Overview.
The 40s are a metabolic inflection point for women. Oestrogen begins its erratic decline, redistributing body fat, increasing cardiovascular risk, accelerating bone loss, and disrupting sleep and mood. Thyroid disease peaks. Insulin sensitivity shifts. Cardiovascular risk — suppressed by oestrogen for decades — begins to catch up with men. These changes are measurable years before they become symptomatic. A targeted annual blood panel in your 40s catches problems when intervention is most effective, not when symptoms force you to act.
Ranked biomarkers.
#1 TSH (Thyroid-Stimulating Hormone)
Women over 40 have the highest prevalence of thyroid disease — over 10% by age 60. Hypothyroidism causes fatigue, weight gain, cold intolerance, and depression that overlaps with perimenopause symptoms. Hyperthyroidism accelerates bone loss. Both are readily treatable once identified.
Optimal range: 0.5-2.5 mIU/L (functional optimal). Lab 'normal' extends to 4.5 but TSH >2.5 with symptoms warrants investigation. Add TPO antibodies if TSH borderline.
Key insight: Perimenopause and hypothyroidism share many symptoms (fatigue, weight gain, mood changes, irregular periods). Without a TSH test, misattribution to 'just perimenopause' delays years of treatable hypothyroidism. This is the single most commonly missed diagnosis in women over 40.
#2 FSH / AMH (Perimenopause Markers)
FSH rising above 25 mIU/mL with irregular cycles confirms the perimenopause transition. AMH approaching undetectable confirms ovarian reserve depletion. Together they provide timeline context for menopause — median age 51, but range is 45-55.
Optimal range: FSH: variable in perimenopause (can spike >40 mIU/mL then return to normal). AMH <0.5 ng/mL suggests menopause within 2-3 years. Single FSH values are unreliable — trend over cycles is more informative.
Key insight: NICE and NAMS guidelines state that hormone testing is NOT routinely needed in women over 45 with typical perimenopausal symptoms — clinical diagnosis is sufficient. Testing is most useful under 45 (premature menopause concern) or when symptoms are atypical and other causes need exclusion.
#3 Vitamin D (25-OH)
Oestrogen decline accelerates bone loss. Vitamin D is essential for calcium absorption and bone remodelling. Deficiency is present in 40-60% of women over 40. It also affects mood, immune function, and muscle strength — all declining in this decade.
Optimal range: 40-60 ng/mL. Standard 'sufficient' (>30 ng/mL) may not be adequate for the bone remodelling demands of the perimenopausal transition.
Key insight: Vitamin D needs increase with age because skin synthesis declines (~50% reduction by age 70 compared to age 20). Women over 40 should be tested annually and supplement proactively, especially during winter months. Most need 2,000-4,000 IU/day to maintain optimal levels.
#4 ApoB (Apolipoprotein B)
Cardiovascular risk in women rises sharply after menopause — oestrogen's cardioprotective effect disappears. By age 65, women match men in CVD risk. ApoB counts all atherogenic particles and is a better predictor of cardiovascular events than LDL-C. Testing in the 40s catches early atherosclerosis when intervention (lifestyle + statins if indicated) is most effective.
Optimal range: <80 mg/dL. Aggressive prevention: <60 mg/dL. Many longevity physicians recommend lifetime ApoB suppression starting in the 40s.
Key insight: LDL-C often rises during perimenopause due to declining oestrogen. A woman whose LDL-C was always 100 may see it jump to 140-160 post-menopause. ApoB may reveal atherogenic particle excess even when LDL-C appears 'acceptable'. This is the decade where cardiovascular primary prevention should begin.
#5 Fasting Insulin / HbA1c
Oestrogen decline worsens insulin sensitivity. Central adiposity increases. The risk of type 2 diabetes approximately doubles in the decade surrounding menopause. Fasting insulin and HbA1c catch the metabolic shift 5-10 years before diabetes diagnosis.
Optimal range: Fasting insulin <5 μIU/mL; HbA1c <5.3%. HOMA-IR <2.0. Standard 'normal' fasting insulin (<25) and HbA1c (<5.7%) miss early insulin resistance.
Key insight: Visceral fat accumulation during perimenopause is driven by declining oestrogen, not just diet. This fat is metabolically active and worsens insulin resistance. Resistance training is the most effective intervention — it improves insulin sensitivity and counters the muscle loss (sarcopenia) that accelerates metabolic decline.
#6 hs-CRP (High-Sensitivity C-Reactive Protein)
Chronic low-grade inflammation accelerates cardiovascular disease, bone loss, and cognitive decline. Oestrogen decline removes an anti-inflammatory influence, and visceral fat gain increases inflammatory cytokines. hs-CRP integrates these signals into a single risk marker.
Optimal range: <1.0 mg/L. >3.0 mg/L doubles cardiovascular risk independent of cholesterol. Persistent elevation warrants investigation and lifestyle intervention.
Key insight: hs-CRP >2.0 mg/L in a woman over 40 should prompt not just cardiovascular risk assessment but also screening for metabolic syndrome, sleep apnoea, and periodontal disease — all inflammatory drivers that become more common in this decade.
#7 Ferritin
Iron dynamics shift dramatically around menopause. Pre-menopause: iron deficiency risk from menstrual losses. Post-menopause: iron accumulation risk (no longer losing iron monthly). Elevated ferritin in post-menopausal women is associated with cardiovascular disease, diabetes, and liver dysfunction.
Optimal range: Pre-menopause: >50 ng/mL. Post-menopause: 40-100 ng/mL (mid-range). >200 ng/mL post-menopause warrants investigation for haemochromatosis or metabolic syndrome.
Key insight: The iron target FLIPS at menopause. Before: supplement to prevent deficiency. After: monitor for excess. Post-menopausal women should not routinely take iron supplements unless deficiency is documented. Blood donation can lower elevated ferritin.
#8 Estradiol (E2)
Estradiol is the primary female sex hormone protecting bones, brain, cardiovascular system, and vaginal/urinary tissue. Its erratic decline during perimenopause drives vasomotor symptoms (hot flashes), mood changes, sleep disruption, and vaginal dryness. Post-menopause, very low estradiol (<20 pg/mL) confirms the transition.
Optimal range: Fluctuates wildly in perimenopause. Post-menopause: typically <20 pg/mL. On HRT: provider-specific targets. Single values are often misleading in perimenopause.
Key insight: Estradiol doesn't simply decline — it roller-coasters during perimenopause, sometimes spiking higher than reproductive years (causing breast tenderness, mood swings) before plummeting (causing hot flashes). A single blood test during this phase may catch a peak or a trough and misrepresent the overall trend.
#9 HbA1c
Glycation — sugar bonding to proteins — accelerates aging of every organ system. HbA1c reflects 90-day average blood glucose and is the most practical marker of metabolic aging. Perimenopausal insulin resistance often pushes HbA1c from 5.0 to 5.4-5.6% — the 'prediabetes creep' that precedes diagnosis by years.
Optimal range: <5.3% (longevity target). <5.7% (standard 'normal'). 5.7-6.4% = prediabetes. ≥6.5% = diabetes.
Key insight: Even within the 'normal' range, each 0.1% increase in HbA1c from 5.0 to 5.6% is associated with increased cardiovascular risk. The goal is not just avoiding diabetes — it's maintaining HbA1c in the low-normal range where glycation-driven aging is minimised.
#10 ALP + Calcium (Bone Health Markers)
Bone loss accelerates 2-3 years before and 3-5 years after the final menstrual period, with women losing up to 20% of bone density in the first 5-7 years post-menopause. ALP (bone isoenzyme) and calcium help screen for bone turnover. DXA scan is the gold standard but blood markers flag early changes.
Optimal range: ALP: 44-147 U/L (elevated may indicate increased bone turnover). Calcium: 8.5-10.5 mg/dL. Vitamin D: 40-60 ng/mL to support calcium absorption.
Key insight: DXA scan (bone density) should be done at age 65, or earlier if risk factors are present: low body weight, smoking, corticosteroid use, family history of hip fracture, early menopause. Blood markers complement DXA but don't replace it. The 5-7 year window around menopause is when bone loss is fastest and intervention (weight-bearing exercise, calcium, vitamin D, and sometimes bisphosphonates or HRT) is most impactful.
How to test.
Request an annual comprehensive panel from your GP: CBC, CMP, TSH + TPO antibodies, lipid panel with ApoB, fasting insulin + glucose, HbA1c, hs-CRP, vitamin D, ferritin. Add FSH/estradiol if menstrual patterns are changing. Add AMH if fertility timeline is a concern. Add DXA scan at 65 (or earlier with risk factors). Most can be done with a single fasting morning blood draw.
FAQs.
Should I get hormone levels tested in perimenopause?
It depends. If you're over 45 with typical symptoms (irregular periods, hot flashes, sleep changes), guidelines say clinical diagnosis is sufficient — no testing needed. Testing is valuable if you're under 45 (premature menopause concern), symptoms are atypical, or you need to exclude thyroid/other causes. FSH and AMH are most useful for timeline estimation.
Why does cardiovascular risk suddenly increase after menopause?
Oestrogen is cardioprotective: it maintains vascular flexibility, keeps LDL low and HDL high, reduces inflammation, and supports endothelial function. As oestrogen declines, LDL-C rises, arterial stiffness increases, and visceral fat accumulates. By 10 years post-menopause, women match men in cardiovascular event rates. ApoB and hs-CRP should be tracked starting in the 40s.
Do I still need iron supplements after menopause?
Almost certainly not, unless documented deficiency exists. Once menstrual losses stop, iron accumulates. Post-menopausal ferritin often rises significantly. Elevated ferritin (>200 ng/mL) in post-menopausal women is associated with cardiovascular disease and metabolic syndrome. Switch from supplementation to monitoring.
How often should I get blood work done in my 40s?
Annually for a comprehensive panel. Every 3-6 months if actively managing a condition (thyroid dose adjustment, metabolic optimisation). TSH and metabolic markers should be checked at least yearly. Lipids every 1-2 years if normal; annually if borderline or on treatment.
Verdict.
The 40s are the decade where preventive health matters most for women. Thyroid disease peaks, perimenopause reshapes metabolism, cardiovascular risk emerges, and bone loss accelerates. These 10 biomarkers capture the complete picture: hormonal transition (FSH, estradiol, TSH), metabolic health (insulin, HbA1c), cardiovascular risk (ApoB, hs-CRP), bone protection (vitamin D, ALP, calcium), and iron balance (ferritin). Annual testing transforms the 40s from a decade of gradual decline into a decade of informed, proactive health management.