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Serum iron Iron in your blood right now

Also called Iron and Serum Fe Not on a standard checkup Best before breakfast

The short answer

Serum iron is the iron moving in your blood when it’s drawn. Your level can shift by a quarter or more from one week to the next, so one result says little on its own. Ferritin is the better test of your iron stores.2,4

A healthy range
27 to 159 µg/dL for women (27 to 139 over 60) and 38 to 169 for men, on Labcorp’s range.1
If yours is low
On this test alone, it points to iron deficiency only when TIBC is high and saturation is low too.2 Infection and inflammation lower it as well. Ferritin settles it.2,3
If yours is high
An iron pill, a multivitamin or IV iron before the test can do it.2,3 If your saturation is 45% or more too, ask about hemochromatosis.6

Check your result

Type the number from your report. It stays on this page.

Which fits you?
27 160
  • Low Under 27
  • In range 27 to 159
  • High 160 or more

Enter your result to see what it means and what to do next.

Got a result from another lab? Ask Picardo about it. The app explains your results, and a physician can follow up.

Cutoffs are Labcorp’s.1 Serum iron moves a lot between tests, so judge it with your saturation and ferritin.2,4 The bar isn’t to scale.

What is a normal serum iron level?

Labcorp’s range depends on your sex and, for women, your age.1 Read your result with the TIBC and saturation from the same test. On this test alone, low iron points to iron deficiency only when TIBC is high and saturation is low too:2

Low Under 27 µg/dL for women; under 38 for men

Low: look at the rest of your report

Low iron on its own doesn’t prove iron deficiency. Labcorp treats iron deficiency as unproven unless TIBC is high and saturation is low on the same test.2 Infection, inflammation and long-term illness also lower serum iron, by holding iron back in your stores.2

How worried to be

Not urgent. Follow it up in the next few weeks, especially if you’re tired or have heavy periods.

What to do next
  1. 1 Check the saturation and TIBC on the same report.2
  2. 2 Check ferritin. US hematologists suggest counting 30 ng/mL or under as iron deficiency, and up to 50 if you have symptoms of low iron or a risk factor such as heavy periods, a vegan or vegetarian diet or donating blood.3
  3. 3 If you’ve been ill recently, recheck once you’re well.2
In range 27 to 159 µg/dL for women 60 or younger, 27 to 139 over 60; 38 to 169 for men

In the lab’s range

Your iron was in the usual range when your blood was drawn. That doesn’t rule out low stores: when iron runs short, ferritin usually falls first.2

How worried to be

Nothing to worry about.

What to do next
  1. 1 Check the saturation on the same report. 20% to 44% is typical.3,6
  2. 2 If you’re tired or have heavy periods, check ferritin.2
High 160 µg/dL or higher for women 60 or younger, 140 or higher over 60; 170 or higher for men

High: check what you took before the test

An iron pill or a multivitamin with iron in the hours before the test can push serum iron up, and IV iron makes it read falsely high.2,3 Other causes include hepatitis, red blood cells breaking down (hemolysis) and hemochromatosis.2

How worried to be

Not urgent. Start with a repeat test.

What to do next
  1. 1 Repeat the iron and TIBC test after 5 to 9 hours without food, iron pills or multivitamins.3
  2. 2 Check ferritin and liver enzymes.2,6
  3. 3 If your saturation is 45% or more again, or your ferritin is high too, ask about a genetic test for hemochromatosis.6
Iron and TIBC test, $6.00
Results in 2 to 3 days, explained in the app
Order

What is serum iron?

Think of serum iron as the iron on the road right now, and ferritin as the iron in the warehouse. A busy or quiet day on the road tells you little about how full the warehouse is.

Serum iron is the iron traveling in your blood, carried by a protein called transferrin.6 It comes on the same report as TIBC and transferrin saturation, and the three are meant to be read together.2

Why does serum iron change so much?

In healthy adults tested every week for 10 weeks, each person’s serum iron typically varied by about a quarter around their own average. In women of childbearing age, it varied by more than a third.4

What you’ve eaten and taken matters too. In a study of 276,000 lab results, serum iron took about 5 hours to settle after a meal. In adults, blood drawn after 5 to 9 hours without food gave a representative result.5 Iron pills and IV iron push it up.2 That’s why US hematologists advise testing after 5 to 9 hours without food, multivitamins or iron pills.3

What causes low or high serum iron?

Low serum iron comes from:2

  • Losing blood over time, such as heavy periods or bleeding in the gut
  • Eating too little iron, or absorbing too little
  • Infection, inflammation and long-term illness, which hold iron back in your stores

High serum iron comes from:2,3

  • An iron pill, a multivitamin with iron or IV iron before the test
  • Blood transfusions
  • Red blood cells breaking down (hemolysis), as in thalassemia
  • Hepatitis and other liver damage
  • Hemochromatosis, an inherited condition that loads your body with iron

How to raise low iron

Check ferritin first. It shows whether your stores are actually low.2 The ferritin guide covers iron-rich food and how long refilling takes.

  • Iron supplements

    Taken every other day, each dose is absorbed better than with daily dosing.7 In a trial in women low on iron, that gave the same ferritin at the same total dose, with fewer stomach side effects, though it took twice as long.8

    How much it helps
    A lot
    How sure we are
    Very sure
  • IV iron

    For people who can’t take iron pills or don’t respond to them, and for some people with kidney disease or heart failure.9

    How much it helps
    A lot
    How sure we are
    Very sure
  • Treating the cause

    Low iron from blood loss, such as heavy periods or bleeding in the gut, needs the cause found as well as iron.2

    How much it helps
    A lot
    How sure we are
    Very sure

One recent change affects IV iron. In September 2026, the FDA added a boxed warning to ferric carboxymaltose (Injectafer) for low phosphate levels. Low phosphate can cause muscle weakness or pain, tiredness and confusion, and over time soft bones and fractures.9 Some of these symptoms can feel like low iron itself. Report them if they start or get worse after an infusion.9

Who should get a serum iron test?

Serum iron comes as part of an iron and TIBC test. It’s worth doing if:

  • You’re anemic, especially with small red blood cells (a low MCV).2
  • Your ferritin is high, to check your saturation for hemochromatosis.6
  • A close relative has hemochromatosis.6
  • You have a long-term illness, where ferritin alone can miss low iron.3
  • You have regular transfusions or dialysis.2

If you only want to know whether you’re low on iron, start with ferritin. It’s the more sensitive test.2

How to get a serum iron test, and what it costs

It comes from the iron and TIBC test, which costs $6.00 through Picardo.

Order the test

Iron and TIBC test

$6.00
Labcorp 001321 · best before breakfast

The test this number comes from.

Order the iron and TIBC test
  • Results in 2 to 3 days, in the app
  • Physician follow-up if you want one
  • Free Labcorp draw, or $75 at home
  • No other fees. HSA and FSA eligible.

It’s also part of the Base Core Annual – Men, Base Core Annual – Women and Celiac / GI panels, if you’d rather test more at once.

Already have a result? Ask Picardo about it

Questions people ask

Should I skip my iron pill before an iron test?

Yes. US hematologists advise 5 to 9 hours without iron pills or multivitamins, and Labcorp asks for blood to be drawn before iron treatment.2,3 If you’ve had IV iron, tell whoever reads your result. It makes serum iron read falsely high.2

Does the time of day matter?

Less than what you’ve eaten. In 276,000 results from one lab, serum iron was fairly steady between 8 a.m. and 3 p.m., but took about 5 hours to settle after a meal.5

What’s the difference between serum iron and ferritin?

Serum iron is the iron moving in your blood when it’s drawn. Ferritin reflects the iron stored in your body, and it’s the more sensitive test for both low and high iron.2

Can my serum iron be normal if I’m low on iron?

Yes. When iron runs short, ferritin usually falls first, so serum iron can still look normal while your stores run low.2

What is the new warning on IV iron?

In September 2026, the FDA added a boxed warning, its most prominent kind, to ferric carboxymaltose (Injectafer) for low phosphate levels. If you need a repeat course within 3 months, your phosphate should be checked first.9

Often checked alongside

Ferritin
How much iron you have in store
Transferrin saturation
How full your iron carriers are
TIBC
How much iron your blood can carry
Hemoglobin
Carries oxygen; low levels mean anemia

Test details

Labcorp test
Iron and Total Iron-binding Capacity (TIBC), 001321
LOINC
2498-4
Sample
Blood
Fasting
Labcorp doesn’t require it.2 But US hematologists advise having iron tests drawn after 5 to 9 hours without food, multivitamins or iron pills, because a recent meal or pill can skew the result.3
Typical lab range
27 to 159 µg/dL for women aged 18 to 60, and 27 to 139 over 60; 38 to 169 µg/dL for men1
Units
µg/dL, which Labcorp prints as ug/dL. For µmol/L, multiply by 0.179.

Sources

  1. 1 Labcorp. Iron, test 001339. Labcorp test menu. Accessed October 28, 2026. www.labcorp.com/tests/001339/iron
  2. 2 Labcorp. Iron and total iron-binding capacity (TIBC), test 001321. Labcorp test menu. Accessed October 28, 2026. www.labcorp.com/tests/001321/iron-and-total-iron-binding-capacity-tibc
  3. 3 Powers JM, Lim MY, Achebe MO, et al. American Society of Hematology 2026 guidelines for diagnosis of iron deficiency. Blood Adv. 2026;10(21):7353–7374. doi.org/10.1182/bloodadvances.2025015950
  4. 4 Carobene A, Aarsand AK, Coşkun A, et al. Biological variation of serum iron from the European biological variation study (EuBIVAS). Clin Chem Lab Med. 2023;61(3):e57–e60. doi.org/10.1515/cclm-2022-1091
  5. 5 Nguyen LT, Buse JD, Baskin L, Sadrzadeh SMH, Naugler C. Influence of diurnal variation and fasting on serum iron concentrations in a community-based population. Clin Biochem. 2017;50(18):1237–1242. doi.org/10.1016/j.clinbiochem.2017.09.018
  6. 6 Kowdley KV, Brown KE, Ahn J, Sundaram V. ACG clinical guideline: hereditary hemochromatosis. Am J Gastroenterol. 2019;114(8):1202–1218. doi.org/10.14309/ajg.0000000000000315
  7. 7 Stoffel NU, Cercamondi CI, Brittenham G, et al. Iron absorption from oral iron supplements given on consecutive versus alternate days and as single morning doses versus twice-daily split dosing in iron-depleted women: two open-label, randomised controlled trials. Lancet Haematol. 2017;4(11):e524–e533. doi.org/10.1016/S2352-3026(17)30182-5
  8. 8 von Siebenthal HK, Gessler S, Vallelian F, et al. Alternate day versus consecutive day oral iron supplementation in iron-depleted women: a randomized double-blind placebo-controlled study. EClinicalMedicine. 2023;65:102286. doi.org/10.1016/j.eclinm.2023.102286
  9. 9 US Food and Drug Administration. FDA adds boxed warning to labeling for ferric carboxymaltose injection (Injectafer) to describe risk of low phosphate levels. Drug Safety Communication. September 1, 2026. www.fda.gov/drugs/drug-safety-communications/fda-adds-boxed-warning-labeling-ferric-carboxymaltose-injection-injectafer-describe-risk-low

Updated 4 Nov 2026.

This is general health information, not medical advice: talk to your clinician about your results and before changing any treatment.