What is blood pressure? How is high and low blood pressure caused?

Blood pressure is a measure of the force that your heart uses to pump blood around your body within the arteries.

Blood pressure is the measurement of force applied to artery walls.(Getty Images 2021)

A blood pressure measurement is recorded by two numbers, a systolic pressure (this is the top number), and diastolic pressure (this is the bottom number). The systolic measurement (top) is when your heart is contracting, the diastolic measurement (bottom) is when your heart is relaxed, or just before your heart contracts. When you have high blood pressure, it’s called Hypertension. Low blood pressure is Hypotension.

A blood pressure measurement is recorded by two numbers.(Getty Images 2021)

Hypertension (High Blood Pressure)

Hypertension is a very common condition in older adults. If your blood pressure is high, it puts extra strain on your heart and blood vessels. Over a period of time, this can lead to health problems such as stroke, heart attack, kidney disease, and some forms of dementia. According to Blood Pressure UK, about a third of adults in the UK have high blood pressure, but many aren’t aware of it. This is because it usually doesn’t have any symptoms, this is why it’s important to have a regular blood pressure check.

Hypertension is a very common condition in older adults.(Getty Images 2021)


You’re likely to be more at risk if you:

  • Are overweight
  • Don’t exercise enough
  • Eat too much salt
  • Drink too much alcohol or coffee (or other caffeine-based drinks)
  • Are over 65
  • Smoke
  • Struggle to get enough sleep
  • Have high blood pressure in your family (genetics)
  • Are of a black African or black Caribbean descent

More often than not, making healthy lifestyle changes can help to reduce your chances of getting high blood pressure & help lower your blood pressure if it’s already high.

According to the NHS, approximately 1 in 20 of high blood pressure occur as a result of an underlying health condition or taking certain medication. The following are known causes of high blood pressure:

Health conditions that can cause high blood pressure include:

  • kidney disease
  • diabetes
  • long-term kidney infections
  • obstructive sleep apnoea – where the walls of the throat relax and narrow during sleep, interrupting normal breathing
  • glomerulonephritis – damage to the tiny filters inside the kidneys
  • narrowing of the arteries supplying the kidneys
  • hormone problems – such as an underactive thyroid, an overactive thyroid, Cushing’s syndrome, acromegaly, increased levels of the hormone aldosterone (hyperaldosteronism), and phaeochromocytoma
  • lupus – a condition in which the immune system attacks parts of the body, such as the skin, joints and organs
  • scleroderma – a condition that causes thickened skin, and sometimes problems with organs and blood vessels

Medicines that can increase your blood pressure include:

  • the contraceptive pill
  • steroids
  • non-steroidal anti-inflammatory drugs (NSAIDs) – such as ibuprofen and naproxen
  • some pharmacy cough and cold remedies
  • some herbal remedies – particularly those containing liquorice
  • some recreational drugs – such as cocaine and amphetamines
  • some selective serotonin-noradrenaline reuptake inhibitor (SSNRI) antidepressants – such as venlafaxine

Hypotension (Low Blood Pressure)

Hypotension (low blood pressure) is when blood pressure is much lower than normal, meaning the heart, brain and other parts of the body aren’t getting enough blood. Low blood pressure can cause dizziness and fainting and in some cases can be life threatening.


According to the British Heart Foundation, low blood pressure can sometimes be the result of another illness or condition. If you are having symptoms such as dizziness or fainting, it is important that you see your doctor.

If your blood pressure is unusually low, your doctor should check to make sure there is not a medical cause. Low blood pressure can sometimes be a side effect of medicines taken for high blood pressure, heart disease or depression. If this happens to you, your doctor may need to adjust the dose of the medicines you are taking, or give you a different medicine. Low blood pressure can also be caused by some over-the-counter and herbal medicines.





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