High blood pressure, or hypertension, starts at a reading of 130/80 mmHg or higher. That threshold, confirmed in the 2025 guidelines from the American Heart Association and American College of Cardiology, is lower than many people expect. Because high blood pressure rarely causes noticeable symptoms, roughly half of people who have it don’t know it.
What the Numbers Mean
A blood pressure reading has two numbers. The top number (systolic) measures the force your blood exerts on artery walls when your heart beats. The bottom number (diastolic) measures that force between beats, when your heart is resting. Both numbers matter, and either one being too high is enough to qualify as hypertension.
Here’s how the categories break down:
- Normal: below 120/80 mmHg
- Elevated: 120 to 129 systolic with a diastolic still below 80
- 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 single high reading doesn’t necessarily mean you have hypertension. Diagnosis typically requires elevated readings on multiple occasions. That’s partly because of a phenomenon called white coat hypertension, where your blood pressure rises simply because you’re in a medical setting. Studies estimate this affects anywhere from 12% to over 30% of people with elevated office readings. The reverse also happens: some people have normal readings at the doctor’s office but high blood pressure the rest of the time, a pattern called masked hypertension that affects roughly 13% of the general population.
Why Most Cases Have No Clear Cause
About 90% to 95% of people with high blood pressure have what’s called primary hypertension. There’s no single underlying disease causing it. Instead, it develops gradually from a combination of genetics, aging, diet, weight, and activity level. Arteries naturally stiffen over time, and factors like excess sodium, chronic stress, and inactivity accelerate the process.
The remaining 5% to 10% have secondary hypertension, meaning another condition is driving their blood pressure up. The most common culprits in adults include kidney disease, a hormonal condition called hyperaldosteronism (where the body produces too much of a hormone that retains salt), obstructive sleep apnea, and thyroid disorders. Certain medications, including some pain relievers, decongestants, and hormonal birth control, can also raise blood pressure. In older adults, narrowing of the arteries supplying the kidneys becomes a more frequent cause.
What High Blood Pressure Does to Your Body
Your arteries are lined with a thin layer of cells that help blood vessels relax and stay flexible. Persistently high pressure damages this lining, triggering inflammation and making vessel walls stiffer. Stiff arteries can’t expand as easily with each heartbeat, which forces the heart to pump harder and raises pressure even further. It’s a cycle that, left unchecked, progressively damages organs over years.
The heart takes the first hit. Pumping against higher resistance causes the main pumping chamber to thicken and enlarge, a condition that significantly raises the risk of heart attack and heart failure. The kidneys are equally vulnerable because they depend on a dense network of tiny blood vessels to filter waste from your blood. High blood pressure damages those vessels, gradually reducing kidney function. It’s one of the most common causes of kidney failure requiring dialysis.
Your eyes are another target. The small blood vessels in the retina (the light-sensing tissue at the back of the eye) can be damaged by sustained high pressure, leading to bleeding, blurred vision, and in severe cases, vision loss. Having diabetes alongside high blood pressure compounds the risk to both the kidneys and eyes.
In the brain, high blood pressure raises the risk of both types of stroke: blockages caused by narrowed arteries and bleeds caused by weakened vessel walls. It also contributes to cognitive decline over time by reducing blood flow to brain tissue.
Symptoms and Warning Signs
Most people with high blood pressure feel completely fine, which is why it’s often called a silent condition. You can have a reading of 160/100 and have no headache, no dizziness, nothing. This is precisely what makes it dangerous. Organ damage accumulates quietly over years.
Symptoms do appear in a hypertensive crisis, which occurs when blood pressure spikes to 180/120 mmHg or higher. At that level, you may experience severe headache, chest pain, blurred vision, confusion, nausea, shortness of breath, or seizures. These symptoms signal possible life-threatening organ damage and require emergency medical attention.
How to Get an Accurate Reading at Home
Home monitoring gives a clearer picture of your blood pressure than occasional office visits. To get reliable numbers, the technique matters. Don’t eat, drink, or exercise for 30 minutes beforehand. Empty your bladder. Then sit in a chair with your back supported and both feet flat on the floor, legs uncrossed, for at least five minutes before taking a reading.
Place the cuff on bare skin at the level of your heart, with your arm resting on a table at chest height. Don’t talk during the measurement. Take at least two readings one to two minutes apart and record both. Doing this at the same times each day gives you and your doctor the most useful data for spotting trends and making treatment decisions.
Lifestyle Changes That Lower Blood Pressure
Regular aerobic exercise is one of the most effective non-drug interventions. Walking, cycling, swimming, or other moderate activity for about 30 minutes on most days can lower systolic pressure by 4 to 10 mmHg and diastolic pressure by 5 to 8 mmHg. That’s comparable to the effect of some medications, and it applies whether or not you lose weight in the process.
Diet plays an equally large role. The DASH diet (Dietary Approaches to Stop Hypertension) emphasizes fruits, vegetables, whole grains, lean protein, and low-fat dairy while limiting saturated fat and added sugar. The standard version caps sodium at 2,300 mg per day, roughly one teaspoon of table salt. A lower-sodium version targets 1,500 mg daily and tends to produce larger reductions in blood pressure. For context, the average American consumes over 3,400 mg of sodium per day, so even modest reductions can make a measurable difference.
Other lifestyle factors that meaningfully lower blood pressure include maintaining a healthy weight, limiting alcohol to one drink per day for women or two for men, managing stress, and getting adequate sleep. For people with Stage 1 hypertension and no additional heart disease risk factors, these changes alone may be enough to bring readings back to normal range.
When Medication Becomes Necessary
If lifestyle changes aren’t enough, or if your blood pressure is already at Stage 2 or you have other cardiovascular risk factors, medication is typically part of the plan. Several classes of drugs lower blood pressure through different mechanisms. Some relax blood vessel walls directly. Others reduce the volume of fluid in your bloodstream by helping your kidneys excrete more salt and water. Another group blocks a hormone called angiotensin that constricts blood vessels, and still others prevent calcium from tightening vessel walls, allowing them to stay loose and open.
Most people start with one medication, but many eventually need two or more from different classes to reach their target. Finding the right combination can take some adjustment. Side effects vary by drug type but are generally mild, and switching to a different class often resolves them. The key point is that blood pressure medication works only as long as you take it. Stopping because you feel fine is one of the most common reasons blood pressure rebounds.