The Ultimate Guide to Pet Pain Assessment Scales

ImmunityQ&AMeongsiljang Veterinary Advisory Board

Pain assessment in pets involves comprehensively observing behavior, posture, and responses to convert the degree of pain into a numerical score. We’ve compiled everything from signs owners can check at home to the official scales used by veterinarians.

What Is a Pet Pain Assessment Scale?

Pet owners and veterinarians observing pain signals in pets

The pain assessment scale for pets is a clinical tool that converts a dog or cat’s pain level into a score by comprehensively evaluating their behavior, posture, and responses. The most critical aspect is objective observation. If you notice persistent behavioral changes such as decreased appetite, a hunched posture, or unusual vocalizations, these may be signs of pain rather than just a temporary mood shift. Veterinary textbooks emphasize that pain often manifests through subtle changes in behavior and temperament, meaning even minor deviations from your pet’s normal routine can indicate discomfort or pain. Therefore, it’s important to carefully monitor even small differences from their usual behavior. Detecting these changes early allows for timely pain assessment and appropriate management.

Why Is Pain Assessment Necessary?

Pain is more than just a feeling of discomfort; it’s a vital signal that significantly impacts an animal’s recovery and quality of life. Veterinary textbooks refer to pain as the “fourth vital sign,” alongside body temperature, pulse, and respiration, emphasizing that pain assessment should be included in the clinical evaluation of every patient. Inadequate pain assessment is often the main reason for insufficient pain management, and when pain isn’t properly controlled, animals suffer, morbidity increases, and recovery outcomes worsen. For pets recovering from surgery or living with chronic joint conditions, regularly recording pain scores is essential so veterinarians can adjust pain medication dosages accordingly. Ultimately, pain assessment is the starting point of effective treatment.

Three Common Pain Assessment Scales

Item	Glasgow Composite Measure Pain Scale (CMPS)	Colorado Acute Pain Scale	Feline Grimace Scale (FGS)
Target	Dogs	Dogs and cats	Cats only
Assessment method	Observation of behavior, posture, and response	Visualization of pain scores	Facial expressions (ears, eyes, whiskers, etc.)
Time required	Relatively long, as multiple items are evaluated	Relatively simple and short	Short, focused on facial expressions
Use by guardians	Difficult	Possible	Possible

Actual diagnosis and medication decisions must always be made by a veterinarian.

Pain Signs You Can Check at Home

The first thing pet owners often notice is a change in behavior. - Posture changes: Crouching or standing with one leg lifted - Decreased appetite: Refusing favorite treats - Grooming changes: Excessively licking a specific area or completely stopping grooming - Hiding behavior: Retreating to corners or under beds and refusing to come out - Vocalization changes: Unusual whining or low growling - Responsiveness changes: Flinching or showing aggression when touched If you observe these signs or notice persistent behavioral changes, your pet may need a pain assessment by a veterinarian.

Pain signals in pets resting in a crouched position

Emergency Signs Requiring Immediate Veterinary Care

If you notice any of the following signs, take your pet to the vet immediately, regardless of their pain score: - Shallow, rapid breathing accompanied by pale or purple gums - A hard, distended abdomen or vocalizing in pain when touched - Seizures, inability to stand, or decreased level of consciousness - Sudden worsening of pain after surgery (possible bleeding or suture issues) - Hiding and refusing to drink water for more than 24 hours These are not just signs of simple pain; they indicate emergency conditions such as shock, abdominal pain, or internal bleeding.

How Veterinarians Assess Pain

After reviewing your observations of any changes in your pet’s daily routine, the veterinarian conducts a three-step assessment: observing from a distance, interacting, and then palpating. According to veterinary internal medicine textbooks, observing natural behavior from a distance provides the most accurate insights. The vet then notes how your pet responds when called or petted, and finally records any flinching, avoidance, or vocalizations when gently pressing on painful areas. This process forms the basis for determining the pain score.

A veterinarian observing a cat from a distance to assess its pain level

Species-Specific Differences in Pain Expression

Dogs and cats express pain in completely different ways. - Dogs: Whining, limping, and seeking physical contact with their owners are common signs. - Cats: Hiding, stopping grooming, and changes in facial expression are key indicators. - Feline-specific traits: Cats have an instinct to hide pain, so it is often discovered only after the condition has worsened. In particular, a cat’s facial expression (assessed using the Grimace Scale) is one of the most reliable indicators. If the ears are flattened sideways or the eyes are partially closed, pain is likely.

What Owners Should Record

Taking notes on the following points before your visit will help your veterinarian assess your pet’s pain more accurately: - When the symptoms started and how long they have lasted - Whether the pain worsens with specific movements (such as standing up or climbing stairs) - Any changes in food intake or frequency of urination and defecation - Activity level compared to normal - Areas that elicit a reaction when touched Recording a short video can also be very helpful, as it allows your veterinarian to observe your pet’s actual gait and posture, aiding in diagnosis.

When to Reassess After Pain Management

Reassessment is essential even after administering pain medication. The frequency of reassessment differs between acute and chronic pain, and your veterinarian will determine the appropriate interval based on the type of surgery, the animal’s condition, and the pain management protocol. If the pain score fails to decrease or actually increases, adjustments to the medication type or dosage may be necessary. For long-term management strategies for chronic pain conditions such as arthritis, please refer to our Pet Joint Care Guide.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Can owners assess their pet’s pain level at home?

While general observation is possible, treatment decisions should never be based solely on formal scoring systems. The most important role you can play is to document any behavioral changes and share them with your veterinarian.

What does it mean that cats hide their pain?

This is an instinct to avoid showing weakness to predators in the wild. As a result, symptoms often don’t appear until the pain has progressed significantly, so it’s important to pay close attention to even subtle changes in their usual behavior.

I gave my pet pain medication, but they still seem to be in pain. Can I increase the dose?

Never increase the dosage on your own. A veterinarian must reassess and adjust the dose based on your pet’s weight, liver, and kidney function, and may need to add other medications as well.

Why is pain assessment important after surgery?

If pain isn’t adequately controlled, your pet may suffer, experience higher complication rates, and have poorer recovery outcomes. Additionally, the frequency of post-operative pain assessments varies depending on the type of surgery, your pet’s pre-surgical condition, and the pain management protocol in place, so it’s important to follow your veterinarian’s guidance.

How can you tell the difference between pain and normal aging in senior dogs?

Don’t brush it off as “just part of getting older.” Reluctance to move may be due to joint pain, and proper pain management can significantly improve your pet’s quality of life. Ask for a pain assessment during regular check-ups.

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References

[1] Cenani A., Barter L.S., Pain Assessment — Small Animal Critical Care Medicine 3rd Ed., Chapter 131

[2] Hansen B.D., Analgesia and sedation in the critically ill, J. Vet. Emerg. Crit. Care 15(4):285–294, 2005

[3] Mathews K.A., Pain assessment and general approach to management, Vet. Clin. North Am. Small Anim. Pract. 30(4):729–755, 2000

[4] International Association for the Study of Pain (IASP), Classification of Chronic Pain 2nd Ed., 2012

[5] Advanced Monitoring for Small Animal Emergency and Critical Care 2nd Ed. — Pain Monitoring Chapter