Blood pressure rises when your heart pumps harder, your blood vessels tighten, or your body holds onto extra fluid. Sometimes all three happen at once. These changes can be triggered by everyday habits like eating too much salt, drinking alcohol, or sleeping poorly, but they can also stem from underlying medical conditions or medications you might not suspect.
How Your Body Controls Blood Pressure
Your blood pressure at any given moment depends on two things: how much blood your heart pushes out with each beat (cardiac output) and how much resistance your blood vessels create as that blood flows through them (vascular resistance). Anything that increases either one raises your blood pressure.
The main control system behind this is a hormone chain reaction involving your kidneys, adrenal glands, and blood vessels. When your kidneys detect low blood flow, they release a signal that ultimately produces a hormone called angiotensin II. This hormone raises blood pressure through several routes at once: it tightens the walls of your arteries, tells your adrenal glands to release aldosterone (which makes your kidneys retain sodium and water), ramps up your nervous system’s “fight or flight” activity, and triggers the release of another hormone that further reduces water loss. The net effect is more fluid in your bloodstream pushing through narrower vessels.
Salt and the Sodium-Potassium Balance
Sodium is the single most studied dietary driver of high blood pressure. The World Health Organization defines excessive intake as more than 5 grams of sodium per day, yet the typical global intake falls between 3.5 and 5.5 grams daily. The WHO recommends limiting sodium to about 2 grams per day, roughly equivalent to 5 grams (one teaspoon) of table salt.
The classic explanation is straightforward: sodium pulls water into your bloodstream, expanding your blood volume and forcing your heart to push more fluid through your arteries. A high-sodium diet can expand your total body water until a new equilibrium is reached, but by that point your blood pressure has settled at a higher baseline. Interestingly, newer research shows sodium can also accumulate in tissues like skin and muscle without pulling water along, suggesting the relationship is more complex than simple fluid retention.
Potassium acts as a natural counterweight. People with the highest sodium intake and lowest potassium intake have systolic blood pressure about 12 mmHg higher and diastolic pressure about 5 mmHg higher than those with the opposite pattern. Research on the DASH diet, which emphasizes fruits, vegetables, and low-fat dairy, found that combining it with low sodium intake lowered systolic pressure by 7 mmHg in people without hypertension and by 11.5 mmHg in those who already had it. If you bring your sodium-to-potassium ratio close to 1:1, studies estimate you could lower systolic pressure by about 6 mmHg. Most people eat far more sodium than potassium, so increasing potassium-rich foods (bananas, potatoes, beans, leafy greens) while cutting back on processed foods can shift this balance meaningfully.
Alcohol’s Direct, Linear Effect
There is no safe threshold for alcohol when it comes to blood pressure. A large meta-analysis published in the American Heart Association’s journal Hypertension found that the relationship between alcohol and systolic blood pressure is direct and linear, meaning any amount raises it. Even a single standard drink per day (about 12 grams of alcohol) was associated with systolic pressure 1.25 mmHg higher than nondrinkers. That may sound small, but across a population it translates to a meaningful increase in heart attacks and strokes.
At two drinks per day (24 grams), the increase was 2.5 mmHg systolic and 2.0 mmHg diastolic. At four drinks per day, systolic pressure was nearly 5 mmHg higher. The effect on diastolic pressure varied by sex and geographic region, but the systolic trend held consistently.
Medications That Raise Blood Pressure
Several common over-the-counter and prescription drugs can push blood pressure up, sometimes without you realizing it. NSAIDs like ibuprofen and naproxen cause your body to retain water, which can stress your kidneys and raise pressure. Decongestants found in cold and sinus medications work by narrowing blood vessels to reduce swelling in your nasal passages, but that same vessel-narrowing effect raises blood pressure throughout your body. Hormonal birth control, including most pills and patches, can also increase blood pressure in some people, which is why regular monitoring is recommended after starting them.
Other culprits include certain antidepressants, stimulant medications for ADHD, immunosuppressants, and some herbal supplements. If your blood pressure has crept up and you’ve recently started or changed a medication, that connection is worth exploring.
Sleep Apnea and the Overnight Surge
Obstructive sleep apnea is one of the most underrecognized causes of high blood pressure. During an apneic episode, the airway collapses and blocks airflow. This drops oxygen levels and raises carbon dioxide, which triggers your sympathetic nervous system, the same system responsible for the fight-or-flight response. Your heart rate increases, your hormonal blood pressure system activates, and your blood pressure spikes.
Normally, blood pressure dips by 10 to 20 percent during sleep as your body relaxes. In people with sleep apnea, the repeated surges of nervous system activity throughout the night override this natural dip, keeping blood pressure elevated even while lying down. Over time, this nightly stress remodels the cardiovascular system, and the elevated pressure persists into the daytime too. If you snore heavily, wake up with headaches, or feel exhausted despite a full night of sleep, untreated sleep apnea could be quietly driving your blood pressure higher.
Chronic Stress and Nervous System Overdrive
Acute stress raises blood pressure temporarily through the same sympathetic nervous system pathway involved in sleep apnea. Your body releases stress hormones that speed up your heart and tighten your blood vessels. In a single stressful moment, this is harmless. But chronic stress, whether from work, relationships, financial pressure, or ongoing anxiety, keeps this system activated far more than it should be. The repeated elevations can damage blood vessel walls over time and contribute to sustained hypertension, especially when paired with stress-related habits like poor sleep, excess alcohol, or high-sodium comfort foods.
How Aging Stiffens Your Arteries
Your aorta, the body’s largest artery, contains more elastic tissue than any other blood vessel. In a healthy, young aorta, this elasticity absorbs the force of each heartbeat and releases it gradually, smoothing out the pressure so blood flows steadily. Think of it as a shock absorber for your circulatory system.
Over decades of use, the elastic fibers in the aorta break down from constant stretching. Enzymes gradually degrade these fibers, and they’re replaced by stiffer collagen. Aortic stiffness increases by roughly 70 percent between ages 10 and 50, compared to only about 20 percent in smaller peripheral arteries. As the aorta stiffens, it loses its ability to cushion each heartbeat. The pressure wave travels faster through rigid vessels and bounces back sooner, piling on top of the next heartbeat instead of smoothing it out. The result is higher systolic (top number) pressure and lower diastolic (bottom number) pressure, a pattern called isolated systolic hypertension. This is the dominant form of high blood pressure in older adults, affecting more than 75 percent of people over age 70.
Underlying Medical Conditions
When high blood pressure is caused by an identifiable disease, it’s called secondary hypertension. Kidney disease is the most common culprit. Damaged kidneys lose their ability to properly filter sodium and regulate fluid balance, leading to volume overload and sustained pressure elevation. Conditions like diabetic kidney damage, chronic inflammation of the kidney’s filtering units, and polycystic kidney disease all fall into this category.
Hormonal disorders account for another significant share. Primary aldosteronism, where the adrenal glands produce too much aldosterone, is the most common endocrine cause. Excess aldosterone drives the kidneys to retain far more sodium and water than normal. Rarer hormonal causes include tumors of the adrenal gland that overproduce adrenaline-like hormones (causing dramatic blood pressure spikes), Cushing’s syndrome from excess cortisol, and thyroid disorders.
Narrowing of the arteries that supply the kidneys can also trigger hypertension by tricking the kidneys into thinking blood flow is low, which activates the hormonal cascade that raises pressure. In younger adults, a structural narrowing of the aorta present from birth is another vascular cause. Obstructive sleep apnea and polycystic ovarian syndrome are also recognized contributors.
Where the Numbers Stand
The current classification system, based on guidelines from the American Heart Association and American College of Cardiology, sets the threshold for hypertension at 130/80 mmHg. Stage 1 hypertension ranges from 130 to 139 systolic or 80 to 89 diastolic. Stage 2 hypertension starts at 140/90 mmHg or higher. These thresholds were lowered from the previous 140/90 cutoff in 2017, which means millions of people who were previously considered borderline are now classified as having hypertension, often manageable through the lifestyle factors described above before medications become necessary.