Planning a trek to the mountains can be exciting, but being physically fit is not always enough to prepare the body for high-altitude conditions. Running regularly, lifting weights or having good stamina does not necessarily mean a person will tolerate low oxygen levels well. As trekkers climb higher, atmospheric pressure falls, reducing the amount of oxygen available with every breath. This can put additional stress on the lungs, heart and other organs. That is why doctors recommend assessing your health and understanding the risks before heading to high altitude. "Many trekkers make the mistake of confusing physical fitness with physiological readiness. It's possible for a person who runs regularly to get very sick at altitude. The mountain doesn't care how good you are at the gym. As we climb higher, the atmospheric pressure decreases. With each breath you take, there's less available oxygen," says Dr Pradeep Bajad, Senior Consultant, Pulmonology, Amrita Hospital, Faridabad. 

Why Fitness Alone Is Not Enough

Altitude affects everyone differently. A person who is otherwise healthy and physically active can still develop altitude-related illness if they ascend too quickly or fail to acclimatise properly. "Anyone who has not acclimatised and sleeps at an altitude above about 2,450 metres can develop altitude illness. There is no routine test that can reliably predict susceptibility. Previous altitude response and rate of ascent are still stronger indicators than age or athletic ability," Dr Bajad explains. He adds that a pre-trek consultation should therefore be viewed as a "risk audit" rather than simply a fitness certificate.

What Health Checks Should You Get Before A Trek?

The exact tests required depend on your age, medical history, fitness level and the altitude of the trek. However, certain areas deserve particular attention.

Check Your Lung Health

A respiratory assessment is particularly important for people with asthma, chronic cough, previous tuberculosis, a history of smoking, sleep apnoea or unexplained breathlessness.

"That's the first step for the lungs, oxygen saturation, and full respiratory history. Spirometry may be needed for people with asthma, a chronic cough, a history of tuberculosis, exposure to smoking, sleep apnoea or unexplained breathlessness," says Dr Bajad.

People who regularly use inhalers should also make sure they understand the correct technique and carry their prescribed medication. A written plan for worsening symptoms can be useful during a trek.

Check For Anaemia

Low haemoglobin can reduce the body's ability to transport oxygen and may make strenuous activity feel more difficult. "Anaemia can insidiously affect exercise tolerance," says Dr Bajad. Depending on the individual's medical history, a doctor may recommend a complete blood count before a demanding high-altitude trek.

Check Blood Pressure And Blood Sugar

High altitude combines several stresses: physical exertion, cold temperatures, reduced oxygen availability and changes in sleep. Uncontrolled hypertension or diabetes can therefore become particularly important to address before a trek. "Uncontrolled blood pressure, diabetes, or an undiagnosed cardiac condition can be consequential when exertion, cold, and low oxygen levels combine," Dr Bajad says. People with existing medical conditions should discuss their trekking plans with their doctor rather than assuming that being physically active automatically makes the trip safe.

Consider A Heart Check-Up

For some trekkers, particularly those who are older or have cardiovascular risk factors, symptoms or a relevant medical history, a doctor may recommend an ECG or exercise evaluation. Dr Bajad says that depending on age, symptoms and medical history, testing may include a complete blood count, blood glucose, kidney function tests, ECG or an exercise assessment. Not everyone needs every test. The goal is to identify individual risks before exposing the body to high-altitude stress. Your Trek Itinerary Is Part Of Your Health Assessment One of the most important factors in preventing altitude illness is how quickly you ascend. "The itinerary is medical information," says Dr Bajad. At higher elevations, the body needs time to adapt to lower oxygen availability. Above 3,000 metres, he recommends that sleeping elevation should generally increase by no more than about 500 metres a day, with an acclimatisation day after every additional 1,000 metres. A rushed itinerary can increase the risk of altitude-related illness even in otherwise fit trekkers.

Can Acetazolamide Prevent Altitude Sickness?

Acetazolamide may be recommended for selected travellers at risk of altitude illness. However, it should not be viewed as a substitute for proper acclimatisation. "Acetazolamide may be helpful for selected travellers, but it is not an oxygen tablet, nor a rescue for a reckless ascent," Dr Bajad says. Anyone considering medication for altitude sickness should discuss it with a healthcare professional beforehand.

Know The Warning Signs Of Altitude Sickness

A headache accompanied by nausea, unusual fatigue or other symptoms after gaining altitude may indicate acute mountain sickness. Mild symptoms should not simply be ignored or pushed through, particularly if they are getting worse. More serious warning signs include difficulty breathing while sitting or lying down, confusion, problems walking in a straight line or a rapidly worsening cough. "These may be a sign of life-threatening pulmonary or cerebral oedema," Dr Bajad warns. In such situations, descending to a lower altitude and obtaining urgent medical help can be critical.

What Trekkers Should Remember

A pre-trek health check cannot guarantee that you will not develop altitude sickness. There is also no single test that can predict exactly how an individual will respond to altitude. What it can do is identify underlying health issues, ensure existing conditions are appropriately controlled and help you understand your personal risks. The most important preparation is therefore not just building stamina in the gym. It is understanding your lungs, heart, blood health, medications, planned altitude and rate of ascent. As Dr Bajad puts it, "A responsible health check doesn't guarantee you won't get altitude sickness. It gives something more valuable: the judgement to know when the body is adapting, and when the mountain is telling you to come down."



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