When women begin exploring factors that may influence fertility after 35, iron is rarely the first thing that comes to mind. Conversations tend to center on egg quality, ovarian reserve, or cycle regularity—all important considerations. But research suggests that iron status may be a meaningful piece of the broader nutritional picture for women trying to conceive, and it’s one that is often overlooked in initial fertility discussions.
Iron deficiency is the most common nutritional deficiency worldwide, according to data from the Centers for Disease Control and Prevention, and women of reproductive age are among those at highest risk—particularly those with heavy menstrual bleeding, those following plant-based diets, or those who have had recent pregnancies. After 35, nutritional needs and absorption patterns may also shift, making periodic assessment of iron status a reasonable consideration.
This article explores what current research suggests about the relationship between iron and fertility, how iron status is assessed, and when it may be worth discussing with a healthcare provider. As with all aspects of fertility health, individual circumstances vary considerably, and professional guidance is essential for personalized assessment.
What Research Suggests About Iron and Ovulatory Function
One of the most frequently cited pieces of research on this topic is the Nurses’ Health Study II, a large prospective study that found an association between iron intake (particularly from non-heme, plant-based sources) and reduced risk of ovulatory infertility. Women with higher iron intake—especially from plant-based sources—appeared to have a somewhat lower likelihood of experiencing infertility related to ovulation.
The proposed mechanism involves iron’s role in overall cellular energy metabolism and in supporting the enzyme systems that regulate ovarian function. However, it’s important to note that associations in observational studies don’t establish direct causation, and the specific relationship between iron and ovulation in women over 35 specifically is an area where more research is needed. The existing evidence is suggestive, not definitive.
Signs That Iron Status May Be Worth Assessing
Iron deficiency exists on a spectrum. Early iron depletion may affect energy levels and mood before it progresses to frank anemia. Women trying to conceive after 35 who notice persistent fatigue, difficulty concentrating, unusual shortness of breath with activity, or feeling unusually cold may find it worthwhile to discuss iron testing with a healthcare provider—though these symptoms have many possible causes and are not specific to iron deficiency.
Who May Be at Higher Risk
Certain factors are associated with a higher likelihood of iron deficiency in women of reproductive age. These include: heavy menstrual bleeding (which can lead to significant monthly iron losses), following a vegetarian or vegan diet (as plant-based iron is less bioavailable than heme iron from animal sources), having recently been pregnant or having had closely spaced pregnancies, regular high-intensity exercise, and having a gastrointestinal condition that may affect nutrient absorption.
If any of these apply to your situation, discussing iron status with your healthcare provider before or during the process of trying to conceive may be a worthwhile step.
Iron Testing: What It Involves
A standard complete blood count (CBC) can identify anemia, but it may not detect iron depletion before anemia develops. More sensitive markers include serum ferritin (which reflects iron stores), serum iron, and transferrin saturation. A healthcare provider or reproductive specialist can recommend which tests are most appropriate for your situation and interpret results in the context of your overall health picture.
Iron and Pregnancy: Why Stores Matter Before Conception
Iron needs increase significantly during pregnancy—the body requires additional iron to support expanded blood volume and fetal development. Beginning pregnancy with adequate iron stores may make it easier to meet these increased demands. Women who enter pregnancy with depleted iron stores may be at higher risk of iron-deficiency anemia during pregnancy, which research associates with fatigue, reduced immune function, and—in more severe cases—potential effects on fetal development.
For this reason, healthcare providers increasingly recognize the value of assessing iron status as part of preconception care for women planning to conceive, particularly those over 35 or those with risk factors for deficiency. For women exploring broader preconception nutrition after 35, iron is one of several nutrients worth discussing with a provider.
Dietary Sources of Iron and Absorption Factors
Iron from food comes in two forms: heme iron (found in red meat, poultry, and seafood), which is more readily absorbed, and non-heme iron (found in plant foods including legumes, tofu, leafy greens, and fortified grains), which has lower bioavailability but can be an important source for those eating plant-based diets.
Research suggests that consuming vitamin C-rich foods alongside non-heme iron sources may enhance absorption, while consuming iron-rich foods alongside coffee, tea, or high-calcium foods may reduce it. These are general principles—individual digestive absorption varies, and dietary modifications alone may not be sufficient if iron stores are significantly depleted.
Iron Supplementation: A Decision for You and Your Provider
Iron supplements are widely available, but they are not appropriate for everyone—taking iron supplements when iron status is already adequate does not provide additional fertility benefits and can cause side effects including constipation, nausea, and gastrointestinal discomfort. In rare cases, excessive iron intake can cause harm.
The appropriate approach—whether dietary modification, supplementation, or a combination—depends on your individual iron status as assessed through laboratory testing. This is a decision best made in collaboration with your healthcare provider, who can also recommend the appropriate dose and form of supplementation if it is indicated.
Women who are actively trying to conceive may also benefit from reviewing their prenatal supplement choices with their provider, as many prenatal vitamins include iron, though at varying doses. For broader guidance on nutrition and supplements when trying to conceive after 35, a healthcare provider or registered dietitian specializing in women’s health can offer personalized guidance.
Frequently Asked Questions
Can iron deficiency cause infertility?
Research suggests an association between iron status and ovulatory function, with some studies finding that women with higher iron intake may have a reduced risk of ovulatory infertility. However, iron deficiency is one of many potential factors that may influence fertility, and it does not independently cause or explain infertility in most cases. A comprehensive fertility evaluation assesses many variables. If iron deficiency is identified, addressing it is a reasonable and worthwhile step regardless of fertility status.
Should I take an iron supplement if I’m trying to conceive?
Iron supplementation should be guided by actual iron status as assessed through laboratory testing. Taking iron supplements without confirmed deficiency is not recommended and may cause side effects. Discuss iron testing with your healthcare provider, and if deficiency is confirmed, work with them to determine the appropriate supplementation approach.
What foods are highest in iron?
Heme iron is found in red meat (particularly beef and organ meats), poultry, and seafood—especially clams and oysters. Non-heme iron sources include lentils, kidney beans, tofu, fortified cereals, pumpkin seeds, and dark leafy greens like spinach. Pairing non-heme sources with vitamin C-rich foods may enhance absorption.
How long does it take to replenish iron stores?
The timeline for restoring iron stores depends on the degree of deficiency, the cause of depletion, and the approach taken (dietary, supplemental, or both). In general, research suggests that iron stores may begin to improve within weeks of beginning supplementation, but full replenishment can take several months. Follow-up testing helps confirm that levels have normalized.
Key Takeaways
- Iron deficiency is the most common nutritional deficiency globally, and women of reproductive age—particularly those with heavy periods or plant-based diets—are among those at highest risk.
- Research suggests an association between iron intake and ovulatory function, making iron status a worthwhile consideration in preconception health discussions, especially after 35.
- Iron testing (serum ferritin, CBC) rather than supplementation based on symptoms alone is the appropriate starting point for assessing iron status.
- Dietary strategies and supplementation decisions should be personalized with the guidance of a healthcare provider or dietitian, based on actual iron status.
- Beginning pregnancy with adequate iron stores is beneficial, as iron needs increase significantly during gestation to support maternal and fetal health.
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.