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You planned for it. Two super tampons and a thick pad, changed before you even got on the train. And by the time you reached the office, you knew. The cold dread of it. The quiet calculation — how far to the bathroom, how much time before you need to move again, whether anyone will notice if you keep your coat on all morning.

This is not a normal period. This is flooding.

You’ve doubled your protection and still bled through it. You’ve passed clots — dark, heavy, the size of a 50p coin — and tried to explain this to your GP, who looked at your blood test results and said: “Everything looks normal.” You’ve been offered the pill, or a Mirena coil. You’ve been told this is just perimenopause. You’ve been sent home.

And the flooding continues.

You’re exhausted in a way that sleep doesn’t fix. You’re anxious. You’ve started wearing dark clothes every day. You’re considering declining social invitations, rearranging meetings, avoiding booking holidays during certain weeks of the month. Your life is being reorganised around your period – possibly multiple periods in a month – and nobody in the medical system seems to understand why.

This article is for you. Not to scare you further, but to explain — in full — what is actually happening in your body. Because heavy bleeding in perimenopause is not random. It is not inevitable. And it is absolutely not something you simply have to endure.

What Is Heavy Bleeding in Perimenopause? Menorrhagia Defined

Clinically, heavy menstrual bleeding (menorrhagia) is defined as blood loss greater than 80ml per cycle — though if you’ve ever flooded through combined protection in under two hours, you already know that numbers don’t capture the reality of what this feels like.

Up to 50% of perimenopausal women experience heavier periods in the years before their final cycle. For many, this represents a dramatic departure from their reproductive norm. Periods that were once predictable and manageable become unpredictable, prolonged (8–10 days is not unusual), and catastrophically heavy. Clots appear. Flooding happens. The standard tampon-plus-pad combination fails within an hour.

This pattern — the escalating heaviness, the clotting, the flooding, the exhaustion — is not random bad luck. It follows a specific biological logic. Understanding that logic is the first step to addressing it.

The Mechanism in a Nutshell

Here is the root cause, compressed into three sentences:

As ovarian function begins to shift in your early 40s, the ovaries become fibrotic and less responsive — causing cycles where ovulation is skipped entirely. When you don’t ovulate, no corpus luteum forms, and no corpus luteum means no progesterone. Without progesterone to balance it, oestrogen runs unopposed — thickening the uterine lining month after month until it becomes unstable, fragile, and prone to chaotic, catastrophic shedding.

This is the heart of The Progesterone Shift — the full mechanism and clinical framework are explained in detail at The Progesterone Shift →

The Structural Mechanism: How the Uterine Lining Becomes Unstable

Under normal hormonal conditions, progesterone has a critical job: it matures the endometrial lining and signals its coordinated, complete shedding. Think of it as the conductor telling the orchestra when to stop. The shedding is organised. The bleeding is contained. The duration is predictable.

Without progesterone — or with insufficient progesterone — this coordination collapses.

Oestrogen continues to thicken the lining, unopposed. Month after month, the endometrium builds beyond its structurally sound limit. It becomes excessively thick, insufficiently supported, and inherently fragile. The blood vessels within it are poorly organised. The tissue is unstable.

When this lining eventually sheds, it does not shed in a controlled, coordinated way. It sheds chaotically. Vessels that would normally be clamped off continue bleeding. Tissue that would normally be expelled in an orderly sequence comes away in clots and fragments. The process takes far longer than it should, and the blood loss is far greater.

This is why the flooding starts. This is why the clots appear. This is the structural foundation — but it is not the whole picture. Because there are systemic drivers that make this structural problem dramatically worse. These are the drivers that conventional medicine rarely looks for — and that Sandra’s clinical approach addresses in full.

The Systemic Drivers: Five Reasons for Heavy Bleeding in Perimenopause

1. The Vicious Iron Deficiency Loop
   This is one of the most important — and most overlooked — mechanisms in heavy perimenopause bleeding, and it operates as a self-reinforcing downward spiral.
   
   Iron is required for platelet function and blood aggregation. When your iron stores (measured as ferritin) become depleted, your blood loses its ability to clot efficiently. Clotting is what stops a period. Without robust clotting, the bleeding continues longer and heavier than it otherwise would.
   
   Here is the vicious loop: heavy periods deplete iron → low iron weakens clotting → the next period is even heavier → iron depletes further → clotting worsens again. Left unaddressed, this loop accelerates. Women arrive in clinical practice with ferritin levels in single figures — profoundly depleted — while their GPs report “normal bloods” because haemoglobin has not yet dropped to the point of clinical anaemia.
   
   The loop must be broken from both ends simultaneously — not just by supplementing iron (though that is essential), but by identifying and addressing the root cause of the excessive bleeding itself. Iron supplementation alone, without addressing the hormonal and systemic drivers, provides temporary relief at best.

2. Liver Congestion and Sluggish Coagulation
   The liver is central to heavy bleeding in two distinct and compounding ways.
   
   First: the liver manufactures critical blood-clotting proteins, including prothrombin and fibrinogen. If liver detoxification pathways are congested — through high alcohol intake, a poor diet, chronic toxic load, or simple metabolic overwhelm — the synthesis of these coagulation factors slows. Less clotting capacity means longer, heavier bleeds.
   
   Second, and simultaneously: a sluggish liver fails to deactivate circulating oestrogen. The liver is responsible for packaging used oestrogen for excretion. When this process is impaired, active oestrogen continues to circulate in potent form, keeping uterine blood vessels highly dilated and primed for rapid, high-volume bleeding.
   
   This is a double hit: impaired clotting from the top, and oestrogen-driven vascular dilation from below. Both pathways lead to heavier bleeding, and both originate in the same compromised organ.

3. Gut Dysbiosis and the Estrobolome: How Your Gut Recycles Oestrogen
   Most women know that the gut affects digestion. Fewer know that it plays a critical role in oestrogen metabolism — and that when gut health is compromised, oestrogen that the body has already packaged for disposal can be reactivated and dumped back into circulation.
   
   The estrobolome is the collective term for the specialised gut bacteria involved in oestrogen metabolism. When the gut microbiome is dysbiotic — disrupted by poor diet, antibiotics, chronic stress, or constipation — there is an overpopulation of bacteria that produce an enzyme called beta-glucuronidase.
   
   This enzyme does something significant: it cleaves the glucuronic acid molecule that the liver has attached to used oestrogen to mark it for excretion. The result? Oestrogen is freed, reactivated, and absorbed back through the gut wall into the bloodstream via the hepatic portal vein — essentially reversing the liver’s detoxification work and flooding the body with oestrogen it had already tried to remove.
   
   This gut-driven oestrogen surge causes pelvic vascular widening — the blood vessels supplying the uterus dilate — and the bleeding accelerates. Chronic constipation, which slows intestinal transit and increases the window for beta-glucuronidase activity, compounds this significantly.

4. Stress, Cortisol, Prostaglandins, and Pelvic Vasodilation
   Chronic stress is not simply an emotional experience. It is a hormonal event with direct, measurable consequences in the uterus.
   
   The pathway works like this: chronic stress drives systemic inflammation, which triggers the overproduction of inflammatory prostaglandins — specifically PGE2 — in uterine tissue. PGE2 acts as a powerful local vasodilator. It physically relaxes and opens the uterine blood vessels, forcing blood to flow more rapidly and making it harder for those vessels to constrict and close during menstruation. In women with heavy menstrual bleeding, endometrial PGE2 levels are measurably elevated, and the ratio of vasodilatory to vasoconstrictive prostaglandins is significantly abnormal.
   
   There is a second stress pathway that compounds this: cortisol fluctuations activate mast cells in the reproductive tract, triggering histamine release. Histamine is itself a potent vasodilator — it increases local vascular permeability, making the vessels leaky and dramatically amplifying bleeding intensity.
   
   The woman who is under sustained pressure at work, struggling with sleep, running on cortisol — she is not simply stressed. Her uterine blood vessels are being held open by a cascade of inflammatory molecules every time she bleeds.

5. Micronutrient Deficiencies: The Nutritional Foundation of Heavy Bleeding
   This section is where functional medicine sees what conventional medicine misses. Blood tests ordered by GPs do not typically screen for the micronutrient deficiencies that directly drive heavy bleeding. “Normal bloods” means normal haemoglobin, normal thyroid — it does not mean adequate Vitamin A, adequate B6, adequate magnesium, or adequate B1. These are the nutrients that regulate the mechanisms described above, and their depletion is both common and clinically significant.
   
   Vitamin A
   Vitamin A regulates cellular turnover and tissue structural integrity. Seminal research by Lithgow and Politzer found that serum retinol levels were significantly lower in women with menorrhagia than in healthy controls — and that correcting subclinical Vitamin A deficiency produced complete or substantial improvement in heavy bleeding in over 92% of treated patients. Vitamin A appears to stabilise tissue fragility at the endometrial level, reducing the chaotic shedding pattern that produces flooding. It is rarely tested, and rarely supplemented, in conventional management of heavy periods.
   
   Magnesium
   Magnesium is a natural smooth-muscle relaxant — and the uterus is smooth muscle.
   
   When magnesium is depleted (as it rapidly is under chronic stress and high cortisol), the uterine muscle walls lose the ability to contract in a coordinated, controlled way. They contract erratically instead — or not at all. This matters because coordinated uterine contractions are a primary mechanism for clamping off bleeding vessels during menstruation. Without that coordinated muscular clamping, the blood vessels remain open longer. The result is prolonged, high-volume blood loss.
   
   Magnesium is also essential for prostaglandin metabolism. Low magnesium allows the inflammatory prostaglandin pathways to run unchecked, further amplifying the PGE2-driven vasodilation described above.
   
   B Vitamins: The Most Depleted and Most Overlooked Category
   B vitamins are water-soluble, which means the body cannot store them in significant quantities. They are depleted continuously — and the chronic stress and high-cortisol state of perimenopause accelerates this depletion dramatically. What follows is a breakdown of the most critical B vitamins in the context of heavy bleeding.
   
   B6 — The Progesterone and Prostaglandin Catalyst
   B6 is a vital co-factor for progesterone production. When B6 is depleted, the body’s enzymatic machinery for synthesising progesterone becomes less efficient — meaning that even where the ovaries are attempting to produce progesterone, insufficient B6 compromises the yield. This is a direct amplifier of the oestrogen dominance that drives heavy bleeding.
   
   B6 is also required for healthy fatty acid metabolism. Without adequate B6, the uterus overproduces inflammatory PGE2 prostaglandins — the same vasodilatory prostaglandins described in the cortisol pathway above. B6 depletion therefore creates a double vulnerability: less progesterone and more inflammatory prostaglandins, both of which drive heavier bleeding.
   
   Chronic stress — the constant companion of perimenopause — depletes B6 directly. The women most likely to be flooding are often the women most likely to be B6-deficient.
   
   B12 and B9/Folate — The Methylation and Red Blood Cell Pipeline
   The liver requires B12 and Folate to fuel methylation — the Phase II detoxification process responsible for deactivating oestrogen and preparing it for excretion. Without adequate B12 and Folate, this methylation pathway slows. The liver loses its ability to deactivate oestrogen efficiently, and potent oestrogen continues to recirculate — over-stimulating pelvic tissue and driving further bleeding.
   
   There is a second, compounding mechanism. Heavy bleeding causes massive red blood cell (RBC) loss. The bone marrow must work at high capacity to produce new RBCs. This process requires B12 and Folate as essential building blocks. When these vitamins are depleted — either from poor diet, poor absorption, or the prior demands of a stressed system — the bone marrow cannot keep pace with RBC loss. The result is anaemia. And anaemia creates its own vascular problem: oxygen-deprived tissues signal blood vessels to dilate in order to capture more oxygen. The uterine blood vessels dilate further. Paradoxically, the anaemia caused by the bleeding can accelerate the bleeding itself.
   
   B1/Thiamine — The Uterine Muscle Tone Anchor
   The uterus stops a period through contraction. Coordinated, strong contractions of the myometrium (the uterine muscle wall) physically clamp off the bleeding vessels during menstruation. This is how a period ends.
   
   B1 (thiamine) is the primary co-factor for ATP production in smooth muscle. ATP is the energy currency that powers every muscle contraction. When B1 is deficient, the myometrium lacks the cellular energy to contract effectively. The contractions become flaccid and erratic. The uterine muscle cannot pinch off the bleeding vessels with sufficient force or consistency. The period drags on. The blood loss escalates.
   
   B1 is water-soluble and — like all B vitamins — is rapidly depleted by the metabolic demands of chronic stress. It is never tested in standard GP blood panels, and its role in menorrhagia is virtually unknown in conventional medicine.

What Makes It Worse: The Cofactors

Several lifestyle and environmental factors compound all of the mechanisms above simultaneously:

• Alcohol:
  Directly suppresses liver detoxification function, impairs oestrogen clearance, and depletes B vitamins (particularly B1 and B12) at an accelerated rate.
• Chronic stress:
  Sustains the cortisol/PGE2/mast cell/histamine cascade; depletes magnesium, B6, B1, and B12; disrupts gut microbiome balance.
• Gut dysbiosis:
  Amplifies estrobolome-driven oestrogen recirculation; worsens constipation, which compounds it further.
• Processed foods and refined sugar:
  Drive inflammation, deplete micronutrients, destabilise blood sugar, and feed dysbiotic bacteria.
• Xenoestrogen exposure:
  Environmental oestrogen-mimicking compounds (in plastics, pesticides, personal care products) add to the total oestrogen load, placing further demands on an already-overwhelmed liver clearance system.

Why Conventional Treatments Often Fail

The pill and the Mirena coil are the two most common interventions offered to perimenopausal women with heavy bleeding. Both can reduce blood loss — but neither addresses the systemic drivers described above.

The pill works by suppressing the hormonal cycle entirely — replacing the natural (chaotic) hormonal environment with synthetic hormones. It is effective at reducing bleeding, but it treats the symptom while leaving the iron deficiency loop, the liver congestion, the gut dysbiosis, the prostaglandin imbalance, and the micronutrient depletion entirely untouched. When the pill is stopped, the underlying drivers remain in place.

The Mirena coil delivers a low-dose local progestin that thins the endometrial lining, which can dramatically reduce or stop periods. Again, effective at the symptomatic level — but the systemic drivers continue running. The oestrogen burden on the liver is not addressed. The estrobolome continues recycling. The B vitamin depletion continues.

“Normal blood tests” is a phrase that needs scrutiny. Standard GP bloods typically include haemoglobin, thyroid function, and perhaps ferritin. They do not include intracellular B12, active B6, RBC magnesium, Vitamin A, or detailed coagulation markers. A woman can be profoundly deficient in the nutrients that govern clotting, muscle tone, prostaglandin balance, and oestrogen clearance — and still be told her blood tests are normal.

The test results look normal because the right tests are not being ordered or the ranges are too wide to identify problems.

Case Study: Sarah, 43

Sarah is a composite illustration based on the clinical patterns I see in practice. All identifying details are fictional.

Sarah came in after what she described as three years of escalating periods. She had always had manageable cycles. But in her early 40s, something shifted. By the time she sought help, she was flooding through super tampons and a thick pad combined — changing protection every 45 minutes on her heaviest days. The clots were the size of 50p coins. Her periods lasted eight to ten days. She was leaving work mid-meeting, sleeping with a towel under her, carrying a change of clothes everywhere.

She was exhausted in a way that felt structural — not tiredness, but a profound depletion. She had become increasingly anxious. Her mood was erratic in the week before her period. She had been to her GP twice. Both times, she was told her blood tests were normal. She was offered the combined pill (she’d had a DVT in her 30s, so this wasn’t appropriate) and then the Mirena coil. She declined both. She wanted to understand why this was happening.

When I reviewed her full case and ran a functional panel, the picture was clear:

• Ferritin: 11 — severely depleted (optimal is 70–100). This alone was sufficient to significantly impair clotting.
• B12: borderline low — not flagged as deficient by standard lab ranges, but insufficient for optimal methylation and RBC production.
• Vitamin D: low — a common co-deficiency reflecting broader nutritional depletion.
• Cortisol: elevated throughout the day — no natural cortisol dip, sustained HPA axis activation.

Sarah was also experiencing significant gut symptoms: bloating, irregular bowel habits, and a history of multiple courses of antibiotics. Her diet was high in convenience foods (she was working 50-hour weeks) and she was drinking more wine than she intended to.

My protocol addressed all drivers simultaneously:

• Iron support: A well-tolerated liquid iron supplement with cofactors for absorption
• B vitamin complex: Focused on B6 (methylated pyridoxal-5-phosphate), B12 (methylcobalamin), folate (methylfolate), and B1 (thiamine)
• Magnesium: Glycinate form for uterine muscle support and cortisol modulation
• Liver support: Milk thistle, DIM (diindolylmethane), and dietary changes to reduce the alcohol and processed-food burden
• Gut work: A targeted probiotic protocol to address dysbiosis and reduce beta-glucuronidase activity, combined with fibre and dietary changes
• Stress reduction: A structured approach to cortisol management, including sleep hygiene, adaptogenic herbs, and nervous system support

Within six weeks, Sarah’s flooding had reduced dramatically. Her periods were back to five days. Energy was returning — not fully, but meaningfully. By three months, her ferritin had climbed to 34 and was still rising. She felt, for the first time in three years, that her body was doing something right.

In her own words:

“I went from wearing maternity pads for fear of flooding to having a normal period. I didn’t know that was still possible.”

The Protocol: Addressing All the Drivers, Because They Are All Connected

Heavy bleeding in early perimenopause is a systemic problem. It requires a systemic response.

Lower the inflammatory prostaglandin burden. Support the liver’s oestrogen clearance pathways. Restore gut health and reduce beta-glucuronidase activity. Replenish the depleted B vitamins — B6, B12, folate, and B1. Restore magnesium to support uterine muscle tone. Break the iron deficiency loop. Quiet the cortisol cascade.

These are not separate interventions. They are one integrated approach to a set of interconnected mechanisms — all of which are driving your bleeding, and all of which can be addressed.

The full Progesterone Shift protocol is explained here: The Progesterone Shift →

A Closing Reframe

Heavy bleeding is not “just your age.” It is not “just perimenopause.” Those phrases, however well-intentioned, communicate something deeply unhelpful: that what is happening to you is inevitable, untreatable, and not worth investigating further.

It is none of those things.

What is happening to you is a set of interconnected systemic failures — in hormonal signalling, in liver function, in gut ecology, in nutrient status, in the stress-inflammation-vascular pathway — each of which has an identifiable cause and a reversible mechanism. Your body is not broken. It is overwhelmed. And an overwhelmed system that is properly supported can, and does, recover.

The flooding is not your fate. It is a signal. And signals, when understood correctly, point the way forward.

Work With Me

Is The Progesterone Shift driving your heavy periods?

If the mechanisms in this article resonate with what you are experiencing, and you are ready to understand what is actually happening in your body and address it systematically, Sandra works with women in early perimenopause to untangle exactly this picture.

Book a consultation with Sandra →

You can also read more about the energy side of perimenopause — another dimension of The Progesterone Shift — on the Energy Shift page →

References

1. Sriprasert I, Pakrashi T, Kimble T, Archer DF. Heavy menstrual bleeding diagnosis and medical management. Contracept Reprod Med. 2017;2:20. DOI: 10.1186/s40834-017-0047-4
   Comprehensive clinical review of the multiple pathways — including prostaglandin E2-driven vasodilation, fibrinolysis, and coagulation — implicated in heavy menstrual blood loss. Confirms that increased PGE2 and COX-2 expression are characteristic findings in women with HMB.
2. Maybin JA, Critchley HOD. Menstrual physiology: implications for endometrial pathology and beyond. Hum Reprod Update. 2015;21(6):748–761. DOI: 10.1093/humupd/dmv038
   Detailed mechanistic paper establishing progesterone withdrawal as the trigger for menstruation, and explaining how disrupted progesterone signalling — via COX-2, NF-κB, and MMP upregulation — leads to abnormal bleeding patterns.
3. Mansour D, Hofmann A, Gemzell-Danielsson K. A review of clinical guidelines on the management of iron deficiency and iron-deficiency anaemia in women with heavy menstrual bleeding. Adv Ther. 2021;38(1):201–225. DOI: 10.1007/s12325-020-01564-y
   Review demonstrating that iron deficiency is systematically underdiagnosed and undertreated in women with heavy menstrual bleeding, and that iron deficiency impairs haemostasis and clotting function — establishing the clinical basis for the iron deficiency loop.
4. Ervin SM, Li H, Lim L, Roberts LR, Liang X, Mani S, Redinbo MR. Gut microbial β-glucuronidases reactivate estrogens as components of the estrobolome. J Biol Chem. 2019;294(49):18586–18599. DOI: 10.1074/jbc.RA119.010950
   Foundational paper establishing the biochemical mechanism by which gut bacterial beta-glucuronidase enzymes cleave glucuronic acid from conjugated oestrogens, reactivating them and returning them to systemic circulation — the core mechanism of estrobolome-driven oestrogen recirculation.
5. Hu S, Ding Q, Zhang W, Kang M, Ma J, Zhao L. Gut microbial beta-glucuronidase: a vital regulator in female estrogen metabolism. Gut Microbes. 2023;15(1):2236749. DOI: 10.1080/19490976.2023.2236749
   2023 review confirming gut microbial beta-glucuronidase as a key regulator of female reproductive endocrine function across the lifespan, with implications for oestrogen-driven conditions including heavy uterine bleeding.
6. Parra M, Stahl S, Hellmann H. Vitamin B6 and its role in cell metabolism and physiology. Cells. 2018;7(7):84. DOI: 10.3390/cells7070084
   Comprehensive review of B6 (pyridoxal-5-phosphate) as a co-factor in over 150 enzymatic reactions, including those governing amino acid metabolism, steroid hormone synthesis (including progesterone), and fatty acid metabolism relevant to prostaglandin production.
7. Edlund M, Andersson E, Fried G. Progesterone withdrawal causes endothelin release from cultured human uterine microvascular endothelial cells. Hum Reprod. 2004;19(6):1272–1280. DOI: 10.1093/humrep/deh256
   Mechanistic study showing that progesterone withdrawal — the event that drives abnormal bleeding in perimenopause — directly alters uterine vascular endothelial cell behaviour, with implications for the vasodilatory mechanisms driving flooding.
8. Lithgow DM, Politzer WM. Vitamin A in the treatment of menorrhagia. S Afr Med J. 1977;51(7):191–193.
   Landmark clinical study demonstrating significantly lower serum retinol in women with menorrhagia versus healthy controls, and showing that Vitamin A supplementation produced complete normalisation or substantial improvement in 92.5% of treated patients.
9. Jakubowitz M et al. The role of prostaglandins and allied substances in uterine haemostasis. Prostaglandins. 1987;33(Suppl):91–98. PMID: 3311624.
   Review establishing that women with menorrhagia have an abnormally low PGF2α:PGE2 ratio — elevated vasodilatory PGE2 relative to vasoconstrictive PGF2α — as a key driver of excessive menstrual blood loss.