Ferritin is a protein that stores iron inside your cells, and a ferritin blood test measures how much of it is circulating in your bloodstream. That number serves as a reliable indicator of your body’s total iron reserves. Typical levels range from 24 to 336 micrograms per liter in men and 11 to 307 micrograms per liter in women, though the number that matters most depends on your specific situation.
How Ferritin Works in Your Body
Think of ferritin as a storage container for iron. The protein forms a hollow shell that can hold thousands of iron atoms inside it. When your body has more iron than it immediately needs, ferritin locks the excess away safely inside cells, primarily in your liver, spleen, and bone marrow. When your body needs iron to make red blood cells or support other functions, ferritin releases it back into circulation.
This storage system matters because iron is both essential and potentially toxic. Your body needs iron to produce hemoglobin, the molecule in red blood cells that carries oxygen. But free-floating iron can damage tissues. Ferritin keeps iron in a safe, usable reserve.
What Ferritin Tells You That Other Tests Don’t
Iron-related blood work includes several different markers, and they each measure something distinct. Serum iron tells you how much iron is in your blood right now. Transferrin (often reported as total iron-binding capacity, or TIBC) measures how much capacity your blood has to transport iron. Hemoglobin reflects whether you have enough iron to make functional red blood cells. Ferritin is the only one that tells you how much iron your body has in reserve.
This makes ferritin the earliest warning sign of iron problems. Your hemoglobin can look perfectly normal while your ferritin is already dropping, because your body pulls from its iron stores to keep producing red blood cells for as long as possible. By the time hemoglobin falls, you’ve been iron-depleted for a while. Cleveland Clinic notes that ferritin is considered a better marker than transferrin for assessing iron deficiency.
Normal Ranges and Diagnostic Cutoffs
The standard reference ranges from Mayo Clinic are 24 to 336 micrograms per liter for men and 11 to 307 micrograms per liter for women. But “normal” on a lab report doesn’t always mean optimal. The World Health Organization uses a ferritin below 15 micrograms per liter as the threshold for depleted iron stores in anyone over age five, and below 12 for children under five.
Those cutoffs shift upward when infection or inflammation is present. The WHO recommends using a threshold of 30 micrograms per liter in children and 70 micrograms per liter in adults to identify iron deficiency in people who are fighting an infection or dealing with chronic inflammation. The reason for the higher cutoff is that inflammation artificially inflates ferritin levels, masking a true deficiency.
Ferritin During Pregnancy
Pregnancy demands significantly more iron, and ferritin levels naturally decline as blood volume expands. Research published in Blood Advances identified trimester-specific thresholds for iron deficiency in pregnant women: roughly 25 micrograms per liter in the first trimester, dropping to about 20 micrograms per liter in the second and third trimesters. These are lower than the general adult cutoffs because some degree of ferritin decline during pregnancy is physiologically normal, not a sign of a problem.
Why Ferritin Rises During Inflammation
Ferritin is what’s called an acute phase reactant, meaning your body produces more of it in response to infection, inflammation, or tissue damage. This happens because the chemical signals your immune system releases (cytokines) directly stimulate ferritin production, independent of how much iron you actually have stored.
This is one of the trickiest parts of interpreting a ferritin result. A person with a serious infection could have a ferritin level that looks normal or even high, while their actual iron stores are depleted. To sort this out, doctors often measure ferritin alongside inflammation markers like C-reactive protein (CRP) and alpha-1-acid glycoprotein (AGP). If those inflammation markers are elevated, the ferritin number needs to be interpreted with a higher cutoff. A ferritin between 30 and 100 micrograms per liter may actually indicate depleted stores when chronic disease or active infection is present.
What Low Ferritin Means
A low ferritin level means your body’s iron reserves are running low. The most common causes are not getting enough iron from food, losing blood (through menstruation, internal bleeding, or frequent blood donation), or poor iron absorption in the gut. Pregnancy and rapid growth in children also draw down iron stores quickly.
Early iron depletion often causes no symptoms at all. As stores drop further and iron deficiency progresses toward anemia, symptoms build gradually: extreme tiredness, pale skin, cold hands and feet, dizziness, headaches, shortness of breath with exertion, and a fast heartbeat. More unusual symptoms include brittle nails, a sore or swollen tongue, restless legs, and pica, which is an unusual craving for non-food items like ice, dirt, or clay. Some people develop odd cravings for specific smells, like rubber or cleaning products. In children, iron deficiency can suppress appetite rather than trigger cravings.
What High Ferritin Means
Elevated ferritin can point to genuinely high iron stores or to inflammation pushing the number up without any excess iron at all. Distinguishing between the two is the central challenge.
When high ferritin reflects true iron overload, the most common cause is hemochromatosis, a genetic condition where the body absorbs too much iron from food. Over time, excess iron accumulates in the liver, heart, and pancreas, potentially causing organ damage. Other causes of genuinely elevated iron stores include frequent blood transfusions and certain rare metabolic conditions.
More often, though, a high ferritin result reflects inflammation rather than iron overload. Liver disease, autoimmune conditions, chronic infections, and some cancers can all push ferritin up significantly. Alcohol use and metabolic syndrome are also common culprits. When ferritin is elevated, additional testing (typically transferrin saturation and inflammation markers) helps clarify whether the issue is too much iron or something else entirely.
Preparing for the Test
Your provider may ask you to fast for up to 12 hours before a ferritin test, and the draw is usually scheduled in the morning. Some medications can raise or lower ferritin levels, so mention anything you’re taking when discussing your results. The test itself is a standard blood draw with no special procedures.
If your result comes back outside the reference range, context matters enormously. A single ferritin number, without knowing your inflammation status, diet, menstrual history, or other lab values, tells only part of the story. The test is most useful when interpreted alongside other iron markers and a clear picture of your overall health.