Most women I see in clinic who are perimenopausal have already spent months feeling "off" before they book an appointment. The fatigue, the broken sleep, the cycles that suddenly make no sense. And many have already been told their blood tests came back "normal."
The reality is more complicated than that. Perimenopause changes your body in ways that don't always show up on a standard five-marker hormone panel. Understanding which tests are genuinely useful, and which have real limitations, puts you in a far stronger position when you sit down with your GP.
What Is Perimenopause?
Perimenopause is the transitional phase before menopause, when your ovaries gradually produce less oestrogen and progesterone. It commonly begins in the mid-forties, though some women notice changes earlier. The average age of menopause in the UK is 51 [NICE NG23, 2024].
If menopause occurs before the age of 40, it's classified as premature ovarian insufficiency (POI), which means the ovarian reserve has depleted much earlier than expected. POI affects roughly 1 in 100 women and carries significant long-term risks for bone density, cardiovascular health, and neurological function. It requires a different diagnostic approach and more urgent treatment.
Common symptoms of perimenopause include:
Irregular periods (longer gaps, heavier or lighter bleeding, or skipped cycles)
Hot flushes and night sweats
Sleep disturbance
Mood changes, irritability, or low mood
Difficulty concentrating or "brain fog"
Reduced libido
Joint aches and dry skin
These symptoms overlap heavily with thyroid conditions, iron deficiency, vitamin D depletion, and even early diabetes. That overlap is exactly why a broader blood panel can be so valuable.
Does the NHS Test for Perimenopause?
The updated NICE guideline on menopause (NG23, revised 2024) is clear: for women aged 45 or over with typical menopausal symptoms, the diagnosis should be made clinically, based on symptoms alone, without routine blood tests.
This isn't a gap in care. It's a deliberate clinical decision. Hormone levels during perimenopause swing wildly from one week to the next, so a single blood test can easily give a misleadingly "normal" result. Your GP knows this, and that's why they may not offer hormone testing if your symptoms and age fit the pattern.
But here's where private testing can genuinely add value. If you want a broader picture, if your symptoms overlap with other conditions, or if you're preparing for a conversation about hormone replacement therapy (HRT), a well-chosen blood panel gives you data that a clinical assessment alone can't provide.
Which Blood Tests Are Useful in Perimenopause?
Not every hormone test is equally helpful at this stage. Here's what I include when I'm building a panel, and why.
FSH (Follicle-Stimulating Hormone)
FSH rises as your ovaries produce less oestrogen, because your pituitary gland is working harder to stimulate egg production. An elevated FSH can support the clinical picture of perimenopause, but there are important caveats.
A single FSH reading has limited diagnostic value during the perimenopausal transition. FSH is released in pulses throughout the day, and levels fluctuate significantly from one cycle to the next. One "normal" result doesn't exclude perimenopause, and one elevated result doesn't confirm it.
The NICE guideline reserves FSH testing for specific clinical situations. If you're under 40 and experiencing symptoms, your GP should check FSH to investigate possible POI. In that context, two separate FSH readings above 25-30 IU/L, taken four to six weeks apart, alongside a history of irregular or absent periods for at least three to four months, support a diagnosis [Davies et al., 2017]. This threshold is a diagnostic tool for POI and early menopause, not a general marker for perimenopause in women over 45.
It's also worth knowing that FSH results are unreliable if you're taking the combined contraceptive pill or high-dose progestogens, because these suppress the hormonal signals that FSH measurement depends on.
Oestradiol (E2)
Oestradiol is the primary form of oestrogen produced by the ovaries. During perimenopause, levels become erratic before eventually declining. Like FSH, a single oestradiol reading is a snapshot, not a full story. But when interpreted alongside FSH, your symptoms, and your cycle history, it strengthens the overall picture.
LH (Luteinising Hormone)
LH works alongside FSH to regulate ovulation. The ratio between FSH and LH can provide additional context. In perimenopause, FSH typically rises faster than LH, so an elevated FSH-to-LH ratio adds another piece to the puzzle.
Testosterone
Testosterone plays a role in libido, energy, and mood in women, and levels do decline gradually with age. But testing testosterone as a routine baseline is not straightforward.
The British Menopause Society (BMS) is specific on this point. Blood levels of testosterone don't reliably correlate with symptoms of low sexual desire in women, because much of testosterone's activity happens locally within tissues rather than in the circulating blood we measure with a standard test [BMS, 2024].
The established clinical pathway is clear. If low libido is a concern, the first step is a full assessment to consider psychological, relational, and medication-related causes (SSRIs are a common culprit). The next step is a trial of conventional oestrogen-based HRT, because oestrogen therapy itself often improves libido, particularly when switching from oral to transdermal oestrogen, which reduces sex hormone-binding globulin (SHBG) and frees up more circulating testosterone. Testosterone supplementation is only considered if low libido persists after an adequate trial of oestrogen HRT, and only for hypoactive sexual desire disorder (HSDD) that causes personal distress [BMS, 2024].
So if loss of libido is one of your main symptoms, the blood test to focus on first is oestradiol. Testosterone testing comes later in the pathway, guided by your prescribing clinician. There is currently no evidence supporting testosterone therapy for general fatigue or brain fog in perimenopausal women.
Thyroid Function (TSH, Free T4, Free T3)
This is one of the most important additions to any perimenopause panel. Thyroid disorders, particularly autoimmune hypothyroidism, are common in midlife women and cause symptoms that look almost identical to perimenopause: fatigue, weight changes, mood disturbance, and irregular periods.
Checking a full thyroid panel helps separate hormonal symptoms from thyroid dysfunction, which is straightforward to treat once identified.
Ferritin
Ferritin measures your iron stores. Many perimenopausal women experience heavier or more frequent periods, which can gradually deplete iron levels without triggering full-blown anaemia. Low ferritin is one of the most common treatable causes of fatigue, and it's frequently overlooked.
Vitamin D
As oestrogen declines, its protective effect on bone density diminishes. Vitamin D is essential for calcium absorption and bone health, and deficiency is widespread in the UK, particularly in winter months. Checking your vitamin D level allows for targeted supplementation before bone density becomes a concern.
HbA1c (Glycated Haemoglobin)
HbA1c measures your average blood sugar control over the previous two to three months. The decline in oestrogen during perimenopause is associated with changes in fat distribution and an increased risk of developing insulin resistance. Catching pre-diabetes early gives you the chance to intervene with diet and activity before it progresses.
Understanding Your Results
A point that's often missed in direct-to-consumer testing: a result that falls outside the laboratory reference range doesn't automatically mean something is wrong.
Reference ranges represent the middle 95% of results from a healthy population. That means 5% of completely healthy people will produce an "abnormal" result by pure statistics. And for hormones like oestradiol and FSH, which fluctuate dramatically during perimenopause, a single out-of-range reading is expected rather than alarming.
Your results need context. What matters is how different markers relate to each other, how they fit with your symptoms, and how they compare over time. A Brooksby report explains what your results mean together, not just whether each number sits inside or outside a range.
When to See Your GP
Some situations need NHS assessment first, not a private blood test:
If you're under 40 and experiencing symptoms that could suggest POI, your GP should investigate this directly. POI requires specialist management, including long-term HRT to protect your bones and cardiovascular system.
If you're between 40 and 45 with menopausal symptoms, your GP may check FSH to clarify the clinical picture.
If you have very heavy bleeding, bleeding between periods, or bleeding after sex, see your GP promptly. These symptoms need clinical investigation regardless of your hormonal status.
If you're experiencing severe mood changes, persistent low mood, or thoughts of self-harm, speak to your GP. These symptoms can overlap with perimenopause but may also indicate a condition that needs separate treatment.
How Brooksby Medical Can Help
If you're over 45 and your symptoms fit the perimenopausal pattern, you don't need a blood test for diagnosis. But many women want more information, particularly if they're considering HRT, if fatigue is a dominant symptom, or if they want to check for overlapping issues like thyroid dysfunction or iron depletion.
The Women's Health Profile covers the core hormonal and metabolic markers discussed in this article: FSH, oestradiol, LH, full thyroid function, ferritin, vitamin D, and HbA1c.
For a broader view that includes liver function, kidney function, cholesterol, and inflammatory markers, the Wellness Profile provides a thorough health baseline.
Every Brooksby report is written personally by a GP who explains what your results mean in context, not just whether they're in range. If anything needs further investigation, we'll tell you clearly and recommend the right next step.
If you're also experiencing symptoms that suggest thyroid dysfunction, our dedicated briefing on thyroid testing explains what to look for.
References
National Institute for Health and Care Excellence. Menopause: diagnosis and management (NG23). Last updated November 2024. NICE NG23
Davies M, Sarri G, Lumsden MA. Diagnosis and management of menopause: summary of NICE guidance. Ann Clin Biochem. 2017;54(5):516-518. doi:10.1177/0004563217706381
British Menopause Society. Testosterone replacement in menopause. BMS Tools for Clinicians, updated 2024. BMS Tools for Clinicians
Written by Dr James Coleman, GP and founder of Brooksby Medical. Dr Coleman is a practising General Practitioner who founded Brooksby Medical to give patients direct access to the blood tests and clinical interpretation they need, without waiting lists.
Medically reviewed: March 2026 | Next review due: March 2027
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Blood test results should always be interpreted by a qualified healthcare professional in the context of your individual symptoms, medical history, and clinical picture. If you have concerns about your health, please consult your GP.
Medical disclaimer. This article is for informational purposes and does not constitute medical advice. Blood test results should always be interpreted by a qualified healthcare professional in the context of your individual symptoms, history, and clinical picture. If you have concerns about your health, please consult your GP.