What Is High Blood Pressure? Normal Ranges, Causes, Home Monitoring, Diet and Exercise

Have you ever checked your blood pressure at a health examination or at home and wondered, "Is my top number too high?", "What does the bottom number mean?", or "How should I interpret a reading of 130 or 140?"

Blood pressure is a measure of the force of blood pushing against the walls of your blood vessels as the heart pumps blood around the body.

High blood pressure, or hypertension, is a common health condition. Because it often develops without obvious symptoms, knowing your usual blood pressure and monitoring changes over time is important.

In this guide, we explain what the upper and lower blood pressure numbers mean, normal blood pressure ranges, the criteria used for hypertension in Japan, how to measure blood pressure at home, and lifestyle factors including salt intake, the DASH diet and exercise.

What Is High Blood Pressure? Understanding the Top and Bottom Numbers

A blood pressure reading is usually shown as two numbers, for example: 120/70 mmHg.

Each number represents a different phase of the heartbeat.

• Systolic blood pressure: the upper number, measured when the heart contracts and pumps blood out
• Diastolic blood pressure: the lower number, measured when the heart relaxes between beats

When interpreting blood pressure, both systolic and diastolic values are important.

In Japan, Hypertension Is Diagnosed from 140/90 mmHg in the Clinic

For blood pressure measured in a medical setting in Japan, hypertension is defined when:

• systolic blood pressure is 140 mmHg or higher
• diastolic blood pressure is 90 mmHg or higher

If either or both values meet these criteria, the reading falls within the hypertension range.

For measurements taken at home, the threshold is slightly lower: 135/85 mmHg or higher.

A diagnosis is generally based on repeated measurements rather than a single reading, and home blood pressure can provide valuable additional information.

Normal, Elevated and High Blood Pressure Ranges

Blood pressure is classified in stages rather than simply as "normal" or "high".

For example, a clinic reading of 130/80 mmHg does not meet the diagnostic threshold of 140/90 mmHg for hypertension, but it falls within the elevated blood pressure range.

Knowing where your readings sit within these ranges can make blood pressure results much easier to understand.

Quick Fact: The Top Number Can Be High on Its Own

When systolic blood pressure is high while diastolic blood pressure remains below 90 mmHg, the condition is known as isolated systolic hypertension.

Changes in the elasticity and structure of blood vessels with age can contribute to higher systolic readings.

This is another reason why it is useful to look at both the upper and lower blood pressure numbers.

Quick Fact: Diagnostic Thresholds and Treatment Targets Are Different

This is an important distinction and one that is often misunderstood.

Under the 2025 Japanese Society of Hypertension guidelines, the general blood pressure target for people being treated for hypertension is below 130/80 mmHg in the clinic and below 125/75 mmHg at home.

The diagnostic threshold for hypertension remains 140/90 mmHg or higher in the clinic and 135/85 mmHg or higher at home.

In simple terms, 140/90 mmHg is the diagnostic threshold, while below 130/80 mmHg is the general treatment target.

Individual treatment targets may be adjusted by a doctor according to age, overall health and other medical conditions.

Why Does Blood Pressure Rise? Causes and Effects on the Body

Blood pressure naturally changes throughout the day.

Physical activity, stress, temperature, sleep, meals, alcohol and the time of day can all influence a reading.

For this reason, repeated measurements are useful for understanding your usual blood pressure pattern.

Many Factors Can Contribute to High Blood Pressure

Most hypertension is classified as primary or essential hypertension, which develops through a combination of factors rather than one single cause.

• Ageing
• Genetic factors
• High salt intake
• Weight gain
• Low levels of physical activity
• Alcohol intake
• Smoking
• Sleep patterns, stress and other lifestyle factors

Understanding these factors can help identify practical areas of everyday health management.

In some people, high blood pressure has an identifiable underlying cause such as kidney disease, hormonal disorders, sleep apnoea or certain medicines. This is known as secondary hypertension.

Why Regular Blood Pressure Checks Matter

High blood pressure often develops without noticeable symptoms.

When elevated blood pressure continues over a long period, it places additional strain on blood vessels and the heart and is associated with a higher risk of conditions such as stroke, heart disease and kidney disease.

Regular measurement therefore provides useful information about your cardiovascular health even when you feel well.

Why Home Blood Pressure Monitoring Matters and How to Measure Correctly

Blood pressure measured at home can provide useful information in addition to readings taken during medical appointments or health checks.

Some people experience white-coat hypertension, where blood pressure rises in a clinical setting because of nervousness or other factors.

Others may have normal readings in a clinic but higher blood pressure during everyday life. This is known as masked hypertension.

Because home readings are taken in a familiar environment, they can provide a useful picture of your usual blood pressure.

Basic Tips for Measuring Blood Pressure at Home

For meaningful comparisons, try to measure blood pressure under similar conditions each day.

• Morning: within one hour of waking, after urination and before breakfast or morning medication
• Evening: before going to bed
• Sit quietly for one to two minutes before measuring
• Sit naturally with your legs uncrossed
• Position the cuff at approximately heart level
• As a general guide, take two measurements in the morning and two in the evening and record the results

Keeping a record over time makes it easier to see your usual range and longer-term trends.

Quick Fact: Blood Pressure Naturally Varies Between Measurements

Blood pressure can change even within a few minutes.

Rather than focusing on a small difference between yesterday and today, or between the first and second measurement, look at the overall pattern under similar measuring conditions.

For home monitoring, upper-arm blood pressure monitors with an inflatable cuff are commonly used.

Diet and Blood Pressure: Salt, Potassium and the DASH Diet

Everyday eating habits are an important part of blood pressure management.

Two particularly useful areas to consider are salt intake and the overall balance of the diet.

Reducing Salt Intake

In the Japanese diet, salt can come from foods and seasonings such as soy sauce, miso, pickles, noodle soups, processed foods and prepared meals.

For people with hypertension in Japan, a salt intake of less than 6g per day is recommended.

According to Japan's 2024 National Health and Nutrition Survey, average salt intake was 9.6g per day.

This was the lowest average recorded over the previous 12 years. Health Japan 21 (Third Term) has set a population target of around 7g per day, so there is still room to continue reducing salt intake gradually.

Quick Fact: One Teaspoon of Salt Is About 6g

A level teaspoon of ordinary table salt contains approximately 6g of salt.

Daily salt intake also includes salt already present in soy sauce, miso, bread, noodles, ham, sausages and other processed foods.

These sources are sometimes described as "hidden salt" because they can add up even when little salt is added during cooking.

Checking the salt-equivalent value on nutrition labels can make it easier to understand how much salt different foods contribute to your daily intake.

Include Potassium-Rich Foods

Potassium, found in foods such as vegetables, fruit, beans and potatoes, is a mineral involved in the body's sodium balance.

Combining a lower-salt eating pattern with a varied diet containing vegetables, fruit and other whole foods can help create a balanced approach to everyday nutrition.

People with impaired kidney function or those who have been advised by a healthcare professional to limit potassium should follow their individual medical guidance.

What Is the DASH Diet?

A well-known eating pattern for people interested in blood pressure management is the DASH diet (Dietary Approaches to Stop Hypertension).

The DASH approach emphasises a balanced intake of vegetables, fruit, low-fat dairy products, fish, legumes and whole grains.

These foods provide a broad range of nutrients including potassium, calcium, magnesium, dietary fibre and unsaturated fats.

One of the key ideas behind DASH is to focus on the overall pattern of the diet rather than relying on one particular food.

Combining lower salt intake with vegetables, fruit, fish, legumes and whole grains can make the DASH approach easier to incorporate into everyday meals.

Exercise, Weight, Alcohol and Sleep: Everyday Lifestyle Factors

Blood pressure management involves more than food alone. Looking at everyday lifestyle as a whole can be useful.

Build Regular Physical Activity into Your Routine

Aerobic activity such as walking is commonly recommended as part of a healthy lifestyle, with an emphasis on physical activity that can be continued comfortably and consistently.

Examples include:

• walking a little further than usual
• walking short distances instead of driving
• using stairs where practical
• breaking up long periods of sitting

Small amounts of activity can add up as part of a daily routine.

Maintain a Healthy Body Weight

Weight gain, particularly an increase in visceral fat, is associated with blood pressure.

Alongside diet and physical activity, checking your weight regularly can be one useful part of general health management.

Be Aware of Alcohol Intake

Alcohol consumption can also influence blood pressure.

If you drink alcohol, being aware of both the amount and frequency of drinking can help you understand how it fits into your overall lifestyle.

Stopping Smoking Supports Cardiovascular Health

Smoking affects blood vessels and cardiovascular health.

Choosing to stop smoking is an important lifestyle step for long-term heart and blood vessel health.

Sleep Is Part of Everyday Health Management

Both sleep duration and sleep quality are associated with overall health, including blood pressure.

Keeping regular sleeping and waking times and allowing enough time for sleep are useful habits to consider.

Loud snoring, pauses in breathing during sleep and significant daytime sleepiness can sometimes be associated with sleep apnoea.

Rather than viewing diet, exercise, weight, alcohol, smoking and sleep separately, gradually improving the overall pattern of daily life can be a practical approach.

Hypertension Treatment, When to Seek Medical Advice and Ongoing Monitoring

Managing high blood pressure may involve lifestyle changes and, when appropriate, prescription medicines.

There are several different types of blood-pressure-lowering medicines, and treatment is selected according to factors such as blood pressure readings, age, kidney function, cardiovascular health and other medical conditions.

For people receiving treatment, recording blood pressure and discussing results with a doctor can help with ongoing management towards an individually appropriate target.

When High Blood Pressure Continues, Speak with a Healthcare Professional

If clinic readings of 140/90 mmHg or higher continue, or home readings remain at 135/85 mmHg or higher, it is appropriate to discuss them with a healthcare professional.

If blood pressure is very high and accompanied by symptoms such as chest pain, shortness of breath, severe headache, visual changes, altered consciousness, weakness or paralysis of an arm or leg, or difficulty speaking, urgent medical assessment is required.

Blood Pressure Management Starts with Knowing Your Numbers

Because hypertension can develop without obvious symptoms, knowing your blood pressure and measuring it regularly is an important first step.

Key points from this guide include:

• The upper number is systolic blood pressure and the lower number is diastolic blood pressure
• Clinic blood pressure of 140/90 mmHg or higher meets the diagnostic threshold for hypertension in Japan
• Home blood pressure of 135/85 mmHg or higher meets the home hypertension threshold
• Isolated systolic hypertension refers to a high systolic reading with a lower diastolic reading
• Diagnostic thresholds and general treatment targets are different
• Regular morning and evening home measurements can help show longer-term trends
• Salt intake and overall dietary balance are important lifestyle considerations
• The DASH diet emphasises vegetables, fruit, fish, legumes, whole grains and other nutrient-rich foods
• Physical activity, body weight, alcohol, smoking and sleep all form part of overall cardiovascular health
• Persistent high readings should be discussed with a healthcare professional

Blood pressure naturally changes from day to day, so understanding your usual range and longer-term pattern is more useful than focusing on one isolated reading.

Combining regular health checks with home blood pressure monitoring can help you stay informed about your cardiovascular health over time.

Reference Information

• Japanese Society of Hypertension, Guidelines for the Management and Treatment of Hypertension 2025
• Ministry of Health, Labour and Welfare, Japan – Information on Hypertension
• Ministry of Health, Labour and Welfare, Japan – Nutrition, Diet and Hypertension
• Ministry of Health, Labour and Welfare, Japan – 2024 National Health and Nutrition Survey