Blood pressure rises when your heart has to pump harder, your blood vessels tighten, or your body holds onto too much fluid. Often, several of these forces act together. A reading of 130/80 or higher is now classified as high blood pressure (hypertension), with Stage 2 starting at 140/90. Understanding the specific causes helps explain why blood pressure can creep up gradually or spike suddenly, and what you can do about it.
How Your Body Regulates Blood Pressure
Your kidneys are the main control center. When they detect a drop in blood flow, they release an enzyme that triggers a hormonal chain reaction. This system produces a powerful vessel-tightening chemical and signals your adrenal glands to release a hormone called aldosterone, which tells your kidneys to hold onto sodium and water. The extra fluid increases blood volume, and the tighter vessels increase resistance. Both push pressure up.
In a healthy body, this system kicks in temporarily, then dials back down. Problems start when something keeps it switched on: a narrowed artery feeding the kidney, excess body fat producing its own supply of the vessel-tightening chemical, or an adrenal gland that won’t stop pumping out aldosterone. Any of these can lock blood pressure into a permanently elevated state.
Excess Body Weight and Visceral Fat
Carrying extra weight, particularly around your midsection, does more than just make your heart work harder to supply a larger body. Visceral fat, the deep abdominal fat surrounding your organs, is metabolically active tissue that directly raises blood pressure through several pathways.
Enlarged fat cells release inflammatory signals that damage blood vessel linings. Immune cells infiltrate fat deposits and amplify the inflammation further. This chronic, low-grade inflammation stiffens arteries and reduces their ability to relax. At the same time, visceral fat produces its own supply of the same vessel-tightening chemical your kidneys use, essentially creating a second source of pressure-raising hormones outside the normal control loop. Fat tissue also reduces production of a protective molecule called adiponectin, which normally helps blood vessels stay flexible by promoting the release of nitric oxide, the chemical that tells vessel walls to relax. Less adiponectin means less relaxation and higher resistance.
High Sodium Intake and Kidney Function
When you eat more sodium than your kidneys can efficiently excrete, your body retains water to dilute it. This increases blood volume and forces your heart to pump against greater resistance. Some people are more “salt-sensitive” than others, meaning the same amount of sodium produces a larger blood pressure response. Salt sensitivity tends to increase with age and is more common in people of African descent.
Kidney disease flips this problem on its head. Damaged kidneys lose their ability to filter sodium and fluid efficiently, so even a normal salt intake can overwhelm them. The kidneys then activate the same hormonal chain that tightens vessels and retains even more fluid, creating a cycle that progressively worsens blood pressure.
Chronic Stress and Your Nervous System
Short bursts of stress temporarily raise blood pressure through adrenaline and the “fight or flight” response. Chronic stress, however, can produce lasting changes. Prolonged psychological stress overactivates the body’s main stress hormone axis, increasing levels of cortisol and stress-signaling chemicals in the brain. Over time, this resets the brain’s baseline for how much “alert” signaling it sends to the cardiovascular system, keeping blood vessels tighter and the heart rate faster even during periods of calm.
Inflammation in the brain regions that regulate the nervous system appears to play a role in this resetting process. Research in animal models shows that chronic stress also alters gut bacteria in ways that further amplify stress hormone production, suggesting the effects reinforce each other across multiple body systems.
Genetics and Family History
Blood pressure has a significant hereditary component. Family studies estimate that 15% to 35% of the variation in resting blood pressure comes from genetics. Twin studies put the number higher, around 60% for men and 30% to 40% for women. This doesn’t mean high blood pressure is inevitable if your parents had it, but it does mean your baseline risk is higher, and lifestyle factors that might not affect someone else could tip you over the threshold.
Most inherited hypertension involves dozens or hundreds of genes, each contributing a small effect. Rarer forms involve single-gene mutations that directly affect how your kidneys handle sodium or how your adrenal glands produce hormones.
Sleep Apnea
Obstructive sleep apnea is one of the most underrecognized causes of high blood pressure. Each time your airway collapses during sleep, your oxygen drops and your body jolts awake just enough to resume breathing. This cycle can repeat dozens of times per hour, and the repeated drops in oxygen trigger inflammation and generate damaging molecules called reactive oxygen species.
Over time, these episodes reprogram the oxygen sensors in your neck and the nerve centers in your brainstem that control blood vessel tone. The result is a permanently elevated baseline for nervous system activation that persists throughout the day, not just during sleep. Even if apnea severity improves, the structural changes in these brain regions can keep blood pressure elevated. This is one reason sleep apnea-related hypertension is often resistant to standard blood pressure medications.
Adrenal Gland Disorders
Your adrenal glands sit on top of your kidneys and produce hormones that directly regulate blood pressure. The most common adrenal cause of high blood pressure is a condition called primary aldosteronism, where one or both adrenal glands overproduce aldosterone. This hormone forces your kidneys to retain sodium and excrete potassium, raising blood volume and pressure.
Primary aldosteronism was once thought to affect about 5% to 10% of people with high blood pressure, but newer research suggests the true prevalence may be at least three times higher. Many cases go undiagnosed because the excess aldosterone production is subtle enough to look like ordinary hypertension. A clue is persistently low potassium levels alongside high blood pressure, though potassium can also be normal. Researchers have identified specific genetic mutations in adrenal cells responsible for the vast majority of aldosterone-producing tumors, confirming that this is a distinct biological problem rather than just an extreme version of regular hypertension.
Kidney Artery Narrowing
When a buildup of plaque or, less commonly, abnormal tissue growth narrows the artery supplying one or both kidneys, the affected kidney perceives the reduced blood flow as a sign that overall blood pressure is too low. It responds by activating the full hormonal cascade to raise pressure. If only one kidney is affected, the other kidney receives the higher pressure and tries to compensate by excreting extra sodium and water, but the vessel-tightening effects of the hormones still push systemic pressure up.
When both kidney arteries are narrowed, or the person only has one functioning kidney, the situation is worse. Neither kidney can properly excrete sodium, so fluid retention compounds the vessel tightening. This form of hypertension is often severe and difficult to control with medications alone.
Medications That Raise Blood Pressure
Several common over-the-counter and prescription drugs can increase blood pressure, sometimes significantly. Anti-inflammatory painkillers like ibuprofen and naproxen are among the most frequent culprits. These drugs block the production of certain chemicals called prostaglandins that normally help blood vessels relax and help your kidneys excrete sodium. Without them, vessels constrict and the kidneys hold onto fluid. About one in four people taking these painkillers regularly will retain enough sodium to measurably raise their blood pressure.
These painkillers can also interfere with blood pressure medications. If you’re taking drugs to lower your blood pressure, adding a regular anti-inflammatory painkiller can partially or fully cancel out their effect. Decongestants containing pseudoephedrine work by constricting blood vessels in your nasal passages, but the effect isn’t limited to your nose. They tighten vessels throughout your body, which is why they carry warnings for people with hypertension. Hormonal birth control, certain antidepressants, and stimulant medications for ADHD can also contribute.
Physical Inactivity and Arterial Stiffness
Regular physical activity keeps your blood vessels flexible by stimulating the release of nitric oxide, which relaxes vessel walls. Without it, arteries gradually stiffen. Stiff arteries can’t expand to absorb the force of each heartbeat, so more of that force is transmitted as higher pressure. This effect compounds with age, which is why sedentary older adults are especially vulnerable.
Exercise also helps regulate the nervous system’s baseline activity level, insulin sensitivity, and body composition, all of which independently influence blood pressure. The effect of regular aerobic activity on systolic blood pressure is roughly equivalent to adding one blood pressure medication, typically a reduction of 5 to 8 points.
Alcohol and Smoking
Heavy alcohol consumption raises blood pressure through multiple routes: it increases cortisol and stress hormone levels, stimulates the nervous system, and can damage kidney function over time. More than two drinks per day for men or one for women is associated with measurably higher blood pressure, and the relationship is dose-dependent, meaning more alcohol equals more pressure.
Smoking causes immediate spikes in blood pressure with each cigarette by releasing adrenaline and tightening blood vessels. Over years, the chemicals in tobacco smoke damage the inner lining of arteries, accelerating stiffness and plaque buildup. Even after quitting, some of this arterial damage persists, though blood pressure typically improves within weeks to months.