You just don't ask. You bring up your symptoms and troubles, and then, they, knowing your health history, physical and emotional, will prescribe what works best for your body.

Fast acting, or not, it's up to the prescribing doctor to know what's best for you.

And by fast acting, being on it myself, as a long term anxiety med, it's not like *poof*, oh wow, I feel better. It's just there. Don't feel a thing, just know that anxious feeling is not there, too.