Is Low Iron Behind Your Fatigue? What Women Need to Know

I can't count how many times a woman has sat across from me in the pharmacy or the clinic, telling me she's exhausted. Her hair's thinning. She can't concentrate. She feels cold even when everyone else in the room is warm. And she's been told, by her GP, by a friend, by the internet, that it's probably perimenopause.

Sometimes it is. But quite often, it isn't. Or at least, not entirely.

Low iron is one of the most underdiagnosed conditions in women over 35. Partly because its symptoms look almost identical to perimenopause, burnout, and thyroid problems. And partly because the standard blood test most GPs run does not always catch it. If you've had blood tests and been told everything looks "normal" but you're still exhausted, keep reading.

Why iron deficiency is so easy to miss

Here's what most people don't know: there are two distinct stages of low iron, and one of them is completely invisible on a standard full blood count.

Iron deficiency anaemia, where your haemoglobin is low, is what most people picture. You look pale, feel very weak, and your doctor catches it on a routine blood test.

But iron deficiency without anaemia is different. Your haemoglobin is still normal. Your red blood cells are still functioning. What's critically low is your ferritin, the protein that stores iron in your body. Ferritin is what your body draws on when it needs iron for energy production, brain function, and hormone regulation.

Think of ferritin as your iron bank account. Anaemia is when the account is overdrawn. Iron deficiency without anaemia is when the balance is still technically positive, but you've been making small withdrawals every month and no deposits for years. You're running on reserves, and your body is telling you about it.

The symptoms that overlap with perimenopause

This is where it gets confusing, and where women often fall through the cracks.

Low ferritin can cause persistent fatigue even after a full night's sleep, poor concentration and brain fog, hair thinning or increased shedding, feeling cold especially in your hands and feet, shortness of breath on minimal exertion, restless legs at night, low mood and irritability, and poor recovery after exercise.

That list looks remarkably like a perimenopause symptom checklist. It also overlaps considerably with burnout and low thyroid function. This is why low iron gets dismissed so often in the 35 to 55 age group. Everyone assumes the obvious cause, and the deficiency quietly continues.

I've worked with women who were on HRT (hormone replacement therapy, a treatment used to manage menopausal symptoms by supplementing declining hormones) and still felt terrible, because their ferritin was never checked. Oestrogen replacement will not do much for your energy if your cells are starved of the iron they need to produce it in the first place.

Why women are disproportionately affected

Women lose iron every month through menstruation. Heavier periods, which are common in perimenopause as oestrogen levels fluctuate, increase that loss significantly. If you've noticed your periods getting heavier in recent years, your iron stores may have been quietly depleting for some time.

There are other risk factors to know about. Plant-based or low-meat diets matter because non-haem iron from plants is less efficiently absorbed than haem iron from meat and fish. Eating substantially less overall is also relevant, particularly if you've been using appetite-suppressing medication or following a very calorie-restricted plan. Regular high-intensity training, previous pregnancy, and gut conditions that affect absorption (such as coeliac disease or low stomach acid) all increase your risk too.

If you're in any of these categories and you've been feeling off, ask about ferritin specifically.

What to actually ask for when you get blood tests

This is probably the most practical thing I can tell you. When you request blood tests, ask for ferritin as a standalone test, not just a full blood count.

A full blood count checks your haemoglobin and the size and number of your red blood cells. It won't tell you what your ferritin stores are. You need to ask for it by name.

The "normal" range for ferritin varies between labs and is quite wide. In clinical practice, many women report feeling their best when ferritin is above 50 ng/mL. Research suggests that symptoms of iron deficiency can persist even at levels that technically sit within the lower end of the "normal" range. If your ferritin comes back below 30, have a proper conversation with your GP or pharmacist, even if you're told it's within range.

And do not be afraid to ask directly: "Was ferritin included in those tests?"

What to do about low ferritin

Food comes first. The best dietary sources of haem iron (the most absorbable form) include red meat, liver, turkey, and oily fish. Non-haem iron from lentils, chickpeas, spinach, tofu, and fortified cereals is also useful, but pair it with vitamin C to improve absorption: a glass of orange juice, a squeeze of lemon, or some berries alongside your meal makes a genuine difference.

It is also worth knowing what reduces absorption. Tannins in tea and coffee, calcium-rich foods, and certain antacids can inhibit iron uptake when consumed at the same time as an iron-rich meal. If you drink tea with every meal, that habit alone could be quietly reducing your absorption without you realising.

If your ferritin is quite low, your GP or pharmacist may recommend a supplement. Different formulations suit different people, and some cause more digestive side effects than others. There is also emerging evidence that taking iron on alternate days rather than daily may improve absorption for some people. A healthcare professional can help you find the right approach.

When to get checked

If you're experiencing three or more symptoms from the list above, ask your GP for a ferritin test at your next appointment. If you've already had blood tests and been told they're normal, ask specifically whether ferritin was included. It often isn't.

It takes five minutes and it could give you some real answers. As a pharmacist, I see this pattern constantly: women who have been tired for years, written it off as just life, and then had ferritin tested and found it sitting at 12. It is not dramatic. But it is entirely fixable.

If you'd like a more comprehensive look at what's going on, a Debora Tentis Clinic consultation covers hormonal health, ferritin, thyroid function, and the full picture. Browse our services or visit our contact page. Find us on Instagram, TikTok, and Facebook.

Debora Tentis is a Women's Health Pharmacist and Independent Prescriber Trainee based in Milton Keynes, UK. This article is for educational purposes and does not constitute medical advice. Please consult your GP or a qualified healthcare professional for a personalised assessment of your iron levels and any symptoms you are experiencing.