Fever

    A dog's normal temperature is 100 degrees to 102 degrees. Any temperature your dog has above or below that indicates that your dog is sick. But it is unlikely that your dog would have just a fever. This could just be a symptom of another disease. But it could also be another thing altogether. Since you put the thermometer through your dog's anus, a rise in temperature could also mean your dog is constipated.  
    First you take your dog's temperature, then you retake it to make sure that your thermometer read your dog's temperature correctly.  Give your dog 1 teaspoon of mineral oil to ease the pain if it's constipation. Don't do anything that may upset your dog. Retake her/his temperature the next day, and if the temperature is worse, take her/him to the vet. Also, if new symptoms appear, take him/her to the vet.