Do You Need a Blood Test?

It's the obvious request. Something is happening, you want it confirmed, and a blood test feels like the way to get an answer rather than an opinion.

For most women over 45, the answer is that the test won't tell you what you want to know — and being refused it is correct practice rather than a brush-off. But there are situations where testing genuinely matters, and there are other tests entirely that often should be done and frequently aren't.

Why FSH doesn't work in the age group that wants it most

Follicle-stimulating hormone rises as ovarian function declines, which is why it seems like the natural test.

The problem is that in perimenopause it doesn't rise smoothly. It swings, sometimes dramatically, within a single cycle. You can be firmly in the transition with substantial symptoms and produce a completely normal result because blood was drawn on the wrong day. A normal FSH does not rule out perimenopause, and a raised one on a single occasion doesn't confirm menopause.

NICE guidance is direct: do not use FSH to diagnose perimenopause or menopause in women aged over 45. Diagnose on symptoms.

The same guidance advises against using anti-Müllerian hormone, inhibin A or B, estradiol, antral follicle count or ovarian volume for this purpose.

Two additional complications. Hormonal contraception suppresses FSH, so results are uninterpretable if you're on a combined pill or high-dose progestogen. And commercial "menopause test" kits measuring FSH in urine or blood are subject to exactly the same limitation as a clinic test, plus no clinical interpretation.

When testing does matter

Under 40. Different situation entirely. Premature ovarian insufficiency needs diagnosing, and diagnosis requires FSH measured on two occasions at least four weeks apart alongside four or more months of irregular or absent periods. This carries long-term consequences for bone and cardiovascular health and specific treatment recommendations, so getting it identified matters. If your periods have stopped or become significantly irregular under 40, ask to be tested.

Between 40 and 45. FSH may be considered where there are menopausal symptoms including a change in the menstrual cycle.

Uncertain situations. After hysterectomy without removal of the ovaries, or where a hormonal coil means there's no bleeding pattern to read.

Monitoring testosterone, if it's been prescribed.

The tests that are often more useful

This is the part worth knowing, because several conditions produce symptoms almost identical to perimenopause and are straightforward to identify.

Thyroid function. Hypothyroidism causes fatigue, low mood, weight change, cold intolerance, joint aches and cognitive slowing. It's common in women in this age group and easily missed because everything on that list is also on the menopause list.

Full blood count and ferritin. Heavy perimenopausal bleeding depletes iron. Low ferritin causes fatigue, breathlessness, poor concentration and hair loss — routinely attributed to hormones and easily corrected. Ferritin needs asking for specifically; it isn't included in a standard full blood count.

Vitamin D. Deficiency causes diffuse aching and fatigue and is widespread at higher latitudes.

Vitamin B12. Deficiency causes fatigue and cognitive symptoms, and is more common with certain medications including long-term metformin and proton pump inhibitors.

HbA1c and lipids. Not diagnostic of anything menopausal, but cardiovascular risk shifts across the transition, and midlife is the right point for a baseline.

None of these confirm perimenopause. They rule out other explanations — which is more useful than confirming something that can be diagnosed from your symptoms anyway.

What to say

If you want testing, be specific about which and why.

"I'd like my thyroid and ferritin checked, because I've had heavy periods and the exhaustion feels out of proportion" is a targeted request with clear reasoning.

If you've asked for FSH and been declined, the reasoning above is why, and it's sound. The useful follow-up is: "That makes sense — can we check thyroid and ferritin instead, to rule those out?"

And if you're under 40 with irregular or absent periods and are told you're too young for this to be menopause, that's the one situation where pressing for testing is clearly warranted. Say the words premature ovarian insufficiency. It changes the conversation.

The underlying point

The absence of a test is not the absence of a diagnosis. Perimenopause is diagnosed on pattern — your age, your cycle changes, your symptoms over time.

Which means the thing you bring to the appointment matters more than the thing they draw from your arm. Four months of cycle dates and a clear account of what's changed will get you further than any hormone panel.

Sources

- National Institute for Health and Care Excellence. Menopause: identification and management (NG23), diagnosis recommendations. Updated 2024. - European Society of Human Reproduction and Embryology. Guideline on the Management of Women with Premature Ovarian Insufficiency. - Harlow SD, Gass M, Hall JE, et al. Executive summary of the Stages of Reproductive Aging Workshop +10. Menopause. 2012;19(4):387–395. - Santoro N, Randolph JF. Reproductive hormones and the menopause transition. Obstetrics and Gynecology Clinics of North America. 2011;38(3):455–466. - National Institute for Health and Care Excellence. Heavy menstrual bleeding: assessment and management (NG88), investigations including ferritin.