Menopur- when to start?

[Jennifer48]

I am going to have an embryo transfer via the natural cycle. According to my treatment plan, I have to start Menopur injections on the evening of the second day of my period. My period started yesterday (Saturday) evening, very late (around 10 p.m.) and VERY light. I don’t know whether to start Menopur this evening or tomorrow - would yesterday evening count as the first day of period? I can't get hold of a doctor today, as it's Sunday.
Thank you in advance

I was told that anything before 7pm is considered today and anything after 7pm-tomorrow

usually the first day is the full day of bleeding. It counts as day zero if it starts in the afternoon

Thank you for your answers. No need for any more responses, I have seen my doctor. Thanks again.