Why are my iron levels low? Specific medical reasons you should know

By Sina Hartung, MMSC-BMI, Harvard Medical SchoolReviewed by Eureka Health Medical Group
Published: July 9, 2025Updated: July 9, 2025

Summary

Low iron most often comes from blood loss (heavy periods, gastrointestinal bleeding), a diet low in absorbable iron, increased needs during pregnancy or growth, poor intestinal absorption (celiac disease, bariatric surgery), or chronic inflammation that traps iron in storage. Pinpointing the exact cause requires looking at bleeding sources, diet, gut health, and blood tests such as ferritin and transferrin saturation.

What medical problems most frequently drain iron from the body?

About half of iron-deficiency cases worldwide are due to hidden or obvious blood loss. The rest stem from low intake, poor absorption, or higher demand. “In most adults, you do not develop iron deficiency unless you’re losing blood somewhere,” notes the team at Eureka Health.

  • Heavy menstrual periods are the top cause in pre-menopausal womenLosing more than 80 mL of blood per cycle can deplete 20-40 mg of iron each month.
  • Gastrointestinal bleeding often goes unnoticed in men and post-menopausal womenUlcers, colon polyps, cancer, or even aspirin can cause slow bleeding; up to 15 % of otherwise healthy adults with low ferritin have a positive fecal occult blood test.
  • Low dietary iron matters if intake stays under 8–18 mg per dayStrict vegans who avoid iron-fortified foods have a 2 × higher risk of deficiency than omnivores.
  • Malabsorption follows gut surgery or celiac diseaseAfter gastric bypass, iron absorption can fall by 50 %, and 30 % of patients need supplements within one year.
  • Rapid growth, pregnancy, and endurance sports raise needsA pregnant person needs about 1 000 mg extra iron across the pregnancy; distance runners lose iron through gut micro-bleeding and sweat.
  • Frequent blood donation can silently empty iron storesWebMD points out that “Frequent blood donations can also deplete iron,” so habitual donors should monitor ferritin levels or supplement. (WebMD)
  • Blood lost during dialysis sessions places patients at risk for deficiencyThe Merck Manual notes that people on dialysis are at higher risk for iron deficiency because blood is routinely lost in the circuit and through repeated lab testing. (Merck)

References

Which warning signs mean low iron has become an emergency?

Most symptoms build slowly, but some call for urgent care. “Shortness of breath at rest is a late sign and should never be ignored,” warns Sina Hartung, MMSC-BMI.

  • Resting heart rate above 100 beats per minuteSevere iron-deficiency anemia forces the heart to pump faster to deliver oxygen.
  • Chest pain or new exercise intoleranceThese can signal that hemoglobin has fallen below 7 g/dL, a threshold where transfusion is often considered.
  • Black or bloody stools point to active bleedingMelena suggests upper GI bleeding that can drop hemoglobin by 1 g/dL every 24 hours.
  • Dizziness when standing may reflect critical oxygen shortageOrthostatic hypotension appears in up to 20 % of patients with severe anemia.
  • Pica (craving ice, clay) can precede dangerously low levelsThough bizarre, pica correlates with ferritin under 15 ng/mL in 70 % of cases.
  • Rapid or irregular heartbeat warrants immediate ER evaluationAdvance ER lists a noticeable rapid or irregular heartbeat among the symptoms that should prompt emergency care for suspected iron-deficiency anemia. (AdvanceER)
  • Long-term iron deficiency can progress to heart failureUntreated anemia may lead to cardiac complications such as an enlarged heart, heart murmurs, and even heart failure, according to a report on the dangers of low iron levels. (SFGate)

References

What everyday habits silently chip away at iron stores?

Some routines reduce iron without obvious bleeding. Adjusting them often stabilizes ferritin within months.

  • Drinking black tea or coffee with meals blocks absorptionTannins cut non-heme iron uptake by up to 60 % when consumed within one hour of eating.
  • Taking antacids or proton-pump inhibitors long termLow stomach acid impairs release of iron from food; studies show a 2–3 × higher risk of deficiency after 2+ years of PPI use.
  • Following low-carbohydrate diets devoid of fortified grainsEliminating cereal products can remove 30 % of daily iron for many U.S. adults.
  • Frequent blood donationEach unit donated removes about 200–250 mg of iron, enough to drop ferritin by 30 ng/mL.
  • High-intensity training without recoveryHeel-strike hemolysis in runners causes measurable iron loss in urine and sweat, especially at weekly mileage above 40 miles.
  • Taking NSAIDs like ibuprofen daily can trigger hidden gut bleedingNHS Inform lists long-term non-steroidal anti-inflammatory drug use as a common cause of stomach or intestinal bleeding that gradually saps iron and can lead to deficiency anaemia. (NHS)
  • Monthly menstruation steadily drains iron stores in many womenThe American Medical Association notes that women lose about 30 mg of iron with each menstrual cycle, underscoring why even small absorption blockers can tip them into deficiency. (AMA)

References

How can I raise my iron levels safely at home?

Correction starts with diet, timing, and monitoring; supplements may be needed but should follow testing. “Food plus targeted supplements restores iron in most people within three to six months,” says the team at Eureka Health.

  • Prioritize heme iron sources twice dailyLean red meat, dark turkey meat, and canned sardines contain 2–3 mg of highly absorbable heme iron per ounce.
  • Pair plant iron with vitamin CAdding ½ cup of bell pepper boosts non-heme absorption by up to 4-fold.
  • Avoid tea, coffee, and calcium within two hours of iron-rich mealsThis small timing change can raise ferritin by 10–15 ng/mL over 12 weeks.
  • Use over-the-counter iron only after a blood testToo much iron can harm the liver; typical elemental doses range from 18–65 mg daily based on deficiency severity.
  • Track fatigue and exercise tolerance weeklyMost people notice more energy once hemoglobin climbs above 11 g/dL, usually after 4–6 weeks of therapy.
  • Typical therapeutic dose is 150–200 mg elemental iron dailyPeople with iron deficiency anemia are often advised to take a total of 150–200 mg elemental iron per day, split into one to three doses, to restore hemoglobin and ferritin efficiently. (MNT)
  • Continue supplements 3–6 months after labs normalizeHealth authorities recommend staying on iron tablets for an extra 3–6 months once hemoglobin is back to normal to fully replenish iron stores, with follow-up blood tests to confirm recovery. (BHC)

References

Which lab tests and medications matter most for diagnosing and treating low iron?

Blood work confirms deficiency and guides therapy choice. “Ferritin below 30 ng/mL with transferrin saturation under 15 % seals the diagnosis in otherwise healthy adults,” explains Sina Hartung, MMSC-BMI.

  • Complete blood count (CBC) reveals microcytic anemiaMean corpuscular volume (MCV) under 80 fL plus low hemoglobin suggests iron deficiency.
  • Ferritin tracks iron storesA value 15–30 ng/mL is borderline; anything under 15 ng/mL is diagnostic unless inflammation is present.
  • Transferrin saturation distinguishes pure deficiency from chronic diseaseLevels under 20 % indicate lack of supply, even when ferritin is falsely normal during infection.
  • Oral ferrous sulfate is first-line when gut can absorbTypical prescription: 325 mg tablet (65 mg elemental) every other day to reduce nausea and improve uptake by 34 % versus daily dosing.
  • Intravenous iron bypasses absorption issuesFormulations like ferric carboxymaltose can replenish 1 000 mg in one sitting and raise hemoglobin by 2 g/dL in two weeks.
  • Iron deficiency without anemia is highly prevalentIron-deficient states that have not yet lowered hemoglobin are at least twice as common as frank iron-deficiency anemia, which itself affects about 1.2 billion people worldwide. (PMC)
  • Taking iron with vitamin C improves absorption and long-term repletionGuidelines advise swallowing tablets on an empty stomach, pairing them with vitamin C to boost uptake, and avoiding antacids; full repletion of body stores often requires several months of therapy. (Mayo)

References

How can Eureka’s AI doctor help uncover the cause of your low iron?

Eureka’s AI doctor listens to your symptom story, reviews past labs, and asks follow-up questions a human doctor might miss. “Our algorithm flags patterns such as heavy cycles plus fatigue and suggests targeted testing, not blanket panels,” notes the team at Eureka Health.

  • Smart triage spots bleeding risks earlyThe AI asks about stool color, NSAID use, and menstrual duration, then recommends fecal occult blood testing if appropriate.
  • Customized lab orders reviewed by physiciansYou can request ferritin, CBC, and C-reactive protein; a licensed clinician approves or revises the order for safety.
  • Evidence-based supplement guidanceIf your ferritin is 12 ng/mL, the AI suggests starting elemental iron 45 mg every other day, with retest in eight weeks, pending physician sign-off.
  • Progress tracking keeps you accountableWeekly check-ins record fatigue scores and remind you to take iron with vitamin C, increasing adherence by 25 % in pilot data.

Why users with iron issues rate Eureka 4.8 out of 5 stars

People appreciate a private, judgment-free space to explore symptoms before a clinic visit. “Eureka took my random bruises seriously when others told me to ‘just eat better’,” shares one user in app feedback.

  • Private and HIPAA-compliantYour health data stays encrypted and under your control.
  • Fast answers, no waiting roomsMost users receive an initial care plan within six minutes, including when to seek urgent care.
  • Integrated approach beyond ironThe AI also screens for thyroid, B-12, and folate deficiencies that can mimic iron-deficiency symptoms.
  • Free to use with optional paid labsConsultations are free; you pay only for labs or prescriptions after clinician approval.
  • Built by clinicians and data scientistsEvery algorithm is reviewed against current guidelines from the American Society of Hematology.

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Frequently Asked Questions

Can I have low ferritin but normal hemoglobin?

Yes. Early iron depletion shows as low ferritin while hemoglobin is still in the normal range.

How long should I stay on iron tablets?

Continue until ferritin rises above 50 ng/mL and hemoglobin normalizes, then stay on a lower dose for three more months to refill stores.

Is constipation from iron pills avoidable?

Taking pills every other day, with food rich in vitamin C, and adding 25 g of fiber daily reduce constipation in most people.

Will cooking in cast-iron pans help?

It can add 1–2 mg of iron per meal, a modest but helpful amount when paired with other strategies.

Does donating blood once a year cause deficiency?

One annual donation usually doesn’t unless your baseline ferritin is already low; regular donors should check ferritin every 6–12 months.

Which medications block iron absorption?

Chronic use of PPIs, H2 blockers, or high-dose calcium supplements can interfere with iron uptake.

Do I need colonoscopy if I’m a 35-year-old woman with low iron?

Not automatically. First investigate menstrual blood loss and diet; colonoscopy enters the work-up if GI symptoms or stool tests suggest bleeding.

Can vegetarians meet iron needs without supplements?

Yes, but it requires careful planning: combine legumes, tofu, and iron-fortified cereals with vitamin C-rich foods and limit tea or coffee at meals.

Is a ferritin of 100 ng/mL too high?

Not usually; it falls within the upper normal range. Higher numbers during infection or liver disease can mask true iron status.

This content is for informational purposes only and is not intended as medical advice. Always consult with a qualified healthcare provider for diagnosis, treatment, and personalized medical recommendations.

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