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Transferrin saturation How full your iron carriers are

Also called Iron saturation, TSAT and Transferrin iron saturation Not on a standard checkup Best before breakfast

The short answer

Transferrin saturation shows how full your blood’s iron carriers are. A result of 45% or more is worth checking for hemochromatosis, an inherited condition that loads your body with iron, even if your report doesn’t flag it.1,3

A healthy range
20% to 44%.2,3 Labcorp’s range is wider, 15% to 55%, so it flags fewer results.1
If yours is low
Under 15% is below the lab’s range. With low iron and a high TIBC on the same report, it points to iron deficiency.1 With a long-term illness, heart failure or kidney disease, under 20% can mean low iron even when ferritin looks normal.2,8
If yours is high
One high result isn’t a diagnosis. Saturation swings from one test to the next, and iron pills push it up.1,5 If it’s 45% or more again, ask about a genetic test for hemochromatosis.3,4

Check your result

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

15 20 45 56
  • Low Under 15
  • Low-normal 15 to 19
  • Typical 20 to 44
  • High-normal 45 to 55
  • High 56 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.

Labcorp flags results under 15% and over 55%.1 The 20% line is where US hematologists suggest iron deficiency in people with inflammation;2 the 45% line is where US liver specialists look for hemochromatosis.3 The bar isn’t to scale.

What is a normal transferrin saturation level?

Labcorp’s range is 15% to 55%,1 but guidelines act on results inside it. Under 20% can mean low iron in people with inflammation,2 and 45% or more is worth checking for hemochromatosis:3

Low Under 15%

Below the lab’s range

Your iron carriers are less than a sixth full. If your iron is low and your TIBC is high on the same report, that pattern indicates iron deficiency.1 Infection and long-term illness, such as kidney disease or cancer, can also pull saturation this low.1,2

How worried to be

Worth seeing a clinician in the next few weeks, and sooner if you’re breathless, dizzy or have black stools.

What to do next
  1. 1 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.2
  2. 2 Check your hemoglobin to see whether you’re anemic.
  3. 3 If you’ve been ill or have a long-term illness, add CRP: inflammation pushes ferritin up, so a normal ferritin can hide low iron.2
Low-normal 15% to 19%

Normal on your report, but low

Labcorp won’t flag this, because its range starts at 15%.1 But in adults with a long-term inflammatory illness, US hematologists suggest that saturation under 20% can mean iron deficiency, even when ferritin looks normal.2 The 2026 European heart failure guideline now supports defining iron deficiency as saturation under 20%.8 If you’re otherwise well, ferritin is the better guide.2

How worried to be

Not urgent. Worth following up if you’re tired, have heavy periods or live with a long-term illness.

What to do next
  1. 1 Check ferritin, and add CRP if you’ve been unwell.2
  2. 2 If you have heart failure or kidney disease, ask whether iron would help. Both have their own guidelines, which use saturation to decide.8,9
Typical 20% to 44%

In the typical range

Your iron carriers are about a fifth to just under half full, the typical range.2,3 With a normal ferritin, a saturation under 45% makes iron overload very unlikely.3 It doesn’t show your stores, though. When iron runs short, ferritin usually falls first.1

How worried to be

Nothing to worry about.

What to do next
  1. 1 If you’re tired or have heavy periods, check ferritin.1
  2. 2 With kidney disease and anemia, ask your kidney team about your own cutoffs. Their guideline can suggest iron at saturations under 40%, depending on ferritin.9
High-normal 45% to 55%

Normal on your report, but high enough to check for hemochromatosis

Labcorp won’t flag this, because its range runs to 55%.1 But US liver specialists use 45% or more as the signal to look for hemochromatosis: over 45% picks up 98% to 100% of people with the common inherited type.3 European guidelines set the line a little higher for men, at over 50%.4 An iron pill before the test can also push it this high.1

How worried to be

Not urgent. One result isn’t a diagnosis.

What to do next
  1. 1 Repeat the iron and TIBC test in the morning, before breakfast and before any iron pill or multivitamin.2,4
  2. 2 Check ferritin and liver enzymes at the same time.3
  3. 3 If your saturation is 45% or more again, or your ferritin is high, ask about a genetic test for hemochromatosis.3,4
High 56% or higher

Above the lab’s range

Your iron carriers are more than half full. An iron pill or IV iron before the test, a recent blood transfusion, red blood cells breaking down or liver damage can all do this.1,4 So can heavy drinking.3 In hemochromatosis, a high saturation is the first sign on a blood test, appearing before ferritin climbs.1,4

How worried to be

Not an emergency. See a clinician in the next few weeks, or within a week or two if your ferritin is 1,000 ng/mL or more.

What to do next
  1. 1 Check ferritin and liver enzymes.3
  2. 2 Repeat the iron and TIBC test in the morning, before breakfast and without iron pills or multivitamins.2,4
  3. 3 If your saturation is 45% or more again, ask about a genetic test for hemochromatosis.3,4
  4. 4 Don’t take iron or vitamin C supplements in the meantime.3
Iron and TIBC test, $6.00
Results in 2 to 3 days, explained in the app
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What is transferrin saturation?

Think of transferrin as a fleet of buses that carries iron around your body. TIBC counts the seats and serum iron counts the passengers. Transferrin saturation is the share of seats that are taken.

Transferrin is the protein, made in your liver, that carries iron in your blood.3 Saturation shows how much of its carrying capacity is in use. It comes from the same test as serum iron and TIBC.1

Because it tracks iron on the move, saturation is thrown off by what you’ve just eaten or swallowed, and it varies from one test to the next.2,5 Ferritin is the better guide to how much iron you have stored.1

What does low transferrin saturation mean?

Your blood is carrying less iron than usual. With a low ferritin, that’s iron deficiency.1

With a long-term illness, it’s harder to read. Inflammation pushes ferritin up, so it can look normal while iron is short.2 For adults with anemia from a long-term inflammatory illness, US hematologists suggest testing saturation as well as ferritin, and considering iron deficiency if saturation is under 20% or ferritin is under 100 ng/mL.2 The illnesses they name include inflammatory bowel disease, kidney disease, heart failure, cancer and rheumatic diseases. It’s a conditional recommendation, based on very limited evidence.2

Two groups have their own guidelines:

  • Heart failure. The 2026 European guideline supports defining iron deficiency as saturation under 20%, in place of an older rule based mainly on ferritin.8 For people with symptoms and a weakened heart pump, it recommends IV iron to ease symptoms and improve quality of life.8
  • Kidney disease. The 2026 KDIGO guideline uses higher cutoffs. For people with anemia who aren’t on hemodialysis, it suggests starting iron when saturation is under 40% with ferritin under 100 ng/mL, or under 25% with ferritin of 100 to 299.9 These suggestions rest on very low-certainty evidence.9

What does high transferrin saturation mean?

More of your iron carriers are full than usual. These can all push it up:

  • An iron pill or a multivitamin with iron in the hours before the test, or IV iron1,2
  • A blood transfusion in the last few days1
  • Red blood cells breaking down (hemolysis)1
  • Liver damage, including cirrhosis and sudden liver injury4
  • Heavy drinking3
  • Hemochromatosis1,3

In hemochromatosis, a high saturation is the first sign on a blood test, appearing before ferritin climbs.1,4 That’s why US liver specialists use a saturation of 45% or more, with ferritin, as the signal to test for it.3

What is hemochromatosis?

Hemochromatosis is an inherited condition in which your body absorbs too much iron and stores it, mainly in the liver.4 Over time, the extra iron can damage the liver, pancreas, heart, joints and other organs.3

Most cases come from two copies of one change in the HFE gene, called C282Y.3 In a large US and Canadian screening study, about 1 in 227 non-Hispanic white people had two copies. It was far rarer in Hispanic, Black and Asian people.6

Having two copies doesn’t mean you’ll get ill. In an Australian study that followed people with two copies for 12 years, 28% of men developed disease from iron overload, against 1% of women.7

If you have hemochromatosis, your parents, brothers, sisters and adult children should be offered testing.3,4 Guidelines advise genetic testing for adults only, because problems rarely start in childhood.3,4 For a child, testing the other parent first can show whether the child needs testing at all.3

How is hemochromatosis treated?

  • Removing blood (phlebotomy)

    Usually 500 mL, about a pint, once a week until ferritin falls to 50 to 100 ng/mL. Then 3 or 4 times a year to keep it there.3

    How much it helps
    A lot
    How sure we are
    Very sure
  • Skipping iron and vitamin C supplements

    Vitamin C helps you absorb iron, so guidelines advise against both.3,4

    How much it helps
    A little
    How sure we are
    Fairly sure
  • Drinking less alcohol

    Alcohol raises saturation and ferritin on its own. With hemochromatosis, more than 60 g a day, about four drinks, goes with a ninefold higher risk of cirrhosis.3

    How much it helps
    A little
    How sure we are
    Fairly sure

Starting early matters, because some damage, including joint disease and diabetes, doesn’t improve with treatment.3 US guidelines say you don’t need to cut out iron-rich food during treatment;3 European guidelines suggest limiting red meat.4 Medicines that remove iron (chelation) are kept for people who can’t have phlebotomy.3

Who should get a transferrin saturation test?

It’s worth checking if any of these apply to you:

  • A parent, brother, sister or child has hemochromatosis.3,4
  • Your ferritin is high.3
  • Your liver enzymes are raised and no one has found out why.3
  • You have heart failure. European guidelines recommend checking saturation and ferritin in everyone being assessed for it.8
  • You have kidney disease and anemia, or take iron for it.9
  • You have a long-term inflammatory illness and anemia.2

How to get a transferrin saturation 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

Is a transferrin saturation of 50% bad?

Not on its own, and Labcorp won’t flag it.1 But it’s above the 45% that US liver specialists use to look for hemochromatosis.3 Repeat the test before breakfast, with ferritin. If it’s 45% or more again, ask about a genetic test.3,4

Why is my saturation high but my ferritin normal?

An iron pill, a multivitamin or a meal before the test can do it.1,2 It can also be early hemochromatosis, where saturation rises before ferritin climbs.1,4 And saturation swings. In a large screening study, 1 in 3 people with two copies of the main hemochromatosis gene change fell below the usual cutoff on at least one of two tests.5

What are the symptoms of hemochromatosis?

Often none at first. Tiredness and joint pain are the most common early symptoms, and the knuckles of the index and middle fingers are a typical spot. Later, the extra iron can cause liver disease, diabetes, darker skin and heart problems. Symptoms usually start earlier in men. Women often notice them only after menopause.3

I carry one copy of the gene. Will I get hemochromatosis?

It’s very unlikely. In an Australian study that followed people for 12 years, only one person without two copies of C282Y developed disease from iron overload, and that person carried two different HFE changes.7 US liver specialists advise that people with the H63D or S65C changes but no C282Y aren’t at higher risk of iron overload.3

Often checked alongside

Ferritin
How much iron you have in store
Serum iron
Iron in your blood right now
TIBC
How much iron your blood can carry
ALT
The enzyme most specific to liver damage

Test details

Labcorp test
Iron and Total Iron-binding Capacity (TIBC), 001321
LOINC
2502-3
Sample
Blood
Fasting
Labcorp doesn’t require it.1 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.2 When the question is hemochromatosis, European liver specialists say a morning sample is enough and fasting doesn’t help.4
Typical lab range
15% to 55%1
Units
%: the share of your blood’s iron-carrying capacity (TIBC) that’s filled with iron

Sources

  1. 1 Labcorp. Iron and total iron-binding capacity (TIBC), test 001321, and sample report. Labcorp test menu. Accessed October 28, 2026. www.labcorp.com/tests/001321/iron-and-total-iron-binding-capacity-tibc
  2. 2 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
  3. 3 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
  4. 4 European Association for the Study of the Liver. EASL Clinical Practice Guidelines on haemochromatosis. J Hepatol. 2022;77(2):479–502. doi.org/10.1016/j.jhep.2022.03.033
  5. 5 Adams PC, Reboussin DM, Press RD, et al. Biological variability of transferrin saturation and unsaturated iron-binding capacity. Am J Med. 2007;120(11):999.e1–999.e7. doi.org/10.1016/j.amjmed.2007.02.027
  6. 6 Adams PC, Reboussin DM, Barton JC, et al. Hemochromatosis and iron-overload screening in a racially diverse population. N Engl J Med. 2005;352(17):1769–1778. doi.org/10.1056/NEJMoa041534
  7. 7 Allen KJ, Gurrin LC, Constantine CC, et al. Iron-overload-related disease in HFE hereditary hemochromatosis. N Engl J Med. 2008;358(3):221–230. doi.org/10.1056/NEJMoa073286
  8. 8 Køber L, Adamo M, Ruwald AC, et al. 2026 ESC Guidelines for the management of heart failure. Eur Heart J. 2026;47(38):5346–5457. doi.org/10.1093/eurheartj/ehag100
  9. 9 Kidney Disease: Improving Global Outcomes (KDIGO) Anemia Work Group. KDIGO 2026 clinical practice guideline for the management of anemia in chronic kidney disease (CKD). Kidney Int. 2026;109(1S):S1–S99. doi.org/10.1016/j.kint.2025.06.006

Updated 4 Nov 2026.

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