A serum iron test can reveal unusually low or high blood iron levels. Your doctor will most likely order this test after another lab test shows an abnormal result.

Having too much iron — or not enough — can cause serious health problems. An iron serum test will help your doctor give you a more accurate diagnosis.

Keep reading to learn more about the serum iron test, what it looks for, what the procedure is like, and more.

A serum iron test is not a routine test. It’s usually ordered as a follow-up when a more common test, such as a complete blood count (CBC) or hemoglobin test, reveals abnormal results.

Your doctor may also order a serum iron test if you’ve had blood loss or if you’re showing symptoms of anemia. Abnormal iron tests could be a sign of iron deficiency or iron overload.

To perform a serum iron test, a healthcare professional will insert a needle into a vein in your arm or hand and draw a small sample of blood. This sample will then be tested in a laboratory.

Your doctor may ask you to fast starting at midnight the night before your procedure. Morning is the best time to conduct this test because that’s when your iron levels are highest.

What are the potential risks of a serum iron test?

You’ll probably experience mild pain or a pricking sensation when you have your blood drawn. You might also bleed slightly afterward or develop a small bruise at the puncture site.

In rare cases, you might experience more serious complications, such as:

Serum iron is measured in micrograms of iron per deciliter of blood (mcg/dL). While normal ranges vary by lab, the following ranges are generally considered healthy ranges for a serum iron test:

  • iron:
    • men 75 to 150 micrograms per deciliter (mcg/dL)
    • women: 60 to 140 mcg/dL
  • transferrin saturation: 20% to 50%
  • ferritin: 30 to 300 ng/mL (nanograms per milliliter)
  • total iron binding capacity (TIBC): 250 to 450 mcg/dL

Transferrin is a protein in the blood that transports iron throughout your body. Examining how much iron is in the transferrin proteins can tell your doctor if you have too much or too little iron in your blood.

TIBC measures how well the transferrin proteins are transporting iron around your body.

It’s worth noting that men typically have slightly higher iron than women.

Abnormally high iron serum levels may mean you’ve consumed too much iron. High levels of iron may indicate:

  • hemolytic anemia or hemolysis: when red blood cells are destroyed faster than your bone marrow can make them
  • liver conditions, such as hepatic necrosis (liver failure) and hepatitis
  • iron poisoning due to having taken more than the recommended dose of iron supplements
  • genetic or hereditary iron overload: your body naturally retains too much iron

Abnormally low iron levels may mean you haven’t consumed enough iron or your body isn’t absorbing the iron properly. Regularly having heavy menstrual periods can also lead to low iron levels.

Low iron levels may also indicate:

Early symptoms of iron deficiency include:

  • chronic fatigue
  • dizziness
  • headaches
  • muscle weakness

You may develop other symptoms as your condition worsens. These may include:

  • difficulty concentrating
  • irritability
  • tongue and mouth sores
  • pica (the compulsion to eat nonfood items, such as paper or ice chips)
  • misshapen nails

Symptoms of iron overload include:

These symptoms generally get worse as your condition progresses.

Many medications can affect the results of a serum iron test by increasing or decreasing your iron levels. For example, birth control pills are commonly used and can affect iron levels.

Tell your doctor before the test if you’re taking any medications.

Your doctor may instruct you to temporarily stop taking medicines that will affect the test. If you can’t stop taking the medication, your doctor will take the medication’s effects into account when interpreting your results.

Your doctor will review the results of your serum iron test with you. They may suggest iron supplements or diet changes, depending on the levels of iron in your blood.

Your doctor may suggest eating more iron-rich foods if your iron levels are too low. Iron-rich foods include:

  • red meats
  • leafy, dark green vegetables
  • beans
  • fish, especially shellfish
  • liver
  • grains

Your doctor may also recommend more tests if they suspect you have an underlying health condition that may be causing your iron levels to be low.