or cardiac disease – asthma, COPD, congenital heart disease, or anemia reduce oxygen delivery.
• Obesity or poor aerobic fitness – larger body mass and low cardiovascular conditioning increase oxygen demand.
• Sleep deprivation – impairs the body’s ability to regulate breathing.
• Medication that depresses respiration – opioids, benzodiazepines, or certain sleep aids.
• Cold, high‑altitude environments – increase metabolic demand and can worsen hypoxia.
• Genetic susceptibility – some people have inherited differences in hypoxia‑sensing pathways.

Associated Symptoms

The presentation of altitude sickness can vary, but typical signs and symptoms fall into three categories: mild (AMS), moderate/severe, and complications (HACE/HAPE).

Mild (Acute Mountain Sickness)

• Headache (often throbbing and worsens with activity)
• Nausea or loss of appetite
• Vomiting
• Fatigue or weakness
• Dizziness or light‑headedness
• Difficulty sleeping (often due to periodic breathing)
• Swelling of hands, feet, or face (mild peripheral edema)

Moderate to Severe

• Persistent or worsening headache despite rest and analgesics
• Increasing nausea/vomiting that interferes with fluid intake
• Severe fatigue that limits ability to walk or perform daily tasks
• Shortness of breath at rest
• Marked swelling (edema) of extremities

Complications

• High‑Altitude Cerebral Edema (HACE) – confusion, ataxia (loss of coordination), inability to walk, altered consciousness, seizures.
• High‑Altitude Pulmonary Edema (HAPE) – severe shortness of breath, cough producing frothy or pink sputum, rapid breathing, low oxygen saturation, bluish lips or fingertips.

When to See a Doctor

Most travelers can manage mild AMS with rest, hydration, and a slower ascent. However, you should seek professional care promptly if you experience any of the following:

• Headache that does not improve after 24 hours of rest and simple analgesics.
• Vomiting that prevents you from staying hydrated.
• Persistent shortness of breath at rest or worsening cough.
• Signs of HACE: confusion, inability to walk straight, severe drowsiness, or seizures.
• Signs of HAPE: severe breathlessness, cough with pink frothy sputum, or blue‑tinged lips.
• Any rapid decline in mental status, regardless of altitude.

Emergency medical evacuation may be necessary in severe cases, especially when you are far from a hospital equipped to deliver supplemental oxygen or hyperbaric treatment.

Diagnosis

Diagnosis of altitude sickness is primarily clinical—based on your recent travel history, rate of ascent, and symptom pattern. A physician may use the following tools:

History and Physical Examination

• Verification of altitude reached, speed of ascent, and recent exertion.
• Assessment of vital signs: heart rate, respiratory rate, oxygen saturation (pulse oximetry), and blood pressure.
• Neurologic exam for ataxia, confusion, or focal deficits (concern for HACE).
• Lung exam for crackles or frothy secretions (concern for HAPE).

Scoring Systems

• Lake Louise Score – a validated questionnaire that grades headache, gastrointestinal symptoms, fatigue, dizziness, and sleep quality. A score ≥ 3 with headache indicates AMS.

Additional Tests (when complications are suspected)

• Chest X‑ray or bedside ultrasound to look for pulmonary edema.
• Arterial blood gas (ABG) to quantify hypoxemia and respiratory alkalosis.
• Complete blood count and metabolic panel to rule out anemia, infection, or electrolyte disturbances.
• Neurologic imaging (CT/MRI) only if head trauma or other intracranial pathology is possible.

Treatment Options

Treatment hinges on severity and the ability to descend to a lower altitude.

Mild AMS – Home/Field Management

• Rest and halt ascent until symptoms improve (usually 24 h).
• Hydration – 2–3 L of water per day; avoid alcohol and excess caffeine.
• Analgesics – acetaminophen or ibuprofen for headache.
• Antiemetics – ondansetron or promethazine if nausea/vomiting persists.
• Acetazolamide (Diamox) – 125 mg–250 mg orally every 12 h, started before ascent, speeds acclimatization by inducing mild metabolic acidosis.

Moderate AMS – Medical Intervention

• All measures above, plus supplemental oxygen (2–4 L/min via face mask) to raise SaO₂ > 90 %.
• Consider a short course of dexamethasone (4 mg orally every 12 h) if acetazolamide is contraindicated or symptoms are severe.
• Begin descent of at least 500 m (1,600 ft) if symptoms do not improve within 24 h.

Severe Cases – HACE or HAPE

• Immediate descent—the single most critical intervention.
• Portable oxygen (≥ 2 L/min) en route and at the treatment site.
• Dexamethasone 4 mg IV/PO every 6 h for HACE.
• Nifedipine 30 mg PO every 12 h (or 10 mg IV) for HAPE to reduce pulmonary artery pressure.
• Portable hyperbaric chamber (Gamow bag) if descent is delayed.
• Rapid transport to the nearest facility capable of advanced respiratory support.

Prevention Tips

Preventing altitude sickness is largely about giving your body time to adapt.

• Plan a gradual ascent – limit gain to ≤ 300 m (1,000 ft) per day above 2,500 m, with a rest day every 3–4 days.
• “Climb high, sleep low” – spend nights at a lower elevation than your daytime high.
• Stay well‑hydrated – drink water regularly; add electrolytes if you sweat heavily.
• Avoid alcohol and excessive caffeine during the first 48 h at altitude.
• Acclimatization medication – start acetazolamide 1 day before ascent (if tolerated) and continue for the first 48–72 h.
• Maintain good sleep hygiene – use a sleeping mask, earplugs, and keep a regular schedule.
• Condition your cardiovascular system before travel with aerobic exercise (e.g., brisk walking, jogging, cycling) 3–4 times per week.
• Pack essential gear: portable oxygen, a pulse oximeter, a basic medical kit (acetazolamide, ibuprofen, anti‑nausea meds, dexamethasone).
• Educate travel companions about warning signs and evacuation plans.

Emergency Warning Signs

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**Sources**: Mayo Clinic. “Altitude illness.”; Centers for Disease Control and Prevention. “Travelers’ Health – High Altitude.”; National Heart, Lung, and Blood Institute (NIH). “High Altitude Pulmonary Edema.”; World Health Organization. “Altitude‑related diseases.”; Cleveland Clinic. “Acute Mountain Sickness.”; Wilderness Medical Society Consensus Guidelines (2023).

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