[header] How to check a dog for a fever [title] Prepare the thermometer. [step] Lubricate the tip with petroleum jelly or water based lubricant such as " ky jelly. " lubricating the thermometer will make the experience slightly less uncomfortable for your dog. 
[substeps] If you have a digital thermometer, turn it on and make sure that it is in working order before inserting it into the rectum. Most digital thermometers can read in fahrenheit or celsius.