A vital sign means little alone. Read the set, then the trend.

01 / Reference

Adult normal ranges.

These are the adult reference ranges given in the open-access Open RN Nursing Skills textbook. Ranges differ slightly between textbooks and facilities, so use the ranges your program and facility teach on exams and at work.

Temperature

Oral 35.8–37.3 °C (96.4–99.1 °F). Normal ranges differ by route: axillary readings run lower, and rectal readings higher.

Pulse

60–100 beats per minute. Also note rhythm and strength.

Respirations

12–20 breaths per minute at rest (Open RN's respiratory chapter; its vital signs chapter lists 10–20). Also note depth, effort, and pattern.

SpO₂

94–98% for most adults. Some patients, such as certain patients with COPD, have a lower prescribed target (often 88–92%). Always check the patient's ordered range.

Blood pressure

Normal is below 120 systolic and below 80 diastolic (see the categories below).

Many facilities also record pain alongside vital signs. Whatever your facility does, a pain score helps explain other numbers: pain can raise heart rate, respiratory rate, and blood pressure.

02 / Blood pressure

Blood pressure categories.

The American Heart Association and American College of Cardiology classify adult blood pressure into four categories. Their 2025 guideline kept the categories from 2017:

Normal

Systolic below 120 and diastolic below 80

Elevated

Systolic 120–129 and diastolic below 80

Stage 1

Systolic 130–139 or diastolic 80–89

Stage 2

Systolic 140 or higher or diastolic 90 or higher

These categories are for diagnosing and managing hypertension over time, using repeated, accurate readings. A single high reading in a hospitalized patient in pain is a cue to reassess and interpret, not a diagnosis. Very high readings, or high readings with symptoms such as chest pain, severe headache, or neurological changes, need prompt escalation according to your facility's parameters.

03 / Accuracy

Get an accurate reading first.

• Use the right cuff size. An undersized cuff gives an artificially high reading, and an oversized cuff gives an artificially low one.
• Check automatic machines against the patient. Automatic monitors may be inaccurate with irregular heart rhythms or tremors. Take a manual reading when in doubt.
• Count respirations without announcing it, for a full 30 to 60 seconds. Patients who know you're counting tend to change their breathing.
• Note the conditions. Record whether the patient was resting, in pain, just ambulated, or on oxygen, and at what flow.
• Recheck a surprising number before acting on it, unless the patient also looks unwell. Then act and recheck at the same time.

04 / Interpretation

Read the set, then the trend.

Here are two sets of vital signs for Mr. D., the fictional 72-year-old with pneumonia from our head-to-toe assessment guide:

0400

Temp 37.9 °C · HR 92 · RR 20 · BP 132/78 · SpO₂ 93% on 2 L/min

0800

Temp 38.4 °C · HR 104 · RR 24 · BP 128/76 · SpO₂ 90% on 2 L/min · pain 4/10

Read value by value against the normal ranges, the 0800 set has a fever, a fast heart rate, and fast breathing. Read as a set and a trend, it says more: everything is moving the same way. The fever is rising, the heart and breathing are speeding up, and oxygen saturation is falling on the same oxygen flow. Together, that pattern points to an infection that isn't yet under control and a patient working harder to breathe.

Ask three questions of every set: How does it compare with the normal range? How does it compare with this patient's baseline and last set? And which values are moving together, and what would explain that? The nurse caring for Mr. D. answered these and called the provider using SBAR.

05 / Orthostatics

Orthostatic vital signs: when the patient gets dizzy standing.

Mr. D. reported dizziness walking to the bathroom. With fever and poor intake, that raises the question of orthostatic hypotension: a drop in blood pressure when moving from lying or sitting to standing. Open RN defines it as a decrease of at least 20 mmHg systolic or 10 mmHg diastolic within three minutes of standing.

To check, measure blood pressure and pulse lying down, then again after the patient stands (or sits, if standing isn't safe), following your facility's procedure and timing. Stay with the patient, have a second person or gait belt ready if needed, and stop if they become symptomatic.

Lying

BP 128/76 · HR 102

Standing, 3 min

BP 106/68 · HR 118 · "a little lightheaded"

The systolic pressure dropped 22 mmHg, which meets the definition. Combined with dry mucous membranes and low urine output, it supports a fluid problem and a real fall risk. Both feed directly into Mr. D.'s care plan.

06 / Action

When the numbers call for action.

Most facilities set parameters, such as early warning scores, sepsis screening tools, or provider-ordered call limits, that tell you when vital signs must be reported. Know them before you take your first set. Beyond the parameters, report when:

• Several values are trending in a worrying direction together, even if none has crossed a limit yet.
• A value has changed sharply from the patient's own baseline.
• The numbers don't match how the patient looks, in either direction.
• You're worried. Concern based on your assessment is a valid reason to escalate.

Keep going with Mr. D.

From numbers to action.