When people bring young kittens into the clinic, the first question I am asked is ‘How old are they?’ Here are the guidelines I use to determine age in very young kittens.
1) In normal development, kittens open their eyes around two weeks of age. The kittens pictured below are less than two weeks old since there eyes are still sealed shut (sorry but the picture is slightly out of focus).
2) At three to four weeks of age, baby teeth start to erupt. The small teeth in the front of the mouth are called incisors. They are the first ones to erupt. I commonly see the gums swell at three weeks, the tips of the tooth poke through at three and a half weeks and the entire tooth exposed at four weeks.
3) The next type of deciduous (baby) tooth to erupt are the premolars. They appear at five to six weeks of age. I always know when these teeth are coming in because the kittens chew on the bottle. They force the nipple into the back of their mouth and grind away.
4) Some of my colleagues use weight as an additional factor to determine age. I only use weight to monitor growth and feeding schedules, not for age.