Understanding Blood Pressure Monitor Readings

A digital blood pressure monitor shows several numbers and symbols at once. Knowing what each one means, and which matter most, lets you read your results with confidence and record them correctly.

The three main numbers

SYS (systolic)

Usually the top and largest number. It is the pressure in your arteries when the heart beats.

DIA (diastolic)

The second number. It is the pressure in your arteries between beats.

PUL or PULSE

Your heart rate in beats per minute, measured during the reading. For adults, a resting rate of 60 to 100 beats per minute is considered normal.

A display showing SYS 124, DIA 78, PULSE 68 would be written as 124/78 mm Hg, pulse 68.

Units

Blood pressure is displayed in millimeters of mercury (mm Hg). Some monitors can also show kilopascals (kPa), used in a few countries. Make sure yours is set to mm Hg if that is what your doctor uses.

Interpreting the result

The American Heart Association’s categories for adults are:

• Normal: below 120 and below 80
• Elevated: 120 to 129 and below 80
• High blood pressure, stage 1: 130 to 139 or 80 to 89
• High blood pressure, stage 2: 140 or higher or 90 or higher

If the two numbers fall into different categories, use the higher one. Your doctor may give you a personal target that differs from these general ranges.

Common symbols

Symbols vary between brands; check your manual. Typical ones include:

Irregular heartbeat symbol

Appears when the monitor detects an uneven rhythm during measurement. Movement or talking can trigger it. Repeat the reading after resting. If it appears often, tell your doctor; the symbol alone does not diagnose a heart rhythm problem.

Movement indicator

Shows that you moved during the measurement. Repeat while keeping still.

Cuff fit indicator

Confirms that the cuff is wrapped correctly, or warns that it is too loose.

Color bar or category indicator

Some monitors show a colored scale next to the result, classifying it against a guideline. Thresholds differ between countries, so treat it as a guide and confirm with your doctor which targets apply to you.

Memory and average

“M” or a number shows a stored reading. Some monitors display an average of recent readings or of the last few taken within ten minutes.

Low battery

Replace the batteries; low power can cause errors.

Error messages

“Err”, “E” followed by a number or a similar code means the measurement failed. Usual causes are:

• movement or talking;
• cuff too loose or incorrectly positioned;
• tube kinked or disconnected;
• cuff over-inflated or under-inflated;
• weak batteries.

Refit the cuff, wait a minute and try again.

Why two readings rarely match

Blood pressure changes from minute to minute. Differences of a few points between consecutive readings are normal. That is why guidance recommends taking at least two readings, one to two minutes apart, and why your doctor looks at the average over several days.

What to record

• Date and time
• Systolic and diastolic values
• Pulse
• Which arm
• Notes on anything unusual

A dedicated record such as our Blood Pressure Log Book keeps these together.

Readings that need action

• Consistently above your target: make an appointment to discuss.
• Higher than 180 systolic or higher than 120 diastolic: rest for a few minutes and measure again. If it remains this high, contact your healthcare professional immediately. With chest pain, shortness of breath, back pain, numbness or weakness, vision changes or difficulty speaking, call 911.
• Low readings with dizziness or fainting: tell your doctor.
• Pulse persistently above 100 or unusually low at rest, or an irregular pulse: mention it to your doctor.

Home and clinic readings

Home readings are often slightly lower than clinic readings because you are more relaxed. Both are useful. Bring your monitor and your record to appointments so the two can be compared.

The bottom line

Read SYS over DIA, note the pulse, treat symbols as prompts to recheck and judge your results by the pattern over time. Our Automatic Upper Arm Blood Pressure Monitor shows all three values on a large display. Browse the heart and blood pressure department.

Sources

1. American Heart Association. Understanding Blood Pressure Readings.
2. Centers for Disease Control and Prevention. Measuring Your Blood Pressure.
3. NHS. Blood pressure test.
4. MedlinePlus. Pulse.