Blood pressure is written as systolic over diastolic (e.g., 120/80 mmHg) — the artery pressure during and between heartbeats. Current US categories: normal below 120/80; elevated 120–129/<80; stage 1 hypertension 130–139 or 80–89; stage 2 at 140/90+; readings of 180/120+ with symptoms are an emergency. Hypertension is symptomless while it damages heart, brain, kidneys and eyes — diagnosis needs repeated or home readings, not one office number. Effect sizes that matter: weight loss ~1 mmHg per kg, the DASH diet ~11 mmHg in hypertensives, sodium reduction 5–6, exercise 5–8, alcohol moderation ~4, and each medication class ~8–10 — usually in combinations.
What the numbers are
Each heartbeat sends a pressure wave into arteries built to cushion it: systolic (the top number) is the peak during the beat, diastolic the trough between beats, both in millimeters of mercury. Pressure is the product of how hard the heart pushes and how much the arteries resist — which is why everything on this page works through blood volume (salt, kidneys), vessel tone (stress hormones, medications) or vessel stiffness (age, damage).
Current categories (US/AHA):
| Category | Reading (mmHg) |
|---|---|
| Normal | Below 120 and below 80 |
| Elevated | 120–129 and below 80 |
| Stage 1 hypertension | 130–139 or 80–89 |
| Stage 2 hypertension | 140+ or 90+ |
| Crisis — urgent/emergency | 180+ and/or 120+ (with symptoms: emergency now) |
(European guidance draws the treatment line nearer 140/90 with a 130s "high-normal" band — a labeling difference; the risk gradient both describe is continuous, roughly doubling cardiovascular risk with every 20/10 rise above 115/75.) Nearly half of adults qualify under the US definitions; most of the risk sits in people who feel fine, per the FAQ.
Why it matters — the quiet spending
Sustained pressure works arteries like over-flexed hose: linings injure and invite plaque, walls thicken and stiffen (raising pressure further — the ratchet), and small vessels fail first in the organs that depend on them. The bill arrives as heart attack and heart failure (a heart pumping uphill thickens, then tires), stroke — hypertension's signature harm, both clot and bleed types — kidney failure (leading cause alongside diabetes), vision damage, erectile dysfunction (small-vessel and drug-choice territory both), aortic aneurysm, and dementia — mid-life pressure control being one of the few interventions trial-linked to less late-life cognitive decline. Treatment buys these risks down with unusually good receipts: trials credit each 10 mmHg systolic reduction with roughly 20% less major cardiovascular disease.
Where it comes from
Primary hypertension (~90–95%): age's stiffening plus the compound interest of weight, sodium-heavy eating, inactivity, alcohol, poor sleep and genetics — the same soil as insulin resistance, which is why the conditions travel together. Secondary causes (worth hunting when pressure arrives young, severe or resistant): kidney disease, primary aldosteronism (more common than assumed), sleep apnea (screen every resistant case), thyroid disease, and drugs — NSAIDs, decongestants, steroids, some antidepressants, licorice, stimulants.
Moving the number — effect sizes, not vibes
Lifestyle, with trial-grade numbers (systolic): - Weight loss — ~1 mmHg per kg lost; the safe-rate playbook applies - DASH pattern (vegetables, fruit, low-fat dairy, whole grains, nuts; less red meat and sweets) — ~11 in hypertensives - Sodium toward ~1.5–2 g/day (processed food carries most of it) — 5–6, more in salt-sensitive, older and diabetic groups; potassium-rich foods amplify it - Exercise — aerobic 5–8; resistance and even isometric handgrip work add - Alcohol to ≤1–2 drinks/day — ~4 in heavier drinkers - Sleep and apnea treatment, stress work — smaller singly, real in aggregate
Medications — for stage 2, most stage 1 with risk factors, or wherever lifestyle stalls: four first-line classes (ACE inhibitors/ARBs, calcium-channel blockers, thiazide diuretics) each average ~8–10 mmHg, are typically combined at low doses (better effect, fewer side effects than maxing one), cost pennies as generics, and adjust until the home numbers sit at target (usually <130/80 US-style). Side effects are manageable and swap-able — the common failure is silent quitting, not the drugs. Supplements' honest corner: potassium via food, the food-pattern effects above, and modest trial signals for a few items (beet nitrate, hibiscus) — adjuncts at best, never substitutes, and never alongside kidney disease or ACE inhibitors without advice (potassium especially).
When to act
Emergency now: 180/120+ with chest pain, breathlessness, severe headache, vision change, confusion or weakness. Same-week: repeated 180/120+ without symptoms; pregnancy readings of 140/90+ (preeclampsia rules differ — urgent same-day with headache, vision change or swelling). Booked and unhurried: any home average ≥135/85, a first-ever reading past 40 (then annually), or the discovery that you've never actually known your number — the cheapest consequential fact in medicine, per the FAQ's protocol.
Frequently asked questions
Why do I need multiple readings — my doctor's office said 145/92?
Because pressure swings 20–30 mmHg through any day, and roughly 1 in 4 people run high only around clinics ("white coat") while a mirror group runs high only outside them ("masked"). Diagnosis rests on patterns: home averages (twice daily for a week, seated protocol) or 24-hour ambulatory monitoring. Home thresholds run ~5 lower — 135/85 home ≈ 140/90 office.
How do I take an accurate home reading?
Validated upper-arm cuff (not wrist), correct cuff size; five minutes seated, back supported, feet flat, arm resting at heart level; no caffeine, smoking or exercise in the prior 30 minutes; no talking; two readings a minute apart, morning and evening for 7 days, average everything after discarding day one. The ritual sounds fussy and is the difference between data and noise — crossed legs alone add several mmHg.
Does high blood pressure cause headaches?
Almost never at ordinary hypertensive levels — the "hypertension headache" is largely myth, and its danger is precisely the absence of symptoms. The exception is hypertensive crisis (180/120+) with headache, chest pain, breathlessness, vision change or confusion — emergency care. A normal-feeling 160/100 is still quietly spending your arteries.
Which single change lowers pressure most?
For most people carrying extra weight: losing it — roughly 1 mmHg per kilogram, so 10 kg rivals a medication. For everyone: the DASH eating pattern posted ~11 mmHg systolic in hypertensive trial participants, before sodium reduction's additional 5–6. Stacked lifestyle changes routinely match or beat a first drug — and combine with drugs rather than competing.
References
- National Heart, Lung, and Blood Institute. High Blood Pressure (2024). https://www.nhlbi.nih.gov/health/high-blood-pressure
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Type 2 Diabetes (2023). https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/type-2-diabetes
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