Normal Blood Pressure According to Current Guidelines
According to the most recent 2017 ACC/AHA guidelines, normal blood pressure is defined as less than 120/80 mm Hg (systolic <120 mm Hg AND diastolic <80 mm Hg). 1
Blood Pressure Classification Framework
The 2017 ACC/AHA guidelines established a four-category classification system that represents a significant departure from previous definitions: 1
Current BP Categories (2017 ACC/AHA):
- Normal BP: <120/<80 mm Hg 1, 2, 3
- Elevated BP: 120-129/<80 mm Hg 1, 2, 3
- Stage 1 Hypertension: 130-139/80-89 mm Hg 1, 2, 3
- Stage 2 Hypertension: ≥140/≥90 mm Hg 1, 2
Key Changes from Previous Guidelines
The definition of normal BP itself remained unchanged from JNC 7 (2003), but the hypertension threshold was lowered. 1 The older JNC 7 guidelines used 140/90 mm Hg as the hypertension cutoff and introduced "prehypertension" for BP 120-139/80-89 mm Hg. 1 The 2017 guidelines reclassified what was previously the upper range of prehypertension as Stage 1 hypertension because observational data demonstrated approximately 2-fold increased cardiovascular disease risk in this range. 1
Measurement Requirements for Diagnosis
Proper classification requires an average of at least 2 readings obtained on at least 2 separate occasions. 1 The guidelines strongly emphasize:
- Confirmation with out-of-office BP monitoring (home or ambulatory monitoring) is recommended to exclude white coat hypertension 1, 3
- Proper measurement technique is critical: 5 minutes of rest, seated position, correct cuff size on bare arm, arm supported at heart level, legs uncrossed with feet flat, back supported, and no talking 3
- When systolic and diastolic readings fall into different categories, the higher category should be used for classification 1
Out-of-Office BP Equivalents
For home and ambulatory monitoring, the corresponding values differ from office measurements: 1
- Office 120/80 mm Hg = Home 120/80 mm Hg = Daytime 120/80 mm Hg
- Office 130/80 mm Hg = Home 130/80 mm Hg = Daytime 130/80 mm Hg
- Office 140/90 mm Hg = Home 135/85 mm Hg = Daytime 135/85 mm Hg 1, 3
Evidence Supporting Normal BP Definition
Observational data from over 1 million individuals demonstrates that cardiovascular mortality increases progressively from BP levels as low as 115/75 mm Hg upward. 1 Meta-analyses show hazard ratios for coronary heart disease and stroke between 1.1-1.5 when comparing BP 120-129/80-84 mm Hg versus <120/80 mm Hg, and between 1.5-2.0 when comparing 130-139/85-89 mm Hg versus <120/80 mm Hg. 1 This gradient of progressively higher cardiovascular risk justified maintaining <120/80 mm Hg as the normal BP threshold. 1
Important Clinical Caveats
The European guidelines (ESC/ESH 2018) differ from ACC/AHA by maintaining 140/90 mm Hg as the hypertension threshold and classify 120-129/80-84 mm Hg as "normal" and 130-139/85-89 mm Hg as "high normal" rather than hypertension. 1, 3 This creates potential confusion when applying guidelines internationally.
Common measurement errors can falsely elevate readings by 5-30 mm Hg, including incorrect cuff size, cuff over clothing, unsupported arm, full bladder, crossed legs, and talking during measurement. 3 These errors can lead to misclassification of normal BP as elevated or hypertensive.