Written by Catherine Scott, Registered Nutritional Therapist | Leeds | Perimenopause Specialist
Something I hear from so many women in clinic, usually mentioned in passing, almost as an aside, as though it's just an accepted fact of life, is that their iron has always been a bit low. Their ferritin too. They've known for years, their GP knows and at some point a supplement was prescribed but it made them constipate so they stopped taking it. Nobody followed up and so the low iron has simply become part of their story.
If that sounds familiar, this post is for you.
Here's what I want you to know: low iron and low ferritin aren't just something to live with. They are not a personality trait or an inevitable consequence of having a female body. And in perimenopause especially, they matter far more than most women are told.
Why Is Iron So Important for Women in Perimenopause?
Iron is a mineral your body uses to make haemoglobin, the protein in your red blood cells that carries oxygen around your body. But iron's role doesn't stop there. It is also essential for energy production inside your cells, for brain function, immune health and thyroid metabolism.
When iron is low, everything slows down. And in perimenopause, when oestrogen is already fluctuating and your body is under hormonal pressure, that slowing down can be profound.
The difficulty is that many symptoms of low iron look almost identical to symptoms of perimenopause itself: exhaustion, brain fog, poor sleep, hair loss, low mood. This is why iron often goes unchecked. Or is checked, comes back 'normal,' and is dismissed.
What Is the Difference Between Iron Deficiency and Iron Deficiency Anaemia?
These two terms are often used interchangeably, but they are not the same thing.
Iron deficiency is when your body's stored iron is running low. In the early stages, your haemoglobin and red blood cell count may still look normal on a blood test, which is why it is so frequently missed.
Iron deficiency anaemia is the more advanced stage, where there is so little iron left that your body can no longer make enough haemoglobin. At this point your red blood cells become fewer, smaller and paler, and carry less oxygen around your body. Classic symptoms include extreme fatigue, breathlessness and a racing heart.
The key point: you can have significant iron deficiency (enough to be causing fatigue, hair loss and brain fog) without it showing up as anaemia. This is why ferritin is the more important marker to look at.
What Is Ferritin, and Why Does It Matter?
Ferritin is the protein that stores iron in your tissues. Think of it like a bank account: your circulating iron is the cash in your wallet and it changes day to day, while ferritin tells you how much you actually have in reserve.
A low ferritin reading, even when your haemoglobin looks fine, tells you that your reserves are depleted. Your body is running on empty and will eventually start pulling from haemoglobin once those reserves are gone.
This is the scenario I see repeatedly in clinic: a woman with a ferritin of 18 or 22 µg/L being told her iron is 'within normal range' and sent away without any further support.
Understanding Your Ferritin Reading
This table is a general guide. Always interpret your own results with a GP or qualified practitioner.
| Ferritin (µg/L) | What it may indicate | What might happen next |
|---|---|---|
| Below 15 | Severely depleted stores — often iron deficiency anaemia | GP likely to prescribe iron supplements; further investigation may follow |
| 15–30 | Low stores; iron deficiency likely (NICE UK cut-off is 30) | Supplements often recommended; diet review helpful |
| 30–50 | Borderline — technically 'normal' but may still be functionally low, especially with symptoms | GP may not act; nutritional therapy review worthwhile |
| 50–100 | Good range for most women; energy and hair supported | Maintain through diet and lifestyle |
| Above 150 | Can indicate inflammation — ferritin rises as an acute-phase protein | Worth investigating alongside other markers |
This table is a general guide. Always interpret your results with a GP or qualified practitioner.
Why Does Perimenopause Make Low Iron So Much More Likely?
Heavy and Erratic Periods
For many women, perimenopause brings heavier, longer or more frequent periods before they eventually stop. This is one of the most significant drivers of iron loss in midlife. You can be eating a perfectly adequate diet and still be losing more iron through menstrual blood than you are taking in.
If your periods have become heavier in your 40s and you feel more exhausted than you used to, it is worth asking your GP to check your ferritin specifically, not just your haemoglobin.
Years of Low-Level Depletion
Many of the women I work with have had low-normal ferritin for years, often since their 20s or 30s. It has never been dramatic enough to trigger treatment, but it has also never truly recovered. By the time perimenopause arrives, they are already running on depleted reserves and the additional demands of hormonal change push them further into deficiency.
The Supplement Problem
If you have ever been prescribed ferrous sulphate, the most common iron supplement on the NHS, and found it made you constipated, nauseous or generally miserable, you are not alone. This is one of the most commonly reported reasons women stop taking prescribed iron.
The problem is that when you stop the supplement and nobody follows up, the low ferritin carries on. Gentler forms of iron such as ferrous bisglycinate, tend to be significantly better tolerated and are worth discussing with a nutritional therapist or GP. But please don't self-supplement without getting your levels tested first; iron is one nutrient where more is not always better.
What Are the Symptoms of Low Iron and Low Ferritin?
SYMPTOMS THAT CAN BE LINKED TO LOW IRON OR FERRITIN
● Persistent fatigue and low energy, even after rest
● Brain fog and difficulty concentrating
● Hair loss or excessive shedding
● Brittle nails
● Headaches
● Shortness of breath on mild exertion
● Heart palpitations
● Restless legs, particularly at night
● Feeling cold all the time
● Irritability and low mood
● Poor sleep quality
Many of these overlap with perimenopause symptoms, which is exactly why iron is so often missed.
Why Is Your Iron Low? Finding the Root Cause
Low iron and low ferritin are symptoms, not a diagnosis. Topping up your levels without understanding why they dropped or why they're not recovering is a bit like putting a bucket under a leak without fixing the pipe. The levels may improve temporarily, but they'll keep falling unless the underlying reason is addressed.
There are several possible reasons, and more than one can apply at the same time.
Heavy or Prolonged Periods
This is the most common cause of low iron in women of reproductive age, and it becomes particularly relevant in perimenopause when periods often become heavier, longer or more erratic. Each period involves blood loss, and blood contains iron. If your flow has become noticeably heavier in your 40s, or you're regularly soaking through protection faster than you'd expect, this may be the primary driver of your depleted stores.
It's worth tracking your periods if you haven't already - how many days, how heavy, any flooding or clots - so you can have an informed conversation with your GP. Heavy periods can also be investigated and managed in their own right; you don't have to just accept them as part of perimenopause.
Poor Dietary Intake
If your diet is low in iron-rich foods, whether because you're vegetarian or vegan, you eat very little red meat, or you're simply not eating enough overall, you may simply not be taking in enough to maintain good stores. This is particularly relevant for plant-based eaters, since non-haem iron (the form found in plants) is less efficiently absorbed than haem iron from meat and fish.
That said, diet alone rarely tells the whole story. Many women with good dietary iron intake still have low ferritin, which points to an absorption issue rather than intake.
Coeliac Disease and Gluten Sensitivity
Coeliac disease is one of the most commonly missed causes of low iron, particularly in women. It's an autoimmune condition in which gluten triggers damage to the lining of the small intestine, specifically the villi, which are the tiny finger-like projections responsible for absorbing nutrients including iron.
What makes coeliac tricky is that it doesn't always present with the classic digestive symptoms most people expect. Many adults with undiagnosed coeliac disease have no obvious gut symptoms at all, or they've had low-level bloating, fatigue or loose stools for so long they've come to think of it as normal. Persistently low ferritin that doesn't respond well to supplementation is one of the most important flags for testing.
The test for coeliac is a blood test (tTG-IgA antibody) and needs to be done while you're still eating gluten regularly to be accurate. If you've already cut gluten out, speak to your GP before retesting. Non-coeliac gluten sensitivity is a separate and less well-defined condition, but it can also affect gut function and absorption capacity.
Other Gut and Digestive Conditions
The small intestine is where most iron is absorbed, so any condition that affects the gut lining or the digestive environment can reduce how much iron you actually take in from food. This includes:
● Inflammatory bowel disease (Crohn's disease and ulcerative colitis) - these cause inflammation of the gut wall and can significantly impair absorption. They can also cause blood loss directly if the gut is inflamed.
● Atrophic gastritis - thinning of the stomach lining, which reduces stomach acid production. Stomach acid is needed to convert iron from food into the form the body can absorb. This becomes more common with age and is also associated with long-term use of proton pump inhibitors (PPIs) like omeprazole.
● Helicobacter pylori infection - this bacterial infection of the stomach lining is strongly associated with iron deficiency, even in the absence of obvious gut symptoms. It's worth testing for if your iron doesn't respond to supplementation.
● Small intestinal bacterial overgrowth (SIBO) - an overgrowth of bacteria in the small intestine can compete with you for iron and interfere with absorption. It often causes bloating, wind and altered bowel habits.
Long-Term Use of Acid-Suppressing Medication
Proton pump inhibitors (PPIs) such as omeprazole and lansoprazole are among the most commonly prescribed medications in the UK, and many people take them for years without review. Stomach acid plays an important role in iron absorption; it converts ferric iron (the form found in most food and supplements) into the ferrous form that the body can actually absorb. Reducing stomach acid over the long term can impair iron absorption without anyone connecting the dots.
This doesn't mean stopping your PPI, there are often good medical reasons for taking them, but if you're on long-term acid suppression and your ferritin is persistently low, it's worth raising with your GP and exploring gentler or more bioavailable forms of iron.
Chronic Blood Loss From Other Sources
In women who are still having periods, menstrual blood loss is the obvious cause. But it's not the only one. Chronic low-level bleeding from the gut, from haemorrhoids, a gastric or duodenal ulcer, or in rare cases from other gut pathology, can also deplete iron over time, often without any obvious symptoms. This is one of the reasons GPs are trained to investigate unexplained iron deficiency anaemia more thoroughly, particularly in older women and in anyone who has been through the menopause.
If you've been through menopause and your iron is low, it is especially important to rule out other causes rather than just supplementing.
What to Do With This Information
If you've been told your iron or ferritin is low, it's worth thinking through which of these factors might apply to you and asking your GP to investigate rather than just prescribe a supplement.
Useful questions to ask:
● Has my ferritin been checked, not just my haemoglobin?
● Should I be tested for coeliac disease?
● Is an H. pylori test appropriate given that my iron isn't recovering?
● Are there any gut or absorption issues that could explain this?
A nutritional therapist can also work with you to look at the broader picture such as what you're eating, how your gut is functioning, what other markers might be relevant and build a practical plan alongside whatever your GP recommends.
What Should You Ask Your GP?
If you suspect low iron or ferritin, the most useful thing you can do is be specific when you speak to your GP. Rather than asking for 'an iron test,' ask for:
● A full blood count (FBC) - this checks haemoglobin and red blood cell markers
● A serum ferritin test - this is the key marker for iron stores and is not always included automatically
If your results come back and you are told they are 'normal,' ask what your ferritin number actually is. A result of 22 µg/L may technically fall within the standard reference range, but it is not optimal and it is worth exploring further if you have symptoms.
Which Foods Are Highest in Iron?
Haem Iron (Animal Sources) - Most Easily Absorbed
● Red meat: beef, lamb, pork
● Liver and other offal (avoid in pregnancy due to vitamin A content)
● Fish and poultry
Non-Haem Iron (Plant Sources) - Still Valuable
● Lentils, chickpeas and kidney beans
● Tofu and tempeh
● Dark leafy greens: spinach, kale, watercress
● Pumpkin seeds, sesame seeds and hemp seeds
● Fortified breakfast cereals
● Dried apricots and figs
What Helps Absorption?
Pairing non-haem iron with a source of vitamin C at the same meal significantly improves absorption. Think lentil soup with a squeeze of lemon, spinach with red pepper, or a glass of orange juice alongside a fortified cereal.
What Can Reduce Absorption?
Tannins in tea and coffee can reduce how much iron you absorb from a meal. If your iron is low, switching to having your tea or coffee between meals rather than with them is a simple, low-effort change. Research suggests leaving an hour after eating halves the effect of tannins on iron absorption.
Calcium (from dairy) can also reduce iron absorption slightly, but the evidence suggests the overall effect on iron status is small for most people. You don't need to avoid dairy but if you're taking an iron supplement, the NHS advises leaving a two-hour gap between it and any dairy, tea or coffee.
What About Iron Supplements - Are They Always the Answer?
Iron supplements are often necessary when stores are significantly depleted, and there are situations where they are the most effective and appropriate route. However, not all iron supplements are equal.
Ferrous sulphate, the standard NHS prescription, is high-dose and notoriously hard on the digestive system. Ferrous bisglycinate (also called iron bisglycinate or gentle iron) is a chelated form that tends to be much better tolerated as it causes fewer gut side effects and is still well absorbed.
Before supplementing, please do get tested. Iron is one of the few nutrients where overloading can cause harm, and testing before and after supplementing helps you track whether your levels are actually improving.
Does Iron Improve Naturally After Menopause?
For many women, yes, once periods stop completely, the monthly blood loss that has been depleting iron is removed, and levels often recover over the following months. This is one of the genuine positives of reaching menopause.
However, if stores have been chronically low for years, recovery can take longer than expected. Absorption of iron from food can also become less efficient with age. So while levels may improve on their own, it is worth checking your ferritin after menopause rather than assuming everything will correct itself without any support.
WANT TO UNDERSTAND YOUR OWN RESULTS?
If you're in perimenopause and you've been told your iron is 'fine' but you still feel exhausted, foggy or your hair is falling out, your results may be telling a different story.
I work with women to look at the full picture: your ferritin, your symptoms, your diet, your cycle history. Together we build a plan that actually makes sense for your body and your life.
You can book a free discovery call to chat things through with me here
Frequently Asked Questions
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Iron refers to the mineral circulating in your blood, while ferritin is the protein that stores iron in your tissues. Ferritin is a more reliable marker of your long-term iron status — you can have normal circulating iron but depleted stores, which is why ferritin is the more useful test.
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The NHS uses a lower limit of 30 µg/L. However, many practitioners working with perimenopausal women consider a functional optimum to be closer to 50–100 µg/L, particularly where symptoms of fatigue, hair loss or brain fog are present.
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Yes. Ferritin is essential for healthy hair follicle cycling. Studies suggest ferritin levels below 30–40 µg/L are associated with increased hair shedding, and this is one of the most common reasons women in perimenopause notice a change in hair thickness or volume.
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The most commonly prescribed supplement, ferrous sulphate, is known to cause digestive side effects including constipation, nausea and dark stools. These side effects are one of the most common reasons women stop taking prescribed iron. Gentler forms such as ferrous bisglycinate or iron bisglycinate tend to be better tolerated — speak to a nutritional therapist or GP before switching
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For many women, yes - once periods stop, the monthly blood loss that depletes iron is removed, and levels often rise naturally. However, if stores have been low for years, recovery can take time. Some women also find their digestive absorption of iron reduces with age, so it is worth checking levels after menopause rather than assuming they will correct themselves.
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Haem iron (most easily absorbed) is found in red meat, liver, fish and poultry. Non-haem iron is found in lentils, beans, tofu, dark leafy greens, pumpkin seeds and fortified cereals. Pairing plant iron sources with a vitamin C-rich food at the same meal helps absorption.
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If you are experiencing significant fatigue, breathlessness, heart palpitations or heavy periods, see your GP. You can request a full blood count and a ferritin test — it is worth asking for ferritin specifically, as it is not always included automatically. If your results come back 'normal' but you still have symptoms, a nutritional therapist can help you interpret them in more detail.