6 Reasons to Test Your Iron Level

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gloved hand holding test tube with blood sample for ferritin test, which is a measure of stored iron

Your body needs iron to make red blood cells, which carry oxygen to your cells and tissues. So, normal iron levels are vital to your health. But there’s more to an iron blood test than you think. There are several tests that together give doctors a complete picture of the overall amount of iron in the body and where problems may lurk. These iron indices include:

  • Serum iron level: This test measures the amount of iron in the serum—the liquid part of the blood.
  • Serum ferritin level: This is a measurement of a protein—ferritin—that helps store iron. Low levels of ferritin mean you may not have enough stored iron. High levels can mean you are storing too much.
  • Transferrin test: This measures the level of another protein—transferrin. It is responsible for transporting iron in the blood. The lab will likely report a transferrin saturation. Normally, about one-third of the total transferrin is saturated, that is, carrying iron.
  • TIBC (total iron binding capacity): This is a measurement of the total amount of protein that can bind iron. Transferrin is the main protein, so it’s a good estimate of transferrin.
  • UIBC (unsaturated iron binding capacity): This is a test for the unbound portion of proteins—mainly transferrin. About two-thirds of transferrin is normally not bound to iron. It reflects transferrin’s reserve capacity.

Here’s a look at the reasons doctors may order these iron tests.

1. You have symptoms of iron-deficiency anemia.

Doctors may recommend iron tests if you have symptoms of iron-deficiency anemia due to low iron. This includes fatigue, weakness, pale skin, dizziness, shortness of breath, and cold hands and feet. This type of anemia happens when you don’t have an adequate amount of iron to make hemoglobin. Hemoglobin is the part of red blood cells that carries oxygen to your cells. Without enough hemoglobin, your cells can’t get the oxygen they need to function normally.

With iron-deficiency anemia, iron test results may come back as follows:

  • Low serum iron
  • Low serum ferritin
  • Low transferrin saturation
  • High TIBC
  • High UIBC

As serum iron levels fall, your body will pull more iron out of storage. So, early in this anemia, serum iron levels can be normal because your body is using stored iron. But ferritin levels will be low because the body is depleting iron stores. As iron stores are used up, it sends a signal to the body that it needs to transport more iron. This stimulates transferrin production and causes TIBC and UIBC to increase.

2. You have symptoms of iron overload.

On the other end of the spectrum, doctors will order iron tests if you have symptoms of iron overload—or hemochromatosis. This condition occurs when you absorb more iron than you need causing high iron levels. The disease can be hereditary—primary hemochromatosis—or due to another condition such as liver disease—secondary hemochromatosis. Symptoms include joint pain, abdominal pain, fatigue, weakness, and changes in skin color.

In iron overload, iron test results may look like the following:

  • High serum iron
  • High serum ferritin
  • High transferrin saturation
  • Low TIBC
  • Low UIBC

Basically, it’s the opposite of iron deficiency. As serum iron levels keep increasing, the body tries to store the extra iron. So, iron and ferritin levels will both be high. Transferrin saturation will also be high because the body is transporting so much iron. There will be very little transferrin free to bind more iron, so TIBC and UIBC will be low. Without treatment to remove the excess iron, iron overload can cause life-threatening complications.

3. You have low red blood cells.

Complete blood counts (CBC) are often part of routine physical exams. A CBC can detect potential problems before symptoms develop. If your red blood cell count is low or the cells don’t look normal, your doctor may order iron tests to find out why. Low red blood cells—or anemia—has several causes other than iron deficiency.

The results of the iron tests can have very different patterns depending on the cause of anemia. For example, hemolytic anemia will show high serum iron levels and look similar to iron overload results. The reason is red blood cells are being destroyed and releasing iron faster than the body can make new ones. In anemia of chronic disease, everything can be low except ferritin. This is because inflammation interferes with the body’s use of iron. So, there’s plenty of stored iron, but the body can’t use it properly.

4. You have a condition that could interfere with iron absorption.

Decreased iron absorption is one cause of iron deficiency. Conditions that interfere with the normal ability of the digestive tract to absorb nutrients, such as celiac disease, can cause this. Surgeries that alter the digestive tract, such as bariatric surgery, can cause it too. Stomach acid is necessary for iron absorption. So, medicines that block stomach acid production can alter iron absorption. If you have any of these conditions, your doctor may monitor your iron tests regularly.

5. You have a condition that causes an increased need for iron.

Certain conditions increase your body’s need for iron. This happens when children and teens go through growth spurts. It also happens when women become pregnant. In fact, iron tests are a regular part of prenatal screening. But diseases that cause bleeding, such as peptic ulcer disease or some cancers, can also increase iron needs. Even heavy menstrual bleeding can dramatically increase iron needs. Any of these conditions can eventually deplete your iron stores due to the high demand for iron.

6. Your diet is low in iron.

Diets low in iron can lead to iron-deficiency if you aren’t taking a supplement. Meat and fish are good sources of iron. But you can get plenty of iron from vegetables and grains too. This includes dark green, leafy vegetables, beans, sweet potatoes, dried fruits, and enriched grain products. If you don’t eat these types of foods, your doctor may be concerned about your iron intake.

Iron supplements can make up for a lack of iron in your diet, but you have to take them correctly. To get the best absorption from an iron supplement, take it on an empty stomach. This is hard for a lot of people because iron can cause stomach upset. So, you may find you need to take it with food. If so, there are some strategies to follow. Take it with vitamin C, such as orange juice or a supplement, to increase absorption. Avoid dairy products because calcium can interfere with iron’s absorption. Similarly, avoid antacids for two hours after and four hours before you take iron.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Apr 8
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. Anemia in People With Cancer. American Cancer Society. https://www.cancer.org/treatment/treatments-and-side-effects/physical-side-effects/low-blood-counts/anemia.html
  2. Hemochromatosis. Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/diseases-conditions/hemochromatosis/symptoms-causes/syc-20351443
  3. Iron. American Association for Clinical Chemistry. https://labtestsonline.org/tests/iron
  4. Iron-Deficiency Anemia. Johns-Hopkins University. https://www.hopkinsmedicine.org/health/conditions-and-diseases/irondeficiency-anemia
  5. Iron Deficiency Anemia. Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/diseases-conditions/iron-deficiency-anemia/symptoms-causes/syc-20355034
  6. Iron Tests. American Association for Clinical Chemistry. https://labtestsonline.org/tests/iron-tests
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