Iron deficiency in pregnancy means your body doesn’t have enough iron to make the extra blood you and your baby need. Your daily iron need rises from 18 mg to 27 mg once you’re pregnant. By the third trimester, about 3 in 10 pregnant women in the US have iron deficiency.
Low iron that isn’t treated can turn into anemia, which is linked to preterm birth, low birth weight, and more blood loss during delivery. A blood test can detect low iron early, even when you feel fine, so you can treat it before it turns into anemia.
If you don’t have a primary care provider, you can get a lab requisition online for the tests you need.
What is iron-deficiency anemia in pregnancy?
Iron deficiency means your body does not have enough stored iron. Low iron levels leave your body unable to make enough hemoglobin, the protein in red blood cells that carries oxygen to you and your baby, leading to iron-deficiency anemia.
During pregnancy, your iron needs increase as your body makes extra blood, builds the placenta, and supplies your baby with iron. Before pregnancy, your body needs to absorb about 0.8 mg of iron a day to maintain its iron balance. By the third trimester, it may need to absorb around 8 mg a day.
How iron deficiency in pregnancy affects you and your baby
Low iron in pregnancy can affect your health and your baby’s health. The risks start small and rise as the deficiency increases.
For your baby
Your baby gets all its iron from you. It uses that iron to make red blood cells, build its brain, and store iron for after birth. When iron runs short, the baby’s body sends it to red blood cells first, so the brain can be low on iron before a blood test shows anemia. Babies who are short on iron may be at higher risk of memory and learning problems, even after their iron levels recover.
Iron deficiency is also linked to preterm birth and low birth weight. And since breast milk is low in iron, babies depend on their stored iron for the first four to six months.
For you
The biggest risk is heavy bleeding after birth. Anemia leaves you with less blood to spare, so the same amount of blood loss affects you more. In a large 2022 study, the odds of heavy blood loss after birth were about 1.5 times higher with mild anemia than with no anemia. They were 3.5 times higher with moderate anemia and more than 15 times higher with severe anemia.
You may also be more likely to need a blood transfusion. Anemia may be linked to a higher risk of postpartum depression, although the evidence is mixed. If low mood lasts for weeks after birth, you can get postpartum depression treatment online.
Signs and symptoms of iron deficiency in pregnancy
Low iron during pregnancy can cause tiredness, trouble concentrating, feeling cold, dizziness, or unusual cravings. These symptoms can be easy to dismiss because they overlap with normal pregnancy changes. Read more about low iron symptoms.
Early signs of low iron
Early signs of low iron are subtle and can start before your hemoglobin drops:
- Tiredness and trouble focusing: You may feel weak or tired more often than usual, or find it hard to concentrate, beyond the usual tiredness of pregnancy.
- Craving ice or other non-food items: This is called pica. Ice cravings in particular can be associated with iron deficiency.
- Restless legs: An urge to move your legs that often gets worse at night. Restless legs syndrome affects 11% to 29% of pregnant women.
- Feeling cold more easily: Iron deficiency can affect how your body regulates temperature.
Symptoms of anemia in pregnancy
As hemoglobin falls, your body may have more difficulty getting enough oxygen. Common symptoms include:
- Dizziness
- Pale skin
- Headaches
- A fast or pounding heartbeat
As anemia becomes more severe, you may also feel short of breath, or lightheaded when standing, or may even develop brittle nails, or have a sore tongue.
When symptoms need urgent care
Most symptoms of anemia can wait for a blood test, but some need care right away. Get medical care right away, or call 911, if you faint or have chest pain or pressure, trouble breathing, a heartbeat that stays fast even when you rest, or dizziness that keeps coming back. For milder symptoms, ask your prenatal provider for a blood test to check your hemoglobin and iron stores.
What causes low iron in pregnancy?
Your body needs more iron during pregnancy. Iron deficiency can develop when you do not get or absorb enough to meet that increased need. Some factors can increase your risk of low iron. Some of them may have started before pregnancy.
- A diet low in iron. Food has two kinds of iron. Heme iron, from meat, poultry, and seafood, is absorbed well. Nonheme iron, from plants and fortified foods, is absorbed less well, so people following vegetarian diets may need about 1.8 times more iron.
- Gut conditions that block absorption or cause bleeding. Iron enters your bloodstream through your gut, so problems there can prevent it from being absorbed. Celiac disease, ulcerative colitis, Crohn’s disease, and stomach or bowel surgery raise your risk, either by blocking absorption or by causing blood loss. Weight-loss surgery can also reduce iron absorption.
- Heavy periods before pregnancy. Heavy periods raise your risk of iron deficiency, so you may start pregnancy with low stores.
- A short gap between pregnancies. Your body has less time to rebuild its stores before the next pregnancy draws on them again.
- Giving blood often. About 25% to 35% of regular blood donors develop iron deficiency, so frequent donating before you conceive can lead to low iron in pregnancy.
- Carrying twins or more. Your body has to supply iron to more than one baby.
- Severe nausea and vomiting. It can make it hard to eat enough iron-rich food.
Some other types of anemia can look similar to iron-deficiency anemia but need different treatment. That’s why your provider checks your ferritin (a blood test that shows how much iron your body has stored), and not just your hemoglobin. Learn more about anemia symptoms and causes.
Blood tests to check your iron levels in pregnancy
A complete blood count (CBC) checks your hemoglobin and shows whether you have anemia. A ferritin test measures the iron stored in your body and can show iron deficiency before anemia develops. Your provider may also check your serum iron and transferrin saturation, which show how much iron is moving through your blood.
When you’ll be tested
You’ll usually have a complete blood count at your first prenatal visit and again around 24 to 28 weeks. Depending on your risk factors and local guidelines, your doctor may also check your iron levels, including ferritin, during pregnancy and again before delivery.
Ferritin is not included in every routine prenatal blood test. If you have symptoms or risk factors for low iron, ask your doctor whether you should have your ferritin checked rather than waiting for anemia to develop.
What your hemoglobin and ferritin results mean
Your hemoglobin level shows whether you have anemia. Normal hemoglobin levels in pregnancy run a little lower than before pregnancy, and the cutoff for anemia changes slightly by trimester:
| Trimester | Anemia | Mild | Moderate | Severe |
|---|---|---|---|---|
| First | Below 11.0 g/dL (110 g/L) | 10.0 to 10.9 g/dL | 7.0 to 9.9 g/dL | Below 7.0 g/dL |
| Second | Below 10.5 g/dL (105 g/L) | 9.5 to 10.4 g/dL | 7.0 to 9.4 g/dL | Below 7.0 g/dL |
| Third | Below 11.0 g/dL (110 g/L) | 10.0 to 10.9 g/dL | 7.0 to 9.9 g/dL | Below 7.0 g/dL |
The liquid part of your blood (plasma) increases by about 40% to 50% during pregnancy, while your red blood cells increase by only about 30%. This dilutes your blood, so hemoglobin levels naturally fall through the first and second trimesters before rising again later in pregnancy. That’s why the anemia cutoff is slightly lower in the second trimester.
Your ferritin shows how much iron you have stored. According to the American Society of Hematology, these ferritin levels in pregnancy mean iron deficiency:
| Your hemoglobin | Ferritin that means iron deficiency |
|---|---|
| Normal | 30 ng/mL (30 µg/L) or lower |
| Low (you have anemia) | 50 ng/mL (50 µg/L) or lower |
How to get tested without a primary care provider
You can get tested without a primary care provider through an online visit. A licensed doctor at Your Doctors Online can send you a lab test requisition online for a CBC and a ferritin test. You get your blood drawn at a lab near you, and the doctor reviews your results and prescribes iron if needed.
You can also start an online pregnancy consultation if you have questions about your prenatal vitamins or other medicines.
Treatment for iron deficiency in pregnancy
Your doctor will use your blood-test results to decide which treatment you need. Iron pills are the first treatment for most people with iron-deficiency anemia, and you can get iron-deficiency treatment online. Some people need IV iron instead. This may be an option if iron pills cause difficult side effects, do not work well enough, or there is not enough time to treat the anemia before delivery.
Iron supplements during pregnancy
A common treatment dose of iron supplements during pregnancy is 40 to 100 mg of elemental iron daily or every other day. Common types include ferrous sulfate, ferrous gluconate, and ferrous fumarate. Your provider will tell you which type and how much to take, and will usually recheck your hemoglobin 2 to 4 weeks after you start iron to make sure it’s rising.
Iron is absorbed best on an empty stomach with a source of vitamin C, such as orange juice. If that upsets your stomach, take it with a small amount of food instead. Some foods and medicines interfere with absorption, so take your iron 1 hour before or 2 hours after:
- Tea and coffee
- Milk, yogurt, cheese, eggs, and soy
- Calcium supplements, or a prenatal vitamin that contains calcium
- Antacids such as Tums, and acid-reducing heartburn medicines
If you take thyroid medicine (levothyroxine), keep it at least 4 hours apart from your iron.
Iron can cause constipation, nausea, and dark stools. Taking it with a small amount of food, drinking more fluids, or using a stool softener can help. Ask your provider before you change your dose or stop taking it.
Iron stores can take 3 to 6 months to rebuild. Your provider may recommend continuing iron for at least 3 months after your hemoglobin returns to normal. Depending on your iron levels and when you give birth, your provider may also recommend continuing treatment after delivery.
Iron infusion (IV iron) in pregnancy
An iron infusion gives you iron through a vein. It skips your digestive system and can raise your hemoglobin faster than iron pills. Your provider may suggest IV iron if:
- Iron pills cause side effects you can’t manage
- Your hemoglobin doesn’t rise enough on iron pills
- Your anemia is moderate or severe
- Your anemia is found close to your due date
IV iron can be used in the second and third trimesters and after delivery. It isn’t usually given in the first trimester because its safety hasn’t been studied that early. Some IV iron products are given as one larger dose, while others require several visits over a few weeks.
Some people have a mild reaction during the infusion, such as flushing or tightness in the chest or back. These mild reactions often settle on their own within about 15 minutes, and your care team watches you during and after the infusion.
What if iron treatment isn’t working?
If your hemoglobin hasn’t risen after 2 to 4 weeks of iron pills, your provider will first check that you’re taking them as prescribed and keeping them apart from foods and medicines that block absorption. If you are, they may switch you to IV iron, look for other causes, or refer you to a specialist.
How to prevent low iron in pregnancy
You can help prevent low iron during pregnancy in three ways: take a prenatal vitamin with iron, eat iron-rich foods, and check your iron before pregnancy if you’re at risk.
Take a prenatal vitamin with iron
Ask your provider about starting a prenatal vitamin with iron early. ACOG recommends low-dose iron during pregnancy for most women, except those with conditions that cause iron to build up in the body, such as hemochromatosis. The US Preventive Services Task Force found there isn’t enough evidence to say whether routine iron supplements help pregnant women who don’t have iron deficiency, so ask your provider what’s right for you.
Most prenatal vitamins contain iron. A review of 188 prenatal vitamins found that 89% contained iron, with a median amount of 27 mg.
Eat iron-rich foods with vitamin C
Iron-rich foods help maintain your iron stores during pregnancy. Fortified breakfast cereal, beans, and oysters are among the richest sources:
| Food | Serving | Iron | Share of your 27 mg daily need |
|---|---|---|---|
| Breakfast cereal fortified with 100% DV iron | 1 serving | 18 mg | 67% |
| White beans, canned | 1 cup | 8 mg | 30% |
| Oysters, cooked | 3 oz | 8 mg | 30% |
| Lentils, boiled | ½ cup | 3 mg | 11% |
| Beef, braised | 3 oz | 2 mg | 7% |
Your body absorbs plant-based iron better when you eat it with vitamin C. Good sources of vitamin C include oranges, strawberries, and red peppers. Eating meat, poultry, or seafood with plant-based foods can also help your body absorb more iron. If you’d like help planning meals, you can talk to a nutritionist online. See our full list of iron-rich foods for anemia.
Check your iron before you get pregnant
If you’re planning a pregnancy, get your iron checked first, especially if you eat a vegetarian or vegan diet or have had low iron before. It’s easier to fix low iron before you conceive than to catch up once pregnancy raises your need.
Tell your doctor if you have heavy periods or often pass large blood clots during your period. You can also ask about iron testing during an online fertility consultation.
How Your Doctors Online can help
A licensed doctor can order your blood tests, go over your results, and prescribe iron if you need it, while your prenatal provider stays in charge of your pregnancy care. You can also book an online pregnancy consultation for questions about prenatal vitamins or other medicines.
Get iron deficiency treatment online
Frequently asked questions
If you have low iron at 35 weeks, talk to your prenatal provider about starting treatment right away. Since iron pills take a few weeks to raise your hemoglobin, IV iron may be considered when anemia is found close to your due date. Read more about how to increase hemoglobin. Ask for a blood count before delivery to see where your levels are.
Iron is important throughout pregnancy. What changes is that your iron requirement becomes high later in pregnancy. That’s also when your baby builds most of the iron stores it will rely on for its first 4 to 6 months.
For routine daily intake, the upper limit for iron during pregnancy is 45 mg a day from food, supplements, and prenatal vitamins combined. This limit is for people who are not being treated for iron deficiency. If blood tests show that you are low in iron, your doctor may prescribe a higher dose, often 40 to 100 mg of elemental iron daily or every other day, for a specific period and monitor your response.
Do not take extra iron on your own to treat or prevent anemia. Higher doses can cause side effects such as nausea and constipation, so follow the dose your provider recommends.
There’s no clear proof that low iron lowers your breast milk supply. Low iron can make you very tired, so ask to have your iron checked if feeding feels harder than expected. If you need iron after birth, iron pills aren’t expected to harm your breastfed baby.
