Nutrition is a topic that comes up frequently in conversations about fertility, and among the many nutrients discussed, iron has received notable attention from researchers. Iron deficiency is one of the most common nutritional deficiencies in women of reproductive age worldwide, and some evidence suggests that adequate iron status may play a role in supporting reproductive function. For women 35 and older who are trying to conceive or planning a pregnancy, understanding what the research currently shows — and what it doesn’t — may be useful context.
It’s important to approach this topic with appropriate nuance. While there is meaningful research on the relationship between iron and fertility, the evidence is not as straightforward as headlines sometimes suggest. Iron status is one factor among many that can affect reproductive health, and both iron deficiency and iron excess can have health consequences. Any significant changes to iron supplementation or diet should be discussed with a healthcare provider who can assess your individual needs through appropriate testing.
This article explores what current research suggests about iron’s role in fertility, how iron deficiency is identified, and what women 35+ might reasonably consider in consultation with their healthcare team.
Iron’s Role in Reproductive Function: What Research Shows
Iron is essential for many bodily functions, including oxygen transport, energy metabolism, and DNA synthesis. Its role in reproductive health appears to be multifaceted. According to a study published through the National Institutes of Health, women who consumed supplemental iron had a lower rate of ovulatory infertility compared to those who did not, even after adjusting for other dietary and lifestyle factors. The researchers hypothesized that adequate iron may support the development and maturation of eggs.
Iron’s connection to fertility may also work through its role in red blood cell production and oxygen delivery to reproductive organs. The ovaries and uterine lining have significant metabolic demands, and adequate oxygen delivery through healthy red blood cells is important for their function. Women who are iron-deficient may not only feel fatigued — they may also have suboptimal conditions for ovulation and implantation, though research in this specific area is still developing.
Additionally, iron deficiency anemia — the more severe form, where red blood cell production is affected — has been associated with irregular menstrual cycles and anovulation (cycles without ovulation) in some studies. Restoring iron status in these cases has been linked to cycle normalization in some women, though individual responses vary.
Identifying Iron Deficiency: More Than Just Anemia
Iron deficiency exists on a spectrum. The earliest stage — iron depletion — occurs when iron stores (measured by ferritin) become low, even before anemia develops. This stage can cause symptoms including fatigue, difficulty concentrating, and reduced exercise tolerance, but may be missed if only a basic blood count (CBC) is checked, since hemoglobin (the red blood cell marker most commonly measured) may still appear normal.
For women trying to conceive or planning pregnancy, checking ferritin — the storage form of iron — alongside hemoglobin can provide a more complete picture of iron status. Some fertility specialists and OB/GYNs now recommend checking ferritin as part of preconception assessments, particularly given that iron requirements increase significantly in early pregnancy.
Common symptoms that may suggest iron deficiency include:
- Persistent fatigue that doesn’t improve with rest
- Pale skin or pale inside the lower eyelids
- Shortness of breath with routine activity
- Frequent headaches
- Cold hands and feet
- Cravings for ice or non-food substances (a symptom called pica, associated with iron deficiency)
- Brittle nails or hair loss
Of course, many of these symptoms can also arise from other causes — a healthcare provider can assess them alongside appropriate blood tests. Women experiencing heavy menstrual periods — which are more common in the perimenopause transition — are at particular risk of iron deficiency due to ongoing blood loss.
Iron Needs in Pregnancy: Why Preconception Status Matters After 35
Iron requirements approximately double during pregnancy, from 18 mg per day (the recommended daily allowance for premenopausal women) to 27 mg per day during pregnancy. The fetus and placenta draw substantially on maternal iron stores, and the expansion of maternal blood volume requires significantly more iron for hemoglobin production.
Beginning pregnancy with adequate iron stores can help protect against pregnancy-related anemia, which is associated with increased risk of preterm birth, low birth weight, and maternal fatigue. For women 35 and older — who may already have lower ferritin due to years of menstrual blood loss — beginning to build iron stores before conception, through diet or supplementation as guided by a provider, may be particularly worthwhile.
For a broader overview of nutritional considerations before and during pregnancy after 35, our article on prenatal nutrition after 35 covers key nutrients including folate, vitamin D, and omega-3 fatty acids alongside iron.
Dietary Sources of Iron: Heme and Non-Heme Forms
Iron in food exists in two forms: heme iron (found in animal products) and non-heme iron (found in plant foods). Heme iron is more readily absorbed by the body, with an absorption rate of approximately 15–35%, compared to 2–20% for non-heme iron.
Good dietary sources of iron include:
- Heme iron: Red meat (especially beef and liver), poultry (especially dark meat), fish and shellfish (especially clams, oysters, sardines)
- Non-heme iron: Lentils, beans, tofu, tempeh, fortified cereals, pumpkin seeds, spinach, quinoa
Pairing non-heme iron sources with vitamin C-rich foods (such as citrus fruit, bell peppers, or tomatoes) can enhance absorption. Conversely, calcium-rich foods and beverages (including dairy and calcium-fortified plant milks), as well as coffee and tea, can inhibit iron absorption when consumed at the same meal.
Iron Supplementation: When It May Be Appropriate
Iron supplementation is appropriate when dietary intake is insufficient to meet needs or when deficiency has been diagnosed — but it should be guided by testing rather than taken routinely without assessment. Excess iron can cause gastrointestinal side effects and, in high amounts over time, may contribute to oxidative stress.
Prenatal vitamins typically contain iron, though the amount varies by brand. For women who are iron-deficient prior to conception, a healthcare provider may recommend additional supplemental iron, with the form and dose depending on the severity of deficiency and individual tolerance.
Women who are vegetarian or vegan may need to pay particular attention to iron, as they rely entirely on non-heme sources, which are less bioavailable. Working with a registered dietitian familiar with reproductive health can be helpful in these cases. You might also find it useful to explore our article on fertility nutrition on plant-based diets for more specific guidance.
Frequently Asked Questions
Can iron deficiency cause infertility?
Some research suggests that iron deficiency may be associated with ovulatory infertility, and severe deficiency can disrupt menstrual cycles. However, iron status is one of many factors that influence fertility, and iron deficiency alone is rarely the sole cause of difficulty conceiving. A comprehensive fertility evaluation with your healthcare provider is the best way to identify contributing factors.
Should I take iron supplements if I’m trying to conceive?
It’s advisable to check your iron and ferritin levels before starting supplements, as iron supplementation without a diagnosed deficiency may not be necessary and can cause side effects. Your OB/GYN or primary care provider can order simple blood tests to assess your status and advise whether supplementation is appropriate for you.
How long does it take to correct iron deficiency?
With appropriate supplementation and dietary changes, iron stores can begin to improve within weeks, though full repletion of ferritin stores may take three to six months. Retesting after a supplementation period helps confirm that levels have improved appropriately.
Are heavy periods a sign of iron deficiency?
Heavy menstrual periods are a common cause of iron deficiency in women of reproductive age, as significant blood loss can deplete iron stores over time. If you experience consistently heavy periods, discussing both the cause of the bleeding and your iron status with your healthcare provider is a useful step.
Key Takeaways
- Iron deficiency is common in women of reproductive age and may affect ovulation and fertility, according to some research — though it’s one factor among many.
- Ferritin (iron stores) is a useful addition to routine iron testing, as deficiency can exist before anemia develops.
- Adequate iron status before pregnancy is particularly important, given that iron requirements increase substantially during pregnancy.
- Dietary iron comes in heme (more absorbable, from animal foods) and non-heme (from plant foods) forms — pairing non-heme sources with vitamin C can improve absorption.
- Supplementation should be guided by testing and healthcare provider assessment, as excess iron is not benign.
Medical Disclaimer: This content is for informational purposes only and does not constitute medical advice. Individual health situations vary significantly. Always consult a qualified healthcare provider before making decisions related to your health, fertility, or pregnancy.
About the Author
Emily Carter is a women’s health writer focused on fertility, pregnancy after 35, and sleep changes in midlife. She writes research-informed, non-alarmist content to help women navigate reproductive and hormonal transitions with clarity and confidence.