Blood Pressure: Normal Ranges by Age

What the Numbers Mean

• Systolic - pressure when the heart contracts
• Diastolic - pressure when the heart relaxes between beats

Adults (18+ years)

Source: Park's Textbook of Preventive & Social Medicine; 2024 ESC Guidelines

Average Blood Pressure by Adult Age Group and Sex

Note: The fact that average BP rises with age does not mean higher BP is "normal" or acceptable in older adults - the clinical targets still apply.

Children and Adolescents

• Estimated average SBP = (Age in years × 2) + 90 mm Hg
• Estimated average DBP = ½ × estimated SBP
• Minimum acceptable SBP (5th percentile):
  • Newborn to 1 month: 60 mm Hg
  • 1 month to 1 year: 70 mm Hg
  • 1 - 10 years: (Age × 2) + 70 mm Hg

  • 10 years: 90 mm Hg

Summary: What to Aim For

• BP should always be measured at least twice, on two separate occasions, to confirm a reading.
• White coat effect (BP higher in clinic), masked hypertension (normal in clinic, high at home), and orthostatic hypotension (drop > 20/10 mm Hg on standing) are all clinically relevant variations.
• Low BP (< 90/60 mm Hg) can also be significant if it causes symptoms such as dizziness or syncope.

Blood Pressure Variation by Body Position

1. The Physiology: Why Position Changes BP

• Blood is evenly distributed; no hydrostatic gradient pulling blood toward the legs
• Venous return to the heart is maximal
• Cardiac output and stroke volume are at their highest
• BP is relatively stable and often slightly lower than sitting
• The heart and cuff are at the same level - measurements are most standardized

• Moderate venous pooling in the legs
• The baroreceptor reflex (carotid sinus and aortic arch) partially compensates by increasing heart rate and peripheral vascular resistance
• BP is typically ~5-10 mmHg higher than supine in healthy adults
• The standard clinical measurement position recommended by WHO and most guidelines

• Blood pools in leg veins (up to 500-800 mL can pool), reducing venous return
• Cardiac output drops via the Frank-Starling mechanism
• Baroreceptor reflex activates: increased sympathetic outflow raises HR and total peripheral resistance
• In a healthy person, BP is restored within 1-2 minutes
• Initially there is a transient dip in BP, then a recovery

"When a person moves from a supine to a standing position, blood pools in the veins of the lower extremities. The capacitance of the veins allows for large blood volumes to accumulate. When blood pools in the veins, venous return to the heart decreases and cardiac output decreases (Frank-Starling mechanism), which results in a decrease in mean arterial pressure."

• Costanzo Physiology, 7th Edition

2. Typical BP Differences Between Positions (Normal Adults)

From Creasy & Resnik's Maternal-Fetal Medicine: "Arterial blood pressures are approximately 10 mm Hg higher in the standing or sitting position than in the lateral or supine position; consistency in position during successive measurements is essential for the accurate documentation of a trend."

3. Orthostatic Hypotension - The Pathological Drop

• Systolic BP drop ≥ 20 mmHg within 3 minutes of standing, or
• Diastolic BP drop ≥ 10 mmHg within 3 minutes of standing
• In hypertensive patients: a drop of ≥ 30 mmHg systolic is a more appropriate threshold
• ESC additionally includes a fall in systolic BP to < 90 mmHg
• A pulse rise of > 30 bpm on standing is also a diagnostic criterion

Source: Symptom to Diagnosis, 4th Ed.; Brenner & Rector's The Kidney

• A fall of 15/7 mmHg from sitting-to-standing is used instead of 20/10 mmHg, due to reduced sensitivity when the supine baseline is skipped (Brenner & Rector's The Kidney).

4. The Normal Tilt Response vs. Orthostatic Hypotension (Illustrated)

5. Standard Measurement Protocol (Clinical)

1. Patient lies supine for 2-3 minutes - record BP and pulse
2. Patient stands - record BP, pulse, and symptoms at 1 minute (and optionally at 2-3 min)
3. Allow immediate return to supine if syncope or near-syncope occurs

• The supine-to-standing comparison is the most sensitive - if supine BP is not measured, up to 67% of orthostatic cases may be missed
• Sitting-to-standing is acceptable in busy clinical practice but less sensitive
• An increase in pulse of > 30 bpm with standing is highly sensitive (97%) and specific (98%) for large volume blood loss (1-2 units)
• Sensitivity falls dramatically if the patient sits instead of stands (39-78% vs 97%)
• Arm position must be held constant throughout all measurements

6. Who Is Most at Risk for Positional BP Changes?

A key differentiator: orthostatic hypotension from autonomic failure does NOT produce reflex tachycardia, whereas hypotension from volume depletion typically does produce a pronounced tachycardia. (Roberts & Hedges)

7. A Recent Note on Supine BP