Seeing your dog looking unusually tired, restless, or uncomfortable understandably leaves you searching for answers on how to help. Knowing how to take your dog’s temperature is an important first step in helping her.

What Is a Normal Temperature for a Dog?

The normal body temperature for a dog is considered between 99.5 and 102.5 degrees Fahrenheit, according to the Merck Manual of Veterinary Medicine.

What Is the Best Way to Take a Dog’s Temperature?

You’ll most likely use a digital thermometer, which you can find online or at pet supply store for about $10 to $20, to take your dog’s temperature in one of these three ways:

1. Rectal temperature: considered the most accurate and reliable method by veterinarians because it measures your dog’s core body temperature.
2. Ear temperature: considered reasonably accurate but generally less precise than rectal temperatures due to variations in ear-canal anatomy, the presence of hair or wax, and positioning issues.
3. Armpit temperature: measures the surface temperature, so it is consistently lower than the rectal temperature and is considered less reliable for core body temperature.

“A rectal temperature using a digital thermometer is considered the gold standard ,” according to Dr. Rebecca Greenstein, chief veterinarian of Kleinburg Veterinary Hospital in Ontario, Canada, and  veterinary medical advisor for Rover.com.

While you may be tempted to use an ear thermometer for convenience, they are often less reliable and can be difficult to use correctly.

How to Take Your Dog’s Rectal Temperature

To take your dog’s rectal temperature, in addition to a digital thermometer, you need a lubricant (like petroleum jelly), and a helper to keep your dog calm.

Follow these steps to take your dog’s rectal temperature:

1. Apply a small amount of lubricant to the tip of the thermometer.
2. Have your dog stand or lie on his side. Ideally, a helper can gently restrain him while offering reassurance and treats
3. Gently lift your dog’s tail and insert the thermometer about one inch into the rectum.
4. Hold the thermometer in place until it beeps, indicating a final reading.
5. Remove the thermometer, clean it with rubbing alcohol or soap and water, and record the reading.

However, VCA Animal Hospitals warns, “If you feel stool in the rectum, try to place thermometer around the fecal matter rather than through it, to ensure an accurate reading. If the pet clamps their anal sphincter, do not force the thermometer into the rectum to avoid injury and pain for the pet.”

What a Dog’s High Temperature Means

“An elevated thermometer reading in an otherwise normal dog may be from anxiety, stress, panting, trembling/shaking, or hot weather. It can also be a sign of heatstroke, infection, inflammation, immune-mediated disease, or certain cancers,” according to Dr. Greenstein.

Remember that a fever is not an illness, but rather a symptom that your dog’s body is fighting something. As Dr. Greenstein notes, high temperatures can be caused by a variety of factors.

Common causes of a high body temperature in a dog include:

• Infection: This is the most common cause. Infections could be a bacterial, viral, or fungal infection.
• Inflammation: Conditions like pancreatitis or arthritis can cause a fever.
• Toxins: Ingesting poisonous plants, certain human foods, or other toxic substances.
• Vaccination: A mild, temporary fever is a common side effect of a recent vaccination.
• Heatstroke: This is an emergency. A temperature of 106°F (41.1°C) or higher is critical and requires immediate cooling and veterinary care.

What a Low Temperature Means

While it’s less common than fever, a low temperature is just as serious. According to the American Red Cross, signs of hypothermia in dogs include body temperature below 98.5 degrees , decreased heart rate, dilated pupils, shivering, unconsciousness or coma, and weak pulse. While dogs can cope with small changes in body temperature, a large or sudden drop can be life-threatening. The serious effects of sustained hypothermia can include a slow, irregular heartbeat, kidney and gut damage, blood clots, and a reduced ability to fight infection.

If you suspect that your dog may be suffering from hypothermia, the Red Cross recommends that you follow these steps:

1. Check your dog’s ABCs, (airway, breathing, and circulation and perform CPR as needed.
2. Take your dog’s temperature; below 98.5 degrees indicates hypothermia.
3. Wrap your dog in a blanket. Place water bottles (wrapped in towel) next to the dog.
4. Take your dog to the veterinary hospital immediately.

When Should You Take Your Dog to the Vet?

You should contact your veterinarian immediately if your dog has a temperature of 104°F or higher or below 99°F, says Dr. Greenstein. However, beyond those extremes, “A lot of it depends on context. If your calm pet has a slightly elevated temperature [of 103.1°F ] or your usually excitable panting dog has a slightly decreased temperature [99.86°F], and is lethargic, not eating, having tummy upset or any unusual behavior, then I’d be concerned enough to have that patient seen by your family doctor.”

Remember that despite your concern, never give your dog Tylenol (acetaminophen) or other human fever reducers like ibuprofen. These are highly toxic to dogs and can be fatal.

As in all cases if you have concerns about your dog’s health or think he or she may be in danger, the best course of action is to contact your veterinarian for professional guidance.