In the USA, I know if the T is a licensed psychologist (or a medical doctor) they just have to sign the form and you are given a 72 hour hold.

It's up to whether your T decides you need it or not.

If you can change your thinking a bit, and how you say things, such as (if it's true only) "I feel SOOOOO bad I think being dead would feel better." Instead of, "I'm going to end this feeling bad." A threat is also against the law, btw.

Many ppl "just" need more help through the dark times. Many Ts don't have that time to give.
Hospitalization is one way to keep you safe, and hopefully make some others changes with you about life, so you don't feel so bad in the future.