BPM - Frequently asked questions about blood pressure measurements
Your blood pressure is measured by two numbers:
- The first corresponds to systole. This is when the heart contracts and ejects blood into the arteries.
- The second corresponds to diastole. This is when the heart relaxes.
- The unit of measurement of blood pressure is the millimeter of mercury (mmHg).
Why do my blood pressure values vary?
Blood pressure is difficult to correctly define as it varies during the day and depends on your physical activity. That is why it is best to make a large number of measurements.
According to international guidelines, home blood pressure must be taken with two consecutive measurements at an interval of 1 to 2 minutes. These measurements must be repeated on at least 3 or 4 consecutive days and preferably for 7 consecutive days1,2.
Sources: 1 Parati G, Stergiou GS, Asmar R, Bilo G, de Leeuw P, Imai Y, et al. European Society of Hypertension practice guidelines for home blood pressure monitoring. J Hum Hypertens 2010; 24:779–785. - 2 Parati G, Stergiou GS, Asmar R, Bilo G, de Leeuw P, Imai Y, et al., European Society of Hypertension Working Group on Blood Pressure Monitoring. European Society of Hypertension guidelines for blood pressure monitoring at home: a summary report of the Second International Consensus Conference on Home Blood Pressure Monitoring. J Hypertens 2008; 26:1505–1526.
Click here to have more information about the best practices.
What is the point of taking my blood pressure at home?
Home blood pressure measurements are more representative of a person's actual blood pressure which varies throughout the day, depending on physical activity. It is therefore necessary to take several measurements to obtain a reliable and representative mean value of a person's actual blood pressure.
In addition, the home blood pressure reading is a better predictor of mortality and cardiovascular morbidity that blood pressure measurements made in the doctor's office1,2.
Note however that self-measurement is not recommended in patients with arrhythmias as this causes erroneous measurements of blood pressure.
Sources: 1 Stergiou GS, Siontis KC, Ioannidis JP. Home blood pressure as a cardiovascular outcome predictor: it’s time to take this method seriously. Hypertension 2010; 55:1301–1303. - 2 Ward AM, Takahashi O, Stevens R, Heneghan C. Home measurement of blood pressure and cardiovascular disease: systematic review and meta-analysis of prospective studies. J Hypertens 2012; 30:449-456.
Why is there a difference between the blood pressure measurements taken by my doctor and those taken at home?
Scientific studies show that the average blood pressure is higher when measured by a health professional than when taken at home1. There are therefore two normal values of blood pressure depending on whether the blood pressure is measured at home or in the doctor's office.
When your blood pressure is higher in the office than at home, this is called "white coat hypertension" or "white coat effect". In general, this effect is more frequent in the elderly, in female subjects and in nonsmokers1,2. This phenomenon is not particularly harmful to health, but it may lead to misdiagnosis of hypertension and cause overdosing of drugs.
Conversely, when your blood pressure measured at home is higher than in the doctor's office, we speak of "masked hypertension". Several factors can cause this phenomenon: young age, male gender, smoking, alcohol consumption, physical activity, anxiety, work stress, obesity, diabetes or a family history of hypertension 3. Unlike the "white coat effect" this situation presents a risk to health and it is important to talk about it with your doctor if you are concerned.
Sources: 1 Staessen JA, O’Brien ET, Amery AK, Atkins N, Baumgart P, De Cort P, et al. Ambulatory blood pressure in normotensive and hypertensive subjects: results from an international database. J Hypertens Suppl 1994; 12:S1–12. - 2 Dolan E, Stanton A, Atkins N, Den Hond E, Thijs L, McCormack P, et al. Determinants of white-coat hypertension. Blood Press Monit 2004; 9:307–309. - 3 Bobrie G, Clerson P, Menard J, Postel-Vinay N, Chatellier G, Plouin PF. Masked hypertension: a systematic review. J Hypertens 2008; 26:1715–1725.
When is the best time to track my blood pressure?
At home, blood pressure measurements should be done in the morning before breakfast (and before any medication) or in the evening before bedtime.
Follow the instructions that appear when you use your blood pressure monitor for a step by step guide on how to correctly measure your blood pressure.
Source: Parati G, Stergiou GS, Asmar R, Bilo G, de Leeuw P, Imai Y, et al. European Society of Hypertension practice guidelines for home blood pressure monitoring. J Hum Hypertens 2010; 24:779–785.