When your dog is unwell, their body often shows it before any obvious symptom appears. Fever in dogs is one of those warning signs worth knowing how to recognise, because acting in time can be important.
The problem is that, unlike humans, dogs cannot tell you they feel ill, and many of the symptoms of canine fever are easy to mistake for simple tiredness or a quiet day. In this article you will find everything you need to know to spot fever in your dog, understand what causes it and know when it is urgent to go to the vet.
What is fever in dogs?
Fever in dogs is a rise in body temperature above normal values as a response of the immune system to an infection, inflammation or another pathological stimulus. In practical terms, we speak of fever when the rectal temperature exceeds 39.5 ºC, although the normal range in dogs is between 38 ºC and 39 ºC. Contrary to what many people believe, fever in itself is not the problem: it is a defensive response of the body, a sign that it is fighting something. The problem arises when that temperature soars or stays high for too long, because it can then damage vital organs.
When fever can be dangerous
A moderate fever, between 39.5 ºC and 40.5 ºC, is uncomfortable for the dog but does not pose an immediate danger if it is detected and treated in time. The critical threshold is 41 ºC: from that temperature, the risk of organ damage becomes real and the situation requires urgent veterinary attention. Very high fevers can cause seizures, organ failure and, in extreme cases, death. That is why it is not enough to know that your dog has a fever: you need to know what to do next.
Normal temperature in dogs
The normal temperature range in a healthy adult dog is between 38 ºC and 39 ºC. Some dogs may naturally have a slightly higher or lower temperature without this indicating any problem, but any reading above 39.5 ºC should be taken seriously. In puppies, the baseline temperature may be somewhat higher. Factors such as stress, intense exercise or ambient heat can also raise the temperature temporarily without any underlying illness.
Symptoms of fever in dogs
The most reliable way to tell whether a dog has a fever is to take its rectal temperature with a thermometer, but there are symptoms that can alert you that something is wrong before you reach for the thermometer.
Physical signs
- Dry, warm nose (although this sign alone is not reliable)
- Red or watery eyes
- Ears that feel hot to the touch
- Trembling or shivering for no apparent reason
- Excessive panting without having exercised
Behavioural signs
- Noticeable lethargy or apathy
- Loss of appetite
- Withdrawing from others or seeking out cold surfaces
- Refusing to move or play
If you notice several of these symptoms at the same time, it is time to take the temperature and decide whether you need to go to the vet.
How to take a dog's temperature
The only reliable way to confirm whether a dog has a fever is with a rectal thermometer or an ear thermometer made specifically for animals. A warm nose or red eyes can give you a clue, but they are not a diagnosis.
Step by step
- Use a digital thermometer with a flexible tip
- Apply lubricant (petroleum jelly or lubricating gel)
- Gently insert the thermometer into the rectum about 2-3 cm
- Wait until it beeps (usually less than a minute)
- Read the result and note the time
If the thermometer reads above 39.5 ºC, the dog has a fever. If it exceeds 40 ºC, call the vet. If it exceeds 41 ºC, go straight to the emergency clinic.
Causes of fever in dogs
Fever is a symptom, not a disease in itself. It can be caused by a wide variety of situations:
- Bacterial or viral infections (parvovirus, distemper, leptospirosis, etc.)
- Internal inflammation (pancreatitis, inflammatory bowel disease)
- Reactions to vaccines (especially in the first 24-48 hours)
- Toxins or poisons (ingestion of toxic substances)
- Tumours (in cases of persistent fever with no apparent cause)
- Autoimmune diseases
- Heatstroke (although technically not a fever, it raises the temperature just the same)
What should I do if my dog has a fever?
Once a fever is confirmed, the first thing is not to panic and to assess the situation.
At home (mild fever, below 40 ºC)
- Offer plenty of fresh water to prevent dehydration
- Take your dog to a cool, quiet place
- Apply damp (not cold) cloths to the paws and ears
- Monitor the temperature every hour
- Do not give human medicines (paracetamol, ibuprofen): they are toxic to dogs
When to go to the vet
- Temperature above 40 ºC
- Fever that does not go down within 24 hours
- Additional symptoms: vomiting, diarrhoea, seizures, difficulty breathing
- Puppy under 6 months old with a fever
- Senior dog or dog with a chronic illness
Fever in dogs: frequently asked questions
Can I give my dog paracetamol if they have a fever?
No. Paracetamol is highly toxic to dogs and can cause serious liver damage even in small doses. Never give your dog human medicines without veterinary advice.
Does a cold nose mean there is no fever?
Not necessarily. The temperature of the nose can vary depending on the environment, hydration level or activity level. Only a thermometer can confirm or rule out a fever.
Can dogs pass their fever on to me?
Most of the illnesses that cause fever in dogs are not zoonotic (they are not transmitted to humans). There are exceptions such as leptospirosis, which is why it is important to wash your hands after handling a sick dog and to follow your vet's instructions.
How long can a fever last in a dog?
It depends on the cause. A fever associated with a vaccine reaction usually disappears within 24-48 hours. A bacterial infection may require antibiotic treatment. If the fever lasts more than two days, you should always consult the vet.
