Perimenopause Blood Test: What to Test and When

Perimenopause — the transition phase before menopause — typically begins between the ages of 40 and 45, though it can start in the late 30s for some women. An estimated 13 million women in the UK are currently perimenopausal or menopausal, and the majority of them struggle to get a clear diagnosis from their GP.

The reason is simple: most doctors rely on a single FSH blood test to assess menopausal status. But FSH fluctuates wildly during perimenopause — it can be sky-high one week and completely normal the next. A single snapshot tells you almost nothing. A proper perimenopause blood test panel needs to be broader, better timed, and interpreted in context.

Why a Single FSH Test Isn't Enough

FSH (follicle-stimulating hormone) rises as ovarian reserve declines. In established menopause, FSH is consistently elevated above 30 IU/L. But during perimenopause, your ovaries are sputtering rather than stopping — they still produce oestrogen intermittently, which suppresses FSH back down. You can have a "normal" FSH reading one day and menopausal-range FSH a fortnight later.

NICE guidelines actually state that FSH testing is not required to diagnose perimenopause in women over 45 with typical symptoms. For women aged 40-45, they suggest FSH can be used but acknowledge its limitations. Despite this, many GPs still order a single FSH test and use a normal result to dismiss symptoms entirely.

This is why testing multiple hormones together — and timing the test correctly — gives you far more useful information.

The Full Perimenopause Blood Test Panel

Reproductive Hormones (Test on Days 2-5 of Your Cycle)

If you're still having periods (even irregular ones), testing on days 2-5 gives the most reliable baseline readings:

• FSH — still useful as part of a wider panel; consistently elevated readings (above 25 IU/L) suggest declining ovarian function
• LH (luteinising hormone) — works alongside FSH; an elevated LH:FSH ratio can indicate ovarian ageing
• Oestradiol (E2) — the primary oestrogen; levels below 100 pmol/L in the early follicular phase suggest low ovarian output. During perimenopause, oestradiol can swing from very high to very low within a single cycle

Progesterone (Test on Day 21 If Still Cycling)

Progesterone is the first hormone to decline in perimenopause — often years before oestrogen drops. Low progesterone causes many classic symptoms: sleep disruption, anxiety, irritability, heavy periods, and shortened cycles. A day-21 progesterone level below 16 nmol/L suggests you're not ovulating consistently.

Thyroid Function — The Critical Overlap

This is where many women get misdiagnosed. Thyroid dysfunction and perimenopause share a striking number of symptoms:

Symptom	Perimenopause	Thyroid Disorder
Fatigue	Yes	Yes (hypo)
Weight gain	Yes	Yes (hypo)
Anxiety	Yes	Yes (hyper)
Brain fog	Yes	Yes (hypo)
Hair thinning	Yes	Yes (both)
Irregular periods	Yes	Yes (both)
Heart palpitations	Yes	Yes (hyper)
Low mood	Yes	Yes (hypo)

Research suggests that up to 1 in 4 women investigated for menopause symptoms actually have a thyroid disorder — either instead of or alongside perimenopause. Autoimmune thyroid disease (Hashimoto's) is particularly common in women aged 40-50.

A proper thyroid panel should include:

• TSH — the screening marker; normal range 0.27-4.2 mIU/L, but many women feel best below 2.5
• Free T4 (FT4) — the main thyroid hormone; low FT4 with elevated TSH confirms hypothyroidism
• Free T3 (FT3) — the active thyroid hormone; some women have poor T4-to-T3 conversion, which TSH alone won't detect

Vitamin D

Vitamin D levels tend to decline around and after menopause, partly due to reduced oestrogen (which helps activate vitamin D). Low vitamin D accelerates bone density loss — a major long-term risk of menopause. The UK recommended minimum is 50 nmol/L, but most specialists suggest 75-100 nmol/L is optimal.

Lipid Panel

Cardiovascular risk increases significantly after menopause. Oestrogen has a protective effect on blood vessels and lipid metabolism — as it declines, LDL cholesterol and triglycerides tend to rise. Getting a baseline lipid panel during perimenopause lets you track this shift and act early if needed.

When to Get Tested

Timing matters more than most people realise:

• If still having periods: Test FSH, LH, and oestradiol on days 2-5 of your cycle. Test progesterone on day 21.
• If periods are very irregular or absent: Test any day — there's no reliable cycle to time against.
• Repeat testing: A single set of results in perimenopause is a snapshot, not a diagnosis. Consider retesting every 3-6 months if symptoms are evolving.

Which Lola Health Test Should You Choose?

The Female Hormones Clarity 31 test (£115) is the best option for investigating perimenopause properly. It covers reproductive hormones (FSH, LH, oestradiol, progesterone), a full thyroid panel (TSH, FT3, FT4), cardiovascular markers, and key vitamins — all in one test. This is the panel that catches the thyroid issues a standard GP hormone check misses.

If you're mainly looking for a focused hormone check and don't need the full thyroid or cardiovascular workup, the Female Hormones 7 test (£95) covers the core reproductive hormones and is a solid starting point.

Don't Wait for Your GP to Join the Dots

Perimenopause is a clinical diagnosis — it's based on symptoms, age, and pattern recognition, not a single blood test. But blood tests provide essential context. They help distinguish perimenopause from thyroid disease, confirm hormonal shifts, and establish baseline cardiovascular and bone health markers before menopause arrives.

If you're over 40 and experiencing fatigue, mood changes, sleep disruption, or cycle irregularities, a proper hormone and thyroid panel is the logical first step. Order the Female Hormones Clarity 31 test and get the full picture — not just an FSH number.