Understanding hormone levels in your blood
Hormone blood tests are not usually needed to diagnose perimenopause or menopause but they can have their uses
- Who needs a blood test for perimenopause or menopause care
- What’s usually measured in a blood test and why
- How blood tests can help monitor the effects of HRT
Blood tests can often tell healthcare professionals a lot about your health. They can be a useful way to check for conditions or can contribute to a diagnosis. However, blood tests are not necessary to diagnose the perimenopause and menopause for most women – diagnosis can usually be confirmed by assessing your symptoms rather than by doing a blood test [1].
Healthcare professionals may recommend a blood test though – the most common reasons for this are to ensure there are no other causes which may explain, or contribute to, your symptoms. For example, low iron or an underactive thyroid gland can cause symptoms of low energy.
It can be confusing to know that some women are offered blood tests, while others aren’t, so read on to understand more about hormone levels in the blood.
Do I need a blood test to diagnose perimenopause or menopause?
Diagnosis of the perimenopause and menopause is usually confirmed by assessing symptoms rather than by doing a blood test. This is because hormone levels in the blood can be very misleading – if you get a normal result this simply means the levels were normal at the time of your blood test, it doesn’t reflect how your hormone levels change at other times during the day or across the month as a whole.
Although various menopause guidelines recommend a Follicle Stimulating Hormone (FSH) blood test for women under 40 years to diagnose Premature Ovarian Insufficiency (POI), levels of this hormone can be low, normal or raised so it is not clinically useful.
Testosterone levels are usually undertaken before starting testosterone so there is a baseline result.
RELATED: How can I diagnose my own perimenopause?
When are blood tests for hormones useful?
The most common reason for doing a blood test as part of perimenopause and menopause care is to check the levels of hormones in the blood when women are taking HRT and testosterone. Specific tests look at levels of oestradiol (oestrogen), testosterone and SHBG (sex hormone binding globulin).
Oestradiol
Oestradiol is the most beneficial form of oestrogen and is important to improve symptoms in perimenopause and menopause and for bone, heart and brain health as well as for reducing your risk of many chronic diseases. Oestradiol is made in your ovaries as well as your brain and other tissues.
RELATED: The power of 3: the role of oestrogen, progesterone and testosterone
During perimenopause, your own oestradiol levels will often fluctuate significantly throughout the month (they can be very high and also very low) whereas during menopause they will usually be consistently low if you do not take HRT.
An oestradiol test measures the level of oestrogen in your body at the time the blood was taken. An oestradiol test is most useful for checking how well oestradiol in a patch, gel or spray is being absorbed in your body.
Whilst the levels of oestradiol can fluctuate, having your level undertaken prior to review appointments will build up a picture of your oestradiol levels over time and allow your clinician to review trends, which can be more helpful than one-off levels.
If your oestradiol level is low and you are still experiencing symptoms, then this suggests that you are not absorbing oestradiol into your bloodstream adequately and you are likely to benefit from either a change in preparation or a change in dose of your oestradiol.
If you are taking oestrogen orally, measuring oestradiol levels is not accurate as the oestrogen is metabolised and processed by your body in a different way.
Young women often need to have higher doses of oestrogen in their HRT to achieve physiological (effective) levels of oestradiol [2].
Testosterone
Testosterone is a hormone produced mainly by your ovaries, brain, adrenal glands as well as other tissues. It can work to improve libido and it can also help to improve mood, energy and concentration, as well as bone and muscle strength.
Testosterone usually is at its highest around the age of 20 years, and levels fall gradually with time. At the age of 40, testosterone levels are approximately half what they were 20 years before. Measuring testosterone, as well as SHBG (below), can help guide treatment with testosterone replacement.
RELATED: The importance of testosterone for women
Sex hormone binding globulin (SHBG)
SHBG is a protein that binds to certain hormones, including testosterone, and it carries these hormones throughout your bloodstream. When hormones are bound to SHBG they are not available for use in your body. If your SHBG levels are low, your body has more unbound sex hormones available for use. If your SHBG levels are high, your body has fewer unbound sex hormones.
Free androgen index (FAI)
Blood tests for testosterone and SHBG levels are usually taken at the same time and a ratio of them is worked out (and multiplied by 100) to give the Free Androgen Index (FAI) score, which is given as a percentage. The FAI score gives clinicians a guide as to how much freely available (unbound) testosterone is present in your body.
On its own, a low testosterone and FAI level doesn’t mean you always need to take testosterone. However, if you have symptoms suggestive of testosterone deficiency such as fatigue, memory problems, brain fog, reduce stamina, muscle and joint pains and reduced libido, and you also have low testosterone and FAI, it’s likely you may benefit from taking testosterone.
Testosterone levels are usually undertaken regularly when women are prescribed testosterone to ensure levels are maintained within the normal female range. If your level is low and you are still experiencing symptoms, despite taking testosterone, then you may need to use a higher dose of testosterone.
If your level is raised and you are not experiencing any side effects from taking testosterone, then you are likely to be advised to repeat the blood test rather than stopping testosterone.
Hormone levels – oestradiol and testosterone – can fluctuate even in women who are menopausal taking HRT so results need to be interpreted in clinical context rather than in isolation.
RELATED: Testosterone: the missing piece of the jigsaw
Follicle Stimulating Hormone (FSH)
FSH levels are sometimes undertaken to help diagnose menopause in younger women with POI. FSH is a hormone produced by your brain to stimulate your ovaries to produce hormones. It usually becomes raised when you are menopausal. However, levels of FSH can really fluctuate and while a raised level can be helpful to make a diagnosis, a low or normal level does not exclude the possibility of you being perimenopausal or menopausal.
What are normal ranges of hormones?
In most cases, it is beneficial to achieve ‘physiological’ levels, which means levels of oestradiol similar to women who have periods. Generally, this means oestradiol levels of approximately 110-1300 pmol per litre [3], but optimal levels really vary between women. Research suggests the optimal level for symptom relief is around 400 pmol/L for most women [4, 5]. However, some women will feel better with higher levels.
Levels of testosterone and SHBG vary between women but generally total testosterone should be less than 2.6nmol/l and FAI less than 5%. In practice the clinical response to testosterone is more important than a one-off blood test result, assessing improvement in symptoms and whether there are any side effects to treatment.
How might my test results affect my treatment?
If you are taking HRT and your blood tests reveal your hormone levels are low, your healthcare professional may suggest changing the dose or type of your HRT. Your clinician will consider the whole clinical picture, how you feel and how your symptoms have changed, to help decide the best course of action and to individualise your care.
For instance, studies show there is a wide variation in the efficiency of transdermal drugs [6] – some women do not absorb oestradiol in the gel, patches or spray as easily as others, so often will need a higher dose to penetrate the skin and become absorbed into the bloodstream. Other women metabolise hormones at different rates so may need to have higher doses to achieve the same levels.
Newson Health’s research on absorption highlighted that some women need higher doses than others for adequate absorption through their skin. Also it showed that measurement of blood levels of oestradiol can be beneficial to identify women who use higher and also off-label doses of oestradiol [7].
RELATED: Newson Health: HRT is not a one-size-fits-all treatment
In addition, testosterone and SHBG tests are usually carried out at frequent intervals (at least annually) to ensure levels are kept in the normal range for women who use testosterone as a gel or cream.
RELATED: Hormones, HRT and advocating for yourself
References
- NICE (2015)
- Kaunitz, Andrew M. MD. Transdermal and vaginal estradiol for the treatment of menopausal symptoms: the nuts and bolts. Menopause, 19(6) pp. 602-603, June 2012. | DOI: 10.1097/gme.0b013e31824c8a5a
- Kuhl, H. (2005), ‘Pharmacology of estrogens and progestogens: influence of different routes of administration’, Climacteric, 8(1): pp3-63. DOI: 10.1080/13697130500148875
- de Lignieres, B. (1996), ‘Hormone replacement therapy: clinical benefits and side-effects’, Maturitas, 23 Suppl: pp. S31-6. DOI: 10.1016/s0378-5122(96)90012-2.
- Steingold, K.A., et al. (1985), ‘Treatment of hot flashes with transdermal estradiol administration’, J Clin Endocrinol Metab. 61(4) pp. 627-32. DOI: 10.1210/jcem-61-4-627.
- Singh I., Morris A.P. (2011), ‘Performance of transdermal therapeutic systems: effects of biological factors’, Int J Pharm Investig, 1(1):4-9. DOI: 10.4103/2230-973X.76721
- Glynne S., Reisel D., Kamal A., Neville A., McColl L., Lewis R., Newson L. (2024), ‘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. doi: 10.1097/GME.0000000000002459. Epub ahead of print. PMID: 39689249.
Written byDr Louise Newson