Your blood pressure reading may not mean what you think it does.

YOUR HEALTH — Issue No. 23

High blood pressure is the condition I treat more than any other in my practice.

Nearly half of American adults — approximately 119 million people — have high blood pressure. And of those, only about 1 in 4 has it under control.

Most people know they should care about their blood pressure. Far fewer understand what the numbers actually mean, why a single reading doesn't tell the story, and what it takes to truly know whether their pressure is controlled.

What blood pressure actually measures

Every time your heart beats, it pushes blood through your arteries. Blood pressure measures the force that blood exerts against the walls of those arteries — the pressure generated by the heart's contraction and the resistance of the arterial system it is pushing against.

Two numbers:

Systolic — the top number — measures pressure when the heart contracts and pushes blood out.

Diastolic — the bottom number — measures pressure when the heart relaxes between beats.

Here is how the 2025 guidelines categorize blood pressure:

Below 120/80 — Normal

120–129 and below 80 — Elevated

130–139 or 80–89 — High Blood Pressure, Stage 1

140 or higher / 90 or higher — High Blood Pressure, Stage 2

And notice the word "or." A reading of 135/78 and a reading of 118/85 are not the same blood pressure — but both fall into Stage 1 because either the systolic or the diastolic alone can put you into a higher category.

These categories are not the same thing as "you need medication." That depends on your average blood pressure, your cardiovascular risk, your medical history, and how your body responds to lifestyle changes. More on that below.

Why blood pressure rises — the mechanism

Blood pressure is determined by two things: how much blood the heart pumps per minute and the resistance of the blood vessels it is pumping against. When either increases — cardiac output goes up, or the blood vessels narrow and stiffen — blood pressure rises.

Think of a garden hose. The same amount of water flowing through a narrower hose creates more pressure against the walls. That pressure, sustained over years, damages the walls themselves.

In hypertension, the arteries progressively stiffen and narrow — through atherosclerosis, through loss of elasticity with age, through the direct structural changes that sustained elevated pressure causes over time. The heart works harder. The arterial walls experience constant excess force. And downstream — in the brain, the kidneys, the heart, the eyes — that sustained excess pressure causes progressive damage.

This is why blood pressure matters. Not because a high number in the moment is acutely dangerous in most cases. Because the sustained elevation — measured in years — is silently damaging the end organs that depend on healthy blood vessels to function.

What the 2025 guidelines say

The 2025 AHA/ACC Hypertension Guideline is the first major update since 2017. Here is what the updated guidance actually says — plainly.

The treatment goal for most adults is below 130/80 mmHg.

How you get there depends on where you are starting and what your overall clinical picture looks like:

For everyone — medication is recommended when the average blood pressure is 140/90 mmHg or higher.

For higher-risk adults — those with established cardiovascular disease, prior stroke, diabetes, or chronic kidney disease, or a 10-year cardiovascular risk above 7.5% — medication should be considered starting at 130/80.

For lower-risk adults with blood pressure in the 130–139/80–89 range — the guideline recommends a trial of lifestyle modification first. Three to six months of meaningful lifestyle change. If blood pressure remains elevated after that window, medication becomes appropriate.

The most important word in all of that is average.

Patients should be categorized based on an average of two or more careful readings taken on two or more separate occasions. One high reading does not establish a diagnosis of hypertension. One normal reading does not mean your blood pressure is controlled.

A blood pressure of 148/86 doesn't tell you nearly as much as you might think. Was it taken after walking in from the parking lot? After coffee? With the wrong cuff size? While you were talking? With a full bladder? After five minutes of seated rest? Was it one reading out of fourteen, or the only reading taken that visit?

The number means something. But the average — taken carefully and consistently — means more.

Was my blood pressure reading accurate?

Blood pressure is not a fixed number. It fluctuates constantly in response to a wide range of factors — and understanding them is the difference between a meaningful reading and a misleading one.

Things that raise a blood pressure reading:

Cuff size — more important than most people realize:

A cuff that is too small for the arm is one of the most common sources of inaccurate blood pressure readings in clinical practice. Using the wrong cuff size can falsely elevate the reading enough to change how someone is classified or treated. The AHA specifically emphasizes correct cuff sizing as a standard of accurate measurement.

If you have ever had a reading taken and felt the cuff was too small — mention it. Ask for the appropriate size. It matters.

White coat effect:

Some people's blood pressure rises specifically in clinical settings — in response to the anxiety of a medical visit or simply the act of being measured. This is called white coat hypertension when blood pressure is consistently elevated in the office but normal at home.

White coat hypertension carries lower cardiovascular risk than sustained hypertension — but it can progress to sustained hypertension over time and warrants monitoring. The 2025 guidelines recommend confirming a hypertension diagnosis with out-of-office measurements for exactly this reason.

"My blood pressure just runs high"

I hear this regularly. A patient whose blood pressure has been consistently elevated tells me it just runs high — as if elevated blood pressure is a personal normal rather than a clinical problem.

Chronically elevated blood pressure is not simply a harmless personal baseline. If your pressure stays consistently above the recommended range, it deserves attention — regardless of how long it has been elevated or how well you feel.

What patients often mean is that their blood pressure has been elevated for a long time and they feel fine. That is the most dangerous aspect of hypertension — it is almost always asymptomatic until the damage it has been quietly causing becomes apparent as a heart attack, a stroke, kidney disease, or heart failure.

"Will I ever be able to get off my blood pressure medication?"

The honest answer is: sometimes yes. For patients who have made meaningful lifestyle changes — lost significant weight, substantially reduced sodium, started exercising regularly, stopped drinking heavily — blood pressure can improve enough to reduce or eliminate the need for medication. This is particularly true for patients whose blood pressure was in the Stage 1 range and who had not been hypertensive for many years.

But for most patients with established hypertension who have been on medication for years — especially those with other cardiovascular risk factors — coming off medication entirely is not realistic or safe without close monitoring and a provider conversation. The medication is not the problem. The blood pressure it is controlling is.

What is always reasonable to ask: "Given where my blood pressure is and the lifestyle changes I have made — is there an opportunity to reduce my dose or simplify my regimen?"

That is a different and more productive question than stopping medication altogether. And it is one your provider should welcome.

"I feel bad when my blood pressure is lower"

This one is real — and it is worth taking seriously rather than dismissing.

When blood pressure has been elevated for a long time, the body can adapt to that higher pressure. When it is then brought down — even to a healthy range — some patients feel lightheaded, fatigued, or generally unwell. They conclude that lower blood pressure makes them feel worse.

This is not imaginary. But it also does not automatically mean the lower pressure is unsafe.

Several things can cause this. The brain's mechanism for maintaining consistent blood flow can shift its operating range upward in people with chronic hypertension, making them temporarily sensitive to reductions. But other causes deserve equal consideration: orthostatic hypotension, a medication that is lowering pressure too quickly or too much, dehydration, or excessive BP lowering beyond the appropriate target.

The right clinical response is careful evaluation — not stopping treatment because the patient feels better at a higher blood pressure. Feeling better at 160/95 than at 130/80 does not mean 160/95 is safe. It means the clinical picture needs a closer look.

What sustained high blood pressure does to the body

The scary part of hypertension is not what you feel today. It is what chronically elevated pressure does quietly over 10, 20, or 30 years.

Heart — the left ventricle thickens in response to pumping against higher resistance over time. This is an independent risk factor for heart failure, arrhythmia, and sudden cardiac death.

Brain — high blood pressure is the single most modifiable risk factor for stroke — both the kind caused by blockage and the kind caused by rupture. Chronic injury to small cerebral vessels also contributes to cognitive decline over time.

Kidneys — the kidneys filter blood through small vessels that are sensitive to elevated pressure. Chronic hypertension damages these vessels progressively — and kidney disease in turn makes blood pressure harder to control, accelerating both conditions.

Eyes — hypertensive retinopathy — damage to the small vessels of the retina — is a direct and visible consequence of sustained elevated pressure.

Why I cannot tell you your blood pressure is controlled from office readings alone

I see you once every three to six months. I get one or two readings taken under specific office conditions. I have no information about what your blood pressure is after a stressful workday, after physical activity, or first thing in the morning.

The 2025 guidelines specifically highlight home blood pressure monitoring for detecting masked hypertension, improving risk stratification, and supporting treatment decisions. Masked hypertension — blood pressure that is normal in the office but elevated at home — carries the same cardiovascular risk as sustained hypertension and is invisible without home monitoring.

What to use — and what not to use:

A validated upper arm automated cuff is the right device for home monitoring. Wrist cuffs are less reliable. The 2025 guidelines specifically state that reliance on cuffless devices, including smartwatches, for accurate blood pressure measurements should be avoided until these devices demonstrate greater precision and reliability.

Correct home monitoring technique:

Sit quietly for five minutes before measuring. Both feet flat on the floor. Back supported. Arm at heart level. No talking during the measurement. Take two readings one minute apart and record both. Morning and evening readings taken consistently give the most useful picture.

A note on why this technique: it is not because this reflects how most of your day is spent — it doesn't. The standardized technique exists because it creates a reproducible baseline. The same conditions each time means changes in the reading reflect actual changes in your blood pressure, not differences in how the measurement was taken. That consistency is what makes home monitoring clinically useful.

Bring those readings to your next provider visit. A log of consistent home blood pressure readings tells me more about your actual blood pressure control than any number of office readings.

Something worth saying plainly:

High blood pressure has no symptoms — until it does. By the time it causes symptoms, it has usually been damaging end organs for years.

The goal of treatment is not to make you feel better in the short term. It is to prevent the heart attack, the stroke, the kidney failure, and the heart failure that chronically elevated blood pressure is building toward silently.

One high reading is not a diagnosis. One normal reading is not reassurance. The average — taken carefully, taken consistently, taken in and out of the office — is what tells the real story.

One important exception:

If your blood pressure is 180/120 or higher — wait at least one minute and repeat the measurement. If it remains that high, contact a healthcare professional promptly.

If you also have chest pain, shortness of breath, weakness or numbness, vision changes, difficulty speaking, severe headache, or other concerning symptoms — seek emergency care immediately. Do not wait.

The Member deep-dive this week goes underneath the number — which medications your provider is choosing and why, the secondary causes of hypertension most often missed including primary aldosteronism and renal artery stenosis, what lifestyle changes actually quantify to, and what resistant hypertension really means when blood pressure won't come down despite multiple medications.

Next week: Supplements — what the evidence actually shows for the most commonly used ones.

Plain Medicine is published for educational purposes only and does not constitute medical advice or establish a patient-provider relationship. Always consult your healthcare provider before making medical decisions.

— Kyle