Blood pressure rises when your heart pumps harder, your blood vessels narrow, or your body holds onto too much fluid. Often, it’s a combination of all three. A reading of 130/80 or higher is now classified as high blood pressure, and the causes range from everyday habits like diet and inactivity to underlying medical conditions and even medications you might not suspect.
How Blood Pressure Works
Blood pressure comes down to a simple relationship: the amount of blood your heart pumps multiplied by the resistance it meets in your blood vessels. If either of those numbers goes up, your blood pressure goes up. There are no other possibilities. So anything that makes your heart pump more blood per minute, or anything that narrows or stiffens your arteries, will raise the pressure inside them.
Your body has a built-in system for adjusting blood pressure on the fly. When pressure drops, your kidneys release an enzyme that kicks off a chain reaction: proteins get converted into a hormone that tightens the muscular walls of small arteries. That same hormone signals your adrenal glands to release another hormone that tells your kidneys to hold onto sodium. More sodium means your body retains more water, which increases blood volume and pushes pressure higher. This system is essential for survival, but when it stays overactive, it becomes a driver of chronic high blood pressure.
Salt, Weight, and Everyday Habits
Salt is one of the most direct dietary influences on blood pressure. When you eat more sodium than your body needs, it holds onto extra water to dilute it. That extra fluid increases the volume of blood inside your vessels, which raises the pressure on artery walls and forces your heart to work harder. The federal recommendation is to stay under 2,300 mg of sodium per day, roughly one teaspoon of table salt, but most people consume well above that.
Carrying extra weight raises blood pressure through a straightforward mechanism: the more tissue your body has, the more blood it needs to supply oxygen and nutrients. That increased blood flow puts additional pressure on artery walls. Losing even a modest amount of weight can produce a measurable drop in blood pressure readings.
Alcohol and smoking both damage blood vessels over time. Chronic use of either one reduces the flexibility of vessel walls through direct injury to the inner lining and ongoing inflammation. Nicotine also triggers a short-term spike in blood pressure by activating the part of your nervous system responsible for the “fight or flight” response, which temporarily narrows vessels and speeds up heart rate. Physical inactivity compounds all of these effects because regular exercise helps keep arteries flexible and strengthens the heart so it can pump blood with less effort.
How Aging Stiffens Your Arteries
Healthy, elastic arteries act like shock absorbers. When your heart contracts, they stretch to accommodate the surge of blood, then gently recoil between beats to keep flow smooth and steady. This stretching lowers the peak pressure during each heartbeat and keeps blood moving during the resting phase.
With age, artery walls gradually lose that elasticity. Collagen replaces the flexible fibers, and calcium deposits can make walls rigid. When a stiff artery can’t expand to absorb the force of each heartbeat, the full impact of that pressure wave travels deeper into smaller vessels and also bounces back toward the heart sooner. The result is a higher top number (systolic pressure) and more strain on the heart. This is why isolated systolic hypertension, where the top number is high but the bottom number is normal, becomes increasingly common after age 60.
Genetics and Family History
Twin and family studies estimate that roughly 30 to 50 percent of the variation in blood pressure between people is inherited. No single gene is responsible. Instead, hundreds of small genetic differences influence how your kidneys handle sodium, how your blood vessels respond to hormonal signals, and how readily your arteries stiffen over time. If both of your parents had high blood pressure, your own risk is substantially higher than average, even before lifestyle factors come into play. That genetic predisposition doesn’t guarantee hypertension, but it does lower the threshold at which salt, stress, or weight gain tips you into an elevated range.
Medical Conditions That Raise Blood Pressure
When high blood pressure is caused by an identifiable underlying condition, it’s called secondary hypertension. Treating the root cause can sometimes resolve the blood pressure problem entirely.
Kidney Disease
Your kidneys are central to blood pressure control because they regulate how much sodium and water stay in your bloodstream. Conditions that damage kidney tissue, including diabetic kidney disease, polycystic kidney disease, and diseases that inflame the tiny filtering units inside the kidneys, can impair that regulation and push pressure up. Narrowing of the arteries that supply the kidneys themselves (renovascular hypertension) also triggers the pressure-raising hormonal chain reaction described earlier, because the kidneys interpret reduced blood flow as low pressure and respond by retaining salt and water.
Hormonal Disorders
Several glands can malfunction in ways that raise blood pressure. Overproduction of the hormone aldosterone tells your kidneys to hold onto sodium and dump potassium, increasing blood volume. Cushing syndrome, where cortisol levels stay chronically elevated, has a similar effect. A rare adrenal tumor called a pheochromocytoma floods the body with adrenaline, causing dramatic spikes. Both an underactive and overactive thyroid can raise blood pressure, as can overactive parathyroid glands, which increase calcium levels in the blood and trigger vessel constriction.
Sleep Apnea
Obstructive sleep apnea repeatedly cuts off oxygen during sleep. The oxygen drops damage the inner lining of blood vessels over time, making them less able to relax. Sleep apnea also keeps the “fight or flight” branch of the nervous system revved up, releasing chemicals that raise pressure even during waking hours. Treating sleep apnea with a breathing device at night often brings blood pressure down noticeably.
Medications and Substances That Raise Blood Pressure
Some of the most common over-the-counter medications can quietly push your numbers up. Pain relievers like ibuprofen (Advil) and naproxen (Aleve) cause the body to retain sodium and water, which raises blood volume. Decongestants containing pseudoephedrine or phenylephrine, found in many cold and sinus products, work by narrowing blood vessels in your nasal passages but narrow them elsewhere too.
Hormonal birth control raises blood pressure in some people. Certain antidepressants can do the same, as can stimulant medications used for ADHD. Caffeine produces temporary spikes, especially in people who don’t consume it regularly. Even herbal supplements that seem harmless, including licorice root, ginseng, guarana, and ephedra, can interfere with blood pressure regulation.
Recreational drugs carry some of the sharpest risks. Cocaine and amphetamines cause intense, sudden spikes by flooding the body with stress hormones and dramatically constricting blood vessels. These spikes can be dangerous even in people with otherwise normal blood pressure.
Blood Pressure Categories
The American Heart Association defines blood pressure in four ranges, based on the top number (systolic) and bottom number (diastolic), measured in millimeters of mercury:
- Normal: below 120/80
- Elevated: 120 to 129 systolic with a 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
Elevated blood pressure is a warning zone. Without changes, it typically progresses to Stage 1 within a few years. At Stage 1, lifestyle modifications alone can sometimes bring numbers back to normal. Stage 2 usually calls for medication in addition to lifestyle changes, because the risk of heart attack, stroke, and kidney damage rises with every point above normal.
Why It Often Has No Symptoms
High blood pressure is sometimes called a “silent” condition because most people feel completely fine even with readings well into Stage 2. Your body adapts to the higher pressure gradually, so there’s no built-in alarm. That’s why it’s frequently discovered during a routine checkup or when someone is being treated for something else entirely. The damage, to artery walls, the heart muscle, the kidneys, and small blood vessels in the brain and eyes, accumulates over years without obvious warning signs. Regular monitoring is the only reliable way to catch it early, especially if you have a family history, are over 40, or carry any of the risk factors described above.