Fever in dogs, fever in cats

What is fever?

Table of contents

Fever is a natural, usually helpful defense reaction of the body to special substances (pyrogens) acting from the outside or released internally. In the thermoregulation center of the brain, a new “setpoint” above the physiological normal range is set. The Increased body temperature is achieved by constricting blood vessels in the periphery of the body (vasoconstriction) and by muscle shivering.

This means that fever is not a disease and does not always require treatment.

Signs of fever

How Do I Recognize Fever in My Animal?

An animal with fever often appears:

  • lethargic or tired
  • eats less or not at all
  • shivers or seeks warmth
  • has a warm nose or hot ears (not a reliable proof of fever!)
  • shows faster breathing or heartbeat

The only reliable method is to measure the fever with a thermometer – preferably rectally.

Measuring fever

Body temperature is a central parameter for assessing an animal’s state of health. Especially with non-specific symptoms such as Apathy, loss of appetite or altered behavior, temperature control is often the first diagnostic step.

Normal Body Temperature Values

  • Dog: 37.5 °C to 39.0 °C
  • Cat: 38.0 °C to 39.3 °C
    Anything above approx. 39.5 °C is considered Fever.

Methods for Measuring Temperature

  1. Rectal measurement (classic with digital thermometer):

The thermometer is carefully inserted into the rectum (anus), usually 1–2 cm deep (slightly less in cats). To prevent Pain and defense reactions, the thermometer must be made well lubricated (oil) before it is inserted into the rectum. The value can be read after approx. 20–60 seconds. This is the usual method in veterinary medicine, as the rectal temperature comes very close to the internal body core temperature.

The disadvantage is the stress possibly associated with the measurement in sensitive animals.

  1. Infrared thermometer (auricular = in the ear or contactless = forehead, flank etc.):

The temperature is measured via the radiant heat of the body (e.g. eardrum or skin surface). The result is available in a few seconds. This method is therefore quick, easy and hardly associated with stress for the animals.

The disadvantage, however, is that this method is significantly less accurate than rectal measurement.

Results are highly dependent on:

  • the position of the thermometer
  • the ambient temperature
  • the coat texture and pigmentation
  • the blood flow to the measured region
  • The ear temperature does not reliably correlate with the rectal temperature, especially in small animals, Inflammatory conditions in the ear or a poorly placed sensor.

Comparison of accuracy

Measurement method

Accuracy

Range of variation

Applicability in everyday life

Rectal measurement

High (± 0.1 °C)

Low

Standard method in practice and clinic

Infrared (ear)

Medium to low

± 0.5 – 1.0 °C

Only suitable for home use to a limited extent

Infrared (contactless)

Low to unreliable

>± 1.0 °C

Not recommended for medical evaluation

Studies show (figure) that infrared thermometers often significantly underestimate or overestimate the body core temperature in dogs and cats. At high ambient temperatures, for example, a false normal temperature can be simulated. Rectal temperature measurement remains the most reliable method for determining body temperature in dogs and cats. Infrared thermometers can be used as a supplement, but are not reliable enough for veterinary diagnostics. For home use, infrared thermometers can be used as an alternative, although they are not as accurate.

Figure: Comparison of the accuracy of different temperature measurement methods (x-axis) between rectal (digital) and infrared measurement methods on the ear or contactless on other body regions

Average deviation from body core temperature (y-axis)

It is clear that rectal measurement has the lowest deviation and therefore the highest reliability. Infrared methods – especially contactless ones – are significantly less accurate.

My dog has fever

Fever is a very non-specific symptom. If fever is present, it is important to assess the animal’s general condition. Are there any other symptoms?

Like:

  • Pain
  • Loss of appetite
  • Lethargy
  • Abnormalities on the skin or mucous membranes
  • Increased breathing rate (rapid, shallow breathing)

This determines whether the animal should be seen by a veterinarian immediately or whether you can wait a little longer and possibly only support your animal with home remedies. Young animals, very old animals and animals with pre-existing conditions should be checked particularly carefully.

If you want to wait, measure the body temperature several times a day and note the values (fever diary). This way you can keep track and immediately recognize a negative trend.

Home remedies and first aid

Home remedies can be helpful in a wait-and-see approach (mild fever without additional complaints). They can also have a supportive effect during veterinary treatment.

These include:

Offer fresh drinking water

  • Fever often leads to Fluid loss (dehydration). Ensure adequate water intake.
  • In case of loss of appetite, some broth (unsalted, without onions!) can also be added to the water to motivate the animal to drink.

Rest and stress reduction

  • Animals with fever should be able to rest.
  • Avoid hectic activity, high temperatures and physical exertion.

Provide a cool place to lie down

  • Especially in summer, a cool floor helps (e.g. tiles, gel mat).
  • Animals usually instinctively look for a pleasantly cool place.

Slight cooling for very high fever (>40 °C)
Only after consultation with the veterinarian!

  • For dogs: place a damp cloth over the paws or inner thighs
  • Do not wet the whole body! Do not use ice water!
  • Cooling is more difficult with cats – they often react with stress. It is better to cool indirectly (e.g. lower the room temperature)

What should You NOT Do?

  • Under no circumstances should medication from human medicine be used. Due to different metabolic processes between humans, dogs and cats, medications that are not suitable for the animal species can lead to serious, even fatal, poisoning.
    → Paracetamol, ibuprofen or aspirin are poisonous to animals!
  • No calf wraps or alcohol compresses like in humans – this causes more stress and is therefore not very helpful.
  • Do not rely on home remedies alone if the fever is high (>39.5 °C) or lasts longer than 2 to 3 days.
  • The diagnosis and treatment of the cause (e.g. infection, Inflammation, parasites) always belongs in veterinary hands.

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Fever reduction - when and why?

Antipyretic Treatment is not Always Useful

Fever is not a disease, but a natural reaction of the body, for example to defend against infections. It supports the immune system in fighting pathogens such as viruses, bacteria or parasites. Therefore, it is not always useful to lower the fever immediately.

Why Fever is Sometimes Useful:

  • Higher temperatures inhibit the growth of pathogens
  • The immune system is activated more effectively
  • Fever signals that the body is actively fighting a cause

When should You NOT Give Antipyretic Medication?

  • In case of moderate fever (up to approx. 40 °C) and without a significant impairment of well-being
  • If the cause is still unclear – antipyretics can mask symptoms and make diagnosis more difficult
  • Without veterinary consultation – many medications are not suitable for animals or require precise dosing

When is Fever Reduction Useful?

  • In case of high fever above 40–40.5 °C, which puts a strain on the circulation
  • If the animal is Apathy, very weak or at risk (e.g. in young, old or pre-existing animals)
  • In addition to veterinary treatment of the cause (e.g. in infections with antibiotics or anti-Inflammatory conditions)

A targeted treatment of the cause is always more important than simply lowering the temperature.
Fever should not be automatically suppressed, but carefully assessed – preferably in consultation with the veterinarian.

Use of antipyretics

A preventive use of antipyretic medication is pointless and can lead to damage.

Antipyretic Medication for Dogs

In dogs, antipyretic and anti-inflammatory drugs from the group of non-steroidal anti-inflammatory drugs (NSAIDs) can be used in certain cases. Commonly used active ingredients are:

  • Metamizole (Novalgin®) – antipyretic and analgesic, often as an injection or drops
  • Carprofen, meloxicam, firocoxib – anti-inflammatory and slightly antipyretic

These medications may only be administered after veterinary examination and dosage. They are not intended for free use by pet owners!

Antipyretic Medication for Cats

Cats are particularly sensitive to many medications. Only very few antipyretic substances are suitable:

  • Metamizole (in the correct dosage) can be used in cats under veterinary supervision.
  • Other NSAIDs such as meloxicam can only be used safely if the dosage and duration are strictly observed.

Under no circumstances should medication for humans be administered – paracetamol or ibuprofen are highly toxic to cats!

When to see a vet?

If the General condition impaired or other symptoms (see above) are present, veterinary advice should be sought. If the fever lasts longer than three days, the animal should be taken to a veterinarian even if the General condition impaired. An immediate visit to the vet is also indicated in case of high fever. Likewise, very young, old or chronically ill animals should not be waited for, but a professional diagnosis should be made as soon as possible.

Summary of when to see a vet immediately:

  • Fever lasting longer than 2–3 days
  • Temperature above 39.5 °C
  • Apathy, shivering, shortness of breath, loss of appetite
  • Very young, old or chronically ill animals

When is fever an emergency?

The therapy in veterinary medicine

  • Causal treatment: targeted depending on the underlying cause
  • Antibiotics: if bacterial infection is detected or strongly suspected (rational use!)
  • Antipyretic medication (antipyretics/non-steroidal anti-inflammatory drugs. NSAIDs, e.g. metamizole, meloxicam): Only when necessary and under veterinary supervision
  • Infusion therapy: If the animal is dehydrated (exsicosis) or has Circulatory weakness
  • Monitoring of body temperature and General condition impaired
  • Rest and care: rest, fresh water, good room climate

Summary

  • Fever is a symptom, not a disease. Fever is a sign that the immune system is working.
  • Measurement with a digital thermometer in the rectum is the most reliable.
  • If fever and other symptoms are present at the same time, the animal should be taken to a veterinarian immediately.
  • A sole “fever reduction” without treating the cause can be dangerous.
  • The right therapy always depends on the cause (e.g. infection, Inflammation, tumor, autoimmune disease).
  • No self-medication without veterinary diagnosis
  • Never give medication from human medicine

The individual symptom is completely non-specific, but in combination with other symptoms it can be relevant and contribute to the diagnosis of the cause. Use our free Symptom Checker or ask our chatbot Petsi.

Frequently asked questions (FAQ)

  1. How do I know if my animal has a fever?
    Fever is often indicated by Apathy, loss of appetite, shivering or a warm nose. However, it can only be determined with certainty by measuring rectally with a thermometer.
  2. From what point does my dog or cat have a fever?
  • Dog: from about 39.5 °C
  • Cat: from about 39.3–39.5 °C
    Everything above this is considered feverish and should be checked by a veterinarian.
  1. Can I give my animal antipyretic medication from the home medicine cabinet?
    No! Medications such as paracetamol or ibuprofen are poisonous to animals. Never give medication without veterinary consultation. Medicines prescribed by the veterinarian such as metamizole or meloxicam (correctly dosed!) are suitable for reducing fever – and also only if necessary.
  2. What can I do at home if my animal has a fever?
    Fresh water, rest and a cool place to lie down help support the animal. If the fever persists or the animal is very unwell, please always visit a veterinary practice.
  3. Does fever always have to be treated?
    Not necessarily. Fever is a useful defense reaction of the body. Treatment is primarily necessary if the temperature is very high (> 40–40.5 °C), the animal appears weakened or there is a serious illness.

6. How can I measure fever at home?

The most reliable method is rectal measurement with a digital thermometer. Infrared devices (e.g. in the ear or contactless) are significantly less accurate and more suitable for rough orientation.

7. When should I take my animal to the vet?

If the fever …

  • is above 39.5 °C
  • lasts longer than 2–3 days
  • is accompanied by other symptoms (Apathy, shivering, shortness of breath)
  • or the animal is young, old or chronically ill – then a visit to the vet is absolutely advisable.

Bibliography

Literature sources

  • https://www.tfa-wissen.de/kontaktloses-fiebermessen-unzuverlaessig-bei-hund-und-katze
  • Nutt, K. R., Levy, J. K., & Tucker, S. J. (2016). Comparison of non-contact infrared thermometry and rectal thermometry in cats. Journal of Feline Medicine and Surgery, 18(10), 798-803.
  • Kreissl, H., & Neiger, R. (2015). Measurement of body temperature in 300 dogs with a novel noncontact infrared thermometer on the cornea in comparison to a standard rectal digital thermometer. Journal of Veterinary Emergency and Critical Care, 25(3), 372-378.