Anaemia rarely appears on a list of fertility problems, which is odd, because iron deficiency is the most widespread nutritional deficiency on the planet and it is concentrated in exactly the group trying to conceive. It also sits inside a loop: heavy periods cause iron loss, iron loss causes fatigue, and the condition causing the heavy periods may itself be affecting fertility.
- You can be significantly iron deficient with a completely normal haemoglobin. Ferritin is the test that finds it.
- Large cohort data links higher iron intake — particularly from supplements and non-haem sources — with lower ovulatory infertility risk.
- Heavy menstrual bleeding is the most common cause in this group, and it often points to fibroids, adenomyosis, a thyroid problem or a bleeding disorder.
- Anaemia entering pregnancy raises the risk of preterm birth, low birth weight and needing a transfusion at delivery.
- Alternate-day iron dosing is absorbed better than daily dosing, and it causes fewer side effects.
Why it gets missed
A normal blood count does not rule out iron deficiency
The body protects circulating haemoglobin at the expense of stored iron. As stores fall, ferritin drops steadily — but haemoglobin stays within the normal range until the stores are nearly gone. So a standard full blood count comes back normal, the person is told they are fine, and the fatigue, breathlessness, hair shedding and brain fog get attributed to stress.
Iron deficiency without anaemia is a real and clinically meaningful state. If you have symptoms and heavy periods, asking specifically for a ferritin test — not just a full blood count — is the single most useful thing you can do. A ferritin below about 30 µg/L indicates depleted stores in most laboratories; below 15 µg/L is unambiguous.
Not all anaemia is iron deficiency
The type changes the treatment entirely, which is why supplementing blind is a poor idea.
| Type | Typical cause | How it is identified | Relevance to conception |
|---|---|---|---|
| Iron deficiency | Heavy periods, poor intake, malabsorption | Low ferritin; small red cells | Most common; treatable and reversible |
| B12 or folate deficiency | Vegan diet, absorption problems, metformin | Large red cells; low B12 or folate | Folate deficiency also raises neural tube defect risk |
| Thalassaemia trait | Inherited | Small cells with normal or high ferritin; needs haemoglobin studies | Partner screening matters before conceiving |
| Sickle cell trait or disease | Inherited | Haemoglobin electrophoresis | Partner screening and specialist pre-conception care |
| Anaemia of chronic disease | Inflammation, kidney disease, autoimmune conditions | Normal or high ferritin with low iron availability | Treat the underlying condition |
Ask for ferritin, not just a full blood count. The difference between the two tests is where most iron deficiency hides.
The loop worth breaking
Heavy periods are a symptom, not a personality trait
Heavy menstrual bleeding drains iron faster than diet can replace it. But heavy bleeding is a symptom, and the conditions behind it — fibroids, adenomyosis, endometrial polyps, an untreated thyroid disorder, an inherited bleeding disorder like von Willebrand disease — are frequently relevant to fertility in their own right. Submucosal fibroids distort the cavity where an embryo would implant. Hypothyroidism disrupts ovulation and raises miscarriage risk.
So the anaemia is worth treating on its own terms, and it is also a lead. If your periods soak through protection hourly, produce clots larger than a ten-pence coin, last more than seven days or make you plan your life around them, that is not something to normalise. It is a finding.
Getting iron in, and keeping it in
Absorption is the whole game — the amount on the label is not the amount you keep.
- Take it every other day. Daily dosing raises hepcidin, which blocks absorption of the next dose. Alternate-day dosing absorbs more in total and causes markedly fewer gut side effects.
- Pair with vitamin C. Orange juice or a vitamin C tablet alongside the dose meaningfully increases uptake of non-haem iron.
- Keep tea and coffee away from meals. Polyphenols and tannins bind iron. An hour either side of a meal is enough separation.
- Separate calcium. Milk, dairy and calcium supplements compete directly with iron for absorption.
- Include haem iron if you eat meat. Red meat, poultry and fish provide iron in the most readily absorbed form.
- Build the plant sources. Lentils, chickpeas, tofu, pumpkin seeds, fortified cereals and dark leafy greens all count, especially with a vitamin C source at the same meal.
- Expect it to take months. Haemoglobin recovers in weeks; ferritin stores take three to six months to rebuild. Stopping when you feel better leaves the stores empty.
Why it matters most before conception
Pregnancy increases iron requirements sharply — plasma volume expands, and the fetus and placenta draw on maternal stores throughout:
- Anaemia in pregnancy is associated with preterm birth and low birth weight.
- It raises the likelihood of needing a blood transfusion around delivery.
- It worsens the fatigue of the first trimester considerably, on top of nausea.
- It is associated with a higher risk of postnatal depression in several studies.
- Correcting stores before conceiving is far easier than correcting them alongside first-trimester nausea, when oral iron is least tolerated.
When to ask for help
Book an appointment, and ask specifically for ferritin, if:
- Your periods are heavy — flooding, clots, needing double protection, or lasting more than seven days.
- You have persistent fatigue, breathlessness on stairs, dizziness, hair shedding or brittle nails.
- You crave and chew ice, or crave non-food substances such as chalk or soil — a specific sign called pica.
- You follow a vegan or vegetarian diet and have not had iron checked while trying to conceive.
- You have coeliac disease, Crohn's disease, or have had bariatric surgery.
- You or your partner have African, Mediterranean, Middle Eastern or South Asian ancestry — haemoglobinopathy screening is worth doing before conceiving.
If something feels wrong and it is not on this list, that is still a reason to call. Lists like this are a floor, not a ceiling.
Questions about underdiagnosed
Can anaemia stop you getting pregnant?
Severe anaemia can disrupt ovulation, and large cohort studies link higher iron intake with lower ovulatory infertility risk. More often, though, it is not the direct cause — it is a marker of heavy bleeding, and the condition causing that bleeding is what matters for fertility.
What ferritin level should I aim for before conceiving?
Most clinicians want to see ferritin comfortably above 30 µg/L, and many aim higher — toward 50 µg/L or more — before pregnancy, given how much demand pregnancy adds. Your own doctor will interpret this alongside your haemoglobin and symptoms.
How long does it take to correct iron deficiency?
Symptoms often improve within two to four weeks and haemoglobin normalises within about two months, but rebuilding ferritin stores takes three to six months of continued treatment. Stopping as soon as you feel better is the most common reason it recurs.
Should I take iron just in case?
No. Test first. Iron overload is its own problem, particularly for anyone with undiagnosed haemochromatosis, and supplementing blind can mask a different type of anaemia that needs a different treatment.
Does anaemia affect male fertility?
Less directly, but it is worth investigating in men because iron deficiency in a man is unusual and usually has a cause — gastrointestinal bleeding, coeliac disease — that needs finding for its own sake.
Sources
Guidance bodies and peer-reviewed literature used while writing this guide.
- Iron deficiency anaemia: assessment and management — NICE Clinical Knowledge Summaries
- Iron intake and risk of ovulatory infertility — Obstetrics & Gynecology
- Heavy menstrual bleeding: assessment and management — NICE guideline NG88
This guide is general information, not medical advice, and it cannot account for your history. See our medical disclaimer and editorial policy.
