Blood Pressure Quick Reference

What Blood Pressure Measures

Blood pressure reflects the force of blood pushing against artery walls as the heart pumps and relaxes.

Term	Definition
Systolic (top number)	Pressure during heart contraction
Diastolic (bottom number)	Pressure during heart relaxation

Blood pressure is expressed as millimeters of mercury (mmHg) and written as systolic over diastolic (for example, 120/80 mmHg). It varies with posture, activity, stress, time of day, illness, and hydration interpretation depends on repeated measurements, not single readings.

Adult Blood Pressure Categories

Source: 2017 ACC/AHA Guideline

Category	Systolic (mmHg)	Logic	Diastolic (mmHg)
Normal	< 120	and	< 80
Elevated	120–129	and	< 80
Hypertension Stage 1	130–139	or	80–89
Hypertension Stage 2	≥ 140	or	≥ 90
Hypertensive crisis	≥ 180	and/or	≥ 120

Classification is based on the higher of the two numbers. A single elevated reading does not establish a diagnosis persistent elevation over multiple measurements is required.

Note: ESC/ESH 2018 defines office hypertension as ≥140/90 mmHg.

Interpreting Common Patterns

Pattern	Meaning
High systolic, normal diastolic	Isolated systolic hypertension (common with aging arteries)
Normal systolic, high diastolic	Isolated diastolic hypertension (less common in adults)
Wide pulse pressure	May reflect arterial stiffness
Highly variable readings	Often related to stress, posture, or measurement technique

Home vs Office Measurements

Pattern	Description
White-coat hypertension	Higher readings in medical settings; normal at home
Masked hypertension	Normal office readings; elevated at home

Home measurements help identify these patterns and improve accuracy of risk assessment. If your home and office readings consistently differ, inform your healthcare provider.

How to Measure Blood Pressure Properly

1. 1. Sit quietly for 5 minutes before measuring
  2. Keep your back supported and feet flat on the floor
  3. Rest your arm on a surface at heart level
  4. Use a properly sized cuff on bare skin
  5. Do not talk during the measurement
  6. Take at least two readings, 1 minute apart, and record the average

Measure at the same time of day for consistency when tracking trends.

Common Sources of Measurement Error

Error	Effect
Cuff too small	Falsely high reading
Cuff too large	Falsely low reading
Arm unsupported or below heart level	Falsely high reading
Back unsupported or legs crossed	Falsely high reading
Talking during measurement	Falsely high reading
Measuring after activity or caffeine	Falsely high reading

Even a 5–10 mmHg error can shift category assignment and affect clinical decisions.

Cuff Size by Arm Circumference

Source: AHA recommendations

Mid-Upper Arm Circumference	Cuff Size
22–26 cm (8.5–10 in)	Small adult
27–34 cm (10.5–13 in)	Standard adult
35–44 cm (13.5–17 in)	Large adult
45–52 cm (17.5–20.5 in)	Extra-large / thigh

Measure arm circumference at the midpoint between shoulder and elbow.

Device Validation

Not all monitors are accurate. Check before purchasing: validateBP.org

Home Monitoring Protocol (7-Day Average)

1. 1. Measure twice in the morning (before medications) and twice in the evening
  2. Wait 1 minute between readings
  3. Continue for 7 consecutive days
  4. Discard day 1 readings
  5. Average the remaining readings

This protocol is recommended by ESC/ESH and NICE guidelines.

Sources

- - Whelton PK et al. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults. Hypertension. 2018;71:e13–e115.
  - Williams B et al. 2018 ESC/ESH Guidelines for the management of arterial hypertension. European Heart Journal.2018;39:3021–3104.
  - Muntner P et al. Measurement of Blood Pressure in Humans: A Scientific Statement From the American Heart Association. Hypertension. 2019;73:e35–e66.
  - Stergiou GS et al. Home blood pressure monitoring: methodology, clinical relevance and practical application — a 2021 position paper by the ESH Working Group on Blood Pressure Monitoring. Journal of Hypertension.2021;39:1742–1767.