Agree with Lilbird he may have eaten something that disagreed with him or perhaps picked up a virus. Whilst you are at the vets you could perhaps ask them to worm him for you.

A light diet of cooked white fish (with/withour boiled rice) and or cooked chicken for 24 hours may help.

Let us know how you get on.

By the way Adovcate is a spot-on treatment for fleas and worms so you may want to consider that instead of tablets!

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Kaz

For kittens, joy is for the asking and smiles are for the giving