A normal serum iron level falls between 60 and 150 mcg/dL for most adults, but that single number doesn’t tell the whole story. Doctors typically order a panel of related tests, and the one that matters most for understanding your iron stores is ferritin. Knowing what each number means, and where yours should fall, helps you make sense of your lab results.
Normal Serum Iron Levels for Adults
Serum iron measures how much iron is circulating in your blood at the moment of the draw. For adult men, the normal range is 75 to 150 mcg/dL. For adult women, it’s 60 to 140 mcg/dL. These numbers can swing significantly throughout the day. Iron levels tend to peak in the morning and drop steadily toward midnight, so the time you get your blood drawn affects the result.
Because serum iron fluctuates so much, doctors rarely use it alone to diagnose a problem. It’s one piece of a larger picture that includes ferritin, transferrin saturation, and total iron-binding capacity.
Why Ferritin Matters More Than Serum Iron
Ferritin is a protein that stores iron inside your cells. The amount of ferritin in your blood directly reflects how much iron your body has in reserve, making it the most reliable single marker of your overall iron status. Normal ferritin ranges are:
- Men: 30 to 400 ng/mL
- Women: 13 to 150 ng/mL
The World Health Organization defines iron deficiency in healthy adults as a ferritin level below 15 ng/mL. If you have an active infection or inflammation, though, ferritin rises on its own as part of the immune response, which can mask a true deficiency. In that case, the WHO uses a higher cutoff of below 70 ng/mL to identify iron deficiency.
This distinction matters because many people with chronic conditions like autoimmune disease or even a lingering infection could look “normal” on a ferritin test while actually being iron-deficient. If your ferritin is technically in range but you’re dealing with fatigue and other symptoms alongside inflammation, a doctor may need to interpret the result differently.
Transferrin Saturation and TIBC
Transferrin is the protein that carries iron through your bloodstream. Transferrin saturation tells you what percentage of that carrier protein is currently loaded with iron. A normal transferrin saturation is 25% to 35%.
Total iron-binding capacity (TIBC) measures how much iron your transferrin could carry if it were fully loaded. A normal TIBC ranges from about 240 to 450 mcg/dL. When your body is low on iron, it produces more transferrin to try to capture whatever iron is available, so TIBC rises. When you have too much iron, TIBC drops because the body scales back production.
These two numbers together help clarify borderline cases. A low transferrin saturation combined with a high TIBC points strongly toward iron deficiency, even if your serum iron is only slightly below normal.
Iron Levels in Children
Children’s iron needs shift dramatically with age. Newborns arrive with substantial iron stores built up during pregnancy, and ferritin levels in infants under 6 months can be as high as 650 ng/mL, which would be flagged as abnormal in an adult. Between 6 months and 15 years, normal ferritin settles into a range of 12 to 140 ng/mL.
The WHO sets the iron deficiency cutoff for infants and preschoolers (up to age 5) at a ferritin below 12 ng/mL. For school-age children and adolescents, the threshold is below 15 ng/mL, the same as for adults. As with adults, these thresholds jump higher (to 30 ng/mL for young children and 70 ng/mL for older kids) when infection or inflammation is present.
Iron Targets During Pregnancy
Pregnancy increases your blood volume by nearly 50%, which dilutes iron concentration and drives up demand. Ferritin levels that would be perfectly fine outside of pregnancy can signal deficiency during it.
Research based on U.S. national health survey data suggests trimester-specific thresholds: a ferritin below about 26 ng/mL in the first trimester indicates deficiency, while in the second and third trimesters the threshold drops to roughly 18 to 19 ng/mL. The first-trimester cutoff is essentially the same as for nonpregnant women of reproductive age. The lower thresholds later in pregnancy reflect normal physiological changes in how the body regulates iron absorption, not a reduced need for iron.
When Iron Is Too High
Iron overload is less common than deficiency but can cause serious organ damage over time, particularly to the liver, heart, and pancreas. Ferritin levels above 300 ng/mL in men or above 150 to 200 ng/mL in menstruating women raise suspicion. A fasting transferrin saturation above 45% strengthens the case, especially when ferritin is also elevated.
The most common genetic cause is hereditary hemochromatosis, a condition where the body absorbs too much iron from food. Both ferritin and transferrin saturation are typically elevated together. Iron overload can also result from frequent blood transfusions or certain blood disorders. Symptoms develop slowly and can include joint pain, fatigue, and abdominal discomfort, which are easy to attribute to other causes, so it often goes undetected for years.
How to Get the Most Accurate Test Results
If you’re getting a serum iron or transferrin saturation test, timing and preparation matter. Mayo Clinic Laboratories recommends having blood drawn before noon, since iron levels are highest in the morning and decline throughout the day. An overnight fast of about 8 hours is preferred but not strictly required.
The most important preparation step is skipping iron supplements for 24 hours before the test. Taking an oral iron supplement within three hours of a blood draw can increase your serum iron reading by three to five times its actual baseline, which would render the results meaningless. This applies to standalone iron pills as well as multivitamins containing iron.
Ferritin is less affected by daily timing and meals, which is another reason doctors favor it as a first-line screening tool. However, it can still be temporarily elevated by recent illness, intense exercise, or liver inflammation, so mention any of those to your provider when reviewing results.