I usually use a first name. Names in my country can be quite long and first names aren't necessarily legal names.

I have only given identifiable names when:

1) A close friend sought therapy at the same clinic so T could check if they were assigned to her

2) A abusive former friend who is T's colleague because there was a huge chance I could run into her at an event held by the clinic where I would be one of the guests talking about lived experiences.

3) T asked the name of a well known therapist who harmed a close friend