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. A normal reading sits below 120/80 mm Hg, and anything consistently at or above 130/80 is considered high blood pressure. The causes range from everyday habits like eating salty food to underlying medical conditions you may not know you have.
How Your Body Controls Blood Pressure
Your blood pressure isn’t a fixed number. It’s constantly being adjusted by a network of hormones, nerve signals, and chemical messengers. Understanding the basics of this system helps explain why so many different things can push your numbers up.
One of the most powerful regulators is a hormone chain reaction that starts in your kidneys. When blood flow to the kidneys drops, they release an enzyme that ultimately produces a hormone called angiotensin II. This hormone does two things: it narrows the walls of small arteries, immediately raising pressure, and it triggers another hormone, aldosterone, that tells your kidneys to hold onto sodium. More sodium in your blood pulls in water, increasing blood volume and pushing pressure higher still.
Your nervous system plays a parallel role. When your body perceives stress or danger, it ramps up nerve signals to the heart and blood vessels. Your heart beats faster and pumps more forcefully, while your arteries become stiffer and less elastic. This combination raises both the top number (systolic) and the overall resistance blood faces as it moves through your body.
There’s also a protective mechanism that works in the opposite direction. The cells lining your blood vessels constantly produce nitric oxide, a molecule that relaxes artery walls and keeps them flexible. Research from the American Heart Association estimates that this single molecule restrains blood pressure by roughly 30 mm Hg. When the lining of your blood vessels is damaged, whether from smoking, high cholesterol, or aging, nitric oxide production drops, and pressure creeps up.
Salt, Alcohol, and Other Dietary Triggers
Sodium is the dietary factor most directly tied to blood pressure. When excess sodium builds up in your bloodstream, it pulls water into your blood vessels, increasing the volume of blood your heart has to pump. The American Heart Association compares it to turning up the water supply to a garden hose: more fluid means more pressure against the vessel walls. Most people consume far more sodium than their body needs, largely from processed and restaurant foods rather than the salt shaker.
Potassium works as sodium’s counterbalance. It helps your kidneys flush out excess sodium, easing the pressure on your blood vessels. When your diet is high in sodium and low in potassium (common with a diet heavy in packaged foods and light on fruits and vegetables), the imbalance pushes blood pressure up.
Alcohol raises blood pressure in a more straightforward way than many people realize. A large meta-analysis published in the AHA journal Hypertension found that the relationship between alcohol and systolic blood pressure is direct and linear, with no safe threshold below which alcohol has zero effect. Any amount of alcohol is associated with higher systolic pressure. The effect also varies by sex and ethnicity, partly due to differences in how the body metabolizes alcohol.
Caffeine can cause a short-term spike in people who don’t consume it regularly. If you’re a daily coffee drinker, your body typically adapts, but occasional users may notice a temporary jump after a cup of coffee, an energy drink, or even caffeine pills.
Medications That Raise Blood Pressure
Several common over-the-counter and prescription medications can push blood pressure up, sometimes without you connecting the dots.
- Pain relievers (NSAIDs): Ibuprofen (Advil) and naproxen (Aleve) cause the body to retain water, which can raise pressure. This is especially relevant if you take them regularly for chronic pain or arthritis.
- Decongestants: Pseudoephedrine and phenylephrine, found in many cold and allergy products, work by narrowing blood vessels. That clears your stuffy nose but also makes it harder for blood to flow, increasing pressure.
- Hormonal birth control: Birth control pills and patches contain hormones that raise blood pressure in some people.
- Antidepressants: Several classes, including SSRIs, tricyclics, and MAO inhibitors, can affect blood pressure.
- ADHD stimulants: Medications like methylphenidate (Ritalin, Concerta) speed up the heart and can raise pressure.
- Herbal supplements: Licorice root, ginseng, guarana, and ephedra (ma-huang) all have blood pressure effects that people often overlook because they think of supplements as harmless.
Recreational drugs, particularly cocaine, methamphetamine, and ecstasy, can cause dangerous spikes in blood pressure and are a well-known cause of hypertensive emergencies in younger adults.
Underlying Medical Conditions
When a specific disease or condition is driving your blood pressure up, doctors call it secondary hypertension. It accounts for a smaller share of high blood pressure cases, but it’s important because treating the underlying problem can sometimes resolve the hypertension entirely.
The most common cause is obstructive sleep apnea. When your airway repeatedly collapses during sleep, your oxygen levels drop and your nervous system fires up in response, raising pressure. Many people with resistant high blood pressure (the kind that doesn’t respond well to medication) turn out to have undiagnosed sleep apnea.
Kidney problems are another major driver. Renal artery stenosis, a narrowing of the arteries that supply the kidneys, tricks the kidneys into thinking blood flow is low, triggering that hormone cascade that retains sodium and tightens blood vessels. Kidney disease itself impairs the organ’s ability to filter fluid properly, leading to increased blood volume.
Hormonal disorders round out the list. Primary aldosteronism (when the adrenal glands overproduce aldosterone) causes excessive sodium retention. Cushing syndrome floods the body with cortisol. Both overactive and underactive thyroid conditions can raise blood pressure through different mechanisms. Rare adrenal tumors called pheochromocytomas release bursts of adrenaline-like hormones, causing dramatic pressure spikes along with a racing heart and sweating.
Genetics and Family History
If both of your parents have high blood pressure, your risk is substantially elevated. More than 100 genetic variations have been linked to essential hypertension, the kind with no single identifiable cause. Many of these genes affect the same systems already discussed: the hormone chain in the kidneys, the function of blood vessel linings, and how your body handles sodium.
Genetics don’t act alone. They set the stage, but lifestyle factors determine how much of that genetic potential gets expressed. Someone with a strong family history who maintains a healthy weight, eats well, and stays active may never develop high blood pressure. Someone with the same genes who gains weight and eats a high-sodium diet is far more likely to.
Stress and Your Nervous System
Acute stress, whether it’s a near-miss on the highway or a tense work meeting, triggers a temporary surge in blood pressure. Your body releases hormones that speed up your heart and narrow your blood vessels. Once the stressor passes, pressure typically returns to baseline.
Chronic stress is more insidious. It keeps the sympathetic nervous system activated at a low hum, which over time increases resting heart rate, stiffens arteries, and reduces their ability to stretch with each heartbeat. This pattern is commonly present at the initiation of hypertension, particularly in younger adults. Chronic stress also drives behaviors that independently raise blood pressure: overeating, drinking more alcohol, sleeping poorly, and skipping exercise.
Weight, Inactivity, and Aging
Carrying extra weight forces your heart to pump more blood to supply the additional tissue. That increased output puts more pressure on artery walls. Excess body fat, particularly around the midsection, also promotes inflammation and hormonal changes that stiffen blood vessels and impair sodium handling.
Physical inactivity compounds the problem. Regular exercise trains your blood vessels to dilate more efficiently and helps your heart pump blood with less effort. Without it, resting heart rate tends to be higher and arteries less flexible.
Aging itself stiffens arteries. The elastic fibers in artery walls gradually break down and are replaced by stiffer collagen. This is why systolic blood pressure (the top number) tends to rise steadily after middle age, even in people who are otherwise healthy. It also explains why isolated systolic hypertension, where only the top number is elevated, is so common in older adults.