I've seen loads of posts today from women saying their blood tests didn't show peri etc.
This is the advice from NICE www.nice.org.uk/guidance/ng23/chapter/Recommendations#diagnosis-of-perimenopause-and-menopause
1.2 Diagnosis of perimenopause and menopause
1.2.1 Diagnose the following without laboratory tests in otherwise healthy women aged over 45 years with menopausal symptoms:
perimenopause based on vasomotor symptoms and irregular periods
menopause in women who have not had a period for at least 12 months and are not using hormonal contraception
menopause based on symptoms in women without a uterus.
1.2.2 Take into account that it can be difficult to diagnose menopause in women who are taking hormonal treatments, for example for the treatment of heavy periods.
1.2.3 Do not use the following laboratory and imaging tests to diagnose perimenopause or menopause in women aged over 45 years:
anti-Müllerian hormone
inhibin A
inhibin B
oestradiol
antral follicle count
ovarian volume.
1.2.4 Do not use a serum follicle-stimulating hormone (FSH) test to diagnose menopause in women using combined oestrogen and progestogen contraception or high-dose progestogen.
1.2.5 Consider using a FSH test to diagnose menopause only:
in women aged 40 to 45 years with menopausal symptoms, including a change in their menstrual cycle
in women aged under 40 years in whom menopause is suspected (see also section 1.6).
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I really do recommend reading the NICE guidelines for menopause because although there was a wave of media publicity in 2015 when it was published, it's obvious that many women and their GPs are not aware of the advice in it.