In the US I've been surprised recently with how much you can say before they need to directly intervene. Very different than years ago. If you are underage, of course, that makes a difference, but as long as you're an adult you can basically say yes I've been thinking about suicide, yes I have a plan and a date set, and even then you will probably walk away unhindered. You want to avoid saying that you intend to do it in the immediate future (like next few days or less) and have everything you need. The more lethal and accessible means you report planning to use, the more concerned they will be. If you say you are still making preparations or the date is at least a few days off, and don't show signs of risk of impulsive attempts right away, they generally don't have enough for an involuntary hold.
One thing to watch out for—If you have a gun, be careful about divulging that, because in some states they can confiscate it until you are cleared by a court to no longer be a danger to yourself. Definitely a concern to me.
If you really want help and want to give it your best shot, be as honest as you can. Within the last month, I not only admitted previous attempts, I told them about an attempt the week before and told them I was still thinking about it all the time and ways I had considered doing it (again—I did not mention guns). They asked about who I had to stay with me/sources of support and talked about who to call in a crisis. I always feel like why not agree to whatever safety plan they request, you don't have to actually follow it when the time comes, after all. I don't know if I really think they can help me but I promised my husband I would try everything first.
Some providers have a higher comfort level than others with frank discussion of suicidal intent, and some have a lower threshold for intervention than others, so feel them out as you go. If you are a minor, all bets are off, keep your mouth shut unless you want your parents notified and advised to admit you somewhere.
Good luck!
