π©Έ Iron Deficiency Checker
Read your iron labs like a clinician.
For informational purposes only, not medical advice. Consult a healthcare professional.
Iron deficiency is diagnosed from labs, not symptoms, and three numbers tell the story. Ferritin reflects stored iron: under 30 ng/mL means deficiency in most adults. Transferrin saturation (TSAT) shows how much iron is moving in the blood: under 20% supports deficiency. Hemoglobin reveals whether the deficiency has progressed to anemia, using WHO cutoffs of 13 g/dL for men and 12 for non-pregnant women.
The order matters. Stores empty first (ferritin falls), transport dwindles next (TSAT falls), and hemoglobin drops last. That means you can be iron deficient for months before anemia appears, which is why ferritin is the earliest and most sensitive marker.
How to Use This Calculator
Enter ferritin in ng/mL, transferrin saturation as a percent, and hemoglobin in g/dL from your lab report, plus sex for the hemoglobin cutoff. The checker flags each marker against its cutoff and names the pattern: no deficiency, early deficiency before anemia, or iron deficiency anemia. Bring the pattern, not just one number, to your appointment.
Enter ferritin (ng/mL): under 30 suggests deficiency.
Enter transferrin saturation (%): under 20% supports deficiency.
Enter hemoglobin (g/dL) and sex: under 13 for men or 12 for women is anemia.
Read the combined pattern and the suggested next step.
The Three-Marker Method
TSAT < 20% = low circulating iron
Hb < 13 (men) / 12 (women) g/dL = anemia
Ferritin is an acute-phase reactant, which is the main subtlety: inflammation, infection, or liver disease can push ferritin into the normal range even when iron is low. That is why TSAT matters as a second witness; it is less fooled by inflammation. Clinicians also use the Mentzer index and red cell indices to separate iron deficiency from thalassemia trait, since both cause small red cells. When ferritin is borderline (30 to 100) with inflammation present, many guidelines accept higher cutoffs, and a therapeutic trial of iron with rechecked labs settles ambiguous cases.
Worked Example
A woman with ferritin 18, TSAT 14%, and hemoglobin 11.2 gets: Iron deficiency with anemia likely. Each marker is below its cutoff (Ferritin low (<30) - TSAT low (<20%) - Hb low), and the pattern reads "Iron deficiency anemia pattern". Contrast that with ferritin 80, TSAT 28%, hemoglobin 13.5: no deficiency pattern at all, even though the person might still feel tired for other reasons.
Reading Your Pattern
All three low is the classic picture: iron deficiency anemia, which needs both iron replacement and a search for the cause (heavy periods, GI blood loss, poor intake, pregnancy). Low ferritin and TSAT with normal hemoglobin is early deficiency: stores are empty but red cell production has not failed yet, and this stage already causes fatigue and restless legs in many people. Low hemoglobin with normal iron markers points elsewhere: B12 or folate deficiency, chronic disease, or blood loss with repleted stores. Normal labs with real symptoms deserve a recheck in a few months, not dismissal.
| Pattern | Ferritin | TSAT | Hemoglobin |
|---|---|---|---|
| No deficiency | Normal | Normal | Normal |
| Early deficiency | Low | Low or normal | Normal |
| Iron deficiency anemia | Low | Low | Low |
| Anemia, other cause | Normal | Normal | Low |
Do Not Self-Treat Anemia Blindly
Iron pills seem harmless but the cause of the deficiency matters more than the supplement: GI bleeding, celiac disease, and heavy menstrual bleeding all need their own workup, and iron can mask ongoing loss. Too much iron harms people with hemochromatosis. Get the labs, find the cause with your doctor, then supplement as directed, usually with vitamin C and away from coffee, tea, and calcium, which block absorption. For informational purposes only, not medical advice. Consult a healthcare professional.
Related tools: Mentzer index (iron vs thalassemia) and Morse fall scale.
For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What ferritin level means iron deficiency?
Under 30 ng/mL indicates deficiency in most adults. With inflammation present, clinicians often use higher cutoffs since ferritin rises with inflammation.
Can you be iron deficient without anemia?
Yes, and it is common. Ferritin falls first, then transferrin saturation, and hemoglobin drops last. Fatigue, restless legs, and hair shedding can appear before anemia.
What is a good transferrin saturation?
Normal is roughly 20 to 50%. Under 20% supports iron deficiency; very high values suggest iron overload.
Why is my ferritin normal but I feel iron deficient?
Ferritin rises with inflammation, infection, or liver issues and can mask deficiency. Check TSAT and consider retesting when well, or discuss a trial of iron with your doctor.
How fast does ferritin rise with supplements?
Typically 4 to 8 weeks to see a meaningful rise, with 3 months to replete stores. Take iron on an empty stomach with vitamin C, away from coffee and calcium.
What causes iron deficiency in men?
In men and postmenopausal women, deficiency usually means blood loss until proven otherwise, most often gastrointestinal. It deserves a proper workup, not just pills.
Can heavy periods cause iron deficiency?
Yes, it is the most common cause in premenopausal women. If you soak through pads or tampons hourly for hours, or periods last over a week, mention it specifically.
Is it safe to take iron without a deficiency?
Routine iron without deficiency is not advised. Excess iron accumulates in organs, and in people with undiagnosed hemochromatosis it can cause real harm.