Before we look at how to use a home blood pressure digital monitor, and which ones are the best, let’s first consider what the blood pressure readings will mean. These figures are taken from the National Heart, Lung and Blood Institute.

Digital Home Blood Pressure Monitors v Doctor’s sphygmomanometer

When you get your blood pressure measured at the doctor’s office, he/she will place a cuff around your upper arm, level with your heart.

The cuff is inflated, and then, while the doctor listens on his/her stethoscope placed on your arm just below the cuff, the cuff is slowly deflated. the doctor is listening out for the first signs of a "tapping sound" which signals the point when the cuffs pressure is just less than the pressure of your blood, and blood flows intermittently past the cuff during heart beat. At this point, the doctor notes the pressure on the sphygmomanometer. This is your systolic blood pressure.

The cuff continues to be deflated until the "tapping" sound completely disappears. This is the point where full blood flow has been restored, and represents your diastolic blood pressure.

Measurements taken by your doctor are the most accurate, and most reliable. However, due to a phenomenon called "White Coat Syndrome", some patients find their blood pressure raised by the mere act of visiting the doctor. I suffer from this, and find that my blood pressure is significantly lower (even normal) at home, yet at the doctor’s office, it is always high. Because of White Coat Syndrome, more and more doctors are recommending digital home blood pressure monitors for their patients.

If decide to buy a home monitor, you MUST get it checked at your doctor’s office for accuracy. These meters can be extremely accurate, but you need to check that yours is calibrated properly. All you need to do is to go and get the doctor to check your blood pressure, wait 2 minutes, and then take your blood pressure using your digital meter. The two readings should be very similar (they wont be 100% the same as blood pressure varies). Once accuracy is confirmed, you can confidently take your blood pressure at home.

Types of personal blood pressure monitors

I have seen and used two types of home monitors. One has a cuff that goes around your wrist, while the other has a cuff that goes around your upper arm (at the level of your heart). While I have not done extensive testing, I did find the wrist cuff more temperamental and inaccurate. My own recommendation is that you buy a blood pressure monitor with the arm cuff. They are both similarly priced and can be bought for between $50 – $100.

Precautions when taking your own blood pressure

It is important that your are completely relaxed when you measure your blood pressure. There are also a few other guidelines that you should stick to before taking your reading:

1. Empty your bladder before sitting down to take a reading.
2. Don’t drink coffee for at least an hour before measuring your blood pressure.
3. Don’t smoke for at least 1 hour before.
4. Sit for five minutes with your back supported and your feet flat on the ground before taking your blood pressure. Keep your arm supported on a table at heart height.
5. Do not wear tight fitting clothes on your arm. When you fit the cuff, your rolled up sleeve should not be constricting your arm at all. If in doubt, take off your top.
6. Take two readings two minutes apart, and find the average.

Where to Buy Blood Pressure monitors

With these personal monitors being relatively cheap and yet highly accurate, we recommend you buy one to use at home. This will prevent "White Coat Syndrome" where your blood pressure is elevated just because you visit the doctors. However, when you get your, you must visit your doctor to check its accuracy. 

Our recommended supplier of blood pressure monitors usually have a range of wrist and upper arm cuff monitor.  See our guidelines to choosing a blood pressure monitor, and see what is available online:

Choosing a blood pressure monitor

To prepare for each set of readings, I sat down for 5 minutes before taking the first reading.

The coffee used in this experiment was strong filtered coffee. After taking a few baseline readings, I drank the coffee in one go. The amount was equivalent to 4 small expresso coffees. I then continued to take my blood pressure every few minutes. I then sat as still as possible, taking my blood pressure every three minutes.

Here are my results:

Here is the data as a graph showing the effect of caffeine coffee on blood pressure:

You’ll see that there is an almost immediate increase in systolic pressure, followed by a drop. This then increases again about 10 minutes after drinking the coffee to a maximum measured blood pressure of 138/89 about 23 minutes after the coffee was drunk. The blood pressure then starts dropping again, until normal blood pressure is restored at around 30 minutes after drinking the coffee.

What we see happening is a temporary increase in blood pressure in response to the coffee, which the body then corrects. How caffeine raises blood pressure seems to be unclear, but what is certain in my case is that it did raise my blood pressure, but only for a short period of time.

For those with high blood pressure, it would appear that coffee could be a problem due to the high spike after drinking the coffee. However, since my blood pressure is normal, I wont be switching to decaf.

My next experiment is to see what effect drinking filtered decaffeinated coffee has. Is it the caffeine in the coffee that raised my blood pressure, or something else?  You can see the results of my experiment on the does decaffeinated coffee affect blood pressure page.  The results may surprise you!

Incidentally, I am not a doctor. These experiments are for my own curiosity, and I do not recommend you do the same.

Here are my results:

Here is the chart of this data:

While the graph may not look too impressive, you can see a large jump in blood pressure almost immediately. Before starting to smoke the cigar, the average blood pressure for the three preceding readings was 133/83. The first reading after starting to smoke was 149/92. That’s quite a jump.

The initial increase in blood pressure is spectacularly quick. Not surprising really, as smoke enters our bodies through the thin membranes of the lungs, as well as through the membranes in our mouth. This is why smokers can get a neat instant “hit” when they light up.

Blood pressure is raised for about 20 minutes before it returns back down to a more normal reading (that’s normal for me). When there is a stimulus to increase blood pressure, our bodies are going to try to combat that increase and lower the blood pressure. In this case it took about 20 minutes for my body to do so. Blood pressure then remained fairly constant for the remainder of the experiment.

It would be interesting to see how blood pressure would be affected if I continued to smoke all day (as in a chain smoker), and whether my body could compensate over a long period of time. I wont, however, be doing that experiment ;o)

Look out for new experiments soon. You’ll find them in the left hand menu.

The readings were not taken at specific intervals, and I have made no attempt to show on this graph when I ate food, did exercise, drank coffee, or anything else that might affect blood pressure. The whole point of this experiment was just to see how my blood pressure varied throughout the day.

Here are my results:

Average Blood pressure over the day: 129/82

Here is the chart of this data:

The fluctuations were not as big as I anticipated, but one thing I have noticed is that my blood pressure does tend to reduce as the evening progresses.

We have to be careful to draw any conclusions from this blood pressure data, but clearly, there is some variation during the day.

I will be looking at specific influences in other experiments, and how they affect my blood pressure, so look out for those. They will be listed down the left of this page.

The pressure of your blood depends on a number of factors including:

• the force created by your heart pumping blood into your arteries
• the volume of your blood
• the resistance your blood encounters as it moves through your blood vessels.

You body needs to make sure that there is sufficient pressure to push the blood into all of the capillaries around your body. Capillaries are the smallest blood vessels in your body, and ensure that all cells in your body receive nutrients they require to live.

Maintaining normal blood pressure is delicately balanced. Too high, and your heart and blood vessels are put under strain. Too low and the low blood pressure means some cells may not get the nutrients they require.

High blood pressure is often called the “Silent Killer” since there are often no symptoms. For this reason, it is important you get your blood pressure checked regularly.

Blood pressure readings can be taken by your doctor using a sphygmomanometer and stethoscope, or at home using a blood pressure monitor (the easiest ones to use are digital monitors). The home monitors generally come in two forms. One places a cuff around your wrist, while the other places a cuff around your upper arm (level with your heart). I personally have tried both types and found the most accurate one to be the upper arm cuff.

The blood pressure “numbers”

The blood pressure reading is two numbers. These are the two pressures of your blood at varying stages of your heart beat cycle:

The larger number is the systolic pressure, the lower number is the diastolic pressure.

Systolic pressure is the blood pressure being pumped into the aorta when the heart beats.

Diastolic pressure is the blood pressure in the arteries when the heart relaxes between beats.

Blood pressure does vary with age, sex and health, but in general, a healthy blood pressure is 120/80, or 120 over 80.

This means that systolic blood pressure is 120 mmHg, and the diastolic blood pressure is 80 mmHg.

Your blood pressure can actually tell a doctor a lot about the health of your heart and blood vessels. High blood pressure means that your heart is having to work harder to push your blood to all the cells in your body.

This can happen if e.g. you have narrowing of the arteries, since this narrowing increases the resistance of your blood vessels, and requires more pressure to get the blood through.

High blood pressure is also called hypertension, and can have serious consequences if not treated. e.g. high blood pressure can weaken the artery walls, and lead to rupture. If this happens in the brain, it can lead to a stroke.

There are a wide range of medicines and medications available to treat high blood pressure, and some alternative therapies such as acupuncture may also help, but you can also take immediate steps by looking at your diet and increasing your daily exercise (walking is a great exercise).

We explore some of the dietary considerations on this site, but please do consult a doctor before changing your diet or undertaking an exercise program.