Ferritin levels: low, high, optimal, and how to raise them

What ferritin measures

Most of your iron sits in hemoglobin, the protein in red blood cells that carries oxygen. Much of the rest is stored as ferritin in the liver, spleen and bone marrow. The small amount of ferritin in your blood tracks those stores, so the test shows how much iron you have in reserve.

Ferritin drops before hemoglobin does. That makes it an early warning: you can have low iron stores while your complete blood count still looks normal. A low MCV alongside a low ferritin points to low iron that has started to affect your red cells.

Ferritin is often ordered as part of an iron panel, which adds serum iron, total iron-binding capacity (TIBC) and transferrin saturation, the share of your iron-carrying protein that is actually loaded with iron.

Low ferritin: causes and symptoms

A ferritin below 30 ng/mL is a sensitive and specific sign of iron deficiency, according to a review in American Family Physician. Many people sit below Gabriel's optimal range without being anemic. Common causes:

• Heavy menstrual periods. The most common reason in people who menstruate. Pregnancy and frequent blood donation also draw down iron.
• Blood loss from the gut. Long-term aspirin or NSAID use, other slow bleeding in the gut and, less often, colon cancer. In men and in women after menopause, low iron calls for a look at the digestive tract.
• Poor absorption. Celiac disease and other gut conditions, and acid-reducing medications called proton pump inhibitors, can limit how much iron you absorb.
• Low intake. Plant-based diets can work well, but plant iron is absorbed less easily than iron from meat and seafood.

Low ferritin symptoms can include tiredness, weakness, shortness of breath, dizziness, pale skin, an irregular heartbeat and restless legs. Some people have no symptoms at all, which is why the number matters.

See a clinician promptly if low iron comes with black or bloody stools, vomiting blood, chest pain, fainting or very heavy bleeding.

Why a normal ferritin can hide low iron

Ferritin is an acute phase reactant: it rises with infection, inflammation, liver disease and other illness, regardless of how much iron you have. So a ferritin that looks normal can mask iron deficiency in someone with an inflammatory condition.

That is why clinicians read ferritin alongside other tests:

• Transferrin saturation and serum iron. A low transferrin saturation with a high TIBC points to iron deficiency even when ferritin looks fine.
• CRP (C-reactive protein). A high CRP says inflammation is likely pushing ferritin up.
• Liver enzymes. Fatty liver and alcohol raise ferritin.

In people with chronic inflammation, the AFP review notes, a ferritin under 50 ng/mL makes iron deficiency likely, and results between about 31 and 99 ng/mL without inflammation need further iron studies to sort out.

How to raise ferritin levels

1. Find the cause first. Raising ferritin without knowing why it fell can miss heavy periods, gut bleeding or celiac disease. Ask your clinician what else to check.
2. Eat iron-rich foods. Heme iron, in red meat, poultry, fish and shellfish, is absorbed best. Non-heme iron, in beans, lentils, tofu, dark leafy greens and fortified cereals, is absorbed less well.
3. Pair plant iron with vitamin C. Citrus, strawberries, peppers, tomatoes or broccoli at the same meal help you absorb more non-heme iron. Eating some meat or fish with beans or greens helps too.
4. Keep tea away from iron-rich meals. Black tea contains substances that bind iron, so you absorb less. Take calcium supplements at a different time from iron.
5. Take iron only with testing and a clinician's guidance. Iron supplements can cause constipation, nausea and stomach pain, and too much is harmful. The upper limit for adults is 45 mg a day unless a clinician prescribes more for a set time to correct a deficiency. Iron can also interfere with levothyroxine and levodopa.
6. Retest. Clinicians usually recheck hemoglobin about a month after starting iron. Iron is typically continued for at least three months after hemoglobin recovers to refill stores, and ferritin is rechecked to confirm.

Keep iron supplements out of reach of children. An accidental iron overdose can be very dangerous for a young child.

What high ferritin can mean

High ferritin has many causes, and most are not iron overload:

• Inflammation or infection, including recent illness or surgery and autoimmune conditions.
• Liver disease, including fatty liver and alcohol-related liver disease.
• Metabolic factors such as obesity, plus hyperthyroidism and some cancers.
• Hemochromatosis, an inherited condition in which the body absorbs and stores too much iron. Without treatment it can damage the liver, heart and pancreas.

If ferritin is high, a clinician usually checks transferrin saturation (normal is about 16% to 45%), CRP and liver enzymes. A high transferrin saturation together with a high ferritin raises the question of iron overload and genetic testing for hemochromatosis. A high ferritin alone does not diagnose it.

Don't take iron or vitamin C supplements while a high ferritin is being worked up. If you were recently sick or had surgery, ask whether to repeat the test once you have recovered, since inflammation lifts ferritin.