Perimenopause Blood Test: Which Tests Help and When

Perimenopause is the time before your periods stop completely, when hormone levels rise and fall unpredictably. It often starts in your 40s and can last several years. Common signs include changes to your periods, hot flushes, night sweats, poor sleep, low mood, anxiety and brain fog. Many women look for a perimenopause blood test or a hormone test to confirm what is happening.

The honest answer is that a blood test often cannot confirm perimenopause, because hormones change from day to day. But blood tests can still be very useful: they can rule out other causes of similar symptoms and, in some age groups, support a diagnosis. This guide explains which tests help, when to test, and what the results can and cannot tell you. If you are under 45, see our guide to blood tests for early menopause.

Test it in Chiswick: our Hormone Health Check costs £69 and measures FSH, LH, oestradiol, progesterone, prolactin, testosterone, SHBG and the free androgen index, with your result explained in person by a practitioner. No GP referral needed. Book this test or call 020 4515 0000.

Checking other causes too: our Hormone and Thyroid Panel costs £99 and adds a full thyroid profile, as thyroid problems can cause very similar symptoms. Both are on our menopause blood test page.

Quick answer

NICE guidance says that if you are over 45 and have typical symptoms, perimenopause can be diagnosed from your symptoms alone, without a blood test. Between 40 and 45, an FSH test may be considered. Under 40, FSH testing is used to look for premature ovarian insufficiency. At any age, blood tests can help rule out other causes of tiredness, low mood or period changes, such as thyroid problems, low iron or low vitamin D. A normal hormone result does not rule out perimenopause, and a result outside the range is a prompt for discussion, not a diagnosis.

Why hormone tests are not always reliable in perimenopause

During perimenopause the ovaries do not wind down smoothly. Oestradiol can be high one week and low the next, and follicle stimulating hormone (FSH) can jump into the menopausal range and then fall back. A single test is only a snapshot of one day, so it may look completely normal even when you have clear symptoms. That is why NICE does not recommend FSH testing to diagnose perimenopause or menopause in women aged 45 and over with typical symptoms.

Hormonal contraception, including the combined pill and some other methods, also changes hormone levels and makes FSH unreliable. Hormone replacement therapy (HRT) does the same.

Which blood tests can help

Hormone tests

• FSH: rises as the ovaries slow down. Most useful between 40 and 45, or under 40, alongside your symptoms. A single FSH test costs £49. Our FSH levels guide explains the ranges.
• Oestradiol: the main form of oestrogen. It varies widely in perimenopause, so it is read with FSH rather than alone. An oestradiol test costs £49. See our oestradiol levels guide.
• LH: luteinising hormone often rises with FSH. A luteinising hormone test costs £49, and our LH levels guide covers it in more detail.
• Progesterone, prolactin and testosterone: can help explain irregular cycles, missed periods and low libido. See our guides to progesterone, prolactin and testosterone in women.

Tests that rule out other causes

• Thyroid: an underactive or overactive thyroid can cause tiredness, weight change, low mood, palpitations and period changes. Our thyroid blood test costs £59.
• Ferritin and iron: heavy periods are common in perimenopause and can lead to low iron and tiredness. A ferritin test costs £49. See our ferritin guide.
• Vitamin D: low levels are common in the UK and matter for bone health as oestrogen falls. Our vitamin D blood test costs £59.
• Blood sugar and cholesterol: heart and metabolic risk rises after the menopause, so a baseline can be useful. See our guides to HbA1c and cholesterol.

For a full overview, browse our women's health blood tests.

When to test

• If you still have periods: hormone tests are often taken on days 2 to 5 of your cycle, counting the first day of bleeding as day 1. We will confirm timing when you book.
• If your periods are very irregular or have stopped: you can usually test on any day.
• If you use hormonal contraception or HRT: tell us before booking, as FSH and oestradiol may not be meaningful.
• Biotin supplements: stop them for at least 48 hours before, as biotin can affect some hormone tests.

What the results can and cannot tell you

• A raised FSH with low oestradiol supports the ovaries slowing down, but a single high FSH does not tell you when your periods will stop.
• A normal FSH does not rule out perimenopause. Your symptoms remain the most important guide.
• Blood tests cannot measure bone density or predict your personal risk of osteoporosis.
• AMH is a fertility marker and is not recommended by NICE to diagnose perimenopause. See our AMH guide.

When to see a GP

Speak to your GP if symptoms are affecting your daily life, if you are under 45 and your periods have changed, or if you want to discuss treatment options. You can find out more about when menopause starts.

• See your GP soon if you have bleeding between periods, after sex, or very heavy bleeding that leaves you dizzy or breathless.
• Contact your GP urgently if you have any bleeding more than 12 months after your last period.
• Call 999 or go to A&E if you have very heavy bleeding with fainting or feeling very unwell, or severe tummy pain with a possible pregnancy.

How often to retest

Because hormones change from month to month, a repeat FSH after 4 to 6 weeks is sometimes used, especially under 45. For other markers, such as thyroid, ferritin or vitamin D, retesting depends on the first result and any changes you make. Your GP will advise on further tests.

Frequently asked questions

Can a blood test confirm perimenopause?

Not reliably. Over 45, it is usually diagnosed from symptoms. Blood tests are more useful to rule out other causes or between 40 and 45.

What hormone test is best for women in their 40s?

FSH, oestradiol and LH together give the clearest hormone picture, ideally with a thyroid test to rule out other causes.

Can I test while on the pill?

Combined hormonal contraception makes FSH unreliable. Discuss timing with your GP or practitioner.

Perimenopause testing in Chiswick

We take your blood sample at our clinic at 8 to 9 Bedford Corner, The Avenue, Chiswick, London W4 1LZ, a short walk from Turnham Green station on the District line (Piccadilly line trains stop there early morning and late evening only), and on the 94, E3 and 272 bus routes. Limited parking is available on request when you book. Your sample is analysed by the Randox laboratory, and a practitioner talks you through what your result means. No GP referral is needed, and we can send a GP feedback report on request.

Book our Hormone Health Check, or browse all women's health blood tests. You can also compare every blood test and price or read our guide to blood tests for early menopause.

This article is general information, not medical advice. Discuss your results with your GP or practitioner.