High blood pressure rarely has a single cause. In about 90% of cases, it results from a combination of factors: genetics, diet, body weight, stress, aging, and habits like drinking or smoking. The remaining cases are driven by an identifiable medical condition like sleep apnea or a kidney problem. Understanding which factors apply to you is the first step toward bringing your numbers down.
What Counts as High Blood Pressure
Blood pressure is measured in two numbers. The top number (systolic) reflects the force when your heart pumps. The bottom number (diastolic) measures pressure between beats. Current guidelines from the American Heart Association define the categories this way:
- Normal: below 120/80
- Elevated: 120 to 129 over less than 80
- Stage 1 hypertension: 130 to 139 over 80 to 89
- Stage 2 hypertension: 140 or higher over 90 or higher
- Severe hypertension: above 180 and/or above 120
A single high reading doesn’t necessarily mean you have hypertension. Anxiety, caffeine, a full bladder, or rushing to the appointment can all inflate the number temporarily. Between 15% and 30% of people with high readings in a clinic actually have “white coat hypertension,” where their blood pressure is elevated only in a medical setting. To rule this out, your provider may ask you to monitor at home or wear a 24-hour device. The diagnostic threshold for white coat hypertension is a clinic reading at or above 140/90, combined with home readings that stay below 135/85.
How Your Body Controls Blood Pressure
Your body has a built-in system for adjusting blood pressure moment to moment. When pressure drops, your kidneys release an enzyme that triggers a chain reaction: your blood vessels tighten, your adrenal glands release a hormone that tells your kidneys to hold onto sodium, and your pituitary gland releases another hormone that retains water. More sodium means more water stays in your bloodstream, which increases blood volume and pushes pressure back up.
This system works well in healthy people. Problems start when it stays turned up too high for too long, or when other factors pile on top of it. The result is sustained high pressure that damages blood vessel walls over months and years.
The Most Common Lifestyle Causes
Too Much Sodium
When you eat a lot of salt, your kidneys take several days to catch up and excrete the extra sodium. In the meantime, your body holds onto water to dilute it, expanding your blood volume and raising pressure. Some people are especially “salt sensitive,” meaning their blood vessels fail to relax in response to extra fluid the way they normally should. In salt-sensitive individuals, the resistance in small blood vessels actually increases a few days into a high-salt diet, making the pressure rise more steeply and stay elevated longer.
Alcohol
Alcohol raises blood pressure in a dose-dependent, linear way, with no safe threshold. A large meta-analysis found that drinking the equivalent of about one standard drink per day (12 grams of alcohol) raised systolic pressure by roughly 1.25 points and diastolic by about 1.14 points compared to nondrinkers. At four drinks per day, those numbers jumped to about 4.90 and 3.10 points. That may sound modest, but even a few points of sustained increase meaningfully raises cardiovascular risk over years.
Weight and Physical Inactivity
Excess body fat, particularly around the abdomen, increases the volume of blood your heart has to pump and promotes chronic low-grade inflammation that stiffens blood vessels. Physical inactivity compounds this. Regular aerobic exercise helps blood vessels stay flexible and improves how efficiently your kidneys handle sodium.
Chronic Stress
Stress triggers your nervous system to release hormones that tighten blood vessels and speed up your heart rate. When stress is constant, these temporary spikes can become a persistent baseline elevation. Stress also tends to drive other habits that raise pressure, like poor sleep, overeating, and drinking more alcohol.
Genetics Play a Significant Role
Family and twin studies estimate that 30% to 50% of blood pressure variation comes from your genes. If one or both of your parents had hypertension, your risk is substantially higher regardless of your lifestyle. Genetics influence how your kidneys process sodium, how reactive your blood vessels are, and how sensitive your nervous system is to stress. This doesn’t mean high blood pressure is inevitable if it runs in your family, but it does mean you may need to work harder on the modifiable factors to keep your numbers in range.
Why Blood Pressure Rises With Age
Even people who do everything right often see their blood pressure creep up after their 40s and 50s. The main reason is that arteries gradually lose their elasticity. Young, healthy arteries contain stretchy fibers that absorb the force of each heartbeat and then recoil. Over decades, those fibers break down and get replaced by stiffer material. Inflammation, oxidative damage, and chronically high blood sugar (even at levels that don’t qualify as diabetes) accelerate this process by promoting cross-linking between structural proteins in the artery wall.
The practical result is “isolated systolic hypertension,” where your top number climbs while the bottom number stays the same or even drops. This is the most common form of high blood pressure in people over 60.
Medical Conditions That Raise Blood Pressure
Sometimes blood pressure is high because of a specific, treatable condition. Experts previously estimated that only 5% to 10% of hypertension cases had an identifiable medical cause, but recent research suggests the true number is considerably higher. The most common culprits, roughly in order of frequency:
- Obstructive sleep apnea: When your airway collapses repeatedly during sleep, oxygen levels drop and your nervous system floods your body with stress hormones. These surges persist into the daytime, keeping blood pressure elevated around the clock. If you snore heavily, wake up tired, or have a large neck circumference, sleep apnea is worth investigating.
- Kidney artery narrowing: A blockage in the artery feeding one or both kidneys tricks your body into thinking blood pressure is too low, activating that pressure-raising chain reaction described above.
- Excess aldosterone production: Your adrenal glands may overproduce the hormone that tells your kidneys to retain sodium. This is more common than previously thought and is sometimes signaled by low potassium levels on routine blood work.
- Thyroid disorders: Both an underactive and an overactive thyroid can raise blood pressure through different mechanisms.
- Kidney disease: Damaged kidneys can’t filter sodium and fluid properly, leading to volume overload.
If your blood pressure is very high despite medication, started suddenly, or developed before age 30, your doctor may test for these secondary causes.
Medications and Substances That Raise Pressure
Several common over-the-counter and prescription medications can push blood pressure up, sometimes without you realizing it.
- Pain relievers like ibuprofen and naproxen: These cause your body to retain water and sodium, which increases blood volume.
- Decongestants (pseudoephedrine, phenylephrine): Found in many cold and allergy products, these work by narrowing blood vessels, which directly raises pressure.
- Hormonal birth control: Pills and patches containing hormones can raise blood pressure in some users.
- Some antidepressants: Several classes of antidepressants, including SSRIs and tricyclics, can have this effect.
- ADHD stimulant medications: These speed up heart rate and can raise pressure.
- Caffeine: Causes short-term spikes, particularly in people who don’t consume it regularly.
- Herbal supplements: Licorice root, ginseng, guarana, and ephedra are all linked to blood pressure increases.
If your blood pressure recently went up and you started a new medication or supplement around the same time, that’s worth mentioning to your provider. Recreational drugs like cocaine, amphetamines, and ecstasy also cause dangerous spikes in blood pressure.
What to Do With a High Reading
If you just got a high reading and you’re wondering what to do next, the first step is to confirm it’s real. Take your blood pressure at home using a validated upper-arm cuff, sitting quietly for five minutes first, with your feet flat on the floor and your arm supported at heart level. Measure at the same time of day for a week and record the results. This gives you and your provider a much clearer picture than any single office reading.
For most people, the controllable factors that matter most are sodium intake (aiming below 2,300 mg per day, ideally closer to 1,500 mg), regular physical activity, maintaining a healthy weight, moderating alcohol, and managing stress. If lifestyle changes aren’t enough, or if your numbers are high enough to pose immediate risk, medication can close the gap effectively. But identifying and addressing the underlying reasons your pressure is high, whether that’s sleep apnea, a medication side effect, or simply too much salt, makes every other intervention work better.