What do the blood pressure numbers mean?

Introduction

In simple terms, your blood pressure numbers measure the force at which blood flows in your arteries. The heart pumps blood to all parts of the body. However, there are periods when the heart muscles relax to allow it to be filled with blood, and also periods when it contracts to pump blood out of the heart.

The blood flow pressure is different during the contracting and relaxing of the heart muscles. Since blood is actively pushed out during the contraction phase, the flow force is higher in the arteries during the contraction phase than during the relaxation phase. Therefore, there are two numbers taken during blood pressure measurements. One for blood pressure during the contraction phase, called systolic blood pressure, and another for blood pressure during the relaxation phase, called diastolic blood pressure.

What does a blood pressure reading look like?

There are two number readings for a blood pressure measurement. The blood pressure tends to be represented this way: 120/80mmHg. The first number shows the systolic blood pressure, while the second represents the diastolic blood pressure. The unit of measurement of blood pressure is millimetres of mercury (mmHg).

Systolic Blood Pressure

Systolic blood pressure gets its name from systole. Systole is the name given to the period when the heart contracts to pump out blood. Hence, the blood pressure at this time is called systolic blood pressure. 

Diastolic Blood Pressure

Diastolic blood pressure also gets its name from diastole. Diastole is when the heart relaxes to allow the filling of blood. Hence, the blood pressure at this time is called diastolic blood pressure. 

The Blood Pressure Chart

How do you read a blood pressure chart?

The American Heart Association categorises blood pressure into five groups:1 

Blood Pressure Category: Normal

Systole Reading (mmHg): < 120

Diastole Reading (mmHg): < 80

Blood Pressure Category: Elevated

Systole Reading (mmHg): 120 to 129

Diastole Reading (mmHg): < 80

Blood Pressure Category: High Blood Pressure (Stage 1)

Systole Reading (mmHg): 130 to 139

Diastole Reading (mmHg): 80 to 89

Blood Pressure Category: High Blood Pressure (Stage 2)

Systole Reading (mmHg): > 140

Diastole Reading (mmHg): > 90

Blood Pressure Category: Hypertensive Crisis

Systole Reading (mmHg): > 180 

Diastole Reading (mmHg): > 120

What do the numbers mean? 

High Blood Pressure: 140/90mmHg or over-high blood pressure

The above numbers mean that your systolic blood pressure is 140 while your diastolic blood pressure is 90 (both in mmHg). At this level, you would be considered to have high blood pressure (hypertension) stage 2.1 Your doctor may prescribe some medications and give you some advice regarding relevant lifestyle changes to help control or lower your blood pressure. Possible signs and symptoms of high blood pressure include:

  • blood-shot eyes
  • headaches
  • dizziness
  • nosebleeds
  • flushing

In addition, some risk factors for high blood pressure include obesity, a high sodium diet, excessive alcohol consumption, smoking, caffeine consumption, and a sedentary lifestyle.

Pre-High Blood Pressure: 120/80mmHg up to 140/90mmHg

The above readings suggest that your systolic blood pressure would range from 120 to nearly 140mmHg. Also, your diastolic blood pressure could range from 80 to almost 90mmHg. Pre-high blood pressure is a risk factor for developing high blood pressure if nothing is done to prevent it.

Ideal Blood Pressure: 90/60mmHg up to 120/80mmHg

The above blood pressure readings translate that your systolic blood pressure ranges from 90 to less than 120mmHg. Meanwhile, your diastolic blood pressure could range from 60 to 80mmHg. This range is desirable for your blood pressure.

Low Blood Pressure: 90/60mmHg or lower

The above blood pressure reading indicates that the systolic blood pressure is below 90mmHg, while the diastolic blood pressure is below 60mmHg. Such readings are considered to be low blood pressure. Some signs and symptoms of low blood pressure are: 

  • dizziness
  • fainting
  • blurry vision
  • fatigue
  • shock

It is important to note that the above list is not exhaustive of the signs and symptoms of low blood pressure. 

Diagnosing High or Low Blood Pressure

High blood or low blood pressure could be without any significant symptoms. Therefore, it may be important to have your blood pressure checked periodically. The NHS suggests that adults over the age of 40 should check their blood pressure at least once every five years.2 Individuals at a high risk of high blood pressure should check their blood pressure at least once a year.2

Tips on Maintaining an Ideal Blood Pressure

There may be some hereditary predisposition to high blood pressure. However, certain lifestyle modifications may help attain/maintain an ideal blood pressure range. Such lifestyle choices include the following:

  • Regular exercise: Mayo clinic states that exercise helps strengthen your heart to pump blood more effectively with less effort.3 This efficient pumping leads to less force on the arteries, hence relatively lower blood pressure.
  • Having healthy meals: A balanced diet is a meal with all the relevant food groups in their suggested proportions. It may be helpful to read food labels as you shop to help you pick healthier food options. The Heart Foundation suggests incorporating vegetables, fruits, whole grains, reduced-fat dairy, and nuts and seeds to help control high blood pressure.4
  • Sodium reduction in meals: Reducing your sodium intake could help control high blood pressure. Sodium tends to occur in small amounts in natural foods. However, significant quantities of sodium may be added to food during food processing to improve taste and, sometimes, preservation. Therefore, it may be best to avoid or limit processed foods. The World Health Organisation recommends that the general populace limits their sodium intake to about 2g per day.5
  • Smoking cessation: Stopping smoking may help to reduce high blood pressure. The American Heart Association states that there is some increase in blood pressure every time one smokes.6
  • Eliminating/reducing alcohol consumption: Alcohol is thought to be able to cause an increase in blood pressure.7 Therefore, it may be better to cut out alcohol or not exceed the recommended levels. The Centres for Disease Control and Prevention recommends that men limit alcohol to 2 drinks or less per day, and women are advised to limit alcohol to one drink or less per day.8
  • Reducing caffeine: Caffeine is thought to be able to increase blood pressure. The NHS states that drinking over four cups of coffee a day could increase blood pressure.9 
  • Reducing weight: For people who are overweight or obese, losing some weight may help control their blood pressure. Research suggests that obesity is a significant risk factor of hypertension.10 
  • Reducing stress: Being stressed could lead to increased blood pressure. Therefore, constant stress can lead to hypertension in the long term. According to the Mayo Clinic, stressful events can lead to a temporal increase in blood pressure.11 And so, it may be beneficial to seek stress-coping mechanisms to help in such situations.

Contacting Your Doctor

As mentioned earlier, some people may not show any signs of high blood pressure. Regardless of this, high blood pressure may be identified during blood pressure measurements. It is essential to see your doctor if your blood pressure is determined to be high. Such increased blood pressure needs to be controlled to prevent further complications like stroke, kidney disease, or damage to the heart.

Conversely, high blood pressure may elicit some symptoms and signs, such as those previously discussed in this article. Although these signs and symptoms are not exclusive to high blood pressure, it is essential to see your doctor for the necessary investigations to be conducted. 

Summary

High blood pressure can lead to life-threatening events. Therefore, it is vital to take steps to avoid or control it. It is essential for people on high blood pressure medications to follow the prescription. If you have any concerns about your medication, speak to your doctor about it. Your doctor can adjust or change your medications if necessary.

It is also necessary to adhere to lifestyle-related advice from your doctor. Such life modifications could be beneficial even to people with a genetic propensity to developing high blood pressure. Apart from helping to control high blood pressure, such lifestyle changes are likely to result in an overall improvement in health. It would be helpful to discuss the type of exercises beneficial to you with your doctor. Your doctor may recommend modifications to the exercise regimen where necessary.

References

  1. The American Heart Association. Understanding blood pressure readings. [internet]. [cited on 2022 April 17]. Available from: https://www.heart.org/en/health-topics/high-blood-pressure/understanding-blood-pressure-readings
  2. NHS. Diagnosis. High blood pressure (hypertension). [internet]. [cited on 2022 April 17]. Available from: https://www.nhs.uk/conditions/high-blood-pressure-hypertension/diagnosis/
  3. Mayo Clinic. Exercise: a drug-free approach to lowering high blood pressure. [internet]. 2021. [cited 2022 April 17]. Available from: https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/in-depth/high-blood-pressure/art-20045206
  4. Heart Foundation. Five foods to help lower blood pressure. [internet]. [cited 2022 April 17]. Available from: https://www.heartfoundation.org.au/blog/five-foods-to-help-lower-blood-pressure
  5. World Health Organisation. Guideline. Sodium intake for adults and children. World Health Organization; Geneva, Switzerland: 2012.
  6. American Heart Association. Smoking, high blood pressure and your health. [internet]. 2016. [cited 2022 April 17]. Available from: https://www.heart.org/en/health-topics/high-blood-pressure/changes-you-can-make-to-manage-high-blood-pressure/smoking-high-blood-pressure-and-your-health
  7. American Heart Association. Limiting alcohol to manage high blood pressure. [internet]. 2016. [cited 2022 April 17]. Available from: https://www.heart.org/en/health-topics/high-blood-pressure/changes-you-can-make-to-manage-high-blood-pressure/limiting-alcohol-to-manage-high-blood-pressure
  8. Centers for Disease Control and Prevention. Dietary guidelines for alcohol. [internet]. 2022. [cited 2022 April 17]. Available from: https://www.cdc.gov/alcohol/fact-sheets/moderate-drinking.htm
  9. NHS. Prevention. High blood pressure. [internet]. 2019. [cited 2022 April 17]. Available from: https://www.nhs.uk/conditions/high-blood-pressure-hypertension/prevention/
  10. Jiang S. Z., Lu W., Zong X. F., Ruan H. Y. and Liu Y. (2016). Obesity and hypertension. Exp Ther Med. 2016 September 6. 12(4), 2395–2399. https://doi.org/10.3892/etm.2016.3667
  11. Mayo Clinic. Stress and high blood pressure: what's the connection? [internet]. 2021. [cited 2022 April 17]. Available from: https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/in-depth/stress-and-high-blood-pressure/art-20044190

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Adwoa Boakye

Master of Research - MRes Dental Public Health, The University of Manchester, England
I have a BSc in Human Biology and BDS. I do like to write about health issues in an easy-to-understand way for the everyday person.

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