Diagnosis

To diagnose iron deficiency anemia, your healthcare professional may run tests to look for:

  • Red blood cell size and color. With iron deficiency anemia, red blood cells are smaller and paler than usual.
  • Hematocrit. This is the percentage of blood volume made up by red blood cells. Standard levels mainly are between 35.5% and 44.9% for adults assigned female at birth and 38.3% to 48.6% for adults assigned male at birth. These values may change depending on age.
  • Hemoglobin. Lower than standard hemoglobin levels mean anemia. Experts define the hemoglobin range as 13.2 to 16.6 grams (g) of hemoglobin per deciliter (dL) of blood for adults assigned male at birth and 11.6 to 15.0 g/dL for adults assigned female at birth. The ranges for children vary depending on their age and sex.
  • Ferritin. This protein helps store iron in the body. A low level of ferritin most often means a low level of stored iron.

Other diagnostic tests

If bloodwork shows iron deficiency anemia, more tests can help find the cause. These tests might include:

  • Endoscopy. This procedure can help check for bleeding from a hiatal hernia, an ulcer or the stomach itself. A healthcare professional passes a thin, lighted tube with a camera from the throat to the stomach. Endoscopy also can show bleeding inside the tube that runs from the mouth to the stomach, called the esophagus.
  • Colonoscopy. This procedure can help rule out bleeding in the lower intestinal tract. A healthcare professional puts a thin, flexible tube with a camera into the rectum and guides it to the colon.

    A colonoscopy lets the healthcare professional look for bleeding inside the colon and rectum.

  • Ultrasound. People who have periods might have a pelvic ultrasound to look for the cause of too much bleeding during periods, such as uterine fibroids.

You might have these or other tests after trying iron supplements to see if the supplements help.


Treatment

Iron supplements most often treat iron deficiency anemia. There also might be treatment for the cause of anemia.

Iron supplements

Your healthcare professional might suggest you take iron tablets you can get without a prescription and how much to take. Iron also comes in liquid form for infants and children.

To help your body take in iron, your healthcare professional may tell you to:

  • Take iron tablets on an empty stomach. If possible, take your iron tablets before you eat. But because iron tablets can upset your stomach, you may need to take your iron tablets with meals.
  • Don't take iron with antacids. Medicines that quickly relieve heartburn can keep the body from taking in iron. Take iron two hours before or four hours after you take antacids.
  • Take iron tablets with vitamin C. Vitamin C might help the body take in iron. Try taking iron tablets with a glass of orange juice or with a vitamin C supplement.
  • Don't drink coffee or tea within an hour of taking iron. Coffee and tea can keep your body from taking in iron.

Iron supplements can cause trouble with passing stool, called constipation. So you might need a stool softener. Iron also can turn stools black. This is harmless.

If iron deficiency anemia is bad, you may need to get iron through a tube in a vein. Rarely, getting donated blood, called a transfusion, can help replace iron and hemoglobin quickly.

You can't fix iron deficiency overnight. You may need to take iron supplements for several months or longer to build up your iron. Ask your healthcare professional when to have your blood rechecked to measure your iron levels. Most people start to feel better after a week or so of treatment.

Treating causes of iron deficiency

If iron supplements don't raise blood-iron levels, the anemia likely is due to bleeding or an issue taking in iron. Your healthcare professional will need to try to find the cause to treat it.


Preparing for your appointment

Make an appointment with your healthcare professional if you have symptoms that worry you. Your healthcare professional might send you to a specialist in blood conditions, called a hematologist.

Here's some information to help you get ready for your appointment.

What you can do

Make a list of:

  • Your symptoms, even ones you don't think are important, and when they began.
  • Key personal information, including any major stresses or recent life changes.
  • All medicines, vitamins and supplements you take, including doses.
  • Questions to ask your healthcare professional.

For iron deficiency anemia, basic questions to ask include:

  • What's the most likely cause of my symptoms?
  • Are there other possible causes of my symptoms?
  • Is my condition likely to go away?
  • What treatment do you suggest?
  • I have another health condition. How can I manage these conditions together?
  • Do I need to change my diet?
  • Are there brochures or other printed information I can have? What websites do you suggest?

Be sure to ask all the questions you have.

What to expect from your doctor

Be ready to answer questions such as:

  • How bad are your symptoms?
  • Does anything seem to make your symptoms better?
  • Does anything seem to make your symptoms worse?
  • Have you noticed bleeding that isn't usual, such as heavy periods, bleeding from hemorrhoids or nosebleeds?
  • Are you a vegetarian?
  • Have you recently donated blood more than once?

Sep 20, 2025

  1. Hoffman R, et al. Disorders of iron homeostasis: Iron deficiency and overload. In: Hematology: Basic Principles and Practice. 8th ed. Elsevier; 2023. https://www.clinicalkey.com. Accessed May 16, 2025.
  2. Auerbach M, et al. Treatment of iron deficiency anemia in adults. https://www.uptodate.com/contents/search. Accessed May 16, 2025.
  3. Iron-deficiency anemia. American Society of Hematology. https://www.hematology.org/education/patients/anemia/iron-deficiency. Accessed May 16, 2025.
  4. DeLoughery TG, et al. AGA clinical practice update on management of iron deficiency anemia: Expert review. Clinical Gastroenterology and Hepatology. 2024; doi:10.1016/j.cgh.2024.03.046.
  5. Powers JM. Iron deficiency in infants and children <12 years: Screening, prevention, clinical manifestations, and diagnosis. https://www.uptodate.com/contents/search. Accessed May 16, 2025.
  6. AskMayoExpert. Iron deficiency anemia in adults. Mayo Clinic; 2024.

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