Ferritin Test: What It Shows and How It Relates to Hemoglobin

You had your blood tested for ferritin and you're holding a form with a single number. Hemoglobin is normal, but ferritin is low — and it's unclear what that means. Let's break down what this test shows and why it's read together with hemoglobin.

What ferritin is

Ferritin is a protein that binds iron and stores it in cells. One ferritin molecule can hold up to 4,000 iron atoms. Iron is needed for red blood cells, muscles, bone marrow, and internal organs.

A blood ferritin test shows the volume of stores, not the amount of iron in food or in hemoglobin. Simply put, it's an indicator of the warehouse.

Why a blood ferritin test is ordered

A doctor writes a referral for a blood ferritin test when iron deficiency or iron excess is suspected. The test helps address iron deficiency anemia, hemochromatosis, liver disease, and restless legs syndrome.

A separate task is monitoring chronic conditions: cancer, kidney disease, autoimmune diseases. And screening people at risk: heavy menstruation, pregnancy, underweight, poor absorption in inflammatory bowel disease or after bowel surgery.

Ferritin and hemoglobin: what's the difference

Hemoglobin carries oxygen from the lungs to the tissues. Ferritin stores iron for future use. These are two different stages of the same process.

Why ferritin is low when hemoglobin is normal

When iron is lacking, the body starts using its reserve, and ferritin drops long before symptoms and anemia appear.

The causes are usually the same as those of anemia. Blood loss: heavy menstruation, bleeding from the stomach and intestines due to ulcers, intestinal inflammation, hemorrhoids, or taking ibuprofen and aspirin. Less commonly — tumors of the stomach or intestines. Also pregnancy, too little iron in the diet, and impaired absorption.

If the deficiency is not treated, hemoglobin will eventually drop too. Then shortness of breath, weakness, and pallor will appear.

How to read the test result

Each laboratory has its own reference values — they are printed on the form. The American Gastroenterological Association revised the norms in 2020: 45–120 nanograms per milliliter.

Low ferritin usually indicates true iron deficiency. High ferritin does not always mean excess: ferritin rises with infection, after surgery, in autoimmune and liver diseases, cancer, obesity, alcohol, and hyperthyroidism. Some medications also shift the number.

Preparation affects the result. Blood is usually drawn in the morning, on an empty stomach, with a 12-hour fast. Three days before the test, iron supplements are stopped; discontinuation is agreed with the doctor. For 30–40 minutes before the procedure, it's best to avoid physical and emotional stress.

Ferritin alone doesn't solve the problem. It is read together with other iron metabolism markers and with the clinical picture.

When to discuss the result with a doctor

You should discuss the number if it falls outside the form's range or if you have symptoms of iron deficiency:

• fatigue and lack of energy;
• shortness of breath with usual exertion;
• noticeable palpitations;
• pale skin;
• headaches;

There can also be less obvious signs: noise or ringing in the ears, a strange taste of food, itching, a sore tongue, hair loss, a craving to eat non-food items — paper or ice, difficulty swallowing, cracks at the corners of the mouth, spoon-shaped nails, restless legs syndrome.

If the cause of the deficiency is unclear, the doctor may order a complete blood count, a fecal occult blood test, and refer you to a specialist.

A ferritin abnormality on its own is not a reason to call an ambulance. 103/112 — for signs of a life-threatening condition, such as suspected stroke or heart attack.

This material is for reference: it explains the numbers on the form but does not replace a doctor's consultation. The decision about your test is made by the doctor who sees the whole picture.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer