How do I know if someone removed me from Twitter?

[Chris H]

I was following a celeb on twitter but now I'm not following them?

[Jenny]

by looking on their or your following lists?

[Ninetales]

The only way that'll happen is if they block you. If they unfollow you, you should still be following them. If they block you you won't be allowed to follow them anymore (if you were following them it will automatically have you unfollow them) and if you mention them in your tweets by putting @theirusername it won't show up on their @Mentions and it won't be clickable on your tweet.