Pain assessment starts with a simple principle: ask the person to describe what they’re feeling, then use a structured tool to turn that description into something measurable. The right tool depends on who you’re assessing. A fully alert adult can rate their pain on a 0-to-10 scale, but someone with advanced dementia or a young child who can’t speak yet requires an entirely different approach based on observable behaviors like facial expressions, body tension, and vocalizations.
The 0-to-10 Numeric Rating Scale
The most widely used pain assessment method is the Numeric Rating Scale (NRS), where the person rates their pain from 0 (no pain) to 10 (worst imaginable pain). It’s popular for good reason. In a systematic review comparing different self-report tools, the NRS had better compliance than both the Visual Analog Scale and Verbal Rating Scale in 15 out of 19 studies, and was the recommended tool in 11 studies based on its ease of use, responsiveness, and broad applicability.
The Visual Analog Scale (VAS) works differently. It presents a 100-millimeter line with “no pain” at one end and “worst pain” at the other. The person marks a point on the line, and the distance from zero is measured in millimeters. VAS and NRS scores generally correspond, though VAS scores tend to run slightly higher. The VAS is more common in research settings, while the NRS dominates everyday clinical use because it requires no ruler, no printed line, and can be done verbally over the phone.
Going Beyond “How Bad Does It Hurt?”
Intensity is only one dimension of pain. A thorough assessment captures when the pain started, what makes it better or worse, what it feels like, where it is, and how it changes over time. The OPQRST framework is a structured way to cover all of these:
- Onset: When did it start? Was it sudden or gradual?
- Provocation and palliation: What makes it worse? What makes it better?
- Quality: Is it sharp, dull, burning, crushing, throbbing, or tearing? Is it constant or does it come and go?
- Region and radiation: Where exactly is it? Does it spread to other areas?
- Severity: How intense is it on a 0-to-10 scale?
- Time: How long has it lasted? Has it changed over time?
These questions matter because two people can both rate their pain at 7 out of 10 while describing completely different problems. A sharp, sudden pain that radiates from the chest to the left arm tells a very different story than a dull, constant ache in the lower back that’s been building for six months. The quality and behavior of pain often reveal more about its cause than the number alone.
Assessing Pain in People Who Can’t Self-Report
Self-report is the gold standard, but it’s not always possible. Infants, young children, people with severe cognitive impairment, and sedated or intubated patients can’t tell you how much pain they’re in. For these situations, behavioral observation tools translate physical cues into a score.
The FLACC Scale
Originally developed for children, the FLACC scale scores five categories from 0 to 2, producing a total between 0 and 10. The categories are Face, Legs, Activity, Cry, and Consolability. A score of 0 across all five means the person is relaxed, lying quietly, content, and not crying. At the other extreme, a score of 2 in each category describes someone with a clenched jaw and constant frown, legs drawn up or kicking, a rigid or arched body, steady crying or screaming, and an inability to be comforted. The FLACC scale is also used for adults with cognitive impairments who can’t reliably use a numeric scale.
The PAINAD Scale for Dementia
People with advanced dementia often express pain through subtle behavioral shifts that caregivers may not immediately recognize as pain-related. The Pain Assessment in Advanced Dementia (PAINAD) scale, developed through the Hartford Institute for Geriatric Nursing, evaluates five indicators, each scored 0 to 2 for a total of 0 to 10:
- Breathing: Normal and effortless scores 0. Occasional labored breathing or short bursts of rapid, deep breaths score 1. Loud, gurgling, or wheezing respirations score 2.
- Negative vocalization: Neutral or pleasant speech scores 0. Occasional moaning, groaning, or low-level muttering and grumbling scores 1. Repeated troubled calling out, loud moaning, or crying with tears scores 2.
- Facial expression: Smiling or a relaxed, blank look scores 0. A sad, frightened, or frowning expression scores 1. Grimacing with a distorted, distressed look and squeezed-shut eyes scores 2.
- Body language: Relaxed posture scores 0, tense or fidgeting scores 1, and rigid or striking out scores 2.
- Consolability: Content scores 0, distractible scores 1, and unable to be consoled scores 2.
What makes this tool valuable is that it picks up on signals like changes in breathing patterns that might otherwise be attributed to other causes. A person with dementia who suddenly develops noisy, labored breathing and starts calling out repeatedly may be in significant pain even if they can’t say so.
Pain Assessment in Critical Care
For patients who are sedated or on a ventilator, the Critical-Care Pain Observation Tool (CPOT) evaluates four behaviors: facial expressions, body movements, muscle tension, and either compliance with the ventilator (for intubated patients) or vocalization (for those breathing on their own). Each is rated 0 to 2, giving a total score of 0 to 8.
Assessing Chronic Pain
Acute pain and chronic pain require fundamentally different assessment approaches. A brief check of intensity and characteristics may be enough for a broken bone or a post-surgical recovery. Chronic pain demands a wider lens because it affects, and is affected by, nearly every part of a person’s daily life.
The Brief Pain Inventory (BPI), developed at MD Anderson Cancer Center, captures this by measuring two distinct dimensions. The severity section asks for four ratings: worst pain in the last 24 hours, least pain, average pain, and pain right now. The interference section then asks how much pain has disrupted seven specific areas: general activity, mood, walking ability, normal work (including housework), relationships with other people, sleep, and enjoyment of life. There’s no single composite score. Instead, you get a picture of both how intense the pain is and how deeply it’s cutting into someone’s ability to function.
The National Institute of Neurological Disorders and Stroke emphasizes that pain assessment should follow a biopsychosocial framework, meaning it accounts for mental health, cognitive patterns, and social factors alongside the physical sensation. In practice, this means a thorough chronic pain assessment may also explore depression, anxiety, stress levels, fear of movement, pain-related beliefs and coping strategies, sleep quality, trauma history, social support, and even experiences of discrimination. The NIH’s core pain research framework identifies nine key domains: pain intensity, pain interference, physical functioning and quality of life, sleep, catastrophizing (the tendency to mentally amplify pain), depression, anxiety, satisfaction with treatment, and substance use.
This broader view matters because someone’s pain experience is shaped powerfully by factors like whether they believe their pain can be controlled, whether they avoid movement out of fear of making things worse, and whether they have a support network. Two people with identical back injuries can have wildly different pain experiences depending on these psychological and social variables.
When and How Often to Reassess
Assessment isn’t a one-time event. Pain needs to be reassessed at regular intervals, especially after treatment. Johns Hopkins guidelines call for reassessment within 60 minutes of administering pain medication, regardless of whether it was given by IV or by mouth. The Joint Commission requires that healthcare organizations have screening and reassessment procedures in place and that the approach be tailored to the patient’s age, condition, and ability to understand.
For practical purposes, reassessment should happen at predictable points: after any intervention meant to reduce pain, during transitions in care (like moving from the emergency department to a hospital room), when a patient reports a change, and at regular intervals during ongoing treatment. Using the same tool each time makes it possible to track whether pain is actually improving, staying the same, or getting worse. A drop from 8 to 4 on the NRS after treatment tells you something concrete. A vague sense that the person “seems a little better” does not.