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Written by Dr Toni Hazell

In medicine, we like testing things. We make diagnoses and plan treatment regimens based on values of blood sugar, cholesterol or blood pressure, and in many cases our services are resourced based on the numbers that we achieved. 

In the world of menopause however, numbers are less important and we might consider sociologist William Bruce Cameron’s quote – “Not everything that can be counted, counts. Not everything that counts can be counted”¹ to be relevant. We know that women can have symptoms of the perimenopause with a normal follicle stimulating hormone (FSH)², and that there is no reason to test an FSH when diagnosing menopause or perimenopause over the age of 45³. We don’t titrate doses of hormone replacement therapy (HRT) to FSH levels and whilst we do monitor testosterone levels before and after prescribing it, this is largely to check that levels aren’t too high, rather than to adjust the dose to match a particular blood level⁴.

So what about serum oestradiol? Is there ever a reason to test it in women who are taking HRT, and if so, what should we do with the result? What should we do if a woman presents requesting an oestradiol level, because she feels that her HRT dose is too low? GP training reminds us not to request a test unless we know how it will change our management, so it’s important to know what you would do with a normal or abnormal result before you request a test. 

Let’s start with a physiology recap. There are four types of oestrogen found in the body: estrone, 17β-oestradiol, estriol and estetrol. Estrone and oestradiol are the most important after the menopause, with estriol being less potent and estetrol only naturally produced during pregnancy. Menopausal women have more estrone than their pre-menopausal counterparts and estrone is not measured when we request a serum oestradiol,⁵ so we are not getting a full picture of all of the oestrogen in the body. There is no clear correlation between oestradiol level and symptoms, which, particularly in the perimenopause, are related to fluctuation in levels rather than just the absolute number⁶. We also can’t say that a given oestradiol value will protect from future osteoporosis⁵. It isn’t even clear whether we know what ‘normal’ is in the perimenopause, as oestradiol values can range from low to supraphysiological⁴, so we might be able to give our patients a number but explaining what that number means might be harder. 

Thinking about the start of a menopause journey, there is very little need for blood tests. We don’t use serum oestradiol to diagnose (peri)menopause in women aged over 45. We also shouldn’t use it to try and say how far through the process a woman is, or to predict or manage her risk of osteoporosis. It also shouldn’t be checked in women taking combined hormonal contraception, nor in those taking oral HRT, because much of the oestrogen in oral HRT is metabolised to estrone⁵. Our holistic GP skills are much more useful than reaching for the blood test – listening to the woman, exploring her symptoms, taking into account any biopsychosocial aspects and using your knowledge to help her reach a shared decision take longer than reaching for a blood form, but will be much more useful. 

So is testing oestradiol ever useful? Perhaps. We know that there is variability in how women absorb oestrogen given transdermally, be that via a patch, gel or spray as up to 20% of women may be poor absorbers⁷. For this cohort of women, a higher than average dose of oestrogen given transdermally may be appropriate⁷, or, if they have no risk factors for venous thromboembolism, they may benefit from a switch to oral HRT. So if you have a patient given transdermal HRT for clear menopausal symptoms, which have not improved at all over at least three months of therapy at a reasonable dose (and you have checked adherence, that she is applying the gel/spray appropriately, or her patches aren’t falling off), it might be worth checking serum oestradiol⁸. You are looking for a very low result, such that you might see in a menopausal woman not taking HRT, which would suggest poor absorption of her HRT causing the lack of effect. Reference ranges can vary by laboratory but a level under 180-200 pmol/L might suggest poor absorption^7,9. International guidance also suggests that testing may be useful in women with a premature (under 40)¹⁰ or early (under 45)⁸ menopause, if it is needed to make the diagnosis in combination with an FSH test. 

As with any test, think before you tick the box on the blood form. Do you know why you are considering testing serum oestradiol, what you will do with the result, and how it will change your management? If not, stop and think; perhaps your patient needs advice from a specialist rather than a number in your pathlinks that you might not know how to interpret. 

References

1. Cameron, William. Informal sociology, a casual introduction to sociological thinking. 1963.
2. RefHelp. FSH Testing for Menopause and Contraception. March 2025. [Accessed October 2026].
3. NICE. NG23. Menopause: identification and management. April 2026. [Accessed October 2026].
4. BMS. Testosterone replacement in menopause. May 2026. [Accessed October 2026].
5. BMS. Measurement of serum estradiol in the menopause transition. July 2025. [Accessed October 2026]. 
6. Patel P, Patil S, Kaur N. Estrogen and Metabolism: Navigating Hormonal Transitions from Perimenopause to Postmenopause. J Midlife Health. 2025 Jul-Sep;16(3):247-256.
7. Glynne S, Reisel D, Kamal A et al. The range and variation in serum estradiol concentration in perimenopausal and postmenopausal women treated with transdermal estradiol in a real-world setting: a cross-sectional study. Menopause. 2025 Feb 1;32(2):103-111.
8. Panay N, Fenton A, Hamoda H et al; IMS Recommendations Writing Group. International Menopause Society (IMS) recommendations and key messages on women's midlife health and menopause. Climacteric. 2025 Dec;28(6):634-656.
9. South Tees Hospitals NHS Foundation Trust. Oestradiol. April 2022. [Accessed October 2026].