“Madam, your blood pressure today is high at 160/80mmHg,” I say. “But my blood pressure is always normal at home. I don’t have high blood pressure, doctor!” she objects.

Does this conversation sound familiar to you? Have you ever wondered why your blood pressure goes up whenever you visit your doctor? It does not have to be only at stressful places like your doctor’s clinic. It can also be in other situations which may not be as stressful.

So why does blood pressure fluctuate? Is it a normal phenomenon? Is high blood pressure a major concern?

One of the biggest problems in Malaysia today is high blood pressure or hypertension. Often a silent killer, hypertension may show no symptoms until levels are very high. In fact, the first presentation may be a stroke or a heart attack.

In my cardiology practice, at least two-thirds of people who walk into my clinic have hypertension. But as a heart doctor, I see a skewed population. What then is the true prevalence of hypertension in Malaysia? In the last National Health and Morbidity Survey conducted in 2011, it was found that 32.7 percent (5.8 million) of adults 18 years and above have hypertension. What makes even more scary reading is that about 60 percent of these individuals were not previously known to have hypertension.

Normal blood pressure

Before we discuss further on problems relating to blood pressure, let us look at what constitutes a normal blood pressure. We need to first understand what the numbers stand for.

The heart pumps blood that gets circulated to different parts of the body. Due to the pumping of the heart, the blood exerts a certain amount of pressure on the walls of the blood vessels. This pressure is termed as blood pressure and is represented by two numbers – systolic and diastolic. The first number is systolic pressure and it is the one which develops when the heart beats. The second number is called diastolic pressure which occurs when the heart relaxes in between two beats.

A normal blood pressure reading is when the systolic and diastolic reading is below 140mmHg and 90mmHg respectively (140/90mmHg). Any value above this is abnormal and if it is consistently high then a person is deemed to have hypertension. An optimal or ideal reading is when the blood pressure is below 120/80mmHg.

A mild fluctuation of about 10 percent is absolutely normal. If there is a fluctuation of blood pressure of around 25 to 30 percent once in a while, then you do not need to worry about it. It does not have any adverse effect on any of the metabolic functions of the body. However, if it becomes a chronic problem, only then it becomes a matter of concern.

Causes of fluctuating blood pressure

Blood pressure varies throughout the day and is influenced by a number of factors. For starters, all humans have a natural daily rise and fall in blood pressure that corresponds with their circadian rhythm. For most people, blood pressure will be at its lowest in the early morning hours and then rise through the late morning and peak in early afternoon. Thereafter, the blood pressure starts to fall. Thus, a person with a resting blood pressure of 120/70mmHg at 3a.m., may have a reading of 140/80 by late afternoon.

However, there are certain conditions and factors which are known to be responsible for marked fluctuations in blood pressure. These include:

(i) Hypertension

One of the main causes behind blood pressure fluctuation is hypertension. This happens because of abnormal blood pressure regulatory mechanism. Other medical conditions like kidney disease and hormonal problems can lead to elevated blood pressure. In many cases, hypertension runs in the family.

(ii) Stress

Anxiety and stress can cause fluctuation blood pressure and can be extreme in some cases. I remember doing an ‘experiment’ on a lady patient of mine whose blood pressure was normal at 120/80mmHg whilst sitting quietly outside my room. However, the same blood pressure machine measured her pressure at 180/90mmHg a couple of minutes after she sat in front of me. I guess I must have that kind of effect on women!

(iii) Sensitivity Towards Foods and Drinks

Certain foods and drinks can elevate the blood pressure suddenly. Caffeine, which is a stimulant, often tends to elevate the blood pressure as it causes constriction of blood vessels. Its effect is more apparent in those people who do not drink coffee regularly. Those people who are sensitive towards salt may notice temporary rise in their blood pressure after ingestion of salty foods. If it occurs on a regular basis, then dietary changes will be necessary.

(iv) Side Effects of Medicines

A number of prescription or over-the-counter medicines can lead to fluctuations of blood pressure. These include painkillers, birth control pills, antidepressants, and common cold medicines.

When the blood pressure is fluctuating towards the lower side, it could be due to low blood volume or the heart is unable to beat fast for any other reason. Some of the reasons are loss of body fluids in severe dehydration and blood loss from a major injury. Nutritional deficiency of some vital minerals and vitamins like iron and B-vitamins can lower production of red blood cells, an important component of blood. As a result, there is not enough blood in the circulatory system which can result in a low blood pressure. Deficiency in certain hormones from the adrenal or pituitary gland can lead also cause extreme fluctuations in blood pressure especially during a change in posture, such as standing up from a lying position.

Women and blood pressure fluctuations

What we have discussed so far affects both men and women. However, there are a few conditions which affect women specifically causing the blood pressure to fluctuate more than normal.

Pregnancy

Blood pressure often fluctuates during pregnancy. The progesterone hormone, which prepares the uterus for pregnancy, dilates the blood vessels, thereby lowering the blood pressure. On the other hand, as blood provides all the nutrients and oxygen to the embryo, the heart has to work overtime to pump blood to the placenta. This may lead to an increase in the blood pressure. Frequent blood pressure checks are required during pregnancy to prevent preeclampsia, which is a condition characterised by high blood pressure and fluid retention.

Menopause

Blood pressure levels may fluctuate during menopause, due to a fall in the levels of oestrogen, which is a hormone that is partly responsible for maintaining blood pressure. Sometimes, the hormonal imbalance may cause weight gain, which in turn may elevate blood pressure. The increase in blood pressure may also be due to hormone therapy that some menopausal women undergo.

Birth control pills

The use of oral contraceptive pills may lead unwanted side effects in women including elevation in blood pressure.

Overcoming blood pressure fluctuation

A visit to the doctor will determine if your blood pressure is abnormal and needs to be addressed. Your doctor will try to identify the underlying cause for the unstable blood pressure. In almost all cases, successful treatment of the underlying cause will improve the blood pressure control.

For blood pressure which is fluctuating above the normal level, your doctor will advise you to follow a diet that is low in sodium and high in fibre content. On the other hand, if it is fluctuating in the lower side the doctor may recommend inclusion of foods that supply high amount of iron, vitamin C, vitamin B-complex on top of keeping yourself well hydrated.

If you are still wondering whether your blood pressure is normal or not, I would suggest that you turn off your computer and make a dash to the nearest doctor. Take control of your health and do not leave it to chance.