A normal blood pressure reading is below 120/80 mmHg. That means the top number (systolic) stays under 120 and the bottom number (diastolic) stays under 80. Once either number crosses those thresholds, your reading falls into a higher category, from elevated all the way up to stage 2 hypertension.
What the Two Numbers Mean
Blood pressure is always expressed as two numbers. The top number, systolic pressure, measures the force inside your arteries when your heart contracts and pushes blood out. The bottom number, diastolic pressure, measures the pressure between beats, when your heart relaxes and refills. Both numbers matter, and if they fall into different categories, the higher category is the one that counts.
Blood Pressure Categories
The 2025 guidelines from the American Heart Association and American College of Cardiology define four categories for adults:
- Normal: below 120 systolic and below 80 diastolic
- Elevated: 120 to 129 systolic and below 80 diastolic
- Stage 1 hypertension: 130 to 139 systolic or 80 to 89 diastolic
- Stage 2 hypertension: 140 or higher systolic or 90 or higher diastolic
European guidelines draw the line even lower, defining “non-elevated” blood pressure as below 120/70 rather than 120/80. They avoid the word “normal” entirely because cardiovascular risk begins creeping up at readings well within what most people would consider a healthy range, particularly among women.
When Blood Pressure Is Too Low
Readings below 90/60 mmHg are generally considered low blood pressure, or hypotension. For many people, especially younger adults, this causes no symptoms and isn’t a problem. It only becomes a concern when pressure drops low enough to reduce blood flow to your brain, heart, or kidneys. Signs that low blood pressure is actually affecting you include dizziness, lightheadedness, blurred vision, or fainting. Without those symptoms, a naturally low reading is usually nothing to worry about.
Why the Numbers Rise With Age
Blood pressure isn’t a fixed number across your lifetime. Systolic pressure tends to climb steadily as you age because your arteries gradually stiffen and lose elasticity. Diastolic pressure follows a different pattern: it typically rises until about age 45 and then starts to decline. This is why older adults often have a wide gap between their two numbers, such as 150/70, with the top number elevated but the bottom number relatively low.
Gender plays a role too. After puberty, women generally have lower blood pressure than men, though the gap narrows after menopause. These age and sex patterns are part of the reason a single “normal” threshold applies to everyone: a reading of 118/76 is normal regardless of whether you’re 25 or 65, even though a 65-year-old is statistically less likely to be there.
How Much Higher Readings Matter
The relationship between blood pressure and cardiovascular risk is remarkably consistent. For every 20-point rise in systolic pressure or 10-point rise in diastolic pressure, the risk of dying from heart disease or stroke doubles. That relationship holds across a wide range of readings, which means the difference between 120 and 140 systolic carries roughly the same proportional increase in risk as the jump from 140 to 160. There’s no safe “plateau” where higher readings stop mattering.
Your Blood Pressure Changes Throughout the Day
A single reading is a snapshot of one moment. Blood pressure follows a daily cycle driven primarily by activity and sleep. It typically drops 10% or more during sleep, then rises between 6 a.m. and 10 a.m. as you wake and start moving. Physical activity, stress, caffeine, and even a full bladder can push readings higher temporarily. This is why one high reading at a pharmacy kiosk doesn’t necessarily mean you have hypertension, and why repeated measurements over time give a much clearer picture.
Some people don’t experience that overnight dip in pressure. These “non-dippers” face a higher cardiovascular risk, though this pattern can only be detected through 24-hour ambulatory monitoring, where you wear a cuff that takes readings automatically throughout the day and night.
Getting an Accurate Reading
The way blood pressure is measured matters more than most people realize. A reading taken under poor conditions can be off by 10 to 15 points in either direction. To get a reliable number:
- Avoid caffeine, exercise, and smoking for at least 30 minutes before measuring.
- Empty your bladder first. A full bladder can raise systolic pressure by several points.
- Sit quietly for five minutes with your back supported, feet flat on the floor, and legs uncrossed.
- Use the right cuff size. A cuff that’s too small will give a falsely high reading. When in doubt, go with the larger cuff.
- Place the cuff on bare skin on your upper arm, with the middle of the cuff at heart level. Don’t roll up a tight sleeve above it.
Home Readings vs. Office Readings
Blood pressure measured at home tends to run a few points lower than readings taken in a doctor’s office. This is partly because of “white coat effect,” the anxiety bump that happens in a clinical setting. Because of this difference, the thresholds used to define hypertension are different depending on the setting. A reading of 140/90 or higher in a clinic is considered hypertensive, while 135/85 is the equivalent cutoff for home and ambulatory monitoring.
Home monitoring is especially useful if your in-office readings are borderline. Taking readings at the same time each day for a week gives a much better picture of your actual blood pressure than a single clinic visit. Many clinicians now base treatment decisions on home or ambulatory readings rather than office readings alone, since home measurements tend to more accurately reflect day-to-day cardiovascular risk.