What Does It Mean When Your Iron Saturation Is Low

At a Glance

Why Get Tested?

Along with other iron tests, to assess your body's ability to transport iron in the blood; to help diagnose iron-deficiency or iron overload

When To Get Tested?

When you have low hemoglobin and hematocrit on a complete blood count (CBC); when your healthcare practitioner suspects you may have too much iron (overload) or too little iron (deficiency) in the body

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

You may be instructed to have your blood drawn in the morning and/or fast for 12 hours before the test; in this case, only water is allowed. Follow any instructions from your healthcare practitioner and/or from the laboratory performing the test.

Order your at-home health test online

A convenient, affordable, and discreet way of getting accurate test results quickly.

Order the right test for you.

We have a wide range of tests to cover your health needs. Order with next day delivery and avoid sitting in a doctor's office or clinic.
Collect your sample

Activate your test and collect your sample in the morning. Return your sample on the same day, using the prepaid shipping label provided.
Discreet Packaging

Free next day shipping and confidential results in 2-5 days

Discreet Packaging

Free next day shipping and confidential results in 2-5 days
Trustworthy Medical Support

Real-time support services from our national network of physicians and nurses
Health Records You Control

Privacy at your fingertips, integrated with your choice of apps and wearables

You may be able to find your test results on your laboratory's website or patient portal. However, you are currently at Testing.com. You may have been directed here by your lab's website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab's website or portal, or contact your healthcare practitioner in order to obtain your test results.

Testing.com is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called "normal" values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

For more information, please read the article Reference Ranges and What They Mean.

What is being tested?

Transferrin is the main protein in the blood that binds to iron and transports it throughout the body. A transferrin test directly measures the level in the blood. Alternatively, transferrin may be measured indirectly (or converted by calculation) so that its level is expressed as the amount of iron it is capable of binding. This is called the total iron binding capacity (TIBC).

Iron is an essential nutrient that, among other…

Iron is an essential nutrient that, among other functions, is necessary for the production of healthy red blood cells (RBCs). It is a critical part of hemoglobin, the protein in RBCs that binds oxygen in the lungs and releases oxygen as blood circulates to other parts of the body. The body cannot produce iron and must absorb it from the foods we eat or from supplements.

Normally, iron is transported throughout the body by transferrin, which is produced by the liver. In healthy people, most iron is incorporated into the hemoglobin within RBCs. The remainder is stored in the tissues as ferritin or hemosiderin, with additional small amounts used for other purposes (e.g., to produce other proteins such as myoglobin and some enzymes).

The transferrin test, TIBC, UIBC, and transferrin saturation, along with other iron tests, help evaluate the amount of iron in the body by measuring several substances in the blood. These tests are often ordered at the same time and the results interpreted together to help diagnose and/or monitor iron deficiency or iron overload.

Serum iron test—measures the total amount of iron in the liquid portion of the blood, nearly all of which is bound to transferrin.
Transferrin test—directly measures the level of transferrin in the blood. The level depends upon liver function and a person's nutritional status. Transferrin is a protein that may decrease during any inflammatory process and is referred to as a negative acute phase reactant.
TIBC (total iron-binding capacity)—measures the total amount of iron that can be bound by proteins in the blood. Since transferrin is the primary iron-binding protein, the TIBC test is a good indirect measurement of transferrin availability—the amount of transferrin that is available to bind to iron. (Note: Though TIBC is a reflection of the amount of transferrin available, TIBC and transferrin are not synonymous.)
UIBC (unsaturated iron-binding capacity)—this test determines the reserve capacity of transferrin, i.e., the portion of transferrin that has not yet been saturated with iron.
Transferrin saturation— dividing the iron concentration by the TIBC produces an estimate of how many of transferrin iron-binding sites are occupied; this is called the transferrin saturation. Under normal conditions, transferrin is typically one-third saturated with iron. This means that about two-thirds of its capacity is held in reserve. (Less commonly, the iron concentration may be divided by the transferrin concentration, not the TIBC. This similar estimate is usually called the transferrin index.)
Ferritin—measures the level of ferritin, a protein made by almost all cells in response to increased iron. The ferritin level reflects the total body iron. It will be low when there is iron deficiency and high when there is an excess of iron in the body.

When the level of iron is insufficient to meet the body's needs, the level of iron in the blood drops and iron stores are depleted. This may occur because:

There is an increased need for iron, for example during pregnancy or childhood, or due to a condition that causes chronic blood loss (e.g., peptic ulcer, colon cancer)
Not enough iron is consumed (either foods or supplements)
The body is unable to absorb iron from the foods eaten in conditions such as celiac disease

Insufficient levels of circulating and stored iron may eventually lead to iron deficiency anemia (decreased hemoglobin and hematocrit, smaller and paler red cells). In the early stage of iron deficiency, no physical effects are usually seen and the amount of iron stored may be significantly depleted before any signs or symptoms of iron deficiency develop. If a person is otherwise healthy and anemia develops over a long period of time, symptoms may not appear before the hemoglobin in the blood drops below the lower limit of normal.

However, as the iron deficiency progresses, symptoms eventually begin to appear. The most common symptoms of anemia include fatigue, weakness, dizziness, headaches and pale skin.

Conversely, too much iron can be toxic to the body. Iron storage and ferritin levels increase when more iron is absorbed than the body needs. Absorbing too much iron over time can lead to the progressive buildup of iron compounds in organs and may eventually cause their dysfunction and failure. An example of this is hemochromatosis, a rare genetic disease in which the body absorbs and builds up too much iron, even on a normal diet. Additionally, iron overload can occur when a person undergoes repeated blood transfusions.

Common Questions

How is it used?

The transferrin, total iron-binding capacity (TIBC) or unsaturated iron-binding capacity (UIBC) test may be used along with other iron tests to assess the amount of iron circulating in the blood, the total capacity of the blood to transport iron, and the amount of stored iron in the body. Testing may also help differentiate various causes of anemia.

Iron tests are often ordered together, and the results of each can help identify iron deficiency, iron deficiency anemia, or too much iron in the body (overload).

When is it ordered?

These tests may be ordered along with other iron tests when results from a routine complete blood count (CBC) show that a person's hemoglobin and hematocrit are low and their red blood cells are smaller and paler than normal (microcytic and hypochromic), suggesting iron deficiency anemia even though other clinical symptoms may not have developed yet.

Iron tests may be ordered when a person develops signs and symptoms of anemia such as:

Chronic fatigue/tiredness
Dizziness
Weakness
Headaches
Pale skin (pallor)

Testing may be ordered when iron overload is suspected. Signs and symptoms of iron overload will vary from person to person and tend to worsen over time. They are due to iron accumulation in the blood and tissues. These may include:

Joint pain
Fatigue, weakness
Weight loss
Lack of energy
Abdominal pain
Loss of sex drive
Organ damage, such as in the heart and/or liver

Testing is also ordered when there is a case of suspected iron poisoning. This is most common in children who accidentally overdose with vitamins or other supplements containing iron.

What does the test result mean?

The results of transferrin tests, TIBC, or UIBC are usually evaluated in conjunction with other iron tests. A summary of the changes in iron tests seen in various diseases of iron status is shown in the table below.

Disease	Iron	TIBC/Transferrin	UIBC	%Transferrin Saturation	Ferritin
Iron Deficiency	Low	High	High	Low	Low
Hemochromatosis/Hemosiderosis	High	Low	Low	High	High
Chronic Illness	Low	Low/Normal	Low/Normal	Low/Normal	High/Normal
Hemolytic Anemia	High	Normal/Low	Low/Normal	High	High
Sideroblastic Anemia	Normal/High	Normal/Low	Low/Normal	High	High
Iron Poisoning	High	Normal	Low	High	Normal

Iron deficiency
The early stage of iron deficiency is the slow depletion of iron stores. This means there is still enough iron to make red cells but the stores are being used up without adequate replacement. The serum iron level may be normal in this stage, but the ferritin level will be low.

As iron deficiency continues, all of the stored iron is used and the body tries to compensate by producing more transferrin to increase iron transport. The serum iron level continues to decrease and transferrin and TIBC and UIBC increase. As this stage progresses, fewer and smaller red blood cells are produced, eventually resulting in iron deficiency anemia. Transferrin saturation is decreased with iron deficiency.

Iron overload
If the iron level and transferrin saturation are high, the TIBC, UIBC and ferritin are normal and the person has a clinical history consistent with iron overdose, then it is likely that the person has iron poisoning. Iron poisoning occurs when a large dose of iron is taken all at once (acute) or over a long period of time (chronic). Iron poisoning in children is almost always acute, occurring in children who ingest their parents' iron supplements. In some cases, acute iron poisoning can be fatal.

A person who has mutations in the HFE gene is diagnosed with hereditary hemochromatosis. However, while many people who have hemochromatosis will have no symptoms for their entire life, others will start to develop symptoms such as joint pain, abdominal pain, and weakness in their 30's or 40's. Men are affected more often than women because women lose blood during their reproductive years through menstruation.

Iron overload may also occur in people who have hemosiderosis and in those who have had repeated transfusions. This may occur with sickle cell anemia, thalassemia major, or other forms of anemia. The iron from each transfused unit of blood stays in the body, eventually causing a large buildup in the tissues. Some persons with alcoholism and with chronic liver disease also develop iron overload.

Is there anything else I should know?

Recent blood transfusions can affect test results as can iron injections or transfused iron. Multiple blood transfusions can sometimes lead to iron overload.

A high TIBC, UIBC, or transferrin usually indicates iron deficiency, but they are also increased in pregnancy and with the use of oral contraceptives.

A low TIBC, UIBC, or transferrin may also occur if someone has malnutrition, inflammation, liver disease, or nephrotic syndrome. However, the tests are usually not used to assess these conditions.

How is transferrin saturation calculated?

The calculation is:

Transferrin saturation (%) = (Serum iron level x 100%) / TIBC

TIBC measures the total amount of iron that can be bound by proteins in the blood. Since transferrin is the primary iron-binding protein, the TIBC test is a good indirect measurement of transferrin availability—the amount of transferrin that is available to bind to iron.

In healthy individuals, transferrin is one-third saturated with iron. This means that there is about two-thirds held in reserve. In iron deficiency, all of the stored iron is used and the body tries to compensate by producing more transferrin to increase iron transport. While the serum iron level continues to decrease, the transferrin level increases. Thus, the amount of transferrin available to bind iron (TIBC) increases and the amount of transferrin saturated with iron (i.e., percent transferrin saturation) decreases.

What other factors affect the transferrin level?

Transferrin is a protein that may decrease during any inflammatory process and is referred to as a negative acute phase reactant. Chronic inflammation, infections, and malignancies may cause changes in transferrin levels.

Are there other things that cause anemia besides iron deficiency?

Yes, there are numerous causes of anemia. However, iron deficiency is one of the most common. If iron tests rule out iron deficiency, another source for the anemia must be found.

Health Professionals – LOINC

LOINC Observation Identifiers Names and Codes (LOINC®) is the international standard for identifying health measurements, observations, and documents. It provides a common language to unambiguously identify things you can measure or observe that enables the exchange and aggregation of clinical results for care delivery, outcomes management, and research. Learn More.

Listed in the table below are the LOINC with links to the LOINC detail pages. Please note when you click on the hyperlinked code, you are leaving Testing.com and accessing Loinc.org.

LOINC	LOINC Display Name
3034-6	Transferrin [Mass/Vol]
22674-6	Transferrin [Moles/Vol]
2501-5	Iron binding capacity.unsaturated [Mass/Vol]
22753-8	Iron binding capacity.unsaturated [Moles/Vol]
2500-7	Iron binding capacity [Mass/Vol]
14800-7	Iron binding capacity [Moles/Vol]
2505-6	Iron/Iron binding capacity.total [Mass ratio]
39778-6	Iron/Iron binding capacity.total [Molar ratio]
2502-3	Iron saturation [Mass fraction]
14801-5	Iron saturation [Molar fraction]

View Sources

Sources Used in Current Review

Devkota, B. (2014 January 16 Updated). Iron-Binding Capacity. Medscape Drugs and Diseases. Available online at http://emedicine.medscape.com/article/2085726-overview. Accessed on May 2017.

Paruthi, S. (2015 January 14 Updated). Transferrin Saturation. Medscape Drugs and Diseases. Available online at http://emedicine.medscape.com/article/2087960-overview. Accessed on May 2017.

Harper, J. and Conrad, M. (2015 November 7 Updated). Iron Deficiency Anemia. Medscape Drugs and Diseases. Available online at http://emedicine.medscape.com/article/202333-overview. Accessed on May 2017.

(© 1995– 2017). Iron and Total Iron-Binding Capacity, Serum. Mayo Clinic Mayo Medical Laboratories Available online at http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/34624. Accessed on May 2017.

(© 1995– 2017). Transferrin, Serum. Mayo Clinic Mayo Medical Laboratories. Available online at http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/34623. Accessed on May 2017.

Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Nader Rifai. 6th edition, Elsevier Health Sciences; 2017. Pg 742.

Wintrobe's Clinical Hematology. 12th ed. Greer J, Foerster J, Rodgers G, Paraskevas F, Glader B, Arber D, Means R, eds. Philadelphia, PA: Lippincott Williams & Wilkins: 2009. Pg. 818.

Sources Used in Previous Reviews

Corbett, JV. Laboratory Tests & Diagnostic Procedures with Nursing Diagnoses, 4th ed. Stamford, Conn.: Appleton & Lang, 1996. Pp. 34-35, 41-43.

Frey, Rebecca J. Iron Tests. Chapter in: Gale Encyclopedia of Medicine, Edition One, 1999 Gale Research Group, Pg. 1648.

Witte DL, Crosby WH, Edwards CQ, Fairbanks VG, Mitros FA. Practice guideline development task force of the College of American Pathologists.

Boston University Medical Center. Community Outreach Health Information System. Available online at http://www.bu.edu/cohis/cardvasc/blood/anemia.htm#prevent.

Lyon, Elaine and Frank, Elizabeth L. Hereditary Hemochromatosis Since Discovery of the HFE Gene. Clinical Chemistry 47:1147-1156 (Jul 2001).

Dugdale III, D. (Updated 2009 February 13). Total Iron Binding Capacity. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003489.htm. Accessed June 2009.

(Modified 2009 March 13). About Iron. Iron Disorders Institute [On-line information]. Available online at http://www.irondisorders.org/Disorders/about.asp. Accessed June 2009.

(Updated 2007 August 24). Dietary Supplement Fact Sheet: Iron. NIH Office of Dietary Supplements [On-line information]. Available online at http://ods.od.nih.gov/factsheets/iron.asp. Accessed June 2009.

Rathz, D. et. al. (Updated 2009 February 02). Toxicity, Iron. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/166933-overview. Accessed June 2009.

Chen, Y. (Updated 2009 April 05). Iron Deficiency Anemia. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000584.htm. Accessed June 2009.

Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. McPherson RA and Pincus MR, eds. Philadelphia: 2007, Pg 506.

Gersten, T. (Updated 2012 February 8). Total iron binding capacity. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003489.htm. Accessed April 2013.

(© 1995-2013). Iron and Total Iron-Binding Capacity, Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/34624. Accessed April 2013.

Devkota, B. (Updated October 4). Iron-Binding Capacity. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/2085726-overview. Accessed April 2013.

(Update 2013 March). Hemochromatosis. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/Hemochromatosis.html?client_ID=LTD#tabs=6. Accessed April 2013.

Yamanishi, H. et. al. (2003 January). Total Iron-binding Capacity Calculated from Serum Transferrin Concentration or Serum Iron Concentration and Unsaturated Iron-binding Capacity. Clinical Chemistry v 49 (1) 175-178 [On-line information]. Available online at http://www.clinchem.org/content/49/1/175.full. Accessed April 2013.

Ask a Laboratory Scientist

This form enables patients to ask specific questions about lab tests. Your questions will be answered by a laboratory scientist as part of a voluntary service provided by one of our partners, American Society for Clinical Laboratory Science. Please allow 2-3 business days for an email response from one of the volunteers on the Consumer Information Response Team.

Send Us Your Question

Source: https://labtestsonline.org/tests/transferrin-and-iron-binding-capacity-tibc-uibc

Posted by: lewiswerve1955.blogspot.com

Lewis Werve1955

What Does It Mean When Your Iron Saturation Is Low