# Understanding Blood Pressure: The Numbers Explained > Blood pressure is written as two numbers - systolic over diastolic - and knowing what they mean helps you understand your own readings. Here is how to read them, what the ranges signify, and what lowers high blood pressure. *Section: Health — By Dr. Nadia Okoro (Science & Health Writer) — Published December 4, 2025 — 4 min read* Canonical URL: https://dailyjunction.org/health/understanding-blood-pressure Tags: blood pressure, hypertension, heart health, cardiovascular, wellbeing ## Key takeaways - Blood pressure is given as systolic (top) over diastolic (bottom), measured in mmHg. - The NHS considers around 90/60 to 120/80 mmHg an ideal range for most adults. - High blood pressure usually has no symptoms, so regular checks are the only reliable way to know. - Lifestyle changes - diet, activity, less salt, less alcohol, not smoking - can meaningfully lower it. - Persistently high or very low readings should be discussed with a clinician, not self-treated. Few health numbers are quoted as often, or understood as poorly, as blood pressure. You are handed two figures with a slash between them and, frequently, very little explanation. Here is what those numbers actually measure and what they tell you. This is general information rather than medical advice — for your own readings and treatment, speak with a clinician or use trusted NHS guidance. ## What blood pressure is **Blood pressure is the force your circulating blood exerts against the walls of your arteries**, recorded as two numbers measured in millimetres of mercury (mmHg). It is always written as one number over another, such as 120/80. - The **systolic** pressure (the top, higher number) is the force when your heart contracts and pushes blood out. - The **diastolic** pressure (the bottom, lower number) is the force when your heart relaxes and refills between beats. So 120/80 is read as "120 over 80": systolic 120, diastolic 80. Both numbers matter, and a problem with either can be significant. ## What the ranges mean Blood pressure exists on a spectrum rather than a simple pass or fail. The NHS describes the following broad categories for adults, though exact thresholds can vary slightly by guideline and where the reading is taken. | Category | Approximate range (mmHg) | |----------|--------------------------| | Low | Below 90/60 | | Ideal | 90/60 to 120/80 | | Pre-high (elevated) | 121/81 to 139/89 | | High (clinic reading) | 140/90 or above | A single high reading is not a diagnosis. Blood pressure naturally fluctuates through the day and rises with stress, activity, caffeine and even the anxiety of being measured — the so-called "white coat" effect. What matters is the pattern across several readings, ideally including measurements taken calmly at home. > One number above the line is not an emergency. A consistent pattern over time is what your clinician acts on. ## Why high blood pressure matters The reason blood pressure is checked so routinely is that **high blood pressure (hypertension) usually causes no symptoms at all.** People can carry it for years feeling completely well. That silence is the danger. Sustained high pressure forces the heart to work harder and gradually damages artery walls, raising the long-term risk of: - Heart attack and heart failure - Stroke - Kidney disease - Vascular damage affecting the eyes and other organs Because you cannot feel it, the only reliable way to know your blood pressure is to measure it. Many UK pharmacies offer free checks, and home monitors are widely available. Understanding your reading sits alongside knowing other key health markers, such as [what your BMI does and does not tell you](/health/what-is-bmi-and-its-limits). ## What raises and lowers it Some risk factors for high blood pressure are outside your control — age, family history and certain conditions. But several of the biggest influences are modifiable, and small changes add up. ### Salt Eating too much salt is strongly linked to raised blood pressure. Most dietary salt is hidden in processed and packaged foods rather than added at the table, so checking labels matters as much as putting down the salt cellar. ### Weight, diet and activity Carrying excess weight raises blood pressure, and losing even a modest amount can help. A diet rich in vegetables, fruit and wholegrains and lower in saturated fat supports healthy pressure. Regular physical activity strengthens the heart so it pumps with less effort — even something as accessible as [regular brisk walking](/health/the-benefits-of-walking) contributes. ### Alcohol, caffeine and smoking Drinking heavily raises blood pressure over time, so keeping within recommended limits helps. Smoking damages arteries and should be stopped. Large amounts of caffeine can cause short-term spikes in some people. ### Stress While the link between stress and long-term hypertension is complex, chronic stress encourages habits — poor sleep, overeating, drinking — that push pressure up. Managing it is worthwhile, and our guide to [the science of stress](/health/the-science-of-stress) covers evidence-based approaches. ## Measuring it well at home If you use a home monitor, a few habits improve accuracy: - Sit quietly for about five minutes first, back supported and legs uncrossed. - Rest your arm on a table at heart height. - Avoid caffeine, exercise and smoking in the 30 minutes before. - Take two or three readings a minute apart and note them, as single readings vary. Home readings are generally a little lower than clinic ones, which is why home thresholds (such as 135/85) differ slightly from clinic figures. ## When to seek help You should speak to a clinician if home readings are consistently high, if a reading is very high, or if you have symptoms such as severe headache, chest pain, vision problems or shortness of breath alongside a high reading — the last of which needs urgent attention. Equally, very low blood pressure causing dizziness or fainting is worth investigating. Do not start, stop or change blood pressure medication on your own; that is always a conversation with a health professional. ## The bottom line Blood pressure is simply the force of blood against your artery walls, written as systolic over diastolic and measured in mmHg. For most adults an ideal reading sits between about 90/60 and 120/80. Because high blood pressure is usually symptomless, regular checks are the only way to catch it — and diet, activity, less salt and alcohol, and not smoking can all help bring it down. Know your numbers, and discuss anything persistently outside the healthy range with a clinician. ## Frequently asked questions ### What do the two blood pressure numbers mean? The top number is systolic pressure, the force in your arteries when the heart beats. The bottom number is diastolic pressure, the force when the heart rests between beats. Both are measured in millimetres of mercury (mmHg). ### What is a normal blood pressure? The NHS describes a reading between roughly 90/60 mmHg and 120/80 mmHg as ideal for most adults. Readings consistently at or above 140/90 mmHg measured at home, or 135/85 at home, are generally considered high, but your clinician interprets your numbers in context. ### Why is high blood pressure called a silent condition? Because it rarely causes noticeable symptoms, many people have raised blood pressure for years without knowing. Left unmanaged it raises the risk of heart attack, stroke and kidney problems, which is why routine checks matter. ### Can I lower my blood pressure without medication? Lifestyle changes such as reducing salt, eating well, staying active, limiting alcohol, maintaining a healthy weight and not smoking can lower blood pressure. Some people still need medication; this is a decision to make with a health professional. ## Sources - [NHS: High blood pressure (hypertension)](https://www.nhs.uk/) - [British Heart Foundation: Blood pressure](https://www.bhf.org.uk/) - [World Health Organization: Hypertension](https://www.who.int/) --- Daily Junction — https://dailyjunction.org/health/understanding-blood-pressure