Iron and Energy: Why So Many Women Feel Exhausted

Why iron matters so much

Iron is required for haemoglobin (which carries oxygen in red blood cells) and for components of the mitochondrial electron transport chain. Iron deficiency reduces oxygen delivery and impairs cellular energy production.¹

Iron deficiency doesn't just affect energy. It affects cognition, mood, temperature regulation, and immune function. Women with low iron are more prone to depression, brain fog, cold hands and feet, and getting sick. You can have all three of these symptoms and still test "normal" on a standard blood test.

Women lose blood monthly. If you've had heavy periods, given birth, or donated blood, you've lost iron you haven't replaced. If your diet is low in bioavailable iron, you're running a deficit. Month after month. Year after year. Until you hit a wall and suddenly everything feels impossible.

How iron deficiency develops in women

Women lose blood monthly. If you're menstruating, you're losing iron every single month. If your cycle is heavy, you're losing more. If your diet is low in bioavailable iron (meat, organs, seafood) and high in processed foods, you're losing more than you're replacing. Over months, iron stores deplete. Over years, you're running on fumes.

Vegetarian and vegan women are at higher risk for iron deficiency because non-heme iron from plants is less bioavailable than heme iron from animal sources; the NIH ODS notes mixed-diet absorption around 14–18% versus 5–12% for vegetarian diets.¹

Pregnancy depletes iron dramatically. Your body needs more iron to support the pregnancy. Postpartum haemorrhage (even minor) depletes it further. Many women emerge from pregnancy with dangerously low stores and spend years replenishing.

Birth control pills can increase iron loss, especially if you have heavy periods. Stress suppresses iron absorption. Intense exercise increases iron loss through sweat. Digestive issues (IBS, coeliac, Crohn's) reduce absorption. It's not just diet. It's the whole picture.

After menopause, iron needs actually decline, which is why postmenopausal women are less likely to be iron deficient than women of reproductive age. Menopause arrives and suddenly you have energy again. This isn't coincidence. It's iron.

The hidden symptoms nobody connects

Doctors are trained to look for obvious signs: pale skin, shortness of breath, dizziness. But low iron presents in ways that get medicalised separately and never connected back to iron.

Restless legs syndrome (RLS) has been associated with low iron stores; current guidelines recommend checking serum ferritin in patients with RLS and considering iron supplementation when ferritin is below 75 ng/mL.²

Hair loss? Low iron. Nails that are thin, flat, or spoon-shaped? Low iron. Brittle nails that break constantly? Often iron (though also sometimes B12).

Brain fog that feels like early dementia? Low iron. You can't think clearly. You walk into a room and forget why. You read the same sentence five times. It feels like your brain is broken. It's not. It's underfed.

Insomnia that gets treated with sleeping pills? Paradoxically, low iron causes insomnia. Your body tries to conserve oxygen at night. You can't relax. You can't sleep. The GP prescribes a benzodiazepine. The real problem is iron.

These symptoms get treated separately, with supplements and medication that don't work, because nobody looked at iron.

What deficiency feels like

Early deficiency: fatigue that coffee can't fix, brain fog, difficulty concentrating, cold hands and feet, hair loss or brittle hair, restless legs at night.

More advanced deficiency: shortness of breath with minor exertion, pale skin, difficulty sleeping (paradoxically), irregular periods or very heavy periods, intense cravings for non-food items (ice, dirt, starch), difficulty exercising.

Severe deficiency: you can barely get out of bed. Normal daily tasks feel impossible. You've been to every specialist. Nothing works. This is when women often get diagnosed with chronic fatigue syndrome or depression, when the actual problem is iron.

If you're exhausted and your tests come back "normal", ask specifically for iron studies. Serum iron, ferritin, TIBC, transferrin saturation. Normal complete blood count doesn't rule out iron deficiency.

Getting tested properly

Your GP can order iron studies: ferritin, serum iron, total iron-binding capacity (TIBC), transferrin saturation. Ferritin is the most useful, it reflects your iron stores.

Normal range for ferritin is often listed as 30-300 ng/mL. But functional iron range is higher. Many women don't feel energetic until ferritin is above 70. You can be "normal" and still deficient in a functional sense.

Optimal for premenopausal women is ferritin around 100-150 ng/mL. If your ferritin is 35 and you're exhausted, you're below functional range even though you're technically "normal."

Ask for the specific numbers, not just "normal" or "abnormal." If testing confirms low iron, the cause matters. Heavy periods? Dietary insufficiency? Malabsorption? The treatment depends on the cause.

Fixing it with food

Liver is the most bioavailable source. One serving per week dramatically improves iron status over months. Beef, shellfish, and eggs are also excellent sources.

Pair iron-rich foods with vitamin C (citrus, tomatoes, peppers) to enhance absorption. Eat them with fat (butter, olive oil, avocado) to further improve absorption. Avoid tea and coffee with meals, as they inhibit iron absorption through tannins.

Cook in cast iron if possible. Small amounts of iron leach from the pan into food, especially when cooking acidic foods like tomatoes. It's not massive, but it adds up over time.

If your diet has been very low in iron, food repletion takes months. If testing shows severe deficiency, iron supplementation speeds repletion. But food remains the foundation.

Once you've repleted iron, eating meat regularly (several times a week) maintains levels and keeps energy and mood steady. This isn't optional for most women. It's the difference between thriving and surviving.

When supplementation is necessary

If ferritin is below 20, food alone usually isn't fast enough. Iron supplements (particularly ferrous forms) accelerate repletion.

Take iron on an empty stomach with vitamin C to enhance absorption. It will make you constipated. Deal with it with magnesium or fibre, not by skipping doses. The constipation is temporary. The iron deficiency is not if you stop taking it.

Retest ferritin after 8-12 weeks of supplementation. Once you're above 50, you can likely drop the supplement and maintain with food. This isn't permanent dependency. It's a temporary tool to get you back to normal range.

Some women need ongoing iron because of heavy periods. If your period is genuinely heavy (changing a pad/tampon more than hourly, bleeding for more than 7 days), talk to your GP about options to reduce bleeding rather than supplementing forever.

The bottom line

You're not lazy or broken. Iron deficiency is common, fixable, and the cause of so much unexplained exhaustion in women. Get tested properly (ask for ferritin levels). Eat meat several times weekly, prioritising liver. Feel the difference. Your energy returns. Your mood lifts. Your brain clears. This is not subtle. This is your life changing because your body finally has the iron it needed all along.

References

1. 1. National Institutes of Health, Office of Dietary Supplements. Iron — Health Professional Fact Sheet. https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/
2. 2. Allen RP, Picchietti DL, Auerbach M, et al. Evidence-based and consensus clinical practice guidelines for the iron treatment of restless legs syndrome/Willis-Ekbom disease in adults and children. Sleep Medicine. 2018. https://pubmed.ncbi.nlm.nih.gov/29495173/