I am on Zoely which contains a relatively low dose of estradiol, and blood tests can be helpful in certain cases when on oral estradiol.
I did test my estradiol on Zoely in my early 40's for two reasons - to make sure I had adequate levels for bone protection, and also because I wanted a baseline level whilst I felt good, so I know what I am shooting for in the future.
I am very happy that I tested, I have consistent estradiol levels of around 400pmol/L which I am happy with for quality of life plus optimal health of all estrogen responsive tissues.
However it is worth knowing that when premenopausal women with healthy ovaries take a combined pill like Zoely, although they are not ovulating, their ovaries are sleeping not dead, and there is a basal low level of ovarian estradiol being secreted, which can be around 100pmol/L.
If someone with failing or postmenopausal ovaries takes Zoely ie 1.5mg of estradiol, this is all they will have, and it's low.
Bone protection has been studied in young women on Zoely, and they didn't lose (or gain) any bone.
However I probably wouldn't rely on 1.5mg oral estradiol if I had no or poor ovarian function, and this may be what is happening in your situation.
I therefore test yearly to make sure I am still therapeutic and if my estradiol starts to decline I would not hesitate to add a patch, which some private specialists would support with endometrial monitoring. The progestin in Zoely is potent enough to carry this, and in fact I would only be replacing what I had lost due to my ovaries having failed in the background, however this would not be available on the NHS.
Obviously if I had become completely menopausal I would no longer require menstrual suppression, however I plan to remain on Zoely until my mid 50s to make sure.
I will also add that my testosterone was virtually zero on Zoely because with any combined pill your ovaries are suppressed, resulting in a loss of androgen production.
This may also be contributing to the symptoms you describe. As there is no safety data for testosterone in combination with an OCP, but there is for DHEA, plus the much lower cost and ease of access, I take DHEA alongside my Zoely which has replenished my testosterone levels to the upper quartile of the female healthy range.
Finally many complaints on the combined pill such as hypoestrogenic symptoms in perimenopausal women are due to the medication only being used for 21 or 24 days out of 28, so I would make sure you are either tossing the 4 yellow dummy pills like I do (the clue's in the name), or if you love spending every 4th week bleeding you could maybe try an estradiol patch during the pill free days if you can get this.
