Type the serum iron — the “Iron” line of your blood test. You see it against the ranges MedlinePlus and Mayo Clinic Laboratories print for women and men, and what each says about how the blood was drawn. Serum iron is one iron test of several: ferritin, your lab’s own range and your doctor have the last word.
90 mcg/dL is
Inside both ranges for women 90 mcg/dL = 16.1 µmol/L
90 mcg/dL: inside the 37–145 mcg/dL MedlinePlus prints for women, and inside the 35–145 mcg/dL Mayo Clinic Laboratories prints for women.
Mayo Clinic Laboratories: “The intraindividual day-to-day variation of iron and iron saturation is approximately 25% to 30%.” One result is one day.
That is inside both ranges for women. Serum iron is one iron test of several — your ferritin and your lab’s own range are what your doctor reads it with.
Mayo Clinic Laboratories: “However, serum ferritin is a much more sensitive and reliable test for demonstration of iron deficiency.” Check a ferritin result.
What moves the number, in the sources’ words
- Normal value ranges may vary slightly among different laboratories.
- MedlinePlus: “If your iron test results are not normal, it does not necessarily mean you have a medical condition that needs treatment.”
- MedlinePlus: “Iron levels may also be lower for women during their menstrual cycles.”
| Source | Women | Men |
|---|---|---|
| MedlinePlus | 37–145 | 59–158 |
| Mayo Clinic Laboratories | 35–145 | 50–150 |
This is not medical advice and it does not diagnose anything. It shows where a number sits against published ranges; what your result means for you depends on your lab, your ferritin, your other results, your history and your doctor.
MedlinePlus prints a normal serum iron of 37 to 145 mcg/dL for women and 59 to 158 mcg/dL for men. Mayo Clinic Laboratories prints 35 to 145 for women and 50 to 150 for men. Serum iron is the iron moving in your blood today. It is not the iron your body has stored: that is the ferritin.
How to use it
Type the line called “Iron”, “Serum iron” or “Iron, total” from your blood test, say whether it is printed in mcg/dL (the same number as µg/dL) or µmol/L, and pick the ranges for women or men. Then say how the blood was drawn. That does not change the number: it picks which of the sources’ own sentences about timing apply to you. You see where your result sits against both sources’ ranges, drawn on one bar, and what MedlinePlus lists as moving it. It does not diagnose anything.
“Normal iron level”: which test is it?
MedlinePlus: “There are different types of iron tests.” It lists four, among them “Serum iron test, which measures the amount of iron in the blood” and “Ferritin blood test, which measures how much iron is stored in the body”. The other two are transferrin and the TIBC. When people search for a normal iron level they usually mean the serum iron, the “Iron” line on a report. MedlinePlus’s encyclopedia: “A serum iron test measures how much iron is in your blood.” For iron stores, the Ferritin Level Checker places a ferritin result. For anemia, the Hemoglobin Level Checker places a hemoglobin.
The ranges the sources print
| Source | Women | Men |
|---|---|---|
| MedlinePlus | 37–145 mcg/dL (6.6–25.9 µmol/L) | 59–158 mcg/dL (10.6–28.3 µmol/L) |
| Mayo Clinic Laboratories | 35–145 mcg/dL (6.3–26.0 µmol/L) | 50–150 mcg/dL (9.0–26.9 µmol/L) |
MedlinePlus’s Serum iron test page prints “Iron: Males: 59 to 158 mcg/dL (10.6 to 28.3 micromol/L); Females: 37 to 145 mcg/dL (6.6 to 25.9 micromol/L)” and says “Normal value ranges may vary slightly among different laboratories.” Mayo Clinic Laboratories (test SFEC) prints “IRON Males: 50-150 mcg/dL Females: 35-145 mcg/dL”, in mcg/dL only. Its µmol/L figures above are ours, converted by iron’s atomic weight (1 µmol/L = 5.5845 mcg/dL). The two sources almost agree for women. For men they differ at both ends: 50 to 58 is inside Mayo’s range and under MedlinePlus’s, and 151 to 158 is the other way round. This checker is for adults.
How the blood was drawn matters
MedlinePlus: “The serum iron level can change, depending on how recently you ingested iron. Your health care provider will likely have you do this test in the morning or after fasting.” Its iron-tests page adds: “The amount of iron in your blood varies throughout the day and may be higher in the morning.” It also says “Your provider may ask you to fast (not eat or drink) for 12 hours before your test.” Mayo Clinic Laboratories asks: “For 24 hours before collection, patient should not take iron-containing supplements.” It also says why one result is only one day: “The intraindividual day-to-day variation of iron and iron saturation is approximately 25% to 30%.” If you take iron, the Iron Tablet Timing Planner shows where it falls in your day. Ask the person who ordered the test before skipping a dose.
What raises or lowers it
MedlinePlus: “A higher-than-normal iron level may be a sign of:” Too much iron in the body (hemochromatosis); Anemia due to red blood cells being destroyed too quickly (hemolytic anemia); Liver tissue death; Inflammation of the liver (hepatitis); Iron poisoning; Frequent blood transfusions. “A lower-than-normal iron level may be a sign of:” Long-term digestive tract bleeding; Heavy menstrual bleeding; Intestinal conditions that cause poor absorption of iron; Not enough iron in the diet; Pregnancy. “Iron levels may also be lower for women during their menstrual cycles.” “Certain medicines may affect the results of this test.” It names Antibiotics; Birth control pills and estrogens; Blood pressure medicines; Cholesterol medicines; Deferoxamine (removes excess iron from the body); Gout medicines; Testosterone. And: “Do not stop any medicine before talking to your provider.” Its iron-tests page: “If your iron test results are not normal, it does not necessarily mean you have a medical condition that needs treatment.” And of low iron: “But not all people who have low iron levels have anemia.”
Ferritin comes first
For the question most readers of this site bring, “is my iron low?”, Mayo Clinic Laboratories is plain: “However, serum ferritin is a much more sensitive and reliable test for demonstration of iron deficiency.” MedlinePlus: “To understand the results of your iron test, your provider will consider your symptoms, age, medical history, and the results of other blood tests.” The same panel usually prints a TIBC, a UIBC and a saturation. The TIBC Level Checker, the UIBC Level Checker and the Iron Saturation Checker read those lines.
Worked examples
- 90 mcg/dL, woman (the page’s example): inside both ranges.
- 36 mcg/dL, woman: under MedlinePlus’s 37, inside Mayo’s 35. The sources differ by one unit here, and the answer says so.
- 155 mcg/dL, man: inside MedlinePlus’s 59–158, above Mayo’s 50–150.
- 20 µmol/L, man: inside MedlinePlus’s 10.6–28.3 µmol/L and inside Mayo’s 9.0–26.9 µmol/L (converted).
- 200 mcg/dL, woman, iron the morning before: above both ranges, with MedlinePlus’s sentence on recent iron and Mayo’s 24-hour preparation shown beside it.
Common mistakes
- Reading serum iron as iron stores. It is the iron in the blood at the moment of the draw. Ferritin is the stored iron.
- Taking an iron tablet before the test. MedlinePlus says the level changes with recent iron, and Mayo asks for 24 hours without iron-containing supplements.
- Comparing an afternoon result with a morning one. MedlinePlus says iron may be higher in the morning, and Mayo puts the day-to-day variation at 25% to 30%.
- Mixing up units. 15 in µmol/L is about 84 in mcg/dL; switch the unit to match your report.
- Using a range from the internet over your lab’s. The two sources here already differ for men; your report prints its own.
Frequently asked questions
What are normal iron levels for women?
MedlinePlus prints 37 to 145 mcg/dL (6.6 to 25.9 µmol/L) for women’s serum iron. Mayo Clinic Laboratories prints 35 to 145 mcg/dL. Your lab’s printed range is the one your doctor uses.
What is an average iron level?
Neither source prints an average, only a normal range. For serum iron that is 37–145 mcg/dL for women and 59–158 for men (MedlinePlus), or 35–145 and 50–150 (Mayo Clinic Laboratories). Mayo puts one person’s day-to-day variation at about 25% to 30%.
What does a low serum iron mean?
MedlinePlus lists long-term digestive tract bleeding, heavy menstrual bleeding, intestinal conditions that cause poor absorption of iron, not enough iron in the diet, and pregnancy. It adds that “not all people who have low iron levels have anemia”. Mayo calls ferritin the more reliable test for iron deficiency.
What does a high serum iron mean?
MedlinePlus lists hemochromatosis, hemolytic anemia, liver tissue death, hepatitis, iron poisoning and frequent blood transfusions. A recent iron tablet can also change the level. An abnormal result “does not necessarily mean you have a medical condition that needs treatment”.
Should I fast before an iron blood test?
MedlinePlus says your provider may ask you to fast for 12 hours and will likely have you do the test in the morning or after fasting. Mayo Clinic Laboratories asks for 24 hours without iron-containing supplements. Follow what whoever ordered the test tells you.
Is serum iron the same as ferritin?
No. MedlinePlus: the serum iron test “measures the amount of iron in the blood”, while the ferritin blood test “measures how much iron is stored in the body”. Mayo calls ferritin “a much more sensitive and reliable test for demonstration of iron deficiency”.
How do I convert iron from µmol/L to mcg/dL?
Multiply by 5.5845, iron’s atomic weight divided by 10: 15 µmol/L is about 84 mcg/dL. MedlinePlus prints both units, and its pairs agree with that factor.
The whole panel at once — every line on one screen, and whether iron + UIBC = TIBC and the saturation add up: the Iron Panel Reader. More iron and blood-count checkers: the Ferritin Level Checker, the TIBC Level Checker, the Hemoglobin Level Checker and the Iron, Zinc & Calcium Form Finder.
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- How to get rid of anemia? The best 4 products
- The best vitamins for women at 30+
- Multivitamins for adults: how to choose
This is not medical advice, and nothing here diagnoses or treats anything. It shows where a number sits against published adult ranges and quotes what the sources say moves it. Your lab’s own range, your ferritin, your other results and your doctor decide what it means. Some links on this site are affiliate links: I buy what I review at full price, and a commission never changes a verdict.