High blood pressure happens when the force of blood pushing against your artery walls stays too high over time. A reading of 130/80 mm Hg or above now qualifies as hypertension, while anything under 120/80 is considered normal. The causes range from everyday habits like salt intake and inactivity to underlying medical conditions, genetics, aging, and even common medications you might not suspect.
How Salt Raises Blood Pressure
Salt is the single most discussed dietary driver of high blood pressure, and the mechanism goes beyond simple water retention. When you consume excess sodium, your body holds onto more water to dilute it, which increases the total volume of blood flowing through your vessels. But that’s only part of the story.
High sodium intake also triggers your adrenal glands to release a hormone that directly acts on the smooth muscle cells lining your artery walls. This hormone disrupts the normal balance of sodium and calcium inside those cells, causing them to contract and stay contracted. The result is narrower, stiffer arteries pushing back harder against blood flow. Over time, this sustained constriction raises your baseline blood pressure. It also reduces the ability of your blood vessel lining to produce signals that relax and widen arteries, making the problem self-reinforcing.
Your Body’s Blood Pressure Control System
Your kidneys, liver, lungs, and adrenal glands work together through a hormonal chain reaction that continuously adjusts blood pressure. When pressure drops, your kidneys release an enzyme called renin. Renin triggers a cascade that ultimately produces a hormone called angiotensin II, which narrows the muscular walls of small arteries. Angiotensin II also signals your adrenal glands to release aldosterone, a hormone that tells your kidneys to reabsorb more sodium and water, increasing blood volume.
This system is designed to be a short-term rescue mechanism. But in people with hypertension, it can become overactive or fail to dial back down. Many blood pressure medications work by interrupting specific steps in this chain, which is why your doctor might describe them as targeting the “renin-angiotensin system.”
Genetics and Family History
Hypertension runs in families, and your risk rises significantly if both parents have it. Researchers have identified more than 100 genetic variations linked to high blood pressure, though no single gene drives the condition on its own. Essential hypertension, the type with no identifiable underlying disease, is the product of many small genetic influences layered on top of environmental and lifestyle factors. You can’t change your genes, but knowing your family history helps you and your doctor decide how aggressively to monitor and manage your other risk factors.
How Aging Stiffens Your Arteries
Young, healthy arteries are elastic. They stretch when the heart pumps and spring back between beats, smoothing out the pressure wave. As you age, the balance between the stretchy fibers (elastin) and the rigid fibers (collagen) in your artery walls shifts toward collagen. Decades of pulsatile stress cause the elastic fibers to fragment and break down, while collagen accumulates and cross-links into a stiffer matrix.
Chronic high blood sugar accelerates this process by promoting the formation of chemical bonds between collagen fibers, making the arterial wall even more rigid. Calcium deposits can also build up in the artery wall, particularly in people with chronic kidney disease. The end result is arteries that no longer absorb the force of each heartbeat. Instead, that force transmits directly into your organs. This is why isolated systolic hypertension, where the top number is high but the bottom number is normal or low, becomes increasingly common after age 60.
Insulin Resistance and Metabolic Health
When your cells stop responding normally to insulin, your pancreas compensates by producing more of it. Those chronically elevated insulin levels don’t just affect blood sugar. High insulin interferes with your kidneys’ ability to excrete sodium, ramps up activity in the sympathetic nervous system (your body’s “fight or flight” wiring), and stimulates the same renin-angiotensin-aldosterone system described above. This is one reason why high blood pressure, prediabetes, and excess abdominal fat so often travel together. Losing even a modest amount of weight can improve insulin sensitivity and lower blood pressure simultaneously.
Sleep Apnea
Obstructive sleep apnea is one of the most underrecognized causes of high blood pressure. Each time your airway collapses during sleep, your blood oxygen drops and carbon dioxide rises. Your nervous system responds with a surge of stress hormones, including adrenaline, that spike your heart rate and constrict your blood vessels. In people with moderate to severe sleep apnea, this cycle repeats dozens of times per hour, all night long. The sympathetic overdrive doesn’t fully reset during the day, meaning the elevated stress hormone levels and blood pressure persist around the clock. If your blood pressure is stubbornly high despite medications, or if you snore heavily and wake up tired, untreated sleep apnea may be the missing piece.
Medical Conditions That Cause Hypertension
About 5 to 10 percent of hypertension cases have a specific, identifiable medical cause. This is called secondary hypertension, and treating the underlying condition can sometimes resolve the blood pressure problem entirely.
- Kidney disease. Damaged kidneys lose the ability to filter waste and regulate sodium properly. Diabetic kidney damage, polycystic kidney disease, and diseases that inflame the kidney’s tiny filtering units can all raise blood pressure.
- Narrowed kidney arteries. When one or both arteries feeding your kidneys become partially blocked, the kidneys sense reduced blood flow and respond by activating the hormonal cascade that raises pressure body-wide.
- Aldosteronism. The adrenal glands overproduce aldosterone, causing the kidneys to retain too much salt and water while losing potassium.
- Cushing syndrome. Excess cortisol production, whether from a tumor or long-term steroid medication use, raises blood pressure through multiple pathways.
- Adrenal tumors (pheochromocytoma). These rare tumors pump out adrenaline and noradrenaline, causing dramatic spikes in blood pressure, rapid heartbeat, and sweating.
Medications That Raise Blood Pressure
Several common over-the-counter and prescription drugs can push your blood pressure up, sometimes without you realizing it.
Pain relievers like ibuprofen (Advil) and naproxen (Aleve) cause your body to retain water and can interfere with kidney function, raising pressure over time. Decongestants found in cold and allergy medicines, including pseudoephedrine and phenylephrine, work by narrowing blood vessels throughout the body, not just in your nose. Hormonal birth control pills and patches raise blood pressure in some people, with the risk increasing if you’re over 35, overweight, or a smoker.
Certain antidepressants, stimulant medications used for ADHD, and immunosuppressants taken after organ transplants can also contribute. Illicit drugs like cocaine, methamphetamine, and ecstasy narrow the arteries that supply the heart, spike heart rate, and can cause dangerous blood pressure surges. If you’re being treated for hypertension and your numbers aren’t improving, it’s worth reviewing every medication, supplement, and over-the-counter product you take regularly.
Lifestyle Factors That Add Up
Beyond salt, several daily habits directly influence blood pressure. Physical inactivity allows your resting heart rate to stay higher and your arteries to lose their flexibility. Regular aerobic exercise, even brisk walking, lowers systolic blood pressure by an average of 5 to 8 points. Excess alcohol consumption raises blood pressure through multiple pathways, including increased cortisol release and direct effects on blood vessel tone. Chronic stress keeps your sympathetic nervous system activated, maintaining elevated levels of the same hormones that spike during a sleep apnea episode.
Most people with high blood pressure have several of these factors overlapping: a genetic predisposition, too much sodium, not enough activity, gradual arterial stiffening with age, and perhaps a medication or two that quietly makes things worse. That overlap is actually useful to understand, because it means improving even one or two of these factors can meaningfully lower your numbers.