Blood pressure is written as two numbers, and almost everyone has seen their own at some point. Rather fewer people know what the two numbers represent, or why a doctor is unwilling to make much of a single reading.
Why this matters
Raised blood pressure is one of the largest contributors to heart attack, stroke and kidney disease worldwide, and it typically produces no symptoms for years. It is also very manageable once identified. Understanding the measurement is what turns a number on a machine into something you can actually act on with your doctor.
What medical guidance says
What the two numbers mean
The first, higher number is systolic pressure — the pressure in your arteries at the moment the heart contracts and pushes blood out. The second, lower number is diastolic pressure — the pressure remaining between beats, while the heart relaxes and refills. Both are reported in millimetres of mercury, written mmHg.
Blood pressure is not a fixed property of a person. It rises and falls through the day, with activity, stress, pain, caffeine, temperature, sleep and even conversation. This normal variation is exactly why one reading is not a diagnosis.
Why one reading is not enough
A diagnosis of hypertension is made on a pattern of raised readings taken correctly on separate occasions, not on a single measurement. Many people show higher readings in a clinic than they do at home — a well-recognised effect of the setting itself — which is one reason doctors often ask for readings taken at home over a period, or arrange monitoring over a full day.
Where your own readings should sit, and what should be done about them, depends on your age, your other conditions and your overall cardiovascular risk. That target is a decision for your doctor rather than a number to take from an article or a chart on a machine.
Measuring properly at home
Home monitors are useful, and a poorly taken reading is worse than none because it can prompt the wrong decision. To measure well:
- Avoid caffeine, tobacco and exercise for about thirty minutes beforehand, and empty your bladder first.
- Sit quietly for five minutes before measuring, with your back supported and legs uncrossed, feet flat on the floor.
- Rest your arm on a table so the cuff is at roughly the level of your heart.
- Place the cuff on bare skin, not over a sleeve, and make sure it is the correct size for your arm.
- Stay still and do not talk during the measurement.
- Take two or three readings a minute apart and record all of them, along with the date and time.
Bring your home monitor to your next appointment. Having it checked against the clinic device tells you whether your readings can be trusted.
What influences blood pressure
Several everyday factors affect blood pressure over the long term. These are general health measures rather than a treatment plan, and they do not replace medicines that have been prescribed to you.
- Dietary salt. Much of the salt in an Indian diet comes from pickles, papad, namkeen, packaged snacks and restaurant food rather than the salt shaker.
- Body weight, particularly weight carried around the abdomen.
- Regular physical activity, which has a measurable effect over time.
- Alcohol intake and tobacco use in any form, including smokeless tobacco.
- Sleep quality and duration.
- Sustained psychological stress.
Never stop or reduce a prescribed blood pressure medicine because your readings have improved. Improved readings often reflect the medicine working. Any change to the dose is a decision for your doctor.
Related reading: Everyday habits for a healthier heart
When to consult a doctor
See a doctor if home readings are repeatedly higher than usual for you, if readings are very variable, if you have been told before that your pressure is borderline, or if you have a family history of hypertension, heart disease, stroke or kidney disease.
Seek emergency care immediately for chest pain or pressure, sudden severe headache, sudden weakness or numbness on one side of the body, difficulty speaking, sudden vision change, or severe breathlessness. Do not wait to repeat a reading.
Frequently asked questions
- Which of the two numbers matters more?
- Both carry information, and their relative importance varies with age and clinical situation. A doctor considers them together, alongside your other risk factors, rather than treating either in isolation.
- My reading was high once. Do I have hypertension?
- Not on that basis. Blood pressure varies normally through the day, and a diagnosis rests on a pattern of correctly taken readings on separate occasions. Record several readings over a period and discuss them with your doctor.
- Are wrist monitors as good as upper-arm ones?
- Upper-arm monitors with a correctly sized cuff are generally preferred, as wrist devices are more sensitive to arm position. Whichever you use, have it checked against a clinic device so you know your readings are reliable.
- Can I stop my medicine if my readings become normal?
- No. Normal readings frequently mean the medicine is doing its job, and stopping can allow pressure to rise again silently. Any change to a prescribed medicine must be decided by your doctor.
References
- Hypertension: key facts — World Health Organization (WHO)
- India Hypertension Control Initiative — programme resources — Indian Council of Medical Research (ICMR) and Ministry of Health & Family Welfare
- Dietary Guidelines for Indians — ICMR — National Institute of Nutrition (ICMR-NIN)