Early cycle blood test before starting letrozole

[Tulpabean]

Long story short - when you've to try and have a blood test as soon as your period starts, what cycle day do they want you on? I'm stuck with going on day 4 at the earliest because of the weekend, and worried that's too late.

The longer version if it matters -
I've got PCOS and receiving treatment at my local NHS fertility clinic. I was told to book in for one last blood test when my next period came, and then start letrozole the period after that if the result of the bloods is fine. I've waited blooming 86 days for this period to come so I can get the test done and sods law, it started at 6pm last night (Friday). I obviously now can't even begin booking the blood test til the clinic reopens on Monday, which will be cycle day 4 by then. Is that too late in the cycle for this type of test? I feel like cycle day 2 or 3 rings a bell for the ideal test date. I'll be so disappointed if I miss the cut off after all this waiting :(

[physicskate]

Nope, you're fine to go ahead. I always counted cd1 as the day I woke up bleeding (because this is how it was judged at my clinic. So by that, you're day 3!

[Nan0second]

Saturday is day 1 as it’s the first full day of your period so don’t worry... Monday will be fine.
Will they let you use norethisterone to induce a period if you haven’t had one after 35 days? It seems ridiculous to be waiting like this.