High blood pressure develops when the force of blood pushing against your artery walls stays elevated over time. A reading of 130/80 mmHg or higher now qualifies as hypertension under current guidelines, with Stage 2 starting at 140/90 mmHg. In 85% to 95% of cases, there’s no single identifiable cause. Instead, a combination of factors, from diet and genetics to stress and aging, push your pressure upward gradually.
Too Much Sodium, Too Little Potassium
The modern Western diet is one of the most common drivers of high blood pressure, and the problem comes down to a lopsided ratio: too much sodium paired with too little potassium. When your kidneys absorb excess sodium, they hold onto more water to dilute it. That extra fluid increases the volume of blood circulating through your vessels. At the same time, low potassium allows the smooth muscle cells lining your blood vessels to contract and stay tight, which narrows the pathway blood has to travel through. The combination of more fluid in tighter pipes is a reliable recipe for higher pressure.
Potassium works as sodium’s counterbalance. It helps your kidneys flush sodium out and relaxes the walls of your blood vessels. Most people eat roughly 3,400 mg of sodium per day (well above the recommended 2,300 mg) while falling short on potassium-rich foods like bananas, beans, potatoes, and leafy greens. Correcting this ratio is one of the most effective dietary changes you can make.
How Your Kidneys Regulate Pressure
Your kidneys don’t just filter waste. They run a powerful hormone system that directly controls blood pressure by adjusting how much sodium and water your body retains. When blood flow to the kidneys drops, they release an enzyme called renin, which kicks off a chain reaction. The end product is a hormone that does five things simultaneously: it tightens blood vessels, tells your adrenal glands to produce a salt-retaining hormone, increases sodium reabsorption in the kidneys, ramps up your sympathetic nervous system (the “fight or flight” wiring), and triggers the release of another hormone that tells your body to hold onto water.
In a healthy system, this process activates temporarily and then dials back down. But when it stays chronically overactive, whether from kidney disease, narrowed arteries feeding the kidneys, or other triggers, the result is persistent high blood pressure. Every gene identified so far that influences long-term blood pressure traces back to this same kidney pathway for handling sodium. It’s the central bottleneck in the system.
Excess Weight and Insulin Resistance
Carrying extra weight raises blood pressure through several overlapping mechanisms, but one of the most important involves insulin. When your cells become resistant to insulin (a hallmark of obesity and metabolic syndrome), your pancreas compensates by producing more of it. Those elevated insulin levels have a direct effect on your kidneys: they increase sodium reabsorption, meaning your body holds onto more salt and water. High insulin also stimulates the sympathetic nervous system, keeping your blood vessels in a more constricted state.
This means that for many people, high blood pressure isn’t an isolated problem. It’s part of a metabolic package that includes insulin resistance, elevated blood sugar, and excess abdominal fat. Losing even a modest amount of weight can improve insulin sensitivity and reduce the pressure your kidneys put on the system.
Chronic Stress and Cortisol
Short bursts of stress temporarily raise your blood pressure, and that’s normal. The problem starts when stress becomes chronic. Prolonged exposure to stressful conditions keeps your body’s stress hormone system (the hypothalamic-pituitary-adrenal axis) activated, flooding your bloodstream with cortisol over extended periods. High cortisol levels interfere with a molecule called nitric oxide, which your blood vessels rely on to stay relaxed and flexible. When cortisol suppresses nitric oxide production, your vessels tighten, regional resistance to blood flow increases, and pressure rises.
Over time, chronically elevated cortisol can also make your body’s cortisol receptors less responsive, creating a cycle where the system keeps pumping out more stress hormones without the usual feedback signals to shut it down.
Sleep Apnea’s Hidden Role
Obstructive sleep apnea is one of the most underrecognized causes of high blood pressure. When your airway repeatedly collapses during sleep, oxygen levels drop and carbon dioxide builds up. These gas changes trigger your sympathetic nervous system to fire, constricting blood vessels and releasing stress hormones called catecholamines. What makes this particularly damaging is that those elevated catecholamine levels don’t just affect you at night. They persist into the daytime, keeping your blood pressure elevated around the clock.
Sleep apnea also activates the same kidney hormone system described above, further increasing sodium retention and blood volume. If your blood pressure is resistant to treatment, or if it’s particularly high in the morning, undiagnosed sleep apnea is a common culprit worth investigating.
Aging and Arterial Stiffness
Your arteries are built from two key structural proteins. Elastin gives them flexibility, allowing them to stretch with each heartbeat and absorb the pulse of blood flow. Collagen provides structure and stiffness. In youth, the ratio between these two materials keeps arteries compliant and springy.
As you age, that balance shifts. The smooth muscle cells responsible for producing elastin decline in number. Elastin fibers break down faster, partly due to increased enzyme activity that degrades them. In response, the body lays down more collagen, which becomes thicker and more rigid. The result is arteries that can no longer expand easily when blood surges through them with each heartbeat. Stiff arteries require higher pressure to move the same volume of blood, and this primarily drives up the top number (systolic pressure) while the bottom number (diastolic) may stay the same or even drop. This pattern, called isolated systolic hypertension, is the most common form in adults over 60.
Existing high blood pressure accelerates this process. Elevated pulse pressure increases the mechanical stress on artery walls, which breaks down elastin even faster, creating a feedback loop where hypertension worsens arterial aging and arterial aging worsens hypertension.
Genetics and Family History
Blood pressure is a heritable trait. Studies estimate that 30% to 70% of the variation in blood pressure between individuals comes from genetic differences. This doesn’t mean hypertension is inevitable if your parents had it, but it does mean your baseline risk is meaningfully shaped by your DNA.
The genetic variants discovered so far almost all point to the same system: how your kidneys handle sodium. Some gene mutations cause rare conditions with extremely low blood pressure due to excessive salt wasting through the kidneys. The flip side, variants that cause your kidneys to retain more sodium, contributes to higher pressure. Most people with genetically influenced hypertension carry many small-effect variants rather than a single dramatic mutation, which is one reason the condition runs in families without following a simple inheritance pattern.
Medications and Substances That Raise Pressure
Several common over-the-counter and prescription medications can push blood pressure up, sometimes significantly:
- Pain relievers (NSAIDs): Ibuprofen (Advil, Motrin) and naproxen (Aleve) cause your body to retain water, which increases blood volume and stresses the kidneys. Regular use is a well-documented cause of elevated pressure.
- Decongestants: Pseudoephedrine and phenylephrine, found in many cold and allergy products, work by narrowing blood vessels. That same vessel-narrowing effect raises blood pressure throughout the body.
- Hormonal birth control: Pills and patches containing hormones can raise blood pressure in some people. The risk is higher if you’re over 35, overweight, or smoke.
Alcohol is another common contributor. Regular heavy drinking raises blood pressure both acutely and chronically. Caffeine produces short-term spikes, though habitual coffee drinkers typically develop tolerance. If your pressure is newly elevated, reviewing everything you take regularly, including supplements and over-the-counter products, is a practical first step.
Secondary Causes: The Other 5% to 15%
In a smaller subset of cases, high blood pressure has a single, identifiable cause. This is called secondary hypertension, and treating the underlying condition can sometimes resolve the blood pressure problem entirely. Common causes include narrowing of the arteries that supply the kidneys, hormone-producing tumors of the adrenal glands, thyroid disorders, and certain rare genetic conditions. Secondary hypertension is more likely when blood pressure rises suddenly, appears at a young age, or doesn’t respond to standard treatment.