What High Blood Pressure Does to Your Heart, Brain and Kidneys
High blood pressure rarely hurts. That is exactly what makes it risky. The CDC reports that high blood pressure was a primary or contributing cause of more than 680,000 U.S. deaths in 2024, most of them through heart attacks, strokes and heart failure that developed over years without warning signs.
Key takeaways
The top number (systolic) is the pressure when your heart beats. The bottom number (diastolic) is the pressure between beats.
Over time, high pressure strains artery walls, which raises the risk of heart attack, stroke, heart failure and kidney disease.
Accurate home readings, taken the same way each time, are one of the most useful things you can bring to your doctor.
Some research, such as the ZENITH study, measures heart attacks and strokes, not just blood pressure numbers.
What the two numbers actually measure
In a reading of 150/88, the 150 is your systolic pressure, the force on your artery walls each time your heart pumps. The 88 is your diastolic pressure, the force while your heart rests between beats. Both matter. After about age 50, the top number tends to rise and becomes an especially strong signal of cardiovascular risk.
What years of high pressure do inside the body
Think of a garden hose left at full pressure for years. The walls thicken, stiffen and develop weak spots. Arteries respond in a similar way, and the effects show up in specific organs:
Heart: the heart muscle thickens from pumping against high pressure, and narrowed coronary arteries raise the risk of heart attack and heart failure.
Brain: damaged or blocked blood vessels raise the risk of stroke. High blood pressure is also linked to memory and thinking problems later in life.
Kidneys: tiny filtering vessels are damaged, which can lead to chronic kidney disease. Kidney damage can in turn push blood pressure higher.
Eyes: blood vessels in the retina can be damaged, affecting vision.
Legs: narrowed leg arteries (peripheral artery disease) can cause pain when walking.
If you already live with one of these conditions, your care team may describe you as having established cardiovascular disease or high cardiovascular risk. We explain those terms in our guide to cardiovascular risk.
How to get a reading you can trust at home
A single reading at the pharmacy tells you little. A week of careful home readings tells your doctor a lot. The CDC recommends:
No food, drinks, caffeine or exercise for 30 minutes beforehand, and empty your bladder first
Sit with your back supported and feet flat on the floor for at least five minutes
Rest your arm on a table at chest height, with the cuff on bare skin
Stay quiet during the reading
Take at least two readings, one or two minutes apart, at the same time each day
Write the results in a log such as the CDC's printable blood pressure log, or use your monitor's app, and bring it to appointments. Also check that your cuff fits: a cuff that is too small can make readings look higher than they are.
When a reading needs urgent attention
If your reading is higher than 180/120, wait one minute and check again. If it is still that high and you have chest pain, shortness of breath, back pain, numbness, weakness, vision changes or trouble speaking, call 911. Without symptoms, contact your healthcare professional right away. This guidance comes from the American Heart Association.
Readings still high even on two or more medicines? A research study may be worth a look.
Why some research looks beyond the numbers
Lowering blood pressure is the means, not the end. What people care about is avoiding a heart attack or stroke. That is why some studies are designed as "cardiovascular outcomes" trials: they follow thousands of people over time and count the events that change lives, not only the readings.
The ZENITH study (NCT07181109) is one of them. It is testing whether zilebesiran, an investigational injection given every six months, lowers the risk of heart attack, stroke, heart failure events and cardiovascular death when added to usual blood pressure medicines in adults whose blood pressure remains high.
Study snapshot: ZENITH (NCT07181109)
What is being studied
Zilebesiran, an investigational medicine given as an injection under the skin every six months, added to a person's usual blood pressure medicines.
Compared with
Placebo (an injection with no active medicine). Participants keep taking their regular blood pressure medicines either way.
Main question
Whether zilebesiran lowers the risk of serious heart and blood vessel events, such as heart attack, stroke, heart failure events or death from cardiovascular causes.
Size and scope
A global Phase 3 study planned to include about 11,000 adults in 35 countries.
Who may be a fit
Adults whose blood pressure stays high despite two or more blood pressure medicines, and who have established cardiovascular disease or high cardiovascular risk.
Local study sites
Research sites working with HEKMA include Birmingham, AL; Evansville, IN; Phoenix, AZ; and San Antonio, TX.
Curious how a trial like this works day to day, including placebo and consent? Read how clinical research works for people on several blood pressure medicines.
Frequently asked questions
Which blood pressure number is more important?
Both matter. For many adults over 50, the top (systolic) number is an especially strong predictor of heart and blood vessel problems. Your healthcare professional looks at both.
Can high blood pressure cause symptoms?
Usually not, which is why it is often called silent. Symptoms such as chest pain, severe headache, vision changes or weakness with a very high reading can signal an emergency and need immediate care.
How often should I check my blood pressure at home?
Ask your healthcare professional. The CDC suggests measuring at the same time each day and taking at least two readings one or two minutes apart when you check.
What is a cardiovascular outcomes trial?
It is a large study that measures whether a treatment reduces events such as heart attacks, strokes and heart failure, not only whether it lowers blood pressure. ZENITH is an example.