A newborn puppy can’t regulate their own body temperature until they are 2 weeks old though some puppy require up to 3 weeks old before their temperature is stable. To help them regulate you can use either a heating pad, a whelping pad, or a heating lamp recommended by your vet. Personally I used both whelping box and heating lamp, depending on the room temperature.
At 1st week old the puppy temperature should be around 94-98 degrees and it will increase each day, by the 3rd week the temperature should be around 99-100 degrees. Afterward their body temperature will be the same as an adult dog’s, which is around 99-102.5 degrees.
How to take puppy temperature
All you need is a rectal thermometer (digital being the easiest) and a lubricant, either baby oil, Vaseline or petroleum jelly. Apply the lubricant at the tip of the thermometer and gently insert into the rectum and wait for the reading. After usage remember to wipe clean the tip of the thermometer and disinfect it with alcohol or similar disinfectant.