Vital Signs & Red Flags

The core vital signs

Vital signs are quick, repeatable measurements that show how well the body's essential systems are working. Trends over time usually matter more than a single reading.

• Heart rate — about 60–100 beats per minute at rest in adults. Fit people may sit lower. ^[1]
• Respiratory rate — about 12–20 breaths per minute at rest in adults. ^[1]
• Blood pressure — below 120/80 mmHg is considered normal for adults. ^[2]
• Temperature — around 36.5–37.5 °C; 38.0 °C or higher is generally treated as fever. ^[1]
• Oxygen saturation (SpO₂) — usually 95–100% on room air in healthy adults. Lower targets apply to some patients, such as those at risk of hypercapnic respiratory failure. ^[3]

Why respiratory rate matters so much

A rising respiratory rate is one of the earliest and most sensitive signs that a patient is getting worse — yet it is the vital sign most often skipped or estimated. Count it for a full 30–60 seconds. ^[4]

Early warning scores

Many hospitals combine vital signs into an early warning score, such as the UK's National Early Warning Score 2 (NEWS2). Each abnormal value adds points, and the total sets how urgently a patient should be reviewed. Scores help staff recognise deterioration consistently instead of relying on instinct. ^[4]

Patterns to recognise

• Fast pulse, low blood pressure, and cool, clammy skin — suggests shock.
• Fever with fast pulse and fast breathing, or confusion — consider sepsis.
• Sudden facial droop, arm weakness, or slurred speech — think stroke (FAST: Face, Arms, Speech, Time).
• Low oxygen saturation with fast breathing — respiratory compromise.