1.4bn
adults aged 30–79 living with hypertension worldwide (2024)
44%
of them — about 600 million people — don’t know they have it
2 in 3
live in low- and middle-income countries
1The awareness gap
Hypertension is called the silent killer because it usually has no symptoms. Of every 100 adults who have it, this is roughly what happens next.1
Have hypertension1.4 billion · 100%
Unaware they have it~600 million · 44%
Diagnosed and treated~630 million · 44%
Actually under control~320 million · 23%
2What the numbers mean
The top number (systolic) is the pressure while your heart beats. The bottom (diastolic) is the pressure while it rests between beats. American Heart Association categories:2
| Category | Systolic | | Diastolic |
|---|
| Normal |
Under 120 | and | Under 80 |
| Elevated |
120–129 | and | Under 80 |
| Hypertension Stage 1 |
130–139 | or | 80–89 |
| Hypertension Stage 2 |
140 or higher | or | 90 or higher |
| Hypertensive crisis |
Above 180 | and/or | Above 120 |
Read the “and” / “or” carefully
Normal and Elevated require both numbers to be in range. From Stage 1 upward, either number on its own is enough to put you in that category. A reading of 118/92 is Stage 1 hypertension, even though the top number looks fine.
At above 180 and/or above 120, wait five minutes and measure again. If it is still that high, contact a doctor. If it comes with chest pain, breathlessness, weakness, numbness, vision changes or trouble speaking, treat it as an emergency and call your local emergency number.2
Why you’ll see two different thresholds
The AHA puts Stage 1 hypertension at 130/80. The World Health Organization and most international guidance define hypertension at 140/90.1 Neither is wrong — the US guideline deliberately flags risk earlier so lifestyle changes start sooner. If you compare a reading against advice from another country, check which threshold it uses before drawing conclusions.
3How to measure so the number is real
Technique is not a detail. Poor measurement routinely shifts readings by more than blood pressure medication lowers them. The AHA’s protocol:3
- No caffeine, smoking or exercise for 30 minutes beforehand. All three temporarily raise pressure.
- Empty your bladder first. A full bladder measurably raises a reading.
- Sit quietly for at least 5 minutes before the first measurement. Not while walking in, not straight after a phone call.
- Bare skin, not over clothing. The bottom of the cuff sits directly above the bend of the elbow.
- Arm supported at heart level on a flat surface — use a pillow if needed. An unsupported or low arm inflates the number.
- Back supported, feet flat on the floor, legs uncrossed. Crossed legs and a dangling arm both push readings up.
- Don’t talk during the measurement, and don’t use your phone.
- Take two readings a minute apart and record both. Measure at the same time each day so you’re comparing like with like.
4What a wrist wearable can honestly tell you
This is where most marketing overstates the case, so here is the current evidence position.
✓ Genuinely useful for
- Spotting trends over weeks — is your usual range drifting up?
- Capturing readings overnight and through the day, when a cuff isn’t practical
- Building the habit of checking at all — which matters when 44% of people don’t know they have it
- Giving you something concrete to take to a doctor and confirm properly
✗ Not a substitute for
- Diagnosis. Only a validated cuff device and a clinician can diagnose hypertension
- Medication decisions. Never adjust doses from a wearable reading
- A single accurate number. Cuffless estimates drift as arterial stiffness and vascular tone change
The evidence position, stated plainly
A 2025 scientific statement from the European Society of Cardiology concluded that cuffless blood pressure devices are not recommended for clinical decisions and lack adequate scientific validation. It characterises cuffless monitors that need an initial calibration as “tracking devices” rather than true measuring instruments, and notes their accuracy can degrade over time.4
The practical read: use a wearable to notice a pattern, then confirm the number with a validated upper-arm cuff. The two tools answer different questions.