Vital signs: the five numbers that frame every case
Temperature, heart rate, blood pressure, breathing rate and oxygen saturation, with normal adult values, the patterns that matter, and why a trend beats a single reading.
Before a single blood test comes back, five quick measurements already say a lot about how unwell someone is. They are called the vital signs, and in most hospitals they are checked on every patient, several times a day. This guide covers what each one measures, typical adult values and the combinations clinicians watch for.
The five vital signs
| Vital sign | Typical resting adult value | Too high | Too low |
|---|---|---|---|
| Temperature | About 36.1–37.2 °C (97–99 °F) | Fever: 38.0 °C (100.4 °F) or more | Hypothermia: below 35 °C (95 °F) |
| Heart rate | 60–100 beats per minute | Tachycardia: over 100 | Bradycardia: under 60 |
| Blood pressure | Under 120/80 mmHg | Hypertension (see below) | Hypotension, often a systolic under 90 mmHg |
| Respiratory rate | 12–20 breaths per minute | Tachypnea | Bradypnea |
| Oxygen saturation | About 95–100% on room air | Not a concern on its own | Hypoxemia, usually under 94% and worrying under 90% |
These are typical values for healthy adults at rest. Children have faster heart and breathing rates, and many people have values outside these ranges without being ill.
Temperature
Body temperature varies through the day and depends on where it is measured: mouth, ear, armpit or rectum. A fever usually means 38.0 °C (100.4 °F) or higher and most often reflects infection, although inflammation, some cancers, blood clots and certain medicines can cause it too. A low temperature can be just as important: older adults and people with overwhelming infection do not always mount a fever, and hypothermia has its own dangers.
Heart rate
A resting heart rate of 60 to 100 beats per minute is typical for adults. Tachycardia, a rate over 100, is a common response to fever, pain, anxiety, dehydration, blood loss, infection, an overactive thyroid or a blood clot in the lungs. It can also come from a heart rhythm problem. Bradycardia, a rate under 60, is normal in many fit people and during sleep, but it can also be caused by medicines such as beta blockers, an underactive thyroid or problems with the heart's electrical system. The rhythm matters too: an irregular pulse may point to atrial fibrillation.
Blood pressure
Blood pressure is written as two numbers: the systolic pressure while the heart contracts and the diastolic pressure while it relaxes. The 2017 American College of Cardiology and American Heart Association guideline uses these categories:
- Normal: under 120 systolic and under 80 diastolic.
- Elevated: 120–129 systolic and under 80 diastolic.
- Stage 1 hypertension: 130–139 systolic or 80–89 diastolic.
- Stage 2 hypertension: 140 or more systolic, or 90 or more diastolic.
Guidelines in other countries use slightly different thresholds. A single high reading does not make a diagnosis of hypertension: it needs repeated measurements, taken properly, with the right cuff size after a few minutes of rest.
Low blood pressure matters most when it is new or causes symptoms. In an acutely unwell patient, a systolic pressure under about 90 mmHg can signal shock, when the circulation is not delivering enough blood to the organs. A fall in blood pressure on standing up, of at least 20 mmHg systolic or 10 mmHg diastolic within three minutes, is called orthostatic hypotension and can come from dehydration, medicines or problems with the nervous system.
Respiratory rate
The breathing rate is the vital sign most often skipped, and one of the most useful. A raised rate is frequently an early sign that someone is deteriorating, well before other numbers change. It rises with lung problems such as pneumonia, asthma or a blood clot, but also with fever, pain, anxiety and conditions that make the blood too acidic. In diabetic ketoacidosis, for example, the body tries to blow off acid with deep, rapid breathing called Kussmaul breathing. A slow breathing rate can be caused by opioids, sedatives or brain injury.
Oxygen saturation
A pulse oximeter clipped to a finger estimates the percentage of hemoglobin carrying oxygen, written SpO2. Healthy adults at sea level usually read 95% or higher. Lower values mean the lungs or circulation are not getting enough oxygen into the blood.
Pulse oximeters have limits worth knowing. They can overestimate oxygen levels in people with darker skin, which can hide low oxygen. They read falsely normal in carbon monoxide poisoning, and they struggle with cold hands, poor circulation and nail polish. In some people with chronic lung disease, a lower target such as 88–92% is deliberately used.
Patterns that matter
Vital signs are most useful in combination. A few classic patterns:
- Fever, fast heart rate, fast breathing and low blood pressure together suggest sepsis, a life-threatening response to infection, and demand urgent assessment.
- Fast heart rate and low blood pressure after an injury suggest significant blood loss.
- Deep, rapid breathing with a high blood glucose suggests diabetic ketoacidosis.
- High blood pressure with a slow heart rate and irregular breathing in someone with a head injury (Cushing's triad) suggests dangerously raised pressure inside the skull.
- A heart rate higher than the systolic blood pressure (a shock index above 1) is a warning sign in trauma and sepsis.
Many hospitals combine the vital signs into an early warning score, such as the National Early Warning Score (NEWS2) used in the United Kingdom, so that deterioration is spotted and escalated consistently.
Trends beat single readings
One number is a snapshot. Clinicians care far more about the direction of travel: a heart rate that has crept from 85 to 115 over a few hours, or a breathing rate that keeps rising, is often more alarming than any single abnormal value.
Vitals in Stat!
In Syndrome, the Vitals tab lets you check temperature, heart rate, breathing rate, blood pressure, oxygen saturation and weight. Each comes back normal or abnormal, so the game tells you that a vital sign is off and leaves you to reason about why. Vitals are free questions with a lot of value: an abnormal temperature or oxygen level can reshape your list of possible diagnoses in one step. See the Syndrome guide for how findings are shown in the game.
Stat! and this guide are for education only. They are not medical advice and not a substitute for professional care. If you have a health concern, talk to a qualified clinician.