Iron and Perimenopause: A Guide to Heavy Periods, Deficiency, and What to Do

Why iron is a real concern during perimenopause

Iron deficiency is one of the most common nutritional deficiencies in women during the reproductive years, and perimenopause creates conditions that make it even more likely. The irregular, often heavier periods that characterize perimenopause can increase blood loss substantially. Iron is a critical component of hemoglobin, the protein in red blood cells that carries oxygen throughout the body. When iron stores are low, the body cannot produce enough functional hemoglobin, and oxygen delivery to tissues decreases.

The symptoms of iron deficiency, and its more advanced form, iron deficiency anemia, overlap significantly with the symptoms that women in perimenopause already contend with: fatigue, brain fog, shortness of breath, reduced exercise tolerance, mood changes, and difficulty concentrating. This overlap means that iron deficiency is often underdiagnosed during perimenopause because the symptoms are attributed entirely to hormonal changes.

Understanding when and why to get tested, and what to do when iron is low, is practical information that can make a meaningful difference in energy, cognitive function, and quality of life during this transition.

How perimenopause changes blood loss and iron needs

In a typical menstrual cycle, blood loss averages around 30 to 40 mL per period, which corresponds to roughly 15 to 20 mg of iron lost. In perimenopause, periods can become heavier, longer, closer together, or all three. Heavy menstrual bleeding is formally defined as blood loss greater than 80 mL per cycle, but women often experience far more than this during the erratic cycles of perimenopause.

The hormonal fluctuations of perimenopause, particularly the irregular surges and drops in estrogen without the predictable progesterone rise that follows ovulation, can cause the uterine lining to build up thicker than normal and shed more heavily. Fibroids, which are more common in the decade before menopause, can significantly increase blood loss as well.

The result is that many women in perimenopause are losing iron at a faster rate than they are replacing it, particularly if their diet does not include substantial iron-rich foods. Vegetarians and vegans face additional risk because plant-based iron (non-heme iron) is absorbed at a much lower rate than iron from animal sources (heme iron).

Recognizing the symptoms of iron deficiency

Iron deficiency exists on a spectrum from depleted stores without obvious symptoms to frank anemia with significant functional impairment. The earlier stages of deficiency often go unrecognized because symptoms are gradual and attributed to other causes.

Fatigue is the most universal symptom. It is a bone-deep tiredness that does not respond well to rest, driven by reduced oxygen delivery to tissues and the metabolic demands of low hemoglobin.

Brain fog and difficulty concentrating are common because the brain is highly oxygen-dependent. Iron is also involved directly in neurotransmitter synthesis, including dopamine and serotonin, so deficiency affects mood and cognition beyond just the oxygen-delivery pathway.

Heart palpitations, particularly during mild exertion or at rest, can occur because the heart works harder to compensate for reduced oxygen-carrying capacity in the blood.

Breathlessness during activities that previously required no effort, such as climbing stairs, is a sign that oxygen delivery is compromised.

Cold hands and feet, pallor (particularly inside the lower eyelids, which should be pink rather than pale), brittle nails, and hair loss are physical signs that may accompany deficiency. A specific form of hair loss called telogen effluvium, where more hairs than usual shift into the shedding phase, can be triggered or worsened by iron deficiency.

A craving for non-food items like ice, clay, or starch, called pica, is a classic sign of iron deficiency anemia, though it is more common with severe deficiency.

What blood tests to ask for and how to interpret them

A standard complete blood count (CBC) can detect anemia (low hemoglobin and hematocrit) but does not capture iron deficiency before it has progressed to affecting red blood cell production. A full iron panel gives a much earlier and more complete picture.

The tests worth requesting include serum ferritin, serum iron, transferrin saturation, and total iron-binding capacity (TIBC). Of these, ferritin is the most important single marker. Ferritin is the storage protein for iron. Low ferritin means iron stores are depleted even if hemoglobin is still normal.

The standard lab reference range for ferritin is typically 12 to 300 ng/mL in women. However, many researchers and clinicians who specialize in this area consider levels below 30 ng/mL to be insufficient for optimal function, and levels below 50 ng/mL have been associated with symptoms including fatigue and hair loss even without anemia. If your ferritin comes back at 15 and your result is flagged as normal, it is worth discussing whether that level is optimal for how you are feeling.

If your ferritin is low, your provider may also want to investigate the source of blood loss more thoroughly, particularly if periods have been very heavy, to rule out other causes such as fibroids, polyps, or other conditions.

Increasing iron through diet

Dietary iron comes in two forms with very different absorption rates. Heme iron, found in meat, poultry, and fish, is absorbed at a rate of roughly 15 to 35 percent. Non-heme iron, found in legumes, tofu, fortified cereals, dark leafy greens, and seeds, is absorbed at only 2 to 20 percent, and the rate is heavily influenced by what else is eaten at the same meal.

Red meat (beef, lamb) and organ meats (liver) are the richest heme iron sources. A 3-ounce serving of beef liver provides around 5 mg of highly absorbable iron. Oysters are exceptionally rich, with 6 to 8 mg per serving. Clams, sardines, and dark poultry meat are good secondary sources.

For plant-based iron, lentils, white beans, chickpeas, tofu, pumpkin seeds, and fortified cereals are among the better options. Pairing non-heme iron foods with vitamin C significantly increases absorption. Eating an orange, bell pepper, or adding lemon juice to a lentil dish at the same meal can increase iron absorption by two to three times.

Inhibitors of iron absorption include calcium (avoid high-calcium foods or supplements at the same meal), tannins in tea and coffee (avoid drinking these with meals if iron status is low), and phytates in whole grains and legumes (soaking and fermenting reduce phytate content).

Iron supplementation: when and how

When dietary changes are insufficient or deficiency is already significant, supplementation is often necessary. But iron supplementation comes with some considerations worth knowing in advance.

Ferrous sulfate is the most commonly prescribed form and the most studied. It is also the form most likely to cause gastrointestinal side effects including nausea, constipation, and stomach cramping. Taking it with food reduces side effects but also reduces absorption somewhat.

Ferrous bisglycinate (sometimes called iron bisglycinate or iron glycinate) is a well-absorbed chelated form that is gentler on the gut and associated with fewer side effects. It is available over the counter and is worth trying if standard ferrous sulfate is not tolerated.

A commonly discussed strategy is taking iron every other day rather than daily. Some research suggests that every-other-day dosing may actually improve absorption because daily high-dose iron can trigger a hormone called hepcidin that downregulates iron uptake. Your provider can guide you on the dosing schedule that fits your situation.

Do not supplement with iron without testing first. Iron overload (hemochromatosis) is a genetic condition that causes iron accumulation and organ damage. Taking iron supplements when stores are already adequate is harmful, not neutral. Testing before supplementing is essential.

Tracking your energy levels, cognitive symptoms, and how you feel after exertion in PeriPlan gives you useful data to monitor whether treatment is making a difference and to bring to follow-up appointments.

This article is for informational purposes only and does not replace medical advice. Iron deficiency and anemia should be evaluated and managed by a healthcare provider.