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

Key Takeaways

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)

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)

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)

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)

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)

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