High blood pressure happens when the force of blood pushing against your artery walls stays consistently too high. A reading of 130/80 mmHg or above now qualifies as hypertension under the 2025 guidelines from the American Heart Association and American College of Cardiology. Most cases have no single identifiable cause, but rather a combination of factors working together, from what you eat and how active you are to your genetics and how your kidneys handle salt.
How Your Body Regulates Blood Pressure
Your body has a built-in pressure control system called the renin-angiotensin-aldosterone system, or RAAS. Your kidneys release an enzyme called renin, which triggers a chain reaction that ultimately produces a hormone called angiotensin II. This hormone tightens blood vessels, promotes inflammation in artery walls, and signals your adrenal glands to release aldosterone. Aldosterone then tells your kidneys to hold onto more sodium and water, which increases blood volume and pushes pressure up. Over 90% of the angiotensin II found in your tissues is produced locally rather than circulating from your bloodstream, which means this pressure-raising machinery is active throughout your body, not just in your kidneys.
Your sympathetic nervous system, the “fight or flight” wiring, also plays a role. When it’s chronically activated, it stimulates renin release and keeps your heart rate and vessel tone elevated. In many people with high blood pressure, both systems are stuck in overdrive without any obvious trigger. That’s why the condition is called “essential” or “primary” hypertension: the machinery itself has shifted to a higher set point.
Too Much Sodium, Too Little Potassium
Sodium is the single most studied dietary driver of blood pressure. When you eat more salt than your kidneys can easily flush out, you retain extra water, expanding blood volume and raising pressure. Cutting sodium intake significantly, from a high level (about 3,500 mg/day) down to below 1,200 mg/day, has been shown to lower systolic blood pressure by roughly 6.7 mmHg. Even a more modest reduction can make a measurable difference. In one large trial of nearly 21,000 people, simply replacing regular salt with a potassium-enriched salt substitute lowered systolic pressure by 3.3 mmHg.
Potassium works as sodium’s natural counterpart. When you eat enough potassium, it triggers a process in your kidney tubules that deactivates a sodium-reabsorbing channel, causing your kidneys to flush out more sodium in your urine. When potassium is low, that channel stays active even if you’re eating a lot of salt, which means your body holds onto sodium it would otherwise excrete. This is why blood pressure advice increasingly focuses on the sodium-to-potassium ratio rather than sodium alone. Bananas get all the credit, but beans, potatoes, leafy greens, and yogurt are all rich potassium sources.
Weight, Insulin Resistance, and Metabolic Health
Carrying excess weight, particularly around the midsection, raises blood pressure through several pathways at once. Extra fat tissue around the kidneys physically compresses them, increasing internal pressure and slowing the flow of urine through the tubules. This mechanical compression causes more sodium to be reabsorbed in the loop of Henle, a key filtering section deep inside the kidney. The result is fluid retention and higher pressure.
Insulin resistance makes things worse. When your cells stop responding normally to insulin, your pancreas pumps out more of it to compensate. Elevated insulin levels activate both the RAAS and the sympathetic nervous system, doubling down on sodium retention and blood vessel tightening. High insulin combined with elevated aldosterone also reduces the availability of nitric oxide, a molecule your blood vessels need to relax and stay flexible. This combination of stiff vessels and excess fluid is a powerful recipe for persistent hypertension.
Genetics and Family History
If your parents or siblings have high blood pressure, your risk is meaningfully higher. Current estimates suggest that common genetic variations account for about 20% of the total variability in blood pressure across the population. Researchers have identified hundreds of specific gene locations linked to blood pressure regulation, though each one contributes only a small amount on its own. No single “hypertension gene” determines your fate. Instead, the genetic contribution is spread across many small effects that, combined with lifestyle factors, tip the scales. This is why two people can eat the same diet and exercise the same amount but end up with very different blood pressure readings.
Alcohol
Alcohol raises blood pressure in a dose-dependent, nearly linear pattern. A large meta-analysis found that drinking above about 12 grams of alcohol per day (roughly one standard drink) is where hypertension risk begins climbing. At two standard drinks daily, the risk is about 11% higher. At three drinks, it’s 22% higher. At four, 33% higher. Interestingly, the analysis found that drinking less than one drink per day was associated with a slightly lower risk than drinking exactly one, but the clearest takeaway is that risk rises steadily with each additional drink.
Medications and Substances That Raise Pressure
Several common medications can raise blood pressure, sometimes enough to push someone from normal into the hypertensive range or to make existing hypertension harder to control.
- Pain relievers (NSAIDs): Ibuprofen (Advil) and naproxen (Aleve) cause your kidneys to retain sodium and water. Regular use can raise blood pressure noticeably.
- Decongestants: Pseudoephedrine and phenylephrine, found in many cold and sinus products, constrict blood vessels throughout the body, not just in your nose.
- Hormonal birth control: Pills and patches containing estrogen and progestin raise blood pressure in some users. Most carry a label warning about this.
- Antidepressants: Several classes, including SSRIs, tricyclics, and MAO inhibitors, can elevate blood pressure.
- ADHD stimulants: Medications like methylphenidate (Ritalin, Concerta) increase heart rate and can raise pressure.
- Immunosuppressants: Drugs used after organ transplants or for autoimmune conditions, such as cyclosporine and tacrolimus, commonly raise blood pressure.
- Recreational drugs: Cocaine, amphetamines, and ecstasy all cause sharp blood pressure spikes and can lead to sustained elevation with repeated use.
If your blood pressure is climbing and you take any of these regularly, it’s worth examining whether the medication itself is contributing.
Medical Conditions That Cause Hypertension
About 5% to 10% 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. The most common causes, ranked roughly by frequency:
- Obstructive sleep apnea: Repeated drops in oxygen during sleep trigger surges in adrenaline that raise pressure overnight and throughout the day.
- Renal artery stenosis: Narrowing of the arteries supplying the kidneys tricks the RAAS into thinking blood pressure is too low, ramping up sodium retention and vessel constriction.
- Primary aldosteronism (Conn’s syndrome): The adrenal glands overproduce aldosterone, causing aggressive sodium retention independent of normal RAAS signals.
- Kidney disease: Damaged kidney tissue loses its ability to properly filter sodium and regulate fluid balance.
- Adrenal tumors (pheochromocytoma): Rare tumors that produce bursts of adrenaline and noradrenaline, causing dramatic blood pressure spikes.
- Thyroid disorders: Both an underactive and an overactive thyroid can raise blood pressure, through different mechanisms.
- Cushing syndrome: Excess cortisol production leads to weight gain, fluid retention, and elevated pressure.
Secondary hypertension is worth considering if your blood pressure was normal and then rose suddenly, if it’s very high at a young age, or if it doesn’t respond well to multiple medications.
Physical Inactivity and Chronic Stress
Regular physical activity makes your blood vessels more flexible and helps your body process sodium more efficiently. When you’re sedentary, you lose those benefits. Your sympathetic nervous system stays more active at rest, your vessels gradually stiffen, and your resting heart rate tends to be higher, all of which push pressure upward over time.
Chronic psychological stress keeps your sympathetic nervous system activated for prolonged periods. This isn’t just about feeling stressed in the moment. Sustained activation raises baseline levels of hormones that constrict blood vessels and promote sodium retention. The effect is compounded when stress leads to poor sleep, increased alcohol use, or overeating, each of which independently contributes to higher readings.
Current Blood Pressure Categories
The 2025 AHA/ACC guidelines define four categories based on in-office measurements. If your top and bottom numbers fall into different categories, you’re classified in the higher one.
- Normal: below 120/80 mmHg
- Elevated: 120 to 129 systolic, with 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
These thresholds matter because cardiovascular risk doesn’t start at some arbitrary cutoff. It rises continuously as pressure climbs above 120/80. The staging system helps guide how aggressively the problem needs to be addressed, from lifestyle changes alone for elevated readings to medication for stage 2.