WOMEN'S HORMONES
Perimenopause Blood Test UK: Which Tests to Ask For & What Your Results Actually Mean
Around 13 million women in the UK are currently perimenopausal or menopausal, according to the British Menopause Society. For many, symptoms begin in their late thirties or early forties — years before periods actually stop — and are frequently dismissed, misdiagnosed as anxiety or depression, or attributed to “just getting older.”
If you've searched for a perimenopause blood test, here is the most important thing to understand: perimenopause is a clinical diagnosis, not a blood test diagnosis. The NICE guideline NG23 is clear that hormone levels fluctuate so wildly during the perimenopause transition that a single FSH or oestradiol result can be normal one week and menopausal the next. Your GP should diagnose perimenopause based on your symptoms and menstrual history, not a blood test.
That does not mean blood tests are useless. Far from it. The right tests can rule out conditions that mimic perimenopause (thyroid disease, iron deficiency, vitamin D depletion), provide a fertility timeline via AMH, and help your GP make informed decisions about HRT. This guide explains exactly which tests are worth doing, which are not, and how to interpret your results.
1. What is perimenopause?
Perimenopause is the transition phase leading to menopause — the point at which your ovaries gradually produce less oestrogen and progesterone and you stop releasing eggs regularly. It typically begins in your early-to-mid forties, though it can start in the late thirties, and lasts on average four to eight years before your final period (NHS).
The hallmark of perimenopause is hormonal volatility. Unlike menopause, where oestrogen is consistently low, perimenopausal hormones swing dramatically — sometimes within the same week. This unpredictability is what causes the classic symptoms: irregular periods, hot flushes, night sweats, brain fog, anxiety, sleep disruption, joint pain, and changes in libido.
The STRAW+10 staging system (Harlow et al., Lancet, 2012) divides the menopausal transition into early and late stages based on menstrual cycle changes and, where available, FSH levels. It remains the international gold standard for classifying reproductive ageing.
2. Why blood tests can't diagnose perimenopause
This is the single most important point in this guide. NICE NG23 explicitly states: “Do not use FSH to diagnose perimenopause in women aged over 45 years with menopausal symptoms.” The guideline is equally clear for women under 45: a single hormone reading cannot reliably confirm or exclude perimenopause.
Why? Because perimenopausal hormones do not decline in a straight line. FSH can be elevated one week (suggesting ovarian decline) and perfectly normal the next (when the ovaries have a “good month”). Oestradiol can spike to levels higher than in young women before crashing. Progesterone fluctuates depending on whether ovulation occurred that cycle.
A snapshot blood test captures one moment in a rollercoaster. A normal FSH does not mean you are not perimenopausal. An elevated FSH does not confirm it. Your GP should diagnose based on your age, symptom pattern, and menstrual history — not a number on a lab report.
3. Five reasons blood tests still matter
If blood tests cannot diagnose perimenopause, why bother? Because the value lies not in confirming the transition, but in what they reveal alongside it:
1. Rule out thyroid disease
Hypothyroidism causes fatigue, weight gain, brain fog, mood changes, and irregular periods — symptoms almost identical to perimenopause. The NICE guideline on thyroid disease notes that hypothyroidism affects approximately 2–5% of UK women, and prevalence increases with age. A simple TSH and fT4 test can confirm or exclude it.
2. Detect iron deficiency from heavy periods
Heavier or more frequent periods are one of the earliest perimenopausal changes. The resulting iron loss causes exhaustion, breathlessness, hair thinning, and poor concentration. The British Society for Haematology recommends checking ferritin in all women with menorrhagia. Ferritin below 30 µg/L indicates depleted iron stores, even if haemoglobin is still “normal.”
3. Baseline AMH for fertility planning
Anti-Müllerian hormone reflects your remaining egg reserve and declines steadily with age. While AMH cannot predict exactly when you will reach menopause, it provides a useful fertility timeline indicator — particularly relevant for women in their late thirties or early forties considering future pregnancies (RCOG).
4. Check vitamin D and testosterone for energy and mood
Vitamin D deficiency affects an estimated 1 in 5 UK adults (SACN, 2016) and worsens fatigue, low mood, and musculoskeletal pain. Testosterone in women declines gradually from the late twenties and contributes to reduced energy, motivation, and libido — symptoms often attributed entirely to oestrogen decline.
5. Inform HRT decision-making
While blood tests are not required to prescribe HRT (NICE CKS), a baseline panel helps your GP or menopause specialist understand the broader picture: thyroid function, liver enzymes (relevant for oral HRT), cardiovascular risk markers, and whether testosterone or DHEA-S supplementation may be appropriate alongside standard oestrogen/progesterone therapy.
4. The 10 biomarkers worth testing
Rather than chasing a single hormone number, a well-chosen panel gives you a complete picture of what the perimenopause transition is doing to your body. Here are the markers that actually help:
FSH (follicle-stimulating hormone)
FSH rises as the ovaries become less responsive to pituitary signals. Levels above 25 IU/L on day 2–5 of the cycle suggest declining ovarian function — but remember, a normal FSH does not exclude perimenopause. NICE NG23 states that FSH may be useful in women under 45 with suspected premature ovarian insufficiency, or in women aged 40–45 with symptoms, but should not be used to diagnose perimenopause in women over 45.
Oestradiol (E2)
The primary oestrogen. In perimenopause, oestradiol swings between very high and very low levels — it does not simply decline. A single reading is unreliable, but consistently low levels (<100 pmol/L in the follicular phase) combined with elevated FSH suggest late-stage transition.
LH (luteinising hormone)
LH works alongside FSH to trigger ovulation. In perimenopause, the FSH:LH ratio often shifts (FSH rises first). LH is most useful when tested alongside FSH and oestradiol for a fuller picture of the pituitary-ovarian axis.
Progesterone
Progesterone is only produced after ovulation. In early perimenopause, anovulatory cycles become more frequent, meaning progesterone drops before oestrogen does. This relative oestrogen dominance drives many early symptoms: breast tenderness, mood swings, heavier periods, and sleep disruption. A day-21 progesterone below 16 nmol/L suggests an anovulatory cycle (NHS).
AMH (anti-Müllerian hormone)
AMH is produced by the small follicles in the ovary and reflects remaining egg reserve. Unlike FSH and oestradiol, AMH is relatively stable across the menstrual cycle, making it a more consistent marker. Levels below 5.4 pmol/L suggest a diminished ovarian reserve. AMH is particularly valuable for fertility counselling rather than menopause diagnosis.
TSH & free T4 (thyroid)
Thyroid dysfunction is common in women over 40 and mimics perimenopause almost perfectly. The NICE thyroid guideline recommends TSH as the first-line test. If TSH is above 4.0 mIU/L, your GP may investigate subclinical or overt hypothyroidism. Missing a thyroid problem means treating the wrong condition.
Ferritin
Ferritin measures your body's iron stores. Heavy or prolonged perimenopausal periods drain iron fast. The British Society for Haematology defines iron deficiency as ferritin below 30 µg/L. Many labs still use a lower cut-off of 12–15 µg/L, meaning women with genuinely depleted stores are told their results are “normal.” Optimal ferritin for energy and cognition is typically above 50 µg/L.
Vitamin D
Oestrogen promotes vitamin D activation. As oestrogen declines, vitamin D status often worsens. The SACN report recommends all UK adults maintain levels above 25 nmol/L, but many clinicians target 75–100 nmol/L for optimal bone health, mood, and immune function — particularly important as osteoporosis risk accelerates in the years around menopause.
Testosterone
Women produce testosterone in the ovaries and adrenal glands. Levels decline gradually from the mid-twenties, and the perimenopause accelerates this. Low testosterone contributes to reduced energy, decreased motivation, loss of muscle mass, and reduced libido. The British Menopause Society supports testosterone supplementation in selected women on HRT who have persistent low libido.
Cortisol & DHEA-S
As ovarian hormone production declines, the adrenal glands become a more important source of sex hormone precursors. DHEA-S is the primary adrenal androgen and declines with age. Cortisol dysregulation — often driven by chronic stress — can worsen perimenopausal symptoms including sleep disruption, weight gain around the middle, and anxiety. Testing the cortisol:DHEA-S ratio helps assess adrenal reserve.
5. NHS reference ranges vs optimal levels
NHS reference ranges are designed to identify disease. Optimal ranges reflect levels associated with the best energy, mood, bone health, and symptom control. In perimenopause, the gap between “not clinically abnormal” and “feeling well” can be enormous.
| Biomarker | NHS range | Optimal range | Notes |
|---|---|---|---|
| FSH | 1.5–12.4 IU/L (follicular) | <10 IU/L | >25 IU/L suggests ovarian decline |
| Oestradiol | 46–607 pmol/L (follicular) | 150–400 pmol/L | Highly variable in perimenopause |
| Progesterone (day 21) | >16 nmol/L (ovulation) | >30 nmol/L | <16 suggests anovulatory cycle |
| AMH | Age-dependent | >5.4 pmol/L (age 35–40) | Stable across cycle; fertility indicator |
| TSH | 0.27–4.2 mIU/L | 0.5–2.5 mIU/L | >4.0 warrants investigation |
| Free T4 | 12–22 pmol/L | 15–20 pmol/L | Low-normal + high TSH = subclinical |
| Ferritin | 13–150 µg/L | 50–100 µg/L | <30 = iron deficient (BSH) |
| Vitamin D | >25 nmol/L | 75–100 nmol/L | Bone + mood + immune protection |
| Testosterone | 0.3–1.7 nmol/L | 0.8–1.5 nmol/L | Low end linked to fatigue + low libido |
| DHEA-S | 0.95–11.67 µmol/L | 3.0–8.0 µmol/L | Adrenal reserve marker; declines with age |
Important: Hormone reference ranges vary significantly depending on cycle day, time of day, and laboratory assay. Always interpret results in context with your symptoms and menstrual history, ideally with a GP or menopause specialist.
6. The FSH myth: why a single test tells you very little
Many women ask their GP for “a menopause blood test” and receive a single FSH result. If it comes back normal, they are told they are not menopausal — and their symptoms are dismissed.
This is a failure of the system, not of the test. NICE NG23 has been clear since 2015: in women over 45 with typical symptoms, no blood test is needed for diagnosis. The GP should diagnose perimenopause clinically and discuss management options including HRT.
For women aged 40–45, NICE suggests that FSH may be considered alongside symptoms. Two elevated FSH readings taken 4–6 weeks apart are more informative than a single test. For women under 40 with suspected premature ovarian insufficiency, FSH testing is essential.
The takeaway: if you are experiencing perimenopausal symptoms and your GP dismisses them based solely on a normal FSH, the NICE guideline supports you in challenging that decision.
7. STRAW+10: understanding the stages of reproductive ageing
The Stages of Reproductive Aging Workshop (STRAW+10) system, published in the Lancet in 2012, defines seven stages from peak fertility to late post-menopause. The key stages relevant to blood testing:
Early menopausal transition (stage −2): Cycle length varies by 7+ days from normal. FSH may be variable (sometimes elevated, sometimes normal). AMH is declining. This is when symptoms often begin but hormone tests look “normal.”
Late menopausal transition (stage −1): Cycles become 60+ days apart. FSH is more consistently elevated (>25 IU/L). Oestradiol drops. Anovulatory cycles are frequent.
Post-menopause (stages +1 to +2): Defined as 12 months without a period. FSH is persistently above 25–30 IU/L. Oestradiol is consistently below 100 pmol/L. This is when blood tests are actually reliable — because the volatility has ended.
Understanding where you are in the STRAW staging helps you set expectations about what blood tests can and cannot tell you at each phase.
8. Five perimenopause result patterns
When we see perimenopausal women's blood results, they typically fall into one of these five patterns. Your results may overlap between categories.
Pattern 1: Thyroid mimicry
Typical results: TSH elevated (>4.0 mIU/L), fT4 low-normal or low, hormones may appear unremarkable.
What it means: Your symptoms may be driven partly or entirely by an underactive thyroid, not perimenopause. Treatment with levothyroxine can resolve fatigue, brain fog, weight gain, and mood changes independently of HRT.
Pattern 2: Iron-depleted exhaustion
Typical results: Ferritin below 30 µg/L (often 10–20), haemoglobin low-normal, hormones variable.
What it means: Heavy periods have drained your iron stores. The exhaustion, breathlessness, hair thinning, and poor concentration are iron deficiency symptoms, not necessarily perimenopause. Iron supplementation or IV iron infusion can produce dramatic improvement within weeks.
Pattern 3: Progesterone-first decline
Typical results: Day-21 progesterone below 16 nmol/L, oestradiol normal or high, FSH normal or mildly elevated.
What it means: Anovulatory cycles are becoming frequent. Without progesterone to balance oestrogen, you experience relative oestrogen dominance: breast tenderness, mood swings, heavier periods, PMS-like symptoms, and sleep problems. This is the most common early perimenopausal pattern and the one most often missed by a simple FSH test.
Pattern 4: Multi-nutrient depletion
Typical results: Vitamin D below 50 nmol/L, ferritin below 30 µg/L, testosterone low-normal, DHEA-S declining.
What it means: Multiple nutritional and hormonal deficits are compounding your perimenopausal symptoms. Fatigue has several overlapping causes. Targeted supplementation (iron, vitamin D, and potentially testosterone via your GP) can substantially improve quality of life even before considering HRT.
Pattern 5: Late transition
Typical results: FSH consistently above 25–30 IU/L, oestradiol below 100 pmol/L, LH elevated, AMH very low or undetectable.
What it means: You are in the late menopausal transition or approaching menopause. Hormones have stabilised at low levels. This is the point at which blood tests become more reliable indicators, and HRT is most clearly indicated if you have vasomotor symptoms (hot flushes, night sweats) or wish to protect bone density.
9. When to test: timing and preparation
Hormone levels vary throughout the menstrual cycle, so timing matters if you still have periods:
- FSH, oestradiol, LH: Day 2–5 of your cycle (day 1 = first day of your period). This is the early follicular phase, when baseline levels are most informative.
- Progesterone: Day 21 (or 7 days before your expected period). This is the window when progesterone peaks after ovulation.
- AMH, thyroid, ferritin, vitamin D, DHEA-S: Any day. These markers are not significantly affected by the menstrual cycle.
- Cortisol: Morning sample (before 10am) captures the cortisol awakening response for the most clinically useful reading.
If your periods have become irregular or have stopped, test on any day — cycle timing becomes irrelevant when cycles are unpredictable.
Preparation: Fast overnight if your panel includes metabolic markers. Avoid biotin supplements for 48 hours before testing (biotin can interfere with immunoassays including thyroid and hormone tests). Test before 10am for consistent cortisol and testosterone readings.
10. Blood tests and HRT: what your GP needs
NICE CKS Menopause confirms that blood tests are not a prerequisite for starting HRT in most women. If you are over 45 with typical symptoms, your GP can prescribe HRT based on clinical assessment alone. However, blood tests add value in several situations:
- Baseline thyroid function — to rule out hypothyroidism before attributing all symptoms to oestrogen decline
- Liver function tests — relevant for oral HRT, which undergoes first-pass hepatic metabolism
- Lipid profile — oestrogen decline shifts cardiovascular risk; a pre-HRT lipid baseline helps track changes
- Testosterone and DHEA-S — the BMS recommends checking testosterone before prescribing testosterone supplementation for persistent low libido on HRT
- Monitoring on HRT — oestradiol levels can help dose-adjust transdermal patches/gel if symptoms persist despite standard doses
Walking into a GP or menopause clinic appointment with a recent comprehensive blood panel means the conversation starts from data, not guesswork. It also saves weeks of waiting for NHS blood test appointments.
11. GP vs Helvy: what you actually get
| Feature | NHS GP | Helvy |
|---|---|---|
| Hormone tests | FSH only (if under 45); not recommended over 45 | FSH, oestradiol, LH, progesterone, testosterone |
| Thyroid | TSH (if GP suspects thyroid) | TSH + free T4 included in every panel |
| Iron | FBC; ferritin if anaemia suspected | Ferritin + iron studies in all panels |
| AMH | Fertility clinic referral only | Included in Hormone Female panel |
| Vitamin D | Not routinely tested | Included in every panel |
| Wait time | GP appointment + 1–2 weeks for results | Home test — results in 5 days |
| Report | “Normal” or referral | Plain-English report with context + next steps |
12. Which Helvy panel covers perimenopause?
Two panels are most relevant for perimenopausal women:
Hormone Female Panel — £119
Covers FSH, oestradiol, LH, progesterone, testosterone, SHBG, prolactin, DHEA-S, and AMH. This is the comprehensive hormone panel for understanding the full reproductive hormone picture alongside adrenal markers.
Essential Panel — £89
Covers thyroid (TSH + fT4), iron studies and ferritin, vitamin D, inflammation markers, and metabolic health. If your main concern is ruling out thyroid disease and iron deficiency as causes of your symptoms, this panel covers the critical non-hormonal markers.
For the most complete perimenopausal assessment, many women choose both panels to cover hormones and the nutritional, thyroid, and metabolic markers that are equally important during this transition.
13. Frequently asked questions
Can a blood test tell me if I'm in perimenopause?
Not reliably. Perimenopause is diagnosed clinically based on your symptoms and menstrual history, not a blood test. NICE NG23 states that FSH should not be used to diagnose perimenopause in women over 45 with typical symptoms. Hormones fluctuate too wildly during this phase for a single test to be conclusive.
What blood tests should I ask my GP for?
Focus on tests that rule out conditions mimicking perimenopause: TSH and free T4 (thyroid), ferritin (iron stores), and vitamin D. If you are under 45 or concerned about fertility, ask about FSH and AMH. Your GP may not offer all of these — a private blood test can fill the gaps.
Do I need blood tests before starting HRT?
Not necessarily. NICE confirms that HRT can be prescribed based on clinical assessment alone in women over 45 with typical symptoms. However, a baseline panel (thyroid, liver function, lipids, and hormone levels) gives your GP a fuller picture and helps personalise your HRT prescription.
My FSH came back normal but I have all the symptoms. What now?
A normal FSH does not mean you are not perimenopausal. NICE guidelines support clinical diagnosis based on symptoms and menstrual changes. If your GP is dismissing your symptoms because of a normal FSH, you are within your rights to request a referral to a menopause specialist or seek a second opinion.
When is the best time in my cycle to test hormones?
FSH, oestradiol, and LH are best tested on day 2–5 of your cycle. Progesterone should be tested on day 21 (or 7 days before your expected period). AMH, thyroid, ferritin, and vitamin D can be tested on any day. If your periods have stopped or become very irregular, test on any day.
Can perimenopause start in your thirties?
Yes. While the average age of onset is the mid-forties, some women begin experiencing perimenopausal symptoms in their late thirties. If you are under 40 and suspect early menopause, see your GP — premature ovarian insufficiency affects approximately 1 in 100 women under 40 (NHS) and requires investigation including FSH testing.
How often should I retest during perimenopause?
For non-hormonal markers (thyroid, ferritin, vitamin D), every 6–12 months is reasonable, especially if supplementing. Hormone levels change so rapidly that serial testing for FSH/oestradiol is generally not useful for tracking perimenopause progression. Instead, monitor symptoms and menstrual patterns.
UNDERSTAND YOUR PERIMENOPAUSE
The right blood tests won't diagnose perimenopause, but they can rule out thyroid disease, detect iron deficiency, and give your GP the data to personalise your care.
Choose your panel