High blood pressure has dozens of possible causes, ranging from the food you eat to the medications you take to conditions you may not know you have. About 90% of cases fall under “primary” hypertension, where no single identifiable cause exists. Instead, a combination of genetics, diet, aging, and lifestyle factors push blood pressure up over time. The remaining roughly 10% of cases are “secondary” hypertension, meaning another medical condition or a medication is directly responsible.
Blood pressure is considered high at 130/80 mm Hg or above under current guidelines, with readings of 140/90 or higher classified as stage 2 hypertension. Understanding what drives those numbers up is the first step toward bringing them down.
Too Much Sodium, Too Little Potassium
Diet is one of the most common and most modifiable causes of high blood pressure. Sodium pulls water into your bloodstream, increasing the volume of fluid your heart has to pump and raising pressure against artery walls. Most people consume far more sodium than the body needs, largely from processed and restaurant food rather than the salt shaker.
Potassium works as sodium’s counterpart. It helps your cells maintain their electrical balance and relaxes blood vessel walls. When potassium is low, your body has a harder time clearing excess sodium through the kidneys, and your blood vessels stay more constricted. Research from the American Heart Association shows that higher potassium intake increases the activity of a cellular pump that helps regulate the electrical charge across cell membranes, which contributes to lower blood pressure. A diet heavy in sodium and light in potassium (common when fruits, vegetables, and legumes are underrepresented) is one of the strongest dietary drivers of hypertension worldwide.
Genetics and Family History
If both of your parents have high blood pressure, your own risk is significantly elevated. More than 100 genetic variations have been linked to primary hypertension, many of them affecting how your kidneys handle sodium, how your blood vessels relax and contract, or how your body produces hormones that regulate fluid balance. The most studied genetic connections involve the same hormonal system (renin-angiotensin-aldosterone) that many blood pressure medications target.
Other gene variants affect the inner lining of blood vessels, influencing how easily they expand when blood flow increases. You can’t change your genes, but knowing your family history helps explain why some people develop high blood pressure despite an otherwise healthy lifestyle, and why others can tolerate a high-sodium diet without much consequence.
How Aging Stiffens Your Arteries
In younger, healthy arteries, a protein called elastin allows vessel walls to stretch and recoil with each heartbeat, absorbing the force of blood flow. Over decades, elastin gradually breaks down and is replaced by stiffer materials: collagen, calcium deposits, and other rigid structural proteins. The result is arteries that no longer cushion each pulse of blood the way they once did.
This stiffening has a specific consequence. In a young person, there’s a natural gradient where arteries get progressively stiffer as they branch toward the extremities, which protects delicate small vessels in organs like the brain and kidneys from excessive pulsating force. With aging, the large central arteries stiffen so much that this protective gradient disappears or even reverses. Pulsatile pressure gets transmitted directly into tiny vessels in the brain, heart, and kidneys, increasing the risk of organ damage. This is why systolic pressure (the top number) tends to climb steadily after middle age even in people who are otherwise healthy.
Excess Weight and Chronic Stress
Carrying excess body fat, particularly around the abdomen, raises blood pressure through several overlapping pathways. Fat tissue isn’t passive storage. It produces hormones and inflammatory signals that make blood vessels less flexible and cause your kidneys to retain more sodium. Visceral fat (the deep abdominal kind) is especially active in this regard.
Chronic psychological stress contributes through a different route. When you’re under sustained stress, your body keeps your “fight or flight” nervous system dialed up, releasing adrenaline and related hormones that constrict blood vessels and increase heart rate. Over time, chronically elevated cortisol (your body’s main stress hormone) promotes insulin resistance, increased abdominal fat, and further blood pressure elevation. It creates a self-reinforcing cycle: stress drives cortisol, cortisol drives weight gain and metabolic changes, and those changes drive blood pressure higher.
Sleep Apnea
Obstructive sleep apnea is one of the most common and most underdiagnosed causes of high blood pressure. During sleep, the upper airway repeatedly collapses, cutting off oxygen for seconds at a time. Each episode triggers a surge of adrenaline as your body fights to resume breathing, and your blood oxygen drops. Over months and years, these nightly oxygen dips keep the sympathetic nervous system in a state of chronic overactivation, even during the day. Sleep apnea also activates the same kidney-based hormonal system involved in many other forms of hypertension and damages the inner lining of blood vessels.
If your blood pressure stays elevated despite medication, or if you snore heavily and wake unrefreshed, untreated sleep apnea may be the missing piece.
Kidney Disease and Other Medical Conditions
Your kidneys are the body’s primary blood pressure regulators. They control how much sodium and fluid stay in your bloodstream, and they produce hormones that tighten or relax blood vessels. When kidney function declines, the kidneys sense reduced blood flow and respond by releasing renin, a hormone that kicks off a cascade (renin to angiotensin to aldosterone) designed to raise blood pressure and retain fluid. In healthy kidneys, this system self-corrects. In damaged kidneys, it can get stuck in the “on” position.
Diabetes accelerates this process. High blood sugar stimulates renin production through a separate chemical pathway, and the resulting sustained high pressure inside the kidneys’ tiny filtering units damages them further. This creates another vicious cycle: diabetes harms the kidneys, the kidneys raise blood pressure, and high blood pressure damages the kidneys more.
Other medical conditions that can cause secondary hypertension include thyroid disorders (both overactive and underactive), adrenal gland tumors that overproduce hormones, and narrowing of the arteries that supply the kidneys.
Medications and Supplements That Raise Blood Pressure
A surprising number of common medications can push blood pressure up, sometimes enough to require treatment. If your readings have climbed recently, it’s worth reviewing what you’re taking.
- Pain relievers (NSAIDs): Ibuprofen, naproxen, and similar drugs cause the kidneys to retain sodium and fluid. In adults 65 and older, regular NSAID use nearly doubled the likelihood of needing blood pressure medication.
- Decongestants: Cold and sinus medications containing pseudoephedrine or phenylephrine constrict blood vessels throughout the body, not just in your nose.
- Caffeine: A dose equivalent to two or three cups of coffee can raise blood pressure by about 8/6 mm Hg in people who already have hypertension, with the effect lasting three hours or more.
- Hormonal medications: Estrogen-containing oral contraceptives, hormone replacement therapy, and testosterone can all elevate blood pressure.
- Antidepressants: Certain classes, including SNRIs and tricyclics, raise blood pressure as a side effect of how they increase neurotransmitter activity.
- ADHD medications: Stimulant-based treatments for attention deficit disorders can elevate blood pressure in both children and adults.
- Steroids: Corticosteroids like prednisone raise blood pressure in a dose-dependent way, meaning higher doses cause bigger increases.
- Herbal supplements: Ephedra, St. John’s wort, and yohimbine have all been linked to blood pressure increases.
Physical Inactivity and Alcohol
A sedentary lifestyle contributes to hypertension both directly and indirectly. Regular physical activity keeps blood vessels flexible, helps the kidneys excrete sodium more efficiently, and lowers resting sympathetic nervous system activity. Without it, vessels gradually lose their ability to dilate in response to increased blood flow, and resting heart rate tends to creep up.
Alcohol raises blood pressure through multiple mechanisms, including stimulating the release of stress hormones and impairing the ability of blood vessels to relax. The effect is dose-dependent: the more you drink regularly, the greater the impact. Even moderate drinking over years can contribute to readings that inch upward.
Why Multiple Causes Often Overlap
For most people with primary hypertension, no single factor is responsible. A person might have a genetic predisposition that makes their kidneys slightly less efficient at excreting sodium, combined with a high-sodium diet, 20 extra pounds of abdominal fat, daily ibuprofen for joint pain, and poor sleep. Each factor adds a few points of pressure on its own, and together they push readings well into hypertensive range. This is also why treatment often involves changes on multiple fronts rather than a single fix, and why identifying every contributing factor matters more than finding the one cause.