The Importance of Iron for Women

If you feel tired in a way that sleep does not fix, iron is one of the first things worth checking. It is the mineral your body uses to carry oxygen from your lungs to every muscle and to your brain, so when stores run low, the whole system runs a little slower. Iron shortfall is genuinely common in women, and the good news is that it is measurable and usually straightforward to correct.

Why iron matters, and why women are more exposed

Most of your body's iron sits inside haemoglobin, the protein in red blood cells that binds oxygen and delivers it around the body. Iron also supports energy production inside your cells and plays a role in normal brain and immune function. When there is not enough, tissues get less oxygen, and that shows up as fatigue, breathlessness on stairs, or foggy concentration.

Women of reproductive age are more exposed for a simple reason: menstruation removes blood, and therefore iron, month after month. Heavy or prolonged periods raise the loss further, and pregnancy increases demand substantially as the body builds extra blood volume and supplies a growing baby. This is context worth knowing, not a reason to worry: it simply means iron is a marker many women benefit from watching.

Deficiency, anaemia, and the difference between them

It helps to separate two stages. Iron deficiency means your stores are running low, even if your blood count still looks normal. Iron-deficiency anaemia is the later stage, where stores are depleted enough that haemoglobin falls and red blood cells become smaller and paler. You can feel the effects of low iron well before you meet the formal definition of anaemia, which is one reason stores are worth measuring directly rather than waiting for a blood count to drop.

Symptoms are often vague and easy to attribute to a busy life: persistent tiredness, dizziness, headaches, cold hands and feet, brittle nails, or difficulty concentrating. Some people notice unusual cravings for ice or a restless-legs feeling at night. None of these prove iron deficiency on their own, which is exactly why testing matters.

Which markers actually tell you something

Ferritin is the most useful single marker for iron stores, because it reflects how much iron you have banked rather than what is circulating right now. Low ferritin is a strong signal of depleted stores. The main caveat is that ferritin rises during infection or inflammation, so a normal-looking value alongside an active cold or a flare can occasionally mask a real shortfall; a good clinician reads it in context.

Haemoglobin tells you whether you have tipped into anaemia, but it changes late, so it is a blunt early-warning tool on its own. Supporting markers such as transferrin saturation and MCV (average red-cell size) add nuance. In practice, ferritin plus haemoglobin gives most women a clear enough picture to know whether to act, and reference ranges vary by lab and by life stage, so read your result against the range your provider gives.

Getting enough from food, and absorbing it

Dietary iron comes in two forms. Heme iron, found in meat, poultry and fish, is absorbed relatively efficiently. Non-heme iron, found in beans, lentils, tofu, dark leafy greens and fortified grains, is absorbed less readily, which is why people eating mostly plant-based diets need to be a bit more deliberate. Pairing non-heme sources with vitamin C, for example a squeeze of lemon over lentils or peppers in a bean stew, meaningfully improves uptake.

A few things blunt absorption in the same sitting: tea and coffee, calcium-rich foods and supplements, and the phytates in some whole grains and legumes. You do not need to avoid these foods; simply spacing your strongest iron meal away from your afternoon coffee is a reasonable, low-effort habit.

Supplements: helpful when needed, not by default

Iron supplements can correct a genuine deficiency effectively, but they are not a wellness add-on to take blindly. Your body has no easy route to excrete excess iron, and too much can cause digestive upset and, rarely, harm in people with conditions such as haemochromatosis. The sensible sequence is to test first, supplement if indicated and ideally guided by a clinician, then retest after a couple of months to confirm stores are rebuilding. Taking iron on an empty stomach or with vitamin C aids absorption, though every-other-day dosing is emerging as gentler and sometimes just as effective.

Test before you treat: iron is one of the few nutrients where guessing in either direction can cost you.

Key takeaways

• Iron carries oxygen; low stores commonly cause fatigue and poor concentration.
• Menstruation and pregnancy make deficiency more common in women.
• Ferritin reflects stores; haemoglobin flags anaemia later.
• Test before supplementing, and retest to confirm you are refilling stores.

The bottom line

Iron is a marker many women benefit from checking, especially if you have heavy periods, follow a plant-based diet, or feel persistently tired. A simple test that includes ferritin tells you far more than symptoms alone, and it turns a vague worry into a clear yes-or-no. Correcting a real deficiency can make a genuine difference to energy and focus, but the goal is a healthy range, not the highest possible number.

What Pheno can add

Pheno reads three layers together rather than a single number in isolation. On the physical layer it measures ferritin and haemoglobin, and supporting markers where relevant, so you can see whether your stores are low, borderline or comfortable. On the wearable layer, resting heart rate and sleep data pulled straight into the platform give context to fatigue that a one-off blood value cannot, and the wellbeing surveys help separate low iron from stress or low mood as a driver of tiredness. The honest limit: a single test is a snapshot. Iron status shifts with your cycle, diet and health, so the real value comes from repeating the test and watching the trend, ideally interpreted with a clinician.

Frequently asked questions

What is a good ferritin level?

Reference ranges vary by lab and life stage, and there is ongoing debate about the ideal lower bound. Read your result against the range your provider gives, and ask them to interpret a low-normal value alongside your symptoms rather than fixating on a single cut-off.

Can I have low iron but normal haemoglobin?

Yes, and it is common. Stores can be depleted while your blood count still reads normal, which is why ferritin often reveals a shortfall earlier than a standard blood count would.

Do I need to eat meat to keep iron up?

No. Plant sources such as lentils, beans, tofu and leafy greens provide iron; you simply absorb non-heme iron less efficiently, so pairing it with vitamin C and monitoring your levels helps.

Can too much iron be harmful?

Yes. Your body cannot easily remove excess iron, so supplementing without a confirmed need can cause digestive problems and, in certain conditions, more serious harm. Test before you supplement.

Can Pheno tell me if my iron is low?

Pheno measures ferritin and haemoglobin and places them against reference ranges, alongside your wearable and wellbeing data for fuller context. It is educational and works best over repeated tests; a clinician should confirm any diagnosis or treatment.

This article is general education, not medical advice. Iron needs and safe levels differ between individuals, and both deficiency and excess carry risks, so do not start or stop supplements without testing. Please consult a qualified clinician about your own results.

Sources & methodology

This article draws on peer-reviewed haematology and nutrition literature and major clinical guidance.

• Camaschella C. Iron deficiency. Blood. 2019;133(1):30-39.
• Pasricha SR, Tye-Din J, Muckenthaler MU, Swinkels DW. Iron deficiency. Lancet. 2021;397(10270):233-248.
• Stoffel NU, et al. Iron absorption from oral iron supplements given on alternate days. Lancet Haematology. 2017;4(11):e524-e533.
• WHO. Guideline: Daily iron supplementation in adult women and adolescent girls. Geneva: World Health Organization; 2016.