1. Check the overall condition of the cage. It should be clean and not overcrowded.
2. Check the overall condition of the other rats in the cage. None should be sneezing, have red stained eyes or noses, or have breathing problems. Even if only a few of the rats seem ill, that means the healthy-looking ones have still been exposed to the illness, and it is not a good idea to risk that.
3. Look at the rat’s eyes. They should be clear, sparkling, and not runny or clouded. They should not be red-stained.
4. The rat's nose should not be stained with red discharge, which can indicate a respiratory problem.
6. The coat should be shiny and have no missing patches. In a hairless rat or double rex rat, the skin should be smooth and not scaly or flaky.
7. Run your finger up the rat’s back (from tail to shoulders) and look at the root of the hair to make sure there are no lice. Lice appear as little red dots, and their eggs appear as tiny white dots along the hairs on the lower back.
9. Put your ear to the rat’s stomach or back and listen to its lungs. There should be no squeaking or rattling as it breathes.
10. Feel the entire body for lumps that may indicate abscesses or tumors, which are unfortunately quite common in pet rats.
11. When you put your hand in the cage, look to see if the rats come up to investigate you, or run and hide. Properly raised rats should not be afraid of humans, and should run to investigate you.
13. Pick the rat up. It should allow you to do so with little struggling.
14. Hold the rat against your body and cradle your arm underneath it. Does it try to hide? Does it make a run for its cage? Does it walk around on you inquisitively?
15. Some rats, especially young rats or babies, will ‘play-bite’ just like puppies. This is common when they are nestlings (2-5 weeks) but after that it is a bad habit that can be broken but it takes time. It is better to not adopt a rat that nips.
Baby or young rats won’t be as tame as adults who have been handled considerably, but their friendliness will improve with handling from you. They should still be tame enough that you can pick them up and hold them without them running away and trying to jump off you.