Does High Altitude Affect Blood Pressure?

  • 1st Revision: Alys Schirmer[Linkedin]
  • 2nd Revision: Kimberly Neil
  • 3rd Revision: Kaamya Mehta[Linkedin]

About blood pressure

Blood pressure is the measurement of the force at which blood is pumped out of the heart and around the body. It is given as a number of X over Y, also written as X/Y, known as systolic pressure (pressure in the arteries after the heart has pumped out blood) over diastolic pressure (when your heart is able to relax before pumping out blood again). It is measured in mmHg, also known as milligrams of mercury.


Elevated blood pressure can be categorised depending on its severity. Normal blood pressure tends to be within the range of 90/60mmHg and 120/80mmHg, whilst high blood pressure (hypertension) is 140/90mmHg or higher. The range between normal and high is elevated blood pressure, but this is not classed as hypertension. 

Blood pressure above 140/90mmHg will be categorised into mild, moderate and severe hypertension depending on how high the figure is.1

What is considered a high altitude?

There are three altitude regions that show the effect of high altitude on the human body:2

  • High altitude: 1500-3500 metres above sea level
  • Very high altitude: 3500-5500 metres above sea level
  • Extreme altitude: above 5500 metres above sea level

Altitude sickness

Altitude sickness tends to occur 6-24 hours after reaching an elevation of 2500m and is sometimes abbreviated to AMS (acute mountain sickness). AMS can be categorised into mild, moderate and severe cases:

  • Mild AMS can be resolved by allowing the body time to acclimatise at the current elevation, with the symptoms being mild and not hindering activity.
  • Moderate AMS presents with slightly more severe symptoms which may require an individual to descend to a lower altitude to feel better.
  • Severe AMS may involve shortness of breath during activity and even at rest, hence requiring descent and medical attention.3


The symptoms of AMS typically include:

  • Headache
  • Nausea and vomiting
  • Dizziness
  • Tiredness
  • Loss of appetite
  • Shortness of breath (this symptom is not likely to occur in mild or moderate AMS)1 

Effects of high altitude on the blood pressure

A correlation between altitude and hypertension has been established, using a study on residents in Tibet; a country with high altitudes. The population with hypertension increased as the altitude increased in different towns.4 This shows that high altitude affects blood pressure. 

How does blood pressure increase at high altitudes?

High altitude has an effect on oxygen saturation levels within the human body. This is due to the low atmospheric pressure in the high altitudes; there is less oxygen available as the atmospheric pressure continues to decrease. This means the oxygen molecules bind to the haemoglobin with a higher affinity, making it harder to penetrate the respiring tissues. Therefore causing a low oxygen saturation in the body. 

Exposure to altitudes of 5400m could increase blood pressure by 14mmHg systolic pressure and 10mmHg diastolic pressure within a 24-hour period.5 

Other effects of high altitude on the human body

HACE is swelling in the brain due to a lack of oxygen. Individuals suffering from HACE will often feel okay and insist they are fine and to be left alone. However, if left untreated, it can be fatal. symptoms of HACE are similar to AMS, but also include loss of coordination, feeling confused and hallucinations. 

HAPE is the buildup of fluid in the lungs. Much like HACE, it is fatal if left untreated. Symptoms of HAPE include cyanosis, difficulty breathing even at rest, chest tightness and a persistent wet cough.6

These conditions are extremely uncommon complications following untreated AMS. 

Who is at risk at high altitude?

All individuals (even experienced climbers) may experience altitude sickness; it is caused by ascending too quickly, therefore the body does not have time to adapt and acclimatise to the low atmospheric pressure.

Some individuals, however, are at greater risk:

  • Pre-existing heart and lung conditions 
  • Pregnant 
  • For those living in a low elevation environment - the body is not used to the pressure
  • Previously suffered from altitude sickness.3

Diagnosis and treatment

The diagnosis of AMS is based upon the prevalence of the number of symptoms within a given time. It also tends to be spotted easily by experienced climbers. HACE requires an MRI or CT scan to confirm; if suspected at a high altitude the individual must immediately be descended to a medical facility for the scan. The same applies to HAPE, although a chest X-ray would be conducted instead to check for fluid.

Treating AMS whilst still at a high altitude involves taking time to acclimatise at the present altitude.


Whilst in high altitude conditions, it is important to increase altitude gradually to allow the body time to adapt to the low atmospheric pressure – acclimatisation decreases the chances of altitude illness.

It is important to stay hydrated and continually sip water as well as to have a light but high-calorie diet. It is also recommended to avoid smoking and drinking.

How to prepare before going to high altitude?

It is important to plan well ahead of a high-altitude climb to best prepare. Cardiovascular activity is key to improving circulation, as well as maybe some small local climbs.

There are some medications that you may consider taking for altitude sickness:

  • Acetazolamide is a medicine used in the prevention and treatment of altitude sickness. It is readily available at travel clinics and may be prescribed by GPs. It will not completely treat AMS but will lessen symptoms
  • Ibuprofen and paracetamol are recommended for headaches that may occur at altitude.
  • Promethazine is an anti-sickness medication that can be purchased over the counter.6 

When to seek medical help


If you suffer from any pre-existing medical conditions, especially heart and lung conditions or hypertension it is important to speak to your GP about how high altitude may affect you and any specific precautions or medications to take. 

During High Altitude

If you suspect severe AMS, HAPE or HACE it is important to descend immediately and seek medical attention as soon as possible. 


Blood pressure increases at high altitudes to increase circulation, allowing more oxygen to tissues. This is required due to the low atmospheric pressures making oxygen bind to haemoglobin with a higher affinity, hence less oxygen available to respiring tissues.

Individuals with hypertension and other pre-existing heart and lung conditions are more likely to experience AMS at high altitudes. High altitude is defined as 2500 metres above sea level.

AMS occurs when you increase in altitude too quickly, not giving the body time to acclimatise. In extreme cases, individuals may develop HACE or HAPE. 


  1. What is blood pressure? [Internet]. 2022 [cited 13 July 2022]. Available from:
  2. Mathew T, Sharma S. High Altitude Oxygenation. 1st ed. StatPearls; 2022. 
  3. Altitude Sickness: Symptoms, Diagnosis, Treatment & Prevention [Internet]. Cleveland Clinic. 2020 [cited 13 July 2022]. Available from:
  4. Mingji C, Onakpoya I, Perera R, Ward A, Heneghan C. Relationship between altitude and the prevalence of hypertension in Tibet: a systematic review. Heart. 2015;101(13):1054-1060. 
  5. Can Hypertensive Patients Travel to High Altitudes? [Internet]. Saw on Hospital. 2022 [cited 13 July 2022]. Available from:
  6. Altitude sickness - NHS [Internet]. [cited 13 July 2022]. Available from:
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Aisha Yasin

Biomedical Science - Biomedical Sciences, General, Lancaster University, England

"I am a recent biomedical science graduate, with ambitions to go on to do post-graduate medicine. During my biomedical science degree I have done a variety of modules including anatomy, physiology, clinical biochemistry and many more... Currently working as a healthcare assistant for P&O Cruises"

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