First Exposure

Non-Anemic Iron Deficiency and Iron Deficiency Anemia in Pregnancy

Authored by Dr. Michelle Sholzberg, Grace Tang, Sherri Storm and reviewed by First Exposure Medical Review Team.

Dr. Michelle Sholzberg, MDCM, MSc., FRCPC is a hematologist and clinician scientist at St. Michael’s Hospital and at the University of Toronto.

Grace Tang, MSc is a senior research associate at St. Michael’s Hospital and PhD Candidate at the University of Toronto.

Sherri Storm is a Registered Dietitian at the Obstetrics, Women’s Health and Academic Family Health Team at St. Michael’s Hospital

This health topic is an expert opinion about iron deficiency during pregnancy.

* The information provided is the expert opinion of the First Exposure Medical Advisors. It is for informational purposes only and does not replace medical care and advice from a healthcare provider. Please contact your healthcare provider if you have any concerns or to discuss any questions that you believe may be relevant to you or your baby. In case of emergency, please go to the emergency room or call 911.

If you do not have a healthcare provider please go to: Finding a Healthcare Provider

Clinical scenario:

I am 15 weeks pregnant. I am feeling tired, and often have brain fog. Do I have iron deficiency?

Q. What is anemia?

A. Anemia is a condition in which the amount of hemoglobin in the red blood cells (RBC) is lower-than-normal. Hemoglobin is the protein in RBC that contains iron and carries oxygen. When someone has anemia low hemoglobin not enough oxygen reaches the tissues and organs in the body.

Q. What is non-anemic iron deficiency (NAID) and iron deficiency anemia (IDA)?

A. Iron is needed for production of hemoglobin, which makes it an essential element for humans and almost all living organisms. Low iron (iron deficiency) may result in anemia, termed iron deficiency anemia (IDA), due to insufficient iron stores to support RBC production. When there is iron deficiency but there is no anemia, it is termed non-anemic iron deficiency (NAID).

Q. How does pregnancy contribute to the risk of NAID and IDA?

A. During states of rapid growth and development such as pregnancy, nutrient needs, including iron, are increased. NAID and IDA may develop when the amounts of iron a person gets through food and/or supplements are lower than the amount of iron required for states of growth/development and to compensate for blood loss (e.g. menstruation). Many individuals have suboptimal (lower than needed) iron stores entering pregnancy. When pregnant, it takes about 1 gram of iron throughout an entire pregnancy to support the growth of the fetus, the placenta, the increase in maternal blood volume and to account for blood loss during and after delivery. One gram of iron is equivalent to 177 large steaks – therefore, it is impossible to “eat your way” out of iron deficiency in pregnancy.

Q. How do you diagnose NAID and IDA

A. To diagnose NAID and IDA, your health care provider will order blood tests:

  • Hemoglobin measures the amount of red blood cells in your body. Hemoglobin is part of a test panel called the Complete Blood Count (CBC).
  • Ferritin: Ferritin is a protein that stores iron in your body. It releases iron when your body needs to make more red blood cells. Ferritin is low when iron deficiency is present.


NAID in adults, including in pregnancy, is generally defined as a serum ferritin <30 µg/L but a ferritin <50 µg/L is in considered early iron deficiency. It is generally recommended to start taking oral iron when the ferritin is below 50 µg/L.

Anemia in pregnancy is generally defined as a hemoglobin of <110 g/L in the first trimester, <105 g/L in the second trimester, and <110 g/L in the third trimester. Iron deficiency is the most common cause of anemia worldwide – including in pregnancy. So, IDA is a diagnosis of both iron deficiency and anemia.

Q. What are the symptoms of NAID and IDA?

A. Symptoms of NAID are fatigue, hair and nail changes, restless legs, poor exercise tolerance, pica (urge to eat inedible things like ice), low mood, brain fog and problems with memory, attention and thought processes.

In addition, to the above, symptoms of IDA include severe fatigue, shortness of breath, chest discomfort, and orthostatic dizziness (dizziness when you go from lying or sitting to standing).

Q. What are the risks of iron deficiency to me and my baby?

A. Uncorrected iron deficiency anemia in pregnant individuals increases the risk of needing a blood transfusion and/or experiencing severe health problems around the time of delivery.

Babies born following an anemic pregnancy seem to be at greater risk of:

  • Premature delivery
  • Being of lower birth weight
  • Neurodevelopmental problems in early childhood (e.g. autism spectrum disorder, intellectual disability, attention deficit hyperactivity disorder)

The good news is that NAID and IDA are completely correctable. Treatment of iron deficiency will help with your symptoms and prevent its harmful effects on you and your baby.

Q. What are treatment options for NAID and IDA?

A. Oral iron is first line therapy. Almost all pregnant individuals need to take a daily iron supplement to provide the extra iron needed to support pregnancy. The amount of iron in prenatal vitamins and in the diet is usually not enough during pregnancy.

There are many different iron supplements that can be purchased from the pharmacy and health food stores. They come in tablets, capsules, powder or liquid forms. Iron salts (ferrous gluconate, sulfate or fumarate) should be used as first line oral iron supplements, because they are less expensive and there is no evidence that the more expensive options are more effective. You can use whichever form of iron you prefer; liquid, powder or pillsas long as you are getting 30 to 150 mg of elemental iron per day. 

Q. How should I take my oral iron supplements?

A. How and when you take your iron supplement can affect how iron is absorbed.

Take your iron supplement on an empty stomach (i.e. two hours from your last meal) with water before bed and at least two hours from when you took your prenatal vitamin. You can also take it anytime in the day as long as it is taken on an empty stomach and away from your prenatal vitamin. If you need to take it with food – please take it with citrus fruits such as (e.g. oranges, tangerines), apples, and tomatoes, because vitamin C in these fruits help your gut to absorb iron. 

Do not take your iron within 2 hours of:

  • Prenatal vitamins
  • Milk
  • Tea or coffee (black)
  • Calcium pills
  • Antacids (e.g. TUMS®, Rolaids®)
  • Acid reducing medications such as proton pump inhibitors (e.g. pantoprazole, Tecta®, Pantoloc®, lansoprazole, Prevacid®) and H2 receptor blockers (e.g. famotidine, Pepcid®)
  • Thyroid medications (e.g. Synthroid®, Eltroxin®)
  • Certain antibiotics (e.g. fluoroquinolones, tetracyclines)

Iron supplements can interact with other medications.  Check with your doctor or pharmacist to make sure there are no interactions with your medications.

Q. What are the side effects of oral iron supplementation?

A. Common side effects of oral iron include nausea, upset stomach, bloating, abdominal pain, diarrhea and/or constipation. The symptoms are usually mild, can be easily tolerated and improved. Dark stools happen in all patients who take iron pills – this is normal and expected.

If you started experiencing constipation after starting an iron supplement, increasing the fibre in your diet (e.g. prunes, fresh fruit and vegetables) and drinking lots of fluids (about 2.5 L of water daily) may help your symptoms. For some, this may not be enough and there may be a need to take an over-the-counter medication such as polyethylene glycol (PEG) 3350 (e.g. Lax-A-Day®, Clearlax®, Hydralax, PEG 3350, Pegalax ™, Relaxa™, RestoraLAX®). Please check with your health care provider if this is appropriate for you. If you are still constipated or experiencing other stomach side effects, try taking your iron pill every other day.

If your symptoms do not improve check with your doctor or pharmacist.

Q. What if oral iron supplementation does not work, or I cannot tolerate it?

A. Sometimes, iron pills are not enough to raise your iron and/or hemoglobin levels. Sometimes, they are poorly tolerated, and the hemoglobin level continues to drop (usually a hemoglobin under 100 g/L is considered the clinical threshold). In these cases, your doctor may discuss giving you intravenous (IV) iron. Intravenous iron, sometimes referred to as an iron infusion, is a way of getting iron directly into your blood. Your care provider will arrange with you to have an IV bag set up to slowly drip iron down a tube, into a vein in your body.  The procedure can take several hours.

Q. How long will I need to take iron supplements?

A. One can notice an improvement in symptoms of anemia as soon as 4 to 8 weeks after iron replacement has started. Usually, you will need to take oral iron supplementation for the entire duration of your pregnancy and continue it after the birth– especially if you are planning to breastfeed. Health care providers may check your CBC and ferritin at your next visit to see if your levels have improved.

Q. Where to get more information?

A. Resources for Patients

Iron Deficiency Anemia

The importance of iron in pregnancy

Intravenous (IV) iron Therapy in Pregnancy

Resources for Health Care Providers

Raise the Bar

This website was developed to help healthcare providers diagnose and treat iron deficiency and iron deficiency anemia.

Key References

Malinowski AK, Murji A. Iron deficiency and iron deficiency anemia in pregnancy. CMAJ Canadian Medical Association Journal. 2021;193(29):E1137-E8. [PMID: 34312167]. 

McMahon LP. Iron deficiency in pregnancy. Obstet. 2010;3(1):17-24. [PMID: 27582835]. 

Parker ML, Storm S, Sholzberg M, Yip PM, Beriault DR. Revising Ferritin Lower Limits: It’s Time to Raise the Bar on Iron Deficiency. J Appl Lab Med. 2021;6(3):765-73. [PMID: 33179023]. 

Ray JG, Davidson A, Berger H, Dayan N, Park AL. Haemoglobin levels in early pregnancy and severe maternal morbidity: population-based cohort study. BJOG: An International Journal of Obstetrics & Gynaecology. 2020;127(9):1154-64. [PMID: 32175668]. 

Tang GH, Sholzberg M. Iron deficiency anemia among women: An issue of health equity. Blood Rev. 2024;64:101159. [PMID: 38042684]. 

Teichman J, Nisenbaum R, Lausman A, Sholzberg M. Suboptimal iron deficiency screening in pregnancy and the impact of socioeconomic status in a high-resource setting. Blood Adv. 2021;5(22):4666-73. [PMID: 34459878]. 

Van Doren L, Steinheiser M, Boykin K, Taylor KJ, Menendez M, Auerbach M. Expert consensus guidelines: Intravenous iron uses, formulations, administration, and management of reactions. Am J Hematol. 2024; Jan 29. [PMID: 38282557]. 

VanderMeulen H, Herer E, Armali C, Kron A, Modi D, McLeod A, et al. Iron deficiency and anemia in pregnancy: a health equity issue. [77th Annual Clinical and Scientific Conference].  Journal of Obstetrics and Gynaecology Canada; May; Virtual, Online.  2021. Abstract 665. 


First Exposure does not offer health care treatment. If you have an urgent question about your pregnancy or your baby’s health, you should contact your health care provider directly. If you don’t have a health care provider and you live in Ontario, you have a variety of health care options. In the case of an emergency, visit a hospital emergency room or call 911.