If someone's a danger to themselves but gives no verbal confirmation that they are, what are the appropriate steps a health professional would take?

If you think someone is at risk for serious harm to themselves but they never say anything about it/admit to it what do you do? Like I guess for an example if someone who is normally super hypervigilant and anxious comes in one day and is abnormally calm and trys to like give you their favorite sweater what would be the appropriate way to respond? And if you ask them if they plan to harm themselves and they say no but, you know they're lying can and do they get sent to a mental health facility? I'm just super curious what would happen in this scenario.