Emergency Department Triage: ESI Levels and Who Goes Back First
The Emergency Severity Index sorts patients on two questions in order: is this person dying or unstable, and if not, how many resources will they need. Level 1 needs immediate life-saving intervention, level 2 is high risk or severely distressed and cannot safely wait, and levels 3 to 5 are sorted by the number of resources. Acuity always beats arrival order: a level 2 who walks in last goes back before a level 3 who has been waiting an hour.
Triage in the emergency department and in a disaster: the ESI levels and who goes back first.
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The Emergency Severity Index sorts patients on two questions, in order: is this person dying or unstable, and if not, how many resources will they need. Acuity always beats arrival order — a level 2 who walks in last goes back before a level 3 who has waited an hour.
The five levels
| Level | Meaning | Examples | Wait |
|---|---|---|---|
| 1 | Immediate life-saving intervention required | Cardiac or respiratory arrest, unresponsive, severe respiratory distress, major trauma with instability, active seizure | None — resuscitation now |
| 2 | High risk; confused/lethargic/disoriented; or severe pain or distress | Chest pain suggesting ischaemia, stroke symptoms within the window, suicidal ideation with a plan, altered consciousness, sepsis, an infant with a fever, compensating respiratory distress | Should not wait — the most important level to recognise |
| 3 | Stable, but expected to need two or more resources | Abdominal pain needing labs and imaging, a laceration needing sutures and X-ray | Can wait safely with reassessment |
| 4 | Expected to need one resource | A simple laceration needing sutures, a suspected simple fracture needing an X-ray | Can wait |
| 5 | Expected to need no resources | Prescription refill, a suture removal, a minor rash | Can wait longest |
“Resources” means laboratory tests, imaging, IV fluids or medication, specialty consultation and procedures. It does not include the history and physical, point-of-care testing, oral medication, a tetanus shot, a prescription, crutches, splints or dressings — those are part of the visit, not a resource.
Level 2 is where students lose marks. It is not “quite sick”; it is this person may deteriorate while sitting in the waiting room. Anything altered, anything with a time-critical treatment window, anything at risk to themselves — that is a 2.
How to work a triage question
- Is anyone dying? Airway, breathing, circulation, level of consciousness. That is your level 1.
- Is anyone at high risk of dying soon, or in severe distress? Time-critical windows, altered mentation, unstable vital signs for age, self-harm risk. Those are level 2.
- Only then count resources for whoever is left.
Presentations that do not wait
- Chest pain that could be cardiac — the ECG happens at triage
- Stroke symptoms with a known onset time
- Any infant under about 3 months with a fever
- Suicidal ideation with a plan or means
- Altered mental status of any cause, including a diabetic with an abnormal glucose
- Signs of sepsis
- Anaphylaxis, active bleeding, an obviously ischaemic limb, testicular or ocular pain of sudden onset
ED triage is not disaster triage
| Everyday ED triage (ESI) | Disaster / mass casualty (START) | |
|---|---|---|
| Goal | Best outcome for each individual | Greatest good for the greatest number |
| The sickest client | Is seen first | May be tagged expectant and passed over if survival is unlikely and resources are scarce |
| Resources | Assumed adequate | Assumed overwhelmed |
| Categories | Levels 1–5 | Red immediate, yellow delayed, green minor, black expectant |
This reversal is one of the most reliably tested contrasts in Management of Care. In an ordinary emergency department the unresponsive client is your first priority. In a declared mass casualty with limited resources, the client who is not going to survive the available care is not the first priority — and choosing them is the wrong answer.
The rest of the triage nurse's job
- Reassess the waiting room. A triage level is a snapshot, not a verdict — clients are re-triaged at set intervals and whenever anything changes.
- Anyone who looks worse gets moved up, immediately and without waiting for permission.
- Recognise infectious presentations early and mask and separate them.
- Document the assessment, the level assigned and the reasoning.
NCLEX tip: When a question lists four waiting-room clients and asks who is seen first, ignore arrival times entirely and look for altered mental status, a time-critical window, or unstable vital signs for that age. Pain severity alone rarely wins; pain that signals ischaemia does.
Educational use only: this article supports nursing review and does not replace clinical judgment, facility protocols, or instructions from an authorised prescriber.
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Frequently asked questions
Common follow-up questions on Prioritization, Delegation & Management of Care.
What are the five ESI triage levels?
Level 1 requires immediate life-saving intervention; level 2 is high risk, altered mentation or severe distress and cannot safely wait; levels 3, 4 and 5 are stable and sorted by whether they will need two or more resources, one resource, or none.
What counts as a resource in ESI?
Laboratory tests, imaging, intravenous fluids or medication, specialty consultation and procedures. The history and physical examination, point-of-care testing, oral medication, a tetanus shot, a prescription, crutches, splints and simple dressings do not count.
Does the client who arrived first get seen first?
No. Emergency triage sorts by acuity, so a higher-acuity client who arrives later is taken back ahead of a lower-acuity client who has been waiting. Arrival order only decides between clients at the same level.
How is ED triage different from disaster triage?
Everyday triage aims for the best outcome for each individual, so the sickest client is seen first. Mass casualty triage aims for the greatest good for the greatest number, so a client unlikely to survive with available resources may be tagged expectant while treatable clients are prioritised.
Which client is a level 2?
Anyone at high risk of rapid deterioration or in severe distress: chest pain suggesting ischaemia, stroke symptoms within the treatment window, altered mental status, suspected sepsis, an infant under three months with a fever, or suicidal ideation with a plan.
How often are waiting clients reassessed?
At set intervals per department policy and immediately whenever anything changes. A triage level is a snapshot; any client who looks worse is moved up without waiting for permission.
Sources and references
- Harding MM, Kwong J, Hagler D, Reinisch C. Lewis's Medical-Surgical Nursing: Assessment and Management of Clinical Problems. 12th ed. Elsevier; 2023; Chapter: Emergency and Disaster Nursing.
- Gilboy N, Tanabe P, Travers D, Rosenau AM. Emergency Severity Index (ESI): A Triage Tool for Emergency Department Care, Version 4. Implementation Handbook 2012 Edition. AHRQ Publication No. 12-0014. Rockville, MD: AHRQ; 2011.
Reviewed by the NCLEXPace team, October 2026.
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