Hello,
I have 3 cats and two of them have been unwell since yesterday morning, they aren't feeding properly and are being very lethargic. They are both 4 years old. They had injections that indicated to may have side effects but this was a week ago could this still be related?
Thanks.

It is wise to monitor animals after injections. Please call your vet asap. There are some circumstances where lethargy can be an indication of something serious. Without more information, it would be difficult to tell.

Hi, laurab,
I do agree with your previous answer.
Please call your Vet. You didn't mention the name of the medication injection, so it's difficult to search the web, finding any side effects.
Medications can sometimes cause these symptoms, but without more info, it's hard to tell.
Again, I second the idea of calling your Vet, explaining it to him/her, and getting their opinion. I do wish you and them the best.