Your blood gets checked for anemia at least twice during pregnancy. The numbers on your results mean something different than they would if you weren’t pregnant, and a normal hemoglobin doesn’t always mean your iron is fine.

The short version

  • When: The American College of Obstetricians and Gynecologists (ACOG) recommends a blood count in the first trimester and again at 24 to 28 weeks.
  • The main numbers: hemoglobin and hematocrit show whether you’re anemic. Ferritin shows how much iron you have stored.
  • Anemia in pregnancy means hemoglobin below 11 g/dL in the first and third trimesters, or below 10.5 g/dL in the second.
  • Low iron can come first. Your iron stores can run low before your hemoglobin drops, so ask about ferritin if you have symptoms or risk factors.
  • If you’re low, it’s treatable. Most women start with iron pills; IV iron is an option if pills don’t work.

When you’re tested, and which tests

ACOG recommends that every pregnant woman have a complete blood count in the first trimester and again between 24 and 28 weeks, according to its practice bulletin on anemia in pregnancy. If the results show anemia, your provider will order more tests to find the cause.

Test What it tells you
Hemoglobin The amount of the oxygen-carrying protein in your red blood cells. The main number for diagnosing anemia.
Hematocrit The share of your blood made up of red blood cells. Usually reported alongside hemoglobin.
Ferritin How much iron your body has stored. The best single test for confirming iron deficiency.
Red blood cell size (MCV) Small cells point toward iron deficiency; large cells point toward low folate or B12.

Hemoglobin and hematocrit are the most common screening tests, but they are neither very sensitive nor very specific for iron deficiency, according to the NIH. That’s why a low result leads to more testing rather than an automatic iron prescription.

The cutoffs for anemia in pregnancy

ACOG uses these levels to define anemia in pregnancy:

Trimester Hemoglobin below Hematocrit below
First 11 g/dL 33%
Second 10.5 g/dL 32%
Third 11 g/dL 33%

Why the numbers are lower than usual. Outside of pregnancy, anemia in women is defined as hemoglobin below 12 g/dL, according to the NIH. During pregnancy, the liquid part of your blood and your red blood cells both expand, which naturally changes the numbers. So a result that would be flagged before pregnancy can be normal now, and the second trimester has the lowest cutoff of all.

When you read your results, compare them with the pregnancy cutoffs above, not the standard range printed next to them, and ask your provider if you’re unsure.

Ferritin: low iron before anemia

Iron runs low in stages. Your stored iron drops first, then your body struggles to make red blood cells, and only at the end does hemoglobin fall low enough to count as anemia, according to the NIH. Ferritin, a measure of stored iron, can show the problem at that early stage.

  • What counts as low: ACOG says a ferritin level below 30 micrograms per liter confirms iron-deficiency anemia. Other groups use lower cutoffs; the World Health Organization uses below 15 in the first trimester, according to the NIH.
  • Inflammation can hide low iron. Illness and inflammation can push ferritin up, so a normal ferritin doesn’t always rule out low iron. Your provider may look at several results together.
  • How common it is: Iron deficiency affects an estimated 10% to 16% of pregnant women in the U.S., and about 25% in the third trimester, when needs are highest. Some of those women won’t show anemia yet.

Ferritin isn’t always part of routine screening. If you’re very tired, are vegetarian or vegan, had heavy periods before pregnancy, or have had low iron before, it’s reasonable to ask whether it should be checked.

If your results are low

  • The first step is finding the cause. Iron deficiency and blood loss are the two most common causes of anemia in pregnancy, according to ACOG. Low folate or B12 and inherited conditions such as thalassemia or sickle cell trait can also cause it, and they need different treatment. See Folic Acid and Anemia.
  • Treatment for iron deficiency usually starts with iron pills on top of your prenatal vitamin. See Iron Supplements in Pregnancy for help with side effects.
  • If pills don’t work or aren’t tolerated, ACOG says IV iron may be considered after the first trimester, especially when severe iron deficiency is found later in pregnancy.
  • Expect a recheck. Your provider will usually repeat the blood test to make sure treatment is working.

Questions to ask at your appointment

  1. What were my hemoglobin and hematocrit, and how do they compare with the pregnancy cutoffs?
  2. Was my ferritin checked? If not, should it be?
  3. If I’m low, what’s causing it?
  4. How much iron should I take, and when will we recheck?

What to do now

  • Ask for your results from your first-trimester blood count.
  • Mark your calendar for the 24 to 28 week recheck.
  • If you have risk factors for low iron, ask whether ferritin should be checked.

Related reading

Sources

Updated October 2026. This article is for general information and is not a substitute for advice from your health care provider.