Rat’s teeth can grow up to 12cm a year, and since they rely on gnawing to keep them down, uneven wear is quite common in rats. Incisors often need to be trimmed to make sure the growth is even, and hard food such as dog biscuits and dry macaroni can help as well. You should be able to tell if your rat’s appetite is normal, or if there are any visible signs of injury around the mouth from overgrown teeth. However, if it is not obvious to you I always suggest that a visit to the vet will do no harm, and in addition your rat can have an all over examination at the same time.