High blood pressure has no single cause. In about 90% to 95% of cases, it develops gradually from a combination of genetic, lifestyle, and age-related factors, a condition doctors call primary hypertension. The remaining 5% to 10% of cases stem from an identifiable medical condition or medication, known as secondary hypertension. Understanding what drives your blood pressure up is the first step toward bringing it down.
Blood pressure is classified as high starting at 130/80 mmHg (Stage 1) under current American Heart Association guidelines, with Stage 2 beginning at 140/90 mmHg.
Genetics and Family History
If high blood pressure runs in your family, your risk is genuinely elevated. Family studies estimate that 15% to 35% of the variation in a person’s resting blood pressure comes from inherited traits. Twin studies put the number even higher, around 60% for males and 30% to 40% for females. Blood pressure isn’t controlled by a single gene. It’s a polygenic trait, meaning dozens or hundreds of small genetic influences add up. That’s why having one parent with hypertension raises your risk, and having two parents with it raises it more.
Genetics alone don’t seal your fate, though. They set a baseline that lifestyle factors then push higher or lower. Someone with a strong family history who eats well, exercises, and maintains a healthy weight can often keep their blood pressure in a normal range longer than someone with no family history who doesn’t.
How Sodium Raises Blood Pressure
Eating too much salt is one of the most well-established dietary causes. The mechanism is straightforward: when you take in more sodium than your kidneys can efficiently excrete, your body holds onto extra water to dilute it. That extra fluid increases your blood volume, which forces your heart to push a larger volume of blood through your arteries with each beat. The result is higher pressure on your artery walls.
Not everyone responds to sodium the same way. Some people are “salt-sensitive,” meaning their blood pressure swings more dramatically with changes in sodium intake. This trait is more common in older adults, Black Americans, and people who already have hypertension. Most adults consume well above the recommended limit of about 2,300 mg of sodium per day, with the average American intake closer to 3,400 mg.
The Role of Excess Weight
Carrying extra body fat does more than just make your heart work harder to supply a larger body. Fat tissue, particularly around the abdomen, is metabolically active in ways that directly raise blood pressure. White adipose tissue is the body’s second-largest source (after the liver) of a protein that kicks off a hormonal chain reaction involved in blood pressure regulation. In people with obesity, the sheer increase in fat tissue mass means more of this protein enters the bloodstream, leading to higher levels of hormones that constrict blood vessels and tell the kidneys to retain sodium and water.
Fat cells also produce their own aldosterone, a hormone that normally comes from the adrenal glands and signals the kidneys to hold onto salt. On top of that, substances released by fat tissue, including leptin, further stimulate aldosterone release. This creates a self-reinforcing cycle: more fat tissue leads to more salt retention, more fluid volume, and higher blood pressure. Losing even a modest amount of weight, around 5% to 10% of body weight, can produce a measurable drop in blood pressure.
Aging and Artery Stiffness
Blood pressure tends to rise with age, and the primary reason is structural. Your arteries contain a mix of elastic fibers (which allow them to stretch) and collagen (which provides rigidity). Over decades, the elastic fibers gradually break down while collagen accumulates and becomes cross-linked, making the artery walls stiffer. Inflammation, oxidized cholesterol particles, and calcification accelerate this process. In people with chronically high blood sugar, advanced glycation end products further stiffen the arterial wall.
Stiff arteries can’t expand and absorb the force of each heartbeat the way flexible ones can. This is why isolated systolic hypertension, where the top number is high but the bottom number stays normal, is so common in older adults. The top number reflects the peak pressure when the heart contracts, and rigid arteries amplify that peak. Arterial stiffness is now recognized as an independent risk factor for cardiovascular complications, not just a byproduct of aging.
Chronic Stress and the Nervous System
Short bursts of stress temporarily spike your blood pressure through the fight-or-flight response. Chronic stress is a different story. Prolonged activation of the sympathetic nervous system increases nerve signaling to the kidneys, which causes them to reabsorb more sodium throughout the filtering tubes of the kidney. More sodium retention means more fluid, higher blood volume, and sustained blood pressure elevation.
This connection between stress and kidney function helps explain why blood pressure can remain elevated long after the original stressor fades. The brain, particularly the hypothalamus, appears to maintain heightened sympathetic signaling to the kidneys even when the acute trigger is gone. High-fat diets compound this effect: research shows that just one week of high-fat feeding can increase sympathetic nerve activity to the kidneys and impair the body’s normal blood-pressure-correcting reflexes.
Alcohol Consumption
Any amount of alcohol raises systolic blood pressure, and the relationship is linear: the more you drink, the higher it goes. There is no safe threshold below which alcohol has no effect. A 2023 meta-analysis published in the AHA journal Hypertension found that as little as one standard drink per day (about 12 grams of alcohol) was associated with a systolic blood pressure increase of 1.25 mmHg compared to nondrinkers. At four drinks per day, the average increase was nearly 5 mmHg. That may sound small on an individual level, but across a population, even 1 to 2 mmHg of added pressure translates into a meaningful increase in heart attacks and strokes.
Medications That Raise Blood Pressure
Several common medications can push blood pressure up, sometimes enough to tip someone from normal into hypertensive range. The most frequently encountered culprits include:
- Pain relievers (NSAIDs): Over-the-counter drugs like ibuprofen and naproxen cause the kidneys to retain sodium and fluid.
- Decongestants: Pseudoephedrine and phenylephrine, found in many cold and sinus products, constrict blood vessels.
- Hormonal birth control: Pills and patches containing estrogen raise blood pressure in some people.
- Antidepressants: Several classes, including SSRIs, tricyclics, and MAO inhibitors, can elevate blood pressure.
- Stimulants: ADHD medications and high-dose caffeine both activate the sympathetic nervous system.
- Herbal supplements: Licorice root, ginseng, guarana, and ephedra (ma-huang) all have blood-pressure-raising effects that people often don’t expect from “natural” products.
If your blood pressure is newly elevated or harder to control than expected, reviewing everything you take, including supplements and over-the-counter products, is a practical first step.
Medical Conditions Behind Secondary Hypertension
When high blood pressure has a specific, identifiable cause, treating that cause can sometimes resolve the hypertension entirely. The most common causes of secondary hypertension, ranked roughly by how often they occur:
- Obstructive sleep apnea: Repeated breathing pauses during sleep trigger surges in sympathetic nerve activity that raise blood pressure around the clock, not just at night.
- Narrowed kidney arteries (renal artery stenosis): When blood flow to a kidney is restricted, the kidney responds as if the whole body’s blood pressure is too low and releases hormones to raise it.
- Excess aldosterone production (primary aldosteronism): The adrenal glands overproduce a hormone that causes severe sodium retention. This is more common than previously thought, affecting up to 10% of people with resistant hypertension.
- Kidney disease: Damaged kidneys lose their ability to properly filter sodium and regulate fluid balance.
- Adrenal tumors: Rare tumors called pheochromocytomas produce adrenaline-like hormones that cause dramatic blood pressure spikes.
- Thyroid disorders: Both overactive and underactive thyroid function can raise blood pressure through different mechanisms.
Secondary hypertension is worth investigating if your blood pressure rises suddenly, is unusually resistant to treatment, or develops before age 30 without obvious risk factors. Identifying and treating the underlying condition can sometimes eliminate the need for lifelong blood pressure medication.
Physical Inactivity
A sedentary lifestyle contributes to hypertension both directly and indirectly. Without regular cardiovascular exercise, your heart has to work harder to circulate blood because it pumps less efficiently. Your arteries also lose some of their natural flexibility. Indirectly, inactivity promotes weight gain, insulin resistance, and increased sympathetic nervous system activity, all of which feed into higher blood pressure. Regular aerobic exercise, even moderate-intensity activity like brisk walking, can lower systolic blood pressure by 5 to 8 mmHg in people with hypertension.
How These Causes Overlap
In most people with high blood pressure, several causes are at work simultaneously. Someone might have a genetic predisposition that makes their kidneys less efficient at excreting sodium, combined with a high-salt diet, 20 extra pounds of abdominal fat, a desk job, and the natural arterial stiffening that comes with being over 50. Each factor adds a few points to their blood pressure, and together they push it well above normal. This is precisely why lifestyle changes that address multiple factors at once, combining improved diet, more movement, weight loss, and reduced alcohol, tend to be more effective than targeting any single cause in isolation.