Do you feel short of breath during normally easy efforts, a fatigue that sets in and headaches that return? Iron deficiency is common and often underdiagnosed. In this clear and practical guide, we review the signs to recognize, the right tests (and how to read them), the most common causes and concrete actions to correct durably, without unnecessary jargon.
To remember: we correct the cause, optimize absorption (diet + habits), then supplement if necessary, with a planned recheck.
Symptoms
- Persistent fatigue, pallor, shortness of breath on exertion, palpitations.
- Brittle nails, dull hair/hair loss; smooth tongue, canker sores; headaches.
- In children and pregnant women: possible impacts on development/pregnancy.
If you combine unusual fatigue + shortness of breath on exertion + fragile nails/hair, talk about a ferritin assessment with your doctor.
Assessment
- Ferritin: central marker for iron status; interpretation with CRP (inflammation).
- Hemoglobin (Hb): detects anemia, but ferritin drops before Hb.
- Serum iron, transferrin, saturation: useful if ferritin ambiguous.
See NIH ODS – Iron for reference values.
Ferritin < 30 µg/L: probable deficiency. 30–50 µg/L: borderline, consider supplementation if symptoms. > 50 µg/L: generally sufficient, but cross with clinical context.
Causes
- Insufficient intake: vegetarian/vegan diet, insufficiently varied diet.
- Increased losses: heavy menstruation, gastrointestinal bleeding, blood donation.
- Malabsorption: celiac disease, inflammatory bowel diseases, bariatric surgery.
- Increased needs: pregnancy/breastfeeding, growth (children/adolescents).
Iron sources in diet
- Heme iron (better absorbed): red meat, poultry, fish.
- Non-heme iron (plant): legumes, green leafy vegetables, fortified products.
- Improve absorption: combine with vitamin C (citrus, peppers); avoid tea/coffee at meals.
Iron doses
- Prevention: 15–30 mg/day elemental iron.
- Deficiency treatment: 50–100 mg/day elemental iron, for 8–12 weeks.
- Preferred forms: ferrous bisglycinate (better tolerance), ferrous fumarate, ferrous sulfate.
See NIH ODS – Iron.
Tolerance
- Common side effects: constipation, nausea, dark stool.
- Improve tolerance: take with meal (slightly reduced absorption), start with low dose and increase gradually, use better tolerated forms (bisglycinate).
- Separate: calcium/magnesium/zinc (2–4 h) to avoid competition.
Interactions and precautions
- Antibiotics (tetracyclines/quinolones): separate 2–4 h from iron.
- Levothyroxine: separate 2–4 h.
- Hemochromatosis: do not supplement without medical advice.
- Pregnancy/breastfeeding: adjust doses; professional advice recommended.
Iron overdose can be toxic, especially in children. Keep out of reach. If in doubt, consult.
FAQ
How long to supplement?
8–12 weeks, then ferritin check. Continue if necessary.
Can iron be taken daily?
Yes, but respect doses and monitor tolerance. Some prefer alternating days (better absorption, fewer side effects).
Iron morning or evening?
On empty stomach (better absorption) or with meal (better tolerance). Avoid tea/coffee.
