High blood pressure develops when the force of blood pushing against your artery walls stays consistently too high, defined as 130/80 mmHg or above. A normal reading is below 120/80. What pushes it higher involves a mix of factors, some you can control and some you can’t, ranging from what you eat and how much you move to your genetics and the way your hormones regulate fluid in your body.
How Blood Pressure Is Categorized
The 2025 guidelines from the American Heart Association and American College of Cardiology break blood pressure into four categories. Normal is below 120/80. Elevated is 120 to 129 systolic (the top number) with a bottom number still under 80. Stage 1 hypertension is 130 to 139 systolic or 80 to 89 diastolic. Stage 2 hypertension is 140/90 or higher. If your top and bottom numbers fall into different categories, you’re classified by whichever one is higher.
Salt and Fluid Retention
Eating a lot of sodium is one of the most well-known contributors. When you take in more salt, your kidneys hold onto extra sodium and water, which increases blood volume, stroke volume, and cardiac output. That much has been understood for decades. But the picture is more nuanced than “salt equals water retention equals high pressure.”
Research published in Circulation found that salt-sensitive people, those whose blood pressure rises noticeably with sodium intake, don’t actually retain more sodium or water than salt-resistant people do. Both groups experience similar increases in blood volume when they eat more salt. The difference is in the blood vessels. In salt-resistant people, arteries relax and widen to accommodate the extra fluid, keeping pressure stable. In salt-sensitive people, the blood vessels fail to open up enough. This inability to lower vascular resistance in response to salt is what actually drives the pressure increase for many people.
Your Blood Vessels Play a Central Role
Healthy arteries are lined with a layer of cells called the endothelium, which constantly releases compounds that keep vessels relaxed and flexible. When this lining is damaged or inflamed, it produces less of the signaling molecule that tells arteries to widen. At the same time, it generates more oxidative stress, which further reduces relaxation signals and triggers inflammation. The result is stiffer, narrower arteries that resist blood flow, forcing the heart to pump harder.
This process, called endothelial dysfunction, connects many different risk factors together. Smoking, high blood sugar, chronic inflammation, and aging all damage the endothelium in similar ways. Arterial stiffness itself worsens with age as structural proteins in vessel walls break down and get replaced by stiffer collagen fibers. Disturbed blood flow patterns in arteries trigger signaling that promotes even more collagen buildup, creating a cycle where stiffness begets more stiffness.
The Hormone System That Controls Pressure
Your body has a built-in pressure regulation system involving three hormones that work in sequence. The kidneys release renin, which triggers production of angiotensin II, which in turn stimulates the adrenal glands to release aldosterone. Together, these hormones raise blood pressure through two main actions: angiotensin II tightens blood vessels directly, while aldosterone tells the kidneys to reabsorb more sodium and water, expanding blood volume.
When this system is overactive relative to how much sodium you have in your body, pressure climbs. Angiotensin II doesn’t just constrict vessels in the short term. It also promotes inflammation, stiffness, and structural remodeling of artery walls over time, making the problem progressively harder to reverse. Some people with hypertension have a form driven primarily by excess volume (with low renin), while others have a form driven by too much renin and angiotensin activity relative to their sodium levels.
Genetics Account for About Half the Risk
Twin studies estimate the heritability of hypertension at 50% to 60%, meaning roughly half of the variation in blood pressure between people comes down to their DNA. This isn’t one gene with one effect. Hundreds of small genetic variations each nudge your pressure slightly higher, and their effects add up. Researchers now use polygenic risk scores that combine these variations to estimate someone’s inherited predisposition alongside traditional risk factors like age, weight, smoking status, and current blood pressure readings.
Your genetic risk is fixed from birth, but it interacts with everything else on this list. Someone with a high genetic predisposition who eats a low-sodium diet and exercises regularly may never develop hypertension, while someone with moderate genetic risk who is sedentary and overweight almost certainly will.
Excess Weight and Insulin Resistance
Carrying extra body fat, particularly around the abdomen, raises blood pressure through several overlapping pathways. One of the most important is its effect on insulin. When your cells become less responsive to insulin (insulin resistance), your body produces more of it to compensate. Those elevated insulin levels activate the sympathetic nervous system, the “fight or flight” wiring that speeds up heart rate and constricts blood vessels.
Studies using precise measurement techniques have confirmed that high insulin levels directly increase nerve signals to blood vessels in skeletal muscle. This happens through the central nervous system, either as a reflex response or through insulin acting on brain areas that control sympathetic outflow. In animal models of obesity-related hypertension, this sympathetic activation impairs the kidneys’ ability to excrete sodium normally and stimulates renin secretion, linking weight gain back to the hormonal and fluid retention pathways described above. It’s one reason why losing even a modest amount of weight often produces a meaningful drop in blood pressure.
Physical Inactivity and Arterial Stiffness
When you’re sedentary, your arteries experience less of the smooth, steady blood flow that keeps them healthy. That laminar flow promotes cell alignment in the artery lining and helps maintain the flexible, intact barrier that controls vessel tone. Without regular physical activity driving that consistent flow, arteries lose some of their ability to relax. Over time, the structural composition of vessel walls shifts toward stiffer connective tissue.
Regular aerobic exercise reverses this. It improves endothelial function, reduces resting sympathetic nerve activity, and helps arteries stay compliant. The blood pressure benefits of exercise are independent of weight loss, meaning even if the number on the scale doesn’t change, your vessels still become more flexible and responsive.
Alcohol Raises Pressure at Any Amount
A large meta-analysis of cohort studies found that the relationship between alcohol and systolic blood pressure is direct and linear, with no safe threshold below which drinking has no effect. Each additional drink pushes systolic pressure a little higher. The exact biological mechanism isn’t fully mapped, but the dose-response pattern is clear: less is better, and none is best when it comes to blood pressure specifically.
Diet Beyond Sodium
Salt gets the most attention, but your overall dietary pattern matters just as much. The DASH eating plan, which emphasizes fruits, vegetables, whole grains, lean protein, and low-fat dairy while limiting saturated fat and added sugars, reduced systolic blood pressure by about 11 mmHg in people with Stage 1 isolated systolic hypertension. Diastolic pressure dropped by roughly 4.5 mmHg compared to a typical American diet. Those reductions are comparable to what a single blood pressure medication achieves.
The DASH effect comes from the combined impact of potassium, magnesium, calcium, and fiber, all of which support healthy vascular function and help the kidneys manage sodium more effectively. Potassium is especially important because it counterbalances sodium’s effects on fluid retention. Most people eat far more sodium and far less potassium than their bodies are designed to handle.
Other Contributing Factors
Several additional factors push blood pressure upward. Chronic stress keeps the sympathetic nervous system activated, maintaining elevated heart rate and constricted vessels for longer than the body can comfortably sustain. Poor sleep and sleep apnea, where breathing repeatedly stops during the night, cause oxygen levels to drop and trigger surges of sympathetic activity that raise blood pressure both during sleep and throughout the next day. Smoking damages the endothelium directly, accelerating the stiffness and dysfunction that narrow arteries over time.
Age is the most universal factor. Arteries gradually stiffen with every decade of life as elastic fibers degrade and collagen accumulates. This is why isolated systolic hypertension, where only the top number is elevated, becomes increasingly common after age 50. The underlying biology of aging overlaps heavily with the vascular damage caused by all the other risk factors, which is why unhealthy habits seem to “age” arteries faster than the calendar alone would predict.