does day of testing matter when on HRT?

Another question about HRT: my hormone specialist always tells me to go to the lab for testing on day 21 of cycle. I know that is when progesterone levels are supposed to peak provided you have a regular 28 days cycle...but is the day really relevant once on HRT?

Also, as far as I understand, estrogen levels start falling after ovulation (which occurs around day 14), so why have them measured on day 21...?

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Anna69,

I'm sorry you've had no replies. Feel free to repost your questions.