Ferritin Blood Test: What Low or High Ferritin Means, and Where Folate Fits

A ferritin blood test measures the level of ferritin, a protein that binds iron and stores it in your body, so it shows how much iron you have in reserve.¹ Low ferritin may mean iron deficiency anemia, while high ferritin can reflect iron overload or other conditions such as inflammation or liver disease.¹ This page explains when the test is used, what results can mean, how iron deficiency anemia differs from folate deficiency anemia, and why both nutrients matter in pregnancy.

What does a ferritin blood test show?

Your body needs iron to make healthy red blood cells, which carry oxygen from your lungs to the rest of your body.¹ Iron is also important for muscles, bone marrow, and organs, including brain development in children.¹ Ferritin holds iron in storage, so measuring it gives an estimate of your stored iron rather than the iron circulating at that moment.¹

Ferritin is one of several iron tests. A clinician may order one or several of them to understand your results better.²

The amount of iron in your blood varies through the day and may be higher in the morning, which is one reason timing matters for iron testing.²

Why is ferritin tested?

A ferritin test is often ordered as part of a group of iron tests to see whether your body is storing the right amount of iron.¹ MedlinePlus lists these uses:¹

• Help diagnose or rule out iron deficiency anemia and hemochromatosis (iron overload)
• Check for liver disease, restless legs syndrome, or adult Still disease
• Monitor long-term conditions that can affect iron, such as cancer, kidney disease, and autoimmune diseases
• Check iron before symptoms develop in people at higher risk: those who are underweight, have heavy menstrual bleeding, are pregnant, or cannot absorb food well (for example, inflammatory bowel disease or after gastrointestinal surgery)
• Check how well treatment for an iron problem is working

You may also need a ferritin test if other blood tests show low hemoglobin or low hematocrit.¹ Those values come from a complete blood count, which our guide to the CBC blood test explains.

How the test is done and how to prepare

A health care professional draws a small blood sample from a vein in your arm, which usually takes less than five minutes.¹ Risks are minimal, mainly slight pain or bruising where the needle went in.¹

Your provider may ask you to fast for 12 hours before the test, and it is usually done in the morning.¹ Some medicines can raise or lower ferritin, so tell the person ordering the test what you take.¹ Birth control pills and estrogen treatments can also affect iron levels, and iron may be lower during a menstrual period.²

What do low and high ferritin results mean?

Results are compared with your laboratory's reference range. Use the range printed on your own report, and have a clinician interpret it with your symptoms, age, history, and other blood tests.²

An abnormal result does not always mean you have a condition that needs treatment.¹ Most conditions that cause too little or too much iron can be treated with medicines, diet, or other therapies.¹

Symptoms that can go with low or high iron

Low iron can cause shortness of breath, weakness or fatigue, dizziness, an irregular heartbeat, pale skin, and restless legs syndrome.¹ Too much iron can cause fatigue, joint pain (often in the knees or hands), belly pain, loss of interest in sex, and skin that looks gray, metallic, or bronze.¹ Mild or moderate iron deficiency anemia may cause no symptoms at all.³

Iron deficiency anemia vs folate deficiency anemia

Both iron and folate are needed to make healthy red blood cells, but they are distinct nutrients, and a shortage of each changes red blood cells in a different way.⁴⁵ The clue is usually on the CBC, in the mean corpuscular volume (MCV), the average size of red blood cells.⁶

Iron deficiency anemia is the most common type of anemia.³ Isolated folate deficiency is uncommon in the U.S. because many grain products are fortified with folic acid, and it often occurs alongside other nutrient deficiencies.⁵

For more on folate testing, see our folate blood test guide, and for symptoms and causes, folic acid deficiency.

Iron, folic acid, and pregnancy

Anemia, especially iron deficiency anemia, is common during pregnancy because the body makes more blood to support the baby's growth.¹¹ Because everyone is at risk of anemia during pregnancy, clinicians check for it with blood tests at different stages.¹¹ Serious or untreated anemia in pregnancy can lead to preterm labor, increased blood loss during delivery, low birthweight, and anemia and developmental delays in the baby.¹¹ NHLBI lists 27 mg of iron per day as the recommended amount during pregnancy.³

Folic acid has a separate job. CDC recommends 400 mcg of folic acid every day for everyone who could become pregnant, to help prevent neural tube defects, and USPSTF recommends a daily supplement of 400 to 800 mcg starting at least one month before conception.¹²¹³ ACOG advises most people to use a prenatal vitamin with at least 400 mcg folic acid.¹⁴

The two nutrients come together in antenatal care. WHO recommends daily iron plus 400 mcg folic acid throughout pregnancy as a strategy to reduce maternal anemia, iron deficiency, low birth weight, and preterm birth in relevant populations, while individual regimens should follow the treating clinician's guidance.¹⁵¹⁶ A combined label does not make the nutrients interchangeable: folic acid is not iron.⁴⁵

Your clinician may recommend an iron supplement on top of your prenatal vitamin.¹¹ Do not double up on prenatal vitamins to get more of one nutrient, because other ingredients, especially preformed vitamin A, can become excessive.¹⁷ See how much folic acid to take for pregnancy and our guide to choosing prenatal vitamins.

How iron deficiency is treated

Iron supplements taken by mouth are the most common treatment for iron deficiency anemia, and it often takes three to six months to restore iron levels.³ Intravenous (IV) iron, medicines that help the bone marrow make red blood cells, blood transfusions, or surgery to stop internal bleeding are used in some situations.³

Diet helps too. NHLBI lists beans, dried fruits, eggs, lean red meat, salmon, iron-fortified breads and cereals, peas, tofu, and dark green leafy vegetables as good iron sources.³ Vitamin C-rich foods such as oranges, strawberries, and tomatoes help the body absorb iron, while black tea can reduce absorption.³ Finding and treating the cause, such as blood loss or poor absorption, is part of treatment.³

When to ask a clinician

Iron levels that are too low or too high can both cause health problems, so treatment should be guided by testing rather than guesswork.¹

This article is for general education and is not medical advice. Doses and needs differ from person to person, so talk with your clinician or pharmacist about your situation. Read our editorial policy and medical disclaimer.