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Iron Blood Test: Ferritin, TIBC, Iron Saturation & How to Interpret Your Results

Medically reviewed by Medical Advisory Board Last reviewed 2026-08-07

Diagnosing iron deficiency, iron overload, and anemia of chronic disease from your iron panel

Iron deficiency affects 14% of US adults and 2 billion people globally, yet it's routinely missed on standard blood work. Ferritin below 30 ng/mL indicates depleted stores; below 15 confirms deficiency. Transferrin saturation below 20% suggests functional iron deficit even when ferritin is normal.

Iron is essential for oxygen transport (hemoglobin), energy production (mitochondrial function), thyroid hormone synthesis, and immune function. Iron deficiency is the world's most common nutritional deficiency, affecting an estimated 2 billion people — and it causes symptoms long before anemia shows up on a CBC. Fatigue, difficulty concentrating, restless legs, exercise intolerance, and hair loss can all occur with depleted iron stores (low ferritin) while hemoglobin remains normal.

A 2025 JAMA review reinforced that serum ferritin is the most specific routine test for diagnosing iron deficiency, but emphasized that the traditional cutoff of 12-15 ng/mL misses many deficient patients. Current evidence supports a ferritin threshold of 30 ng/mL for iron deficiency in otherwise healthy individuals — and 70+ ng/mL when inflammation is present, since ferritin is an acute-phase reactant that rises with infection and chronic disease.

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Iron Panel Reference Ranges

Test	Normal Range	Optimal	What It Measures
Serum Iron	60 – 170 μg/dL	80 – 120 μg/dL	Iron circulating in blood right now
Ferritin	Men: 24 – 336 ng/mL / Women: 11 – 307 ng/mL	40 – 150 ng/mL	Iron storage protein (most useful single test)
TIBC (Total Iron Binding Capacity)	250 – 370 μg/dL	—	Transferrin capacity — rises when stores are low
Transferrin Saturation	20 – 50%	25 – 45%	% of transferrin carrying iron (Iron ÷ TIBC × 100)
Transferrin	200 – 360 mg/dL	—	Iron transport protein

Key diagnostic thresholds:

Ferritin <15 ng/mL: Confirmed iron deficiency
Ferritin <30 ng/mL: Iron deficiency (current evidence-based cutoff per 2025 JAMA review)
Ferritin 30-70 ng/mL with inflammation (elevated CRP): Possible functional iron deficiency
Transferrin saturation <20%: Functional iron deficit
Ferritin >300 ng/mL (men) or >200 ng/mL (women): Investigate for iron overload (hemochromatosis)

Iron Deficiency vs. Anemia of Chronic Disease

Not all anemias are iron deficiency, and distinguishing the cause determines treatment:

Marker	Iron Deficiency	Anemia of Chronic Disease	Both (Mixed)
Ferritin	Low (<30)	Normal or high	Low-normal (30-100)
TIBC	High (>370)	Low (<250)	Normal-low
Transferrin Sat	Low (<20%)	Low (<20%)	Low
Serum Iron	Low	Low	Low
CRP	Normal	Elevated	Elevated

In anemia of chronic disease, the body actively sequesters iron to starve pathogens (a defense mechanism called nutritional immunity). Ferritin may be normal or even elevated because it's an acute-phase reactant. This is why a ferritin of 50 ng/mL with an elevated CRP doesn't rule out functional iron deficiency.

Common Causes of Iron Deficiency

Menstruation: The #1 cause in premenopausal women. Heavy periods (menorrhagia) deplete stores faster than diet can replace them.
Diet: Vegetarian/vegan diets provide only non-heme iron, which is 2-10× less bioavailable than heme iron from animal sources. Pair iron-rich plant foods with vitamin C to improve absorption.
GI absorption issues: Celiac disease, H. pylori infection, inflammatory bowel disease, gastric bypass, and chronic PPI (proton pump inhibitor) use all impair iron absorption.
Pregnancy: Iron requirements roughly double during pregnancy (from ~18mg/day to ~27mg/day).
Occult GI bleeding: In men and postmenopausal women, iron deficiency should prompt evaluation for GI blood loss (colonoscopy, upper endoscopy) to rule out colon polyps, ulcers, or malignancy.
Intense exercise: Endurance athletes (especially runners) have increased iron losses through foot-strike hemolysis, GI losses, and sweat. Ferritin below 30-40 ng/mL impairs performance even without frank anemia.

How to Increase Ferritin Levels

How to increase ferritin levels depends on why ferritin is low. Ferritin reflects iron storage, so it usually rises only when intake, absorption, and blood loss are addressed together. First confirm low ferritin with a full iron panel — including serum iron and a TIBC test — plus CBC, CRP, and symptom context.

Use heme iron when appropriate: Beef, lamb, liver, oysters, sardines, and dark poultry meat are more efficiently absorbed than plant iron.
Pair plant iron with vitamin C: Lentils, beans, spinach, tofu, and pumpkin seeds absorb better with citrus, peppers, or kiwi.
Avoid blockers around iron: Calcium, tea, coffee, and high-fiber supplements can reduce absorption if taken near iron-rich meals or supplements.
Consider every-other-day iron: Many clinicians use alternate-day oral iron to improve absorption and reduce GI side effects.
Find the leak: Heavy periods, GI bleeding, frequent blood donation, and endurance training can keep ferritin low despite supplementation.

What Does Iron Do for the Body?

What does iron do for the body? Iron carries oxygen in hemoglobin, stores oxygen in myoglobin, supports mitochondrial energy production, helps thyroid hormone metabolism, and supports immune function. Low iron can therefore show up as fatigue, shortness of breath on exertion, poor exercise tolerance, restless legs, hair shedding, cold intolerance, and brain fog before frank anemia appears.

Heme iron comes from animal foods and is absorbed more efficiently. Non-heme iron comes from plant foods and is more affected by meal composition. Do eggs have iron? Yes, but modestly: eggs contain some iron, mostly in the yolk, but they are not a high-iron food compared with red meat, shellfish, legumes, or fortified foods.

Iron and Ferritin Levels During Pregnancy

Iron needs increase substantially during pregnancy, and the ferritin threshold used to diagnose deficiency is set higher than the general cutoff used elsewhere on this page. The American College of Obstetricians and Gynecologists (ACOG) defines iron deficiency in pregnancy as a ferritin below 30 ng/mL in any trimester — a threshold that catches deficiency with about 92% sensitivity, according to a 2023 review in Hematology, the American Society of Hematology Education Program. This is notably higher than the 15 ng/mL cutoff the World Health Organization uses in the general population, reflecting how much more sensitive pregnancy is to iron depletion.

Daily iron requirements roughly double across pregnancy, and the Centers for Disease Control and Prevention recommends low-dose iron supplementation (about 27 mg of elemental iron daily) beginning at the first prenatal visit for most pregnant patients, with higher therapeutic doses used to treat confirmed iron deficiency anemia. Because normal blood volume expansion in pregnancy dilutes hemoglobin even when iron stores are adequate — sometimes called physiologic anemia of pregnancy — ferritin is a more reliable early marker than hemoglobin alone. Untreated iron deficiency in pregnancy is linked to fatigue, reduced work capacity, and in more severe cases low birth weight and preterm delivery, which is why most prenatal panels screen for it at least once each trimester.

How to Lower High Iron Levels

How to lower high iron levels depends on confirming that iron is actually elevated, not just borderline. This section applies specifically to a ferritin or transferrin saturation result that meets the overload thresholds in the reference ranges above — ferritin above roughly 300 ng/mL in men or 200 ng/mL in women, or a transferrin saturation persistently above 45-50% — most often reflecting hereditary hemochromatosis or another iron overload condition. It is the mirror image of the "How to Increase Ferritin Levels" advice above, and following it without a confirmed overload diagnosis isn't appropriate — if your iron panel is normal or low, the sections above apply to you instead.

Cut back on heme iron: Red meat, organ meats, and shellfish supply the most efficiently absorbed form of dietary iron. Shifting meals toward poultry, fish, eggs, and plant-based proteins reduces the amount of iron actually reaching the bloodstream, since non-heme iron from plants is absorbed far less efficiently to begin with.
Don't pair iron-rich meals with vitamin C: Vitamin C substantially increases non-heme iron absorption — useful for someone trying to raise ferritin, counterproductive here. Keep citrus fruit, peppers, and vitamin C-rich foods to separate meals rather than combining them with iron-containing dishes.
Drink tea or coffee with meals: Tannins in tea and coffee bind non-heme iron in the gut before it can be absorbed. Controlled studies have found tea can reduce non-heme iron absorption by roughly a third to more than half depending on strength and timing, according to research on tea and iron absorption — the opposite of the advice given to someone trying to correct a deficiency.
Stop iron and vitamin C supplements: Multivitamins or supplements containing iron, and standalone high-dose vitamin C, both work against the goal of lowering iron stores. Discontinue them unless a doctor has a specific reason for you to keep taking one.
Avoid alcohol: Iron and alcohol are a particularly damaging combination for the liver. In people with hereditary hemochromatosis, alcohol has been shown to accelerate hepatic iron-related injury and substantially raise the risk of cirrhosis and liver cancer, according to case-based research on alcohol use in hereditary hemochromatosis. This is one of the few lifestyle measures with real evidence behind it — even moderate drinking is typically discouraged once iron overload is confirmed, and monitoring liver enzymes (see our liver function test guide) is often part of ongoing care.

Therapeutic phlebotomy — the scheduled removal of blood, essentially the same procedure as donating blood — is the standard treatment for confirmed hereditary hemochromatosis, not diet alone. Removing blood removes iron along with it, since the body draws on its iron stores to rebuild the red blood cells that were lost. Per the American Association for the Study of Liver Diseases (AASLD) practice guideline, the induction phase typically removes about 1 unit (450-500 mL) of blood weekly or every other week until ferritin falls to roughly 50 ng/mL, followed by a lower-frequency maintenance phase — often every 2-3 months — to hold ferritin in the 50-100 ng/mL range, according to the AASLD 2011 practice guideline on hemochromatosis. Diet and lifestyle changes support this process but don't replace it once overload is confirmed.

When HFE genetic testing is warranted: Testing for the HFE gene mutations most responsible for hereditary hemochromatosis (C282Y and H63D) is generally appropriate when a ferritin or transferrin saturation result meets the overload thresholds described above, or when a first-degree relative — a parent, sibling, or child — has been diagnosed with hereditary hemochromatosis, even if your own current iron panel looks normal. Hereditary hemochromatosis is one of the most common inherited conditions in people of Northern European descent, according to MedlinePlus, which is part of why family history alone is considered a reasonable trigger for testing, independent of current lab results. A positive HFE test doesn't automatically mean phlebotomy is needed — many people who carry two copies of C282Y never develop clinically significant iron overload — but it does mean ferritin and transferrin saturation should be monitored periodically going forward.

Where to Find Iron & Ferritin Test Kits

Many labs and direct-to-consumer services let you order a iron and ferritin test without a doctor's visit. If you'd rather compare kits yourself, here's where to start looking:

At-home iron and ferritin test kits on Amazon — compare brands, prices, and Prime shipping.

Frequently Asked Questions

What is ferritin in a blood test?

Ferritin is a protein that stores iron inside cells. Your serum ferritin level reflects your body's total iron reserves — it's the most useful single test for diagnosing iron deficiency. Low ferritin (below 30 ng/mL) indicates depleted iron stores, often before anemia develops on a CBC. However, ferritin is also an acute-phase reactant — it rises with infection and inflammation, so a 'normal' ferritin in someone with chronic inflammation doesn't rule out iron deficiency. In that case, transferrin saturation below 20% is a more reliable indicator.

What are symptoms of iron deficiency?

The classic '5 weird signs of iron deficiency' beyond just fatigue: (1) Pica — craving ice, dirt, or non-food items; (2) Restless legs syndrome — irresistible urge to move legs, especially at night; (3) Spoon-shaped nails (koilonychia); (4) Pagophagia — specifically craving and chewing ice; (5) Difficulty concentrating and 'brain fog.' Other symptoms include fatigue, weakness, exercise intolerance, shortness of breath, pale skin, cold hands/feet, brittle nails, and hair loss. Symptoms often appear with low ferritin before hemoglobin drops.

What is low iron saturation?

Low iron saturation (transferrin saturation below 20%) means less than 20% of your blood's iron-carrying protein (transferrin) is actually loaded with iron. It indicates your tissues aren't receiving adequate iron delivery, even if your ferritin appears normal. Low saturation with low ferritin = classic iron deficiency. Low saturation with normal/high ferritin = anemia of chronic disease (iron is locked in storage, not available for use). It's calculated as serum iron divided by TIBC times 100.

How long does it take to raise iron levels?

With oral iron supplementation (typically 325mg ferrous sulfate, containing 65mg elemental iron): symptoms may improve in 1-2 weeks, hemoglobin rises 1-2 g/dL per month, and ferritin normalizes over 3-6 months. Continue supplementation for 3 months after ferritin reaches 50+ ng/mL to fully replenish stores. Take iron with vitamin C on an empty stomach for best absorption. Every-other-day dosing may be as effective as daily (better absorption per dose, fewer side effects). IV iron works faster — ferritin can normalize in 1-2 weeks.

What's the difference between iron deficiency and anemia?

Iron deficiency and anemia are related but not the same thing. Iron deficiency is a depleted-iron-stores state, shown by a falling ferritin, while anemia is a specific diagnosis based on low hemoglobin or hematocrit. You can have iron deficiency for months or years before hemoglobin ever drops low enough to be labeled anemia — sometimes called iron deficiency without anemia — and it still causes real symptoms like fatigue, hair loss, restless legs, and reduced exercise capacity, because iron does far more than build red blood cells; it also supports mitochondrial energy production and thyroid function. Anemia is the later, more severe stage: by the time hemoglobin falls, iron stores have typically been depleted for a long time already. This is why ferritin, not hemoglobin or a standard CBC, catches the problem earliest — see the reference ranges above for the specific cutoffs.

How can you tell iron deficiency anemia apart from thalassemia trait?

Iron deficiency anemia and thalassemia trait can look identical on a basic CBC — both cause microcytic anemia with a low MCV — but they need very different management, so telling them apart matters. The simplest bedside tool is the Mentzer index, calculated as MCV divided by red blood cell count: a result above 13 points toward iron deficiency, while a result below 13 points toward thalassemia trait, according to a peer-reviewed validation study. The underlying reason is that iron deficiency reduces the number of red blood cells the marrow can make, while thalassemia trait produces a normal or high number of small, fragile cells because of a genetic defect in hemoglobin production, not a lack of iron. Ferritin is the other key differentiator: it's low in true iron deficiency and normal — sometimes even elevated — in thalassemia trait, since thalassemia doesn't deplete iron stores. If your iron panel comes back normal or high despite a low MCV, ask your doctor about a hemoglobin electrophoresis to check for thalassemia, especially with a family history or Mediterranean, African, Middle Eastern, or Southeast Asian ancestry, where thalassemia trait is more common.

What is the difference between iron levels and ferritin levels?

"Iron level" usually means serum iron — the iron actively circulating in your bloodstream right now. It's a snapshot, not a savings account: serum iron shifts noticeably with your last meal and follows a daily rhythm, so a single low or high reading can reflect timing as much as your true iron status. Ferritin measures something different — your body's stored iron reserves, packed inside cells in the liver, spleen, and bone marrow for later use. Because serum iron swings so much day to day, it's a poor stand-alone marker for diagnosing deficiency or overload; ferritin is far more stable and is the single best routine test for whether your iron stores are actually depleted (low ferritin) or excessive (high ferritin). That's why the reference range table above lists both: serum iron shows what's circulating today, while ferritin shows your underlying reserves.

How does iron deficiency anemia differ from vitamin B12 deficiency anemia?

Iron deficiency anemia and vitamin B12 deficiency anemia sit at opposite ends of the same CBC measurement: iron deficiency produces small red blood cells (microcytic, low MCV, typically under 80 fL), while B12 deficiency — like folate deficiency — produces abnormally large red blood cells (macrocytic, high MCV, typically over 100 fL), as reflected in the CBC red cell indices. Beyond cell size, B12 deficiency has a distinguishing feature iron deficiency doesn't share: it can directly damage nerves. According to the National Institutes of Health, B12 deficiency causes numbness and tingling in the hands and feet, and these neurological changes can occur even without anemia being present — which is why early diagnosis matters even before a CBC looks abnormal. Left uncorrected, more severe or prolonged B12 deficiency can progress to peripheral neuropathy and problems with balance and coordination, and in advanced cases a spinal cord condition called subacute combined degeneration, because B12 is required to maintain the myelin sheath that insulates nerves. Iron deficiency doesn't cause this kind of nerve damage, so unexplained numbness, tingling, or balance problems alongside anemia point toward checking B12 rather than iron.

Can you test iron levels at home?

Yes, but with real limitations depending on what the kit actually measures. Many consumer at-home fingerstick kits test hemoglobin only — useful for flagging anemia, but hemoglobin is a late-stage marker: as noted above, iron stores can be depleted for months before hemoglobin ever falls low enough to register as anemia. Confirming true iron deficiency or iron overload requires ferritin specifically, along with serum iron, TIBC, and transferrin saturation — the full iron panel described in the reference ranges above — and most inexpensive hemoglobin-only kits don't measure any of these. A smaller number of at-home kits mail a fingerstick sample to a lab for ferritin or a fuller iron panel, and these can be reasonably accurate for ferritin specifically, since fingerstick ferritin results generally correlate well with standard venous blood draws in validation studies. Even with a lab-processed kit, a fingerstick sample is more prone to collection error than a venous draw, so an abnormal or borderline at-home result is still worth confirming with a standard blood draw ordered by a doctor, especially before starting or stopping iron or vitamin C supplementation.

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Medical Disclaimer: This content is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before making changes to your health regimen.

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