Vital signs are a group of the four (or five) most important medical signs that indicate the status of the body’s life-sustaining functions.
These measurements are taken to help assess the general physical health of a person, give clues to possible diseases, and show progress toward recovery. They do not lead to a specific diagnosis, i.e. cause of the change in vital signs.
In a hospital or GP setting, “taking your vitals” is the first step in any clinical assessment.
We will start with a summary of what is normal for a normal healthy adult.
| Vital Sign | Normal (Average) Value | Typical Range |
| Body Temperature | 37.0°C (98.6°F) | 36.5°C – 37.2°C |
| Pulse Rate | 80 bpm | 60 – 100 bpm |
| Respiratory Rate | 15 breaths | 12 – 18 breaths |
| Blood Pressure | 120/80 mmHg | 90/60 – 135/85 |
| Oxygen Saturation | 98% | 95% – 100% |
Body temperature measures the body’s ability to generate and get rid of heat. The body is very tight at controlling this to keep enzymes and organs functioning.
Normal: 37.0°C (range = 36.5°C to 37.2°C; 97.8°F to 99°F).
Fever (Pyrexia): Generally considered a temperature over 38°C (100.4°F). This is often the body’s way of fighting an infection.
Hypothermia: A drop in body temperature below 35°C (95°F).
The pulse rate is a measurement of the heart rate, or the number of times the heart beats per minute. As the heart pushes blood through the arteries, the arteries expand and contract with the flow of the blood.
Normal (Average) Heart Rate: 80 beats per minute (range = 60 to 100) for a healthy adult at rest.
The exact average adult human heart rate is not known (like all these vital signs, actually). In one large study, it was 79 beats per minute (Avram, 2019). This figure was based on over 3 million measurements from about 67,000 patients.
Interestingly, adult women often have a slightly higher resting heart rate (average ~79 BPM) than men (average ~74 BPM), perhaps because their hearts are smaller and pump less blood per beat.
Tachycardia: A resting heart rate that is too fast (over 100 bpm).
Bradycardia: A resting heart rate that is too slow (under 60 bpm), though this is common in elite athletes.
What it tells us: The pulse not only measures the rate but also the rhythm (steady vs. irregular) and the strength of the beat.
The respiration rate is the number of breaths a person takes per minute. The rate is usually measured when a person is at rest and involves simply counting the number of breaths for one minute by counting how many times the chest rises.
Normal Respiratory Rate: 15 breaths per minute (range = 12 to 18).
Factors: Respiratory rates may increase with fever, illness, and other medical conditions.
What is blood pressure? It is the force of the blood pushing against the artery walls during contraction and relaxation of the heart. It is recorded as two numbers:
Systolic (Top number): The pressure inside the artery when the heart contracts and pumps blood through the body.
Diastolic (Bottom number): The pressure inside the artery when the heart is at rest and filling with blood.
Hypertension (High Blood Pressure): Generally defined as peristently 140/90 mmHg or higher. High blood pressure is often called a ‘silent killer’ because it may have no symptoms but increases the risk of heart disease and stroke
While the four above are the ‘standards,’ many clinicians now include Oxygen Saturation as a fifth vital sign, measured using a pulse oximeter (the clip placed on your finger).
Normal Oxygen Saturation: 98% (range = 95% to 100%).
Hypoxia: Anything below 92% (in a patient without chronic lung disease) usually requires medical attention or supplemental oxygen.
Vital signs are not just ‘numbers’; they are a snapshot of your homeostasis. Doctors and nurses look for trends.
For example, a single high blood pressure reading might be due to stress (‘White Coat Syndrome’), but a consistently rising heart rate combined with a falling blood pressure can be an early warning sign of Sepsis or internal bleeding.
The normal (average) values (and ranges) given above and below are clearly too neat to be true. There is no human being with vital signs of temp 37.0°C, HR 80, RR 15, BP 120/80 and 98% sats.
There are average values, with ranges based on 95% of people (2 Standard Deviations (SDs) from the mean). These ranges vary according to many factors (some below); and the precise values vary in an individual person all day long.
Vitals are dynamic and can change based on several physiological factors:
Age: Infants and children have significantly higher heart and respiratory rates than adults.
Physical Activity: Exercise increases BP, heart rate, and respiration.
Pregnancy: Blood volume increases, often leading to a higher heart rate and changes in blood pressure.
Stress & Emotion: Anxiety can cause temporary “spikes” in vitals (often called “White Coat Hypertension”).
Heart Rate (HR) & Blood Pressure (BP): These show a steady, elevated plateau during the day, following wakefulness, and dip into a low during sleep. This nocturnal ‘dipping’ is a sign of a healthy cardiovascular system.
Body Temperature: Core temperature rises during the day, supporting alertness and metabolism, and has a lowest point around 3–4 am. This is why you may feel coldest in the early hours of the morning regardless of the room temperature.
Respiratory Rate (RR): Similar to heart rate, respiratory rate tends to peak in the late afternoon or evening (around 8 pm) and is lowest early in the morning during deep sleep phases.
Oxygen Saturation (SpO2): Circadian, 24-hour variations are observed in pulse oximetry readings. These subtle fluctuations are often monitored in ICU settings to help measure disease severity and the timing of therapeutic interventions.
Vital signs are the primary language of the body. Whether you are at a routine GP check-up or in the A&E (ER in the US), these measurements provide the essential data needed to keep you safe.
Summary Table: Vital Signs at a Glance (Healthy Adults)
| Vital Sign | Normal Value | Typical Range | Meaning & Significance |
| Body Temperature | 37.0°C (98.6°F) | 36.5°C – 37.2°C | Indicates the body’s ability to regulate heat; signals infection or metabolic issues. |
| Pulse Rate | 80 bpm | 60 – 100 bpm | Measures heart frequency and rhythm; reflects cardiovascular stress or fitness. |
| Respiration Rate | 15 breaths | 12 – 18 breaths | Measures breathing frequency; sensitive indicator of respiratory or metabolic distress. |
| Blood Pressure | 120/80 mmHg | 90/60 – 135/85 | Measures force against artery walls; critical for assessing heart and kidney health. |
| Oxygen Saturation | 98% | 95% – 100% | Measures the percentage of haemoglobin carrying oxygen; vital for lung function assessment. |
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