Heavy periods in your 40s: why it happens and what to test.

Heavy periods in your 40s usually come down to perimenopause: cycles where ovulation is skipped or delayed let the uterine lining build for longer under unopposed oestrogen, and when it finally sheds, it floods. But heavy bleeding at this age can also be caused by fibroids, polyps, thyroid problems, adenomyosis or a bleeding disorder, and whatever the cause, it quietly drains your iron. Heavy or changed bleeding in your forties always needs a doctor's assessment; a blood test then tells you what the bleeding has cost you.

Here is why it happens, what "heavy" actually means, what to test, and the signs that mean you should not wait.

What counts as heavy

Doctors use the term heavy menstrual bleeding for periods that interfere with your life, and the practical markers are more useful than any measurement:

• Soaking through a pad or tampon every hour or two for several hours in a row.
• Doubling up, or needing to change during the night.
• Clots larger than a 50 cent coin.
• Bleeding for more than seven days, or flooding through clothes and bedding.
• Planning your life around it, cancelling things or avoiding leaving the house on the heavy days.
• Symptoms of low iron during or after: exhaustion, breathlessness, dizziness, a racing heart.

If your periods used to be manageable and now they are not, that change on its own is worth raising with a doctor.

Why heavy periods in your 40s are so common

In a regular ovulatory cycle, oestrogen builds the lining in the first half and progesterone, produced after ovulation, stabilises it in the second half. When progesterone falls, the lining sheds in an orderly way. In perimenopause, ovulation becomes hit and miss. In a cycle where you do not ovulate, or ovulate late, there is little or no progesterone: oestrogen keeps building the lining unopposed for weeks, and the eventual period is heavier, longer and often more clotty. Cycles can also run closer together for a while, so there is less recovery time between bleeds.

This is normal physiology, but "normal" does not mean "fine to ignore", for two reasons. First, the same symptoms can come from other causes that need their own treatment. Second, the iron loss adds up.

The other causes a doctor will consider

• Fibroids. Non-cancerous growths in the muscle of the uterus. Very common in the forties, and a leading cause of heavy, prolonged bleeding and pelvic pressure. Usually found on ultrasound.
• Polyps. Small overgrowths of the lining that cause heavy or irregular bleeding and bleeding between periods.
• Adenomyosis. Lining tissue growing into the uterine muscle, causing heavy painful periods and a tender, enlarged uterus.
• Thyroid disorders. An underactive thyroid in particular can make periods heavier and is checked with a blood test.
• Bleeding disorders. Less common, but worth considering if you have always bled heavily, bruise easily or have a family history.
• Medicines. Blood thinners and some other medicines increase menstrual bleeding.
• Changes in the lining. Prolonged unopposed oestrogen can thicken the lining in ways that need checking, which is one reason persistent heavy or irregular bleeding in the forties is investigated rather than watched.

Sorting these out involves an examination and usually an ultrasound, which is why the first stop for heavy bleeding is a doctor rather than a pathology form.

What heavy bleeding does to your iron

Every heavy period removes iron faster than food replaces it. Iron stores (measured as ferritin) drop first, often for months or years without anaemia showing up on a full blood count. During this stage women feel tired, foggy, breathless on stairs and short-tempered, and are frequently told their blood count is "fine" because haemoglobin has not fallen yet. Once stores are exhausted, haemoglobin drops and iron deficiency anaemia follows, with the fatigue becoming harder to push through and the heart working harder to compensate.

Low iron does not just make you feel awful. It mimics perimenopause itself, adding to the fog, palpitations and exhaustion that get blamed on hormones. Our article on low iron and heavy periods goes into the detail.

What to test

Blood tests do not diagnose the cause of heavy bleeding; that is the job of the history, examination and ultrasound. What they do is measure what the bleeding is costing you and check the common contributors:

• Iron studies. Ferritin (stores), serum iron, transferrin and transferrin saturation. Ferritin is the key number, and reference ranges vary between laboratories, so a doctor interprets it in context. Ferritin also rises with inflammation, which can hide a low result.
• Full blood count. Haemoglobin, red cell size and other markers that show whether iron loss has progressed to anaemia.
• Thyroid function. Because an underactive thyroid contributes to heavy bleeding and to fatigue.
• Cycle hormones, where a doctor wants perimenopause context, and a pregnancy test if there is any chance.

If a GP orders these for a clinical reason, they are generally Medicare-rebated, and that is the right path if you are being investigated for heavy bleeding. Self-pay testing is not rebated, but it suits women who want a baseline or a recheck without a wait, and KnowLuna's women's health doctors can request the tests and explain the results by video if you do not already have a request. Whichever route you take, a heavy-bleeding result belongs in front of a doctor who can look at the cause as well as the number.

When to see a doctor without waiting

Seek medical care promptly if you are soaking through a pad or tampon every hour for more than a couple of hours, passing large clots repeatedly, feeling faint, dizzy or short of breath, bleeding between periods or after sex, or bleeding at all after 12 months without a period. Bleeding that is new, changed or persistent in your forties should always be assessed, even when the most likely explanation is perimenopause, because the other causes are common and treatable, and because iron loss compounds with every cycle.

Common questions

General information only, not medical advice. If your symptoms are severe or sudden, see a doctor promptly.