High blood pressure has many causes, and most people with it have more than one working against them at the same time. Some are things you can change, like diet and activity level. Others, like aging and genetics, you can’t. And sometimes a medication you’re already taking or a condition you didn’t know about is quietly pushing your numbers up. Here’s a breakdown of the most common culprits.
How Blood Pressure Is Classified
Before diving into causes, it helps to know where the lines are drawn. The 2025 guidelines from the American Heart Association and American College of Cardiology define the categories this way:
- Normal: below 120/80 mm Hg
- Elevated: 120 to 129 systolic (the top number) with diastolic (the bottom number) 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
If your top and bottom numbers fall into different categories, you’re classified by whichever one is higher.
Too Much Sodium
Sodium is one of the most direct drivers of high blood pressure. When you eat a lot of salt, your body holds onto extra fluid to dilute it. That extra fluid increases the volume of blood flowing through your vessels, which raises the pressure on artery walls. The recommended upper limit is 2,300 milligrams per day, roughly one teaspoon of table salt. Most people eat well beyond that, largely from processed and restaurant foods rather than the salt shaker.
Your body has a built-in system for managing sodium and fluid balance. Your kidneys release a chain of hormones and enzymes that regulate how much sodium you reabsorb versus how much you flush out. When this system is working well, your kidneys adjust. But a consistently high sodium load overwhelms the process, and your kidneys start retaining more water than they should. That’s how a daily dietary habit turns into a chronic blood pressure problem. The same hormonal chain also causes the muscular walls of small arteries to tighten, which further increases resistance and raises pressure.
Physical Inactivity and Excess Weight
A sedentary lifestyle independently increases your risk of developing hypertension. When you’re inactive, your heart has to work harder to pump blood, and your arteries lose the flexibility that regular exercise helps maintain. Over time, this makes elevated readings more likely. Carrying extra weight compounds the problem because your heart has to push blood through a larger network of tissue, and fat cells release signals that promote inflammation and fluid retention.
Exercise works in the opposite direction. Regular physical activity helps your blood vessels stay elastic, improves your kidneys’ ability to handle sodium, and lowers the resting workload on your heart. It doesn’t take extreme effort. Consistent moderate activity, like brisk walking, makes a measurable difference.
Alcohol and Caffeine
Alcohol raises blood pressure in two ways. In the short term, it causes a temporary spike each time you drink. Over months and years, heavy drinking contributes to weight gain through empty calories, and the repeated spikes can lead to sustained elevation. Current guidelines suggest limiting intake to two drinks per day for men and one for women if you already have high blood pressure.
Caffeine is more of a short-term actor. It can cause a brief rise in blood pressure, typically 5 to 10 points, peaking somewhere between 30 minutes and two hours after you drink it. This effect is most pronounced if you don’t consume caffeine regularly. Habitual coffee drinkers tend to develop a tolerance. If you’re curious whether caffeine is affecting your numbers, check your blood pressure before a cup of coffee and then again about an hour later.
Aging and Genetics
As you age, your arteries gradually stiffen. They lose elasticity in their walls, which means they can’t expand as easily when your heart pumps blood. This is one of the main reasons blood pressure tends to rise with age, even in people who are otherwise healthy. Aging and blood pressure are, in fact, the two strongest predictors of arterial stiffness.
Genetics plays a real but partial role. Studies estimate that roughly 23% to 37% of the variation in arterial stiffness between people can be attributed to genetic factors. That means your family history matters, but it’s far from the whole story. Having a parent with hypertension increases your risk, yet lifestyle factors still account for the majority of what determines your blood pressure over a lifetime.
Medications That Raise Blood Pressure
Several common over-the-counter and prescription medications can push blood pressure up, sometimes without you realizing it.
- Pain relievers (NSAIDs): Ibuprofen (Advil) and naproxen (Aleve) cause your body to retain water, which can affect kidney function and raise pressure. This is especially relevant if you take them frequently for chronic pain.
- Decongestants: Ingredients like pseudoephedrine and phenylephrine, found in many cold and allergy products, work by narrowing blood vessels to reduce nasal swelling. That same narrowing raises blood pressure.
- Hormonal birth control: Birth control pills and patches contain hormones that can raise blood pressure in some people. Most carry warnings about this potential side effect.
- Antidepressants: Several classes of antidepressants, including SSRIs, tricyclics, and MAO inhibitors, can elevate blood pressure.
- ADHD stimulants: These medications speed up heart rate and can cause blood pressure to rise.
Herbal supplements can be sneaky contributors too. Licorice root, ginseng, guarana, and ephedra (ma-huang) have all been linked to blood pressure increases. If you’re taking any supplement regularly and your readings are creeping up, it’s worth investigating whether there’s a connection.
Underlying Medical Conditions
When a specific, identifiable disease is driving your high blood pressure, doctors call it secondary hypertension. This accounts for a smaller share of cases overall, but it’s important to recognize because treating the underlying condition can sometimes resolve the blood pressure problem entirely.
The most common cause of secondary hypertension is obstructive sleep apnea. When your airway repeatedly closes during sleep, your body releases stress hormones that raise blood pressure. Many people with sleep apnea don’t know they have it, so unexplained high blood pressure, especially alongside snoring, daytime fatigue, or morning headaches, is sometimes the clue that leads to diagnosis.
Kidney problems are another major category. Narrowing of the arteries that supply the kidneys (renal artery stenosis) or disease within the kidney tissue itself can disrupt the hormonal system that regulates blood pressure. When your kidneys sense reduced blood flow, they trigger a cascade that retains sodium and water while tightening blood vessels, all of which drives pressure higher.
Less common but still significant causes include overproduction of the hormone aldosterone by the adrenal glands, which leads to excess sodium retention; thyroid disorders, both overactive and underactive; and rare adrenal tumors that flood the body with adrenaline-like hormones, causing dramatic blood pressure spikes. A structural heart defect called coarctation of the aorta, where the main artery leaving the heart is abnormally narrow, can also cause high blood pressure, usually detected earlier in life.
Stress and Other Temporary Triggers
Acute stress, whether from a work deadline, an argument, or a medical appointment, triggers your fight-or-flight response. Your body releases hormones that temporarily speed up your heart and constrict your blood vessels, producing a short-term spike. This is why some people get high readings at the doctor’s office but normal ones at home, a phenomenon known as white-coat hypertension.
On its own, a temporary spike isn’t dangerous for most people. The concern is when stress is chronic. Ongoing psychological stress keeps those hormones elevated more often, and the coping behaviors that tend to accompany it (eating more, sleeping less, drinking, skipping exercise) compound the effect. The stress itself may not permanently damage your arteries, but the lifestyle it creates often does.
How Diet Lowers Blood Pressure
If many of these causes feel dietary, that’s because they are. The DASH eating plan (Dietary Approaches to Stop Hypertension) is one of the best-studied interventions for blood pressure. It emphasizes fruits, vegetables, whole grains, and low-fat dairy while limiting sodium, red meat, and added sugars.
In clinical trials, people following the DASH diet at the lowest sodium level (about 1,150 mg per day) had an average systolic blood pressure of 123 mm Hg, compared to 133 mm Hg for those eating a typical diet at higher sodium levels. That 10-point difference is comparable to what some medications achieve. Even at moderate sodium intake, the DASH diet consistently produced lower readings than the standard diet. The combination of eating pattern and sodium reduction works better than either one alone, making dietary changes one of the most effective non-drug strategies for managing blood pressure.