High blood pressure develops when the force of blood pushing against your artery walls stays elevated over time. Nearly half of American adults have it: CDC data from 2021 to 2023 puts the prevalence at about 48%. Most people with high blood pressure have what’s called primary (or essential) hypertension, which accounts for 85% to 95% of all cases. It has no single identifiable cause. Instead, it builds from a combination of genetics, daily habits, aging, and how your body handles salt and fluid.
How Your Body Regulates Blood Pressure
Your body controls blood pressure through a hormone system that adjusts how much water and salt your kidneys hold onto and how tightly your blood vessels squeeze. When blood pressure drops, your kidneys release an enzyme called renin, which kicks off a chain reaction. That chain produces a hormone called angiotensin II, which narrows small arteries and signals your adrenal glands to release aldosterone. Aldosterone tells your kidneys to retain sodium, which pulls water back into your bloodstream, raising blood volume and pressure.
This system works well when it responds proportionally to what your body needs. Problems start when it stays activated too long or too aggressively, keeping your blood vessels constricted and your fluid volume higher than necessary. Many blood pressure medications work by interrupting specific steps in this chain.
Sodium and Your Blood Vessels
Salt is one of the most direct dietary drivers of high blood pressure, and the mechanism goes beyond just holding onto extra water. When you eat a lot of sodium, the thin protective layer lining the inside of your blood vessels gets damaged. Research from the American Heart Association shows that sustained high sodium exposure reduces a key component of that lining by 68%, stripping away its ability to buffer sodium before it enters cells.
Once sodium gets into the cells of your vessel walls, those walls stiffen. Stiffer vessels can’t flex as easily when blood pulses through them, so pressure rises. The damage also reduces your body’s production of nitric oxide, a molecule that tells blood vessels to relax and widen. Less nitric oxide means more constriction. High sodium intake has also been linked to a reduction in the number of tiny blood vessels in your tissues, which forces the same volume of blood through fewer channels and increases resistance.
Genetics and Family History
Your genes play a meaningful role in whether you develop high blood pressure. More than 100 genetic variations have been linked to essential hypertension. None of them single-handedly cause it, but together they influence how your body handles sodium, how your blood vessel linings function, and how active that pressure-regulating hormone system is. The most studied genetic connections involve genes that control the renin-angiotensin-aldosterone system, along with genes that affect the health of blood vessel walls.
If one or both of your parents had high blood pressure, your risk is higher. That doesn’t guarantee you’ll develop it, but it does mean that the same lifestyle habits that might be harmless for someone else could tip you over the threshold.
How Aging Raises Blood Pressure
Arteries naturally stiffen as you get older. Young, healthy arteries are rich in elastin, a stretchy protein that lets them expand and snap back with each heartbeat. Over decades, elastin breaks down and gets replaced by collagen, which is tough but rigid. Additional changes pile on: calcium deposits form in vessel walls, inflammation increases, and the smooth muscle cells in arteries become stiffer on their own.
This is why older adults often develop a pattern called isolated systolic hypertension, where the top number climbs while the bottom number stays normal or even drops. The heart pumps blood into vessels that can no longer absorb the pulse, so peak pressure spikes. Arterial stiffness is considered a major independent risk factor for cardiovascular complications.
Lifestyle Factors That Drive It Up
Beyond sodium, several everyday habits raise blood pressure over time.
Alcohol has a clear dose-dependent relationship with blood pressure. Even moderate drinking matters: as little as one standard drink per day (about 12 grams of alcohol) is associated with systolic blood pressure averaging 1.25 mmHg higher than nondrinkers. At four drinks per day, the gap widens to nearly 5 mmHg systolic and 3 mmHg diastolic. Those numbers might sound small, but across a population, even a few points of elevation substantially increase the risk of heart attack and stroke.
Physical inactivity, excess body weight, chronic stress, and smoking all contribute through overlapping pathways. Extra body fat increases the volume of blood your heart needs to pump and promotes inflammation. Chronic stress keeps your nervous system in a state that constricts blood vessels and raises heart rate. Smoking damages the inner lining of arteries directly, accelerating the same stiffening process that happens with aging.
Medications and Substances That Raise Blood Pressure
Several common over-the-counter and prescription drugs can push blood pressure higher, sometimes without you realizing it.
- Pain relievers (NSAIDs): Ibuprofen and naproxen cause your body to retain sodium and fluid. Regular use can meaningfully raise blood pressure.
- Decongestants: Pseudoephedrine and phenylephrine, found in many cold and sinus products, constrict blood vessels.
- Hormonal birth control: Pills and certain devices containing hormones can raise blood pressure in some people.
- Antidepressants: Several classes, including SSRIs, tricyclics, and MAO inhibitors, can affect blood pressure.
- Stimulants: ADHD medications and high doses of caffeine both raise blood pressure through nervous system activation.
- Herbal supplements: Licorice root, ginseng, ephedra, and guarana can all increase blood pressure or interfere with blood pressure medications.
- Recreational drugs: Cocaine, amphetamines, and ecstasy cause sharp, dangerous spikes in blood pressure.
If you’re taking any of these regularly and your blood pressure readings are creeping up, the medication itself could be a factor worth discussing with your provider.
Secondary Causes
In 5% to 15% of cases, high blood pressure is directly caused by an identifiable medical condition. This is called secondary hypertension. Common culprits include kidney artery narrowing, adrenal gland tumors that overproduce hormones, and certain rare genetic disorders. Secondary hypertension tends to appear suddenly, resist standard treatment, or show up at an unusually young age. Treating the underlying condition often brings blood pressure back down.
What the Numbers Mean
The 2025 guidelines from the American Heart Association and American College of Cardiology define blood pressure categories as follows:
- Normal: below 120/80 mmHg
- Elevated: 120 to 129 systolic with 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
If your top and bottom numbers fall into different categories, the higher category is the one that applies. A reading of 138/72, for instance, counts as Stage 1 hypertension because of the systolic number, even though the diastolic is normal. A single high reading doesn’t mean you have hypertension. The diagnosis requires consistently elevated readings across multiple visits or confirmed by home monitoring over days or weeks.