Iron: Everything You Need to Know

Iron is one of the most discussed nutrients in pregnancy, and one of the most misunderstood. Most women know they are supposed to have enough iron. Far fewer know what their blood test results actually mean, what the difference is between a "normal" result and an optimal one, or why the number most GPs check is not the most useful one for assessing iron status. This article covers what iron does, why demand changes so dramatically across preconception, pregnancy, and postpartum, how to read your iron results, and what to look for when choosing a supplement.

What does iron actually do in the body?

Iron is a trace mineral that sits at the centre of several processes critical to life. Its most well-known role is in haemoglobin, the protein in red blood cells that binds to oxygen and transports it throughout the body. Every cell requires oxygen to produce energy, which means iron is foundational to energy production at a cellular level.

Beyond haemoglobin, iron plays important roles in:

• Myoglobin production: the oxygen-storing protein in muscle tissue that supports physical endurance and muscular function
• Immune function: iron supports the proliferation and activity of immune cells, including lymphocytes and neutrophils
• Cognitive function and neurodevelopment: iron is required for the synthesis of dopamine and serotonin and for myelination of nerve fibres, which is why iron deficiency impairs concentration, mood, and cognitive performance
• Thyroid hormone synthesis: iron-containing enzymes are involved in the conversion of thyroid hormones
• Energy metabolism: iron is a component of cytochromes, the enzymes involved in the mitochondrial electron transport chain that produces cellular ATP

When iron stores are low, all of these processes are compromised, often before anaemia is detectable on a standard blood count.

Why do iron needs change so dramatically in pregnancy?

Pregnancy demands more iron than almost any other physiological state. The Australian recommended dietary intake (RDI) for iron rises from 18 mg per day for women of childbearing age to 27 mg per day during pregnancy, an increase of 50 percent (NHMRC, 2006). This is driven by three simultaneous demands:

• Expanded blood volume: blood volume increases by approximately 50 percent during pregnancy, requiring a corresponding increase in haemoglobin and therefore iron
• Foetal iron accumulation: the developing baby actively draws iron from the mother, accumulating stores in the liver throughout pregnancy. Approximately two-thirds of foetal iron accumulates in the final ten weeks, building the stores the newborn will rely on for the first six months of life
• Placental requirements: the placenta itself requires iron for its development and function

The physiological demand for iron is three times greater during pregnancy than at any other life stage (Bothwell, 2000). This is why entering pregnancy with well-established iron stores matters, and why depletion, even from a technically normal starting point, can occur rapidly as pregnancy progresses.

Iron across each stage of the motherhood journey

Preconception

Iron stores built before conception provide a critical buffer for the demands that pregnancy will place on the body. Research suggests that iron status at conception is a meaningful predictor of iron status throughout pregnancy, women who enter pregnancy depleted are disproportionately likely to develop iron deficiency anaemia in the second and third trimesters (Milman, 2006). Beyond the pregnancy preparation rationale, adequate iron in the preconception period is associated with healthier ovulation. A landmark study in the Nurses' Health Study found that women with lower iron intake had a significantly higher risk of ovulatory infertility (Chavarro et al., 2006). Regular iron assessment and supplementation where stores are low is a legitimate preconception priority, not just a pregnancy concern.

Pregnancy

The World Health Organization estimates that 37 percent of pregnancies globally are affected by anaemia, the majority caused by iron deficiency (WHO, 2021). In Australia, the rate is lower but not trivial. Iron deficiency in pregnancy is associated with increased risk of preterm birth, low birth weight, postpartum haemorrhage, and impaired foetal brain development (Rahman et al., 2016). The timing of iron supplementation matters: most practitioners recommend assessment in the first trimester, with supplementation initiated based on results, rather than waiting for symptoms to appear. Symptoms are a late signal.

Postpartum

Postpartum iron depletion is among the most common and most undertreated deficiencies in the early motherhood period. A typical vaginal birth involves blood loss of 300 to 500 mL; a caesarean section involves 500 to 1000 mL or more. Postpartum iron deficiency is associated with extreme fatigue, poor concentration, low mood, and reduced capacity to breastfeed effectively (Bodnar et al., 2005). The breastfeeding RDI for iron drops to 9 mg per day, reflecting the temporary suppression of menstruation during lactation, but this does not mean iron repletion is less important postpartum. Women who enter the postpartum period with depleted iron stores need active replenishment, not just maintenance. Ferritin levels should be checked at the six-week postpartum visit, not assumed to be adequate.

Understanding your iron blood test: what the numbers actually mean

This is the section most iron guides skip over. It is also the most practically important.

A standard iron test typically includes several values. Understanding each one, and knowing which matters most at each stage, gives you a far more useful picture than a single pass/fail result.

The key markers explained

Marker	What it measures	Standard lab normal range	What you need to know
Ferritin	Stored iron, the body's iron reserve	12 to 150 mcg/L (women)	The most sensitive early marker of iron deficiency. Can be depleted while haemoglobin remains normal.
Haemoglobin (Hb)	The oxygen-carrying protein in red blood cells	120 to 160 g/L (non-pregnant women)	Only falls below normal once iron stores are significantly depleted. A normal haemoglobin does not rule out iron deficiency.
Serum iron	The amount of iron circulating in blood plasma	10 to 30 mmol/L	Fluctuates significantly day to day and is affected by recent meals. Less reliable as a standalone measure.
Transferrin saturation	The percentage of the iron transport protein (transferrin) that is carrying iron	20 to 50%	A transferrin saturation below 20% indicates insufficient iron reaching tissues, even if ferritin appears borderline.
TIBC (Total Iron Binding Capacity)	How much iron could be transported if transferrin were fully saturated	45 to 72 mmol/L	Rises when iron is low, the body produces more transferrin to capture what little iron is available. High TIBC + low ferritin = depletion.

Why ferritin is the number to watch

Ferritin is the most clinically important marker for iron status assessment, particularly in the preconception and pregnancy context, and it is the one most likely to be missed if only a full blood count is ordered.

Here is the critical distinction that is not well-communicated in standard care: the lower limit of the laboratory "normal" range for ferritin is 12 mcg/L. A result at 12 mcg/L is technically within range. But a ferritin of 12 mcg/L is associated with significant symptom burden, fatigue, poor concentration, impaired exercise tolerance, and reduced mood, in a substantial proportion of women (Verdon et al., 2003). This is not an optimal level. It is the floor of what the laboratory considers "not anaemic."

The distinction between a normal ferritin and an optimal ferritin matters particularly in preconception and pregnancy:

• Laboratory normal range: 12 to 150 mcg/L
• Associated with symptomatic iron deficiency even without anaemia: below 30 mcg/L (Bruner et al., 1996)
• Generally considered optimal for preconception and pregnancy: 50 to 80 mcg/L or above
• In established pregnancy, levels below 30 mcg/L should prompt supplementation regardless of haemoglobin

If your GP tells you your iron is normal, ask specifically what your ferritin number is. A result in the low-normal range (12 to 30 mcg/L) may explain symptoms you have been told are unrelated to iron.

How to read your result in context

Two women can both have ferritin results that fall within the laboratory normal range but have very different iron status pictures:

Woman A: Ferritin 15 mcg/L, haemoglobin 125 g/L, transferrin saturation 18%. Symptoms: significant fatigue, poor concentration, cold hands and feet. This picture is consistent with functional iron deficiency, iron stores are depleted relative to physiological need, even though haemoglobin is technically within range.

Woman B: Ferritin 75 mcg/L, haemoglobin 138 g/L, transferrin saturation 32%. No symptoms. This is a meaningfully different picture representing adequate stores and good iron availability.

Both results might be reported as "normal" on a lab print-out. They are not equivalent, and the clinical response to each should be different.

Recognising iron deficiency: what does it feel like?

Iron deficiency produces symptoms well before anaemia develops. The most commonly reported early signs include:

• Persistent fatigue that does not resolve with sleep, often described as a bone-deep exhaustion
• Pale or sallow skin, particularly noticeable on the inner lower eyelids
• Breathlessness on mild exertion
• Brain fog, difficulty concentrating or remembering things
• Headaches, particularly tension-type and morning headaches
• Cold hands and feet
• Brittle or spoon-shaped nails
• Restless legs syndrome, particularly at night
• Increased frequency of infections
• Low mood and irritability
• Reduced exercise tolerance, feeling significantly more fatigued during physical activity than previously

In pregnancy specifically, severe iron deficiency is associated with increased risk of preterm labour, reduced birth weight, and impaired foetal brain development (Frayne and Pinchon, 2019). Postpartum, low iron has been linked to increased risk of postnatal depression and impaired bonding, thought to be related to the role of iron in neurotransmitter synthesis (Corwin and Pajer, 2008).

How is iron absorbed? The haem and non-haem distinction

Not all dietary iron is equal. Understanding the two forms of dietary iron, and how to optimise absorption of each, is practically important.

Haem iron

Found in animal-based foods: red meat, organ meats, chicken, and fish. Haem iron is absorbed directly through a specific intestinal receptor, with bioavailability of approximately 15 to 35 percent (Monsen, 1988). It is not affected by other dietary components in the same meal to the same degree as non-haem iron, making it the more reliable dietary iron source.

Non-haem iron

Found in plant-based sources: lentils, legumes, spinach, fortified cereals, tofu, pumpkin seeds, dried apricots. Bioavailability of non-haem iron is lower, approximately 2 to 20 percent, and is significantly influenced by other components of the meal (Monsen, 1988). Vitamin C consumed at the same meal can increase absorption by two- to threefold. Calcium (from dairy), tannins (from tea and coffee), and phytates (from wholegrains and legumes) all inhibit non-haem iron absorption when consumed simultaneously.

Practical dietary sources

Food	Iron per serve (approx)	Form
Beef liver (100g)	6.5 mg	Haem
Lean beef (100g)	2.7 mg	Haem
Oysters (85g)	8 mg	Haem
Chicken breast (100g)	1.3 mg	Haem
Cooked lentils (1 cup)	6.6 mg	Non-haem
Cooked spinach (1 cup)	6.4 mg	Non-haem
Tofu (100g)	3 mg	Non-haem
Pumpkin seeds (30g)	2.5 mg	Non-haem
Dried apricots (1/2 cup)	2 mg	Non-haem

Sources: NHMRC (2006), Moustarah and Daley (2024).

Choosing the right iron supplement

When dietary iron is insufficient or stores are significantly depleted, supplementation is often necessary. Not all iron supplements are equivalent, the form of iron in the supplement significantly affects both how well it is absorbed and how well it is tolerated.

Iron forms compared

Form	Absorption	Tolerability	Notes
Iron bisglycinate (iron glycinate)	High, chelated form absorbed via amino acid transport	Excellent, well tolerated, low GI side effects	Preferred form for preconception, pregnancy, and postpartum supplementation; less likely to cause constipation or nausea
Ferrous sulphate	Moderate	Poor, commonly causes constipation, nausea, dark stools	Widely prescribed due to low cost; significant side effect burden reduces adherence
Ferrous fumarate	Moderate	Poor, similar GI effects to ferrous sulphate	Common in prescription formulations; not well tolerated by many women in pregnancy
Ferrous gluconate	Moderate	Better than sulphate or fumarate; not as well tolerated as bisglycinate	A mid-point option

A systematic review and meta-analysis by Fischer et al. (2023) found that iron bisglycinate supplementation significantly improved both haemoglobin and ferritin levels in adults and children, with a tolerability profile meaningfully superior to ferrous sulphate. The clinical case for bisglycinate in pregnancy supplementation is well-supported, and it is the form of iron used in our Complete Support  prenatal.

What to look for on a label

Look for the form of iron listed (bisglycinate, glycinate, or iron II glycinate are equivalent terms) rather than the total milligram content of the compound. The elemental iron content, the amount that is actually available for absorption, should be clearly stated. A comprehensive prenatal vitamin should list the form of iron in the ingredient list; if it simply says "iron" without specifying the form, it is worth checking further.

Absorption tips

• Take iron with vitamin C (orange juice, a capsicum, or a dedicated vitamin C supplement) to enhance absorption
• Avoid calcium supplements, dairy, tea, and coffee within one to two hours of an iron supplement
• If nausea occurs when taking iron in the morning, try shifting to the evening with a small meal
• Do not exceed 45 mg of elemental iron per day from supplements without medical guidance; excess iron accumulation can cause harm

How long does it take to restore iron stores?

This is one of the most clinically important and under-communicated points about iron supplementation. Haemoglobin typically begins to improve within two to four weeks of starting iron supplementation. Ferritin, the stored form of iron, takes significantly longer to normalise: three to six months is common for ferritin to move from a depleted level to an optimal range, and sometimes longer when depletion is severe (Nguyen and Tadi, 2023). Feeling better often happens before iron stores are fully replenished, which can lead women to stop supplementing prematurely. Regular monitoring with repeat ferritin testing at three-month intervals is the appropriate approach to track recovery.

All content and media on the Mother Natal website are created and published online for informational purposes only. It is not intended to substitute professional medical advice and should not be relied on as health or personal advice.

Frequently Asked Questions

What is ferritin and why does it matter more than haemoglobin? Ferritin is the protein that stores iron in your cells. It represents your iron reserves, the buffer your body draws from when dietary iron is insufficient. Haemoglobin only falls below normal once iron stores are already significantly depleted, meaning a normal haemoglobin result does not rule out iron deficiency. Ferritin is a more sensitive early marker of depletion and is the most clinically useful measure for assessing iron status before anaemia develops.

What is a normal ferritin level and what is optimal? The laboratory reference range for ferritin is 12 to 150 mcg/L for women. However, a ferritin in the low-normal range (12 to 30 mcg/L) is associated with symptomatic fatigue and other signs of iron deficiency even when haemoglobin remains in range. Most practitioners consider ferritin above 50 mcg/L as a more meaningful target for women in the preconception and early pregnancy period. If your result is in the 12 to 30 mcg/L range and you are experiencing fatigue, poor concentration, or other symptoms, it is worth discussing with your GP.

What is the recommended dietary intake for iron in pregnancy? The Australian RDI for iron is 18 mg per day for women of childbearing age, rising to 27 mg per day during pregnancy, and dropping to 9 mg per day during breastfeeding (reflecting the temporary suppression of menstruation during lactation). These are total daily intake targets from all sources, diet plus supplementation combined.

Why do some iron supplements cause constipation? Ferrous sulphate and ferrous fumarate, the two most commonly prescribed forms, irritate the gastrointestinal tract and are poorly absorbed, leaving a high proportion of unabsorbed iron to reach the colon, where it disrupts the gut microbiome and causes constipation and nausea. Iron bisglycinate (iron glycinate) is absorbed via a different pathway (amino acid transport) and has a significantly lower rate of GI side effects. If you are experiencing constipation from an iron supplement, ask your GP or pharmacist about switching to a bisglycinate form.

Can I get enough iron from food alone during pregnancy? For most women, meeting the pregnancy RDI of 27 mg per day from food alone is challenging, particularly given that morning sickness and food aversions can significantly reduce intake in the first trimester. A prenatal vitamin that includes iron is a practical safety net. Women with already-depleted iron stores at the start of pregnancy, vegetarians, and those carrying multiples are particularly unlikely to meet requirements from diet alone and will typically need additional supplementation.

Is it safe to take iron supplements every day in pregnancy? Yes, within appropriate dosing. A prenatal vitamin containing iron at typical formulation levels (around 18 to 27 mg elemental iron per day) is appropriate for daily use throughout pregnancy. Higher supplemental doses should be under GP guidance, as iron accumulation above the upper tolerable intake (45 mg per day) can cause harm. Always account for total iron from all supplemental sources when assessing your intake.

How does iron affect my baby's brain development? Iron is required for myelination of nerve fibres and for the synthesis of dopamine and serotonin in the developing brain. Maternal iron deficiency in pregnancy is associated with impaired foetal brain development, and research links it to reduced cognitive and behavioural outcomes in children assessed in early childhood (Lozoff, 2007). The foetus accumulates iron stores primarily in the final ten weeks of pregnancy, making third-trimester iron status particularly important for the baby's neurological foundations.

When in pregnancy is iron most important? Iron is important throughout pregnancy, but the demands peak in the second and third trimesters as blood volume expansion accelerates and foetal iron accumulation reaches its highest rate. The final ten weeks are particularly significant for building the foetal iron stores the newborn will rely on for the first six months of life. That said, building adequate stores in the preconception period and maintaining them throughout the first trimester gives the body the best foundation to meet these later demands.

Should I check my iron levels postpartum? Yes. Blood loss at birth directly reduces iron and haemoglobin, and many women enter the postpartum period with significantly depleted stores. A full iron studies panel including ferritin is worth requesting at the six-week postnatal visit, not just a full blood count. Postpartum iron deficiency is one of the most common and most treatable drivers of new-mother exhaustion.

What impairs iron absorption? Tea, coffee, and other tannin-containing beverages reduce non-haem iron absorption when consumed in the same meal or within an hour of supplementation. Calcium (from dairy or supplements) similarly reduces absorption. High-dose zinc supplementation can also compete with iron absorption. For maximum benefit, take iron supplements separately from calcium supplements and avoid tea or coffee within one hour of supplementation.

Is it possible to have too much iron? Yes. Iron accumulation above the tolerable upper intake level (45 mg per day from supplements) can cause toxicity over time. The body has limited ability to excrete excess iron, which is why supplementation should be based on assessed need rather than taken in addition to a comprehensive prenatal without checking the total dose. If in doubt, discuss total daily iron intake with your GP or pharmacist.

References

Bodnar, L.M., Cogswell, M.E. and McDonald, T. (2005) 'Have we forgotten the significance of postpartum iron deficiency?', American Journal of Obstetrics and Gynecology, 193(1), pp. 36-44. https://pubmed.ncbi.nlm.nih.gov/16021056/

Bothwell, T.H. (2000) 'Iron requirements in pregnancy and strategies to meet them', The American Journal of Clinical Nutrition, 72(1 Suppl), pp. 257S-264S. https://pubmed.ncbi.nlm.nih.gov/10871591/

Chavarro, J.E., Rich-Edwards, J.W., Rosner, B.A. and Willett, W.C. (2006) 'Iron intake and risk of ovulatory infertility', Obstetrics and Gynecology, 108(5), pp. 1145-1152.  https://pubmed.ncbi.nlm.nih.gov/17077236/

Fischer, J.A.J., Cherian, A.M., Bone, J.N. and Karakochuk, C.D. (2023) 'The effects of oral ferrous bisglycinate supplementation on haemoglobin and ferritin concentrations in adults and children: a systematic review and meta-analysis of randomized controlled trials', Nutrition Reviews, 81(8), pp. 904-920. https://pubmed.ncbi.nlm.nih.gov/36728680/

Frayne, J. and Pinchon, D. (2019) 'Anaemia in pregnancy', Australian Journal for General Practitioners, 48(3), pp. 158-163. Lozoff, B. (2007) 'Iron deficiency and child development', Food and Nutrition Bulletin, 28(4 Suppl), pp. S560-S571. https://pubmed.ncbi.nlm.nih.gov/31256475/

Milman, N. (2006) 'Iron and pregnancy, a delicate balance', Annals of Hematology, 85(9), pp. 559-565. Monsen, E.R. (1988) 'Iron nutrition and absorption: dietary factors which impact iron bioavailability', Journal of the American Dietetic Association, 88(7), pp. 786-790. https://pubmed.ncbi.nlm.nih.gov/16691399/

Moustarah, F. and Daley, S.F. (2024) 'Dietary iron', in StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. Available at: https://www.ncbi.nlm.nih.gov/books/NBK540969 (Accessed: June 2026).

National Health and Medical Research Council (NHMRC) (2006) Nutrient Reference Values for Australia and New Zealand Including Recommended Dietary Intakes. Canberra: NHMRC. Available at: https://www.eatforhealth.gov.au/nutrient-reference-values/nutrients/iron (Accessed: June 2026).

Nguyen, M. and Tadi, P. (2023) 'Iron supplementation', in StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. Available at: https://www.ncbi.nlm.nih.gov/books/NBK557376 (Accessed: June 2026).

Rahman, M.M., Abe, S.K., Rahman, M.S., et al. (2016) 'Maternal anaemia and risk of adverse birth and health outcomes in low- and middle-income countries: systematic review and meta-analysis', The American Journal of Clinical Nutrition, 103(2), pp. 495-504. https://pubmed.ncbi.nlm.nih.gov/26739036/

Verdon, F., Burnand, B., Stubi, C.L., et al. (2003) 'Iron supplementation for unexplained fatigue in non-anaemic women: double blind randomised placebo controlled trial', British Medical Journal, 326(7399), p. 1124. https://pubmed.ncbi.nlm.nih.gov/12763985/

World Health Organization (WHO) (2021) Anaemia. Available at: https://www.who.int/news-room/fact-sheets/detail/anaemia (Accessed: June 2026).