A healthy blood pressure reading is below 120/80 mm Hg. That means the top number (systolic) stays under 120 and the bottom number (diastolic) stays under 80. Once either number climbs above those thresholds, the reading falls into progressively higher-risk categories, from elevated blood pressure all the way to a hypertensive emergency.
What the Two Numbers Mean
A blood pressure reading always gives you two numbers, written as one over the other. The top number, systolic pressure, measures the force against your artery walls when your heart contracts and pushes blood out. The bottom number, diastolic pressure, measures that force between beats, when your heart is relaxing and refilling with blood. Both numbers matter, and if they fall into two different categories, the higher category is the one that counts.
Blood Pressure Categories for Adults
The 2025 guidelines from the American Heart Association and American College of Cardiology define four categories:
- 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
A reading above 180/120 is considered a hypertensive emergency. Symptoms at that level can include chest pain, shortness of breath, numbness, weakness, vision changes, and difficulty speaking.
Children and Teens Have Different Targets
The categories above apply to adults. For children and adolescents, healthy blood pressure depends on age, sex, and height. A typical 10-year-old boy at average height has a normal systolic pressure around 102 mm Hg, while a 17-year-old boy at the same relative height averages about 118. For girls, those numbers are roughly 102 at age 10 and 111 at age 17. As children grow, their expected blood pressure naturally rises, so pediatricians compare readings against percentile charts rather than using a single cutoff.
Why High Blood Pressure Is Harmful
When blood pressure stays elevated over time, the extra force damages artery walls, creating tiny tears. The body patches those tears with cells and other material, and cholesterol and fats gradually accumulate at the repair sites. This buildup, called plaque, narrows the arteries and restricts blood flow, a process known as atherosclerosis.
That narrowing raises the risk for a range of serious problems. Heart disease is the most common consequence, as the heart has to work harder to pump blood through stiffened, narrower vessels. Over time, the heart can enlarge and weaken. High blood pressure also damages the small arteries in the kidneys, potentially leading to kidney disease or failure, and can strain blood vessels in the eyes enough to cause vision loss. It can contribute to erectile dysfunction in men and reduced sex drive in women.
Your Reading May Not Be What You Think
Blood pressure isn’t always the same in a clinic as it is at home. About 20 to 30 percent of people diagnosed with high blood pressure in a medical office actually have normal readings outside of it. This is called white-coat hypertension, and it happens because the stress of a medical visit temporarily raises the numbers. Without other risk factors, white-coat hypertension appears to be relatively benign, though it may carry slightly more risk than truly normal blood pressure.
The opposite problem, masked hypertension, is more concerning. Roughly 12 to 13 percent of adults have normal readings at the doctor’s office but elevated readings during daily life. These people look healthy on paper but carry the cardiovascular risks of sustained high blood pressure. The only way to catch masked hypertension is through home monitoring or a 24-hour ambulatory blood pressure device.
How to Get an Accurate Reading
Small details can throw off a reading by 10 or more points. The CDC recommends this protocol for reliable results:
- Avoid food and drink for 30 minutes before measuring.
- Empty your bladder before sitting down.
- Sit with your back supported for at least 5 minutes before the reading.
- Keep both feet flat on the ground, legs uncrossed.
- Position your arm on a table at chest height, cuff on bare skin.
- Stay silent while the measurement is being taken.
Crossing your legs, talking, or resting the cuff over clothing can all inflate the numbers enough to push a normal reading into the elevated range.
Monitoring Blood Pressure at Home
Home monitoring gives a more complete picture than occasional office visits. The AHA recommends taking two readings at least one minute apart, both morning and evening, for at least three days and ideally a full week. That means 12 to 28 total readings. Once your blood pressure is stable for several months, checking one to three days per week is generally enough to stay on track.
Home readings tend to run slightly lower than office readings. A home average of 135/85 roughly corresponds to 140/90 in the office. Under the current guidelines, a home average of 130/80 or above is considered high. If your home monitor consistently shows readings in that range, it’s worth discussing with your provider even if your office numbers have looked fine.