Low vitamin D is common in pregnancy for some groups of women, and severe deficiency can affect a baby’s bones. Not every pregnant woman needs a vitamin D test, though. The American College of Obstetricians and Gynecologists (ACOG) recommends testing women at higher risk rather than everyone.

The short version

  • Who’s at higher risk: women who get little sun, have darker skin, are vegetarian, have obesity, or have had gastric bypass surgery.
  • Testing: ACOG doesn’t recommend routine vitamin D testing for all pregnant women, but says a blood test can help for women at higher risk.
  • The test: a blood test for 25-hydroxyvitamin D. Levels below 12 to 20 ng/mL are generally considered too low, according to MedlinePlus.
  • Treatment: if you’re low, ACOG says 1,000 to 2,000 IU a day is generally considered safe in pregnancy. Your provider will set the dose.
  • For your baby: severe deficiency in pregnancy has been linked to bone problems in newborns, including rickets.

Who is more likely to run low

ACOG’s committee on obstetric practice noted that vitamin D deficiency is common in pregnancy among women who are vegetarian, women with limited sun exposure, and women with darker skin. Other groups also face a higher risk:

Risk factor Why it lowers vitamin D
Little time in the sun Your skin makes vitamin D from sunlight. Cloudy weather, shade, winter, living farther north, and covering most of your skin all cut down on it (MedlinePlus).
Darker skin Skin with more pigment makes less vitamin D from the same amount of sun (MedlinePlus).
Vegetarian or vegan diet Few foods have much vitamin D naturally, and the best natural source is fatty fish.
Obesity or past gastric bypass surgery People in these groups may need more vitamin D than others (NIH).

Keep wearing sunscreen; sun exposure raises the risk of skin cancer. That’s why food and your prenatal vitamin matter more than sunlight for most women.

Testing: when it’s done and what results mean

Not routine for everyone. In its 2011 committee opinion, ACOG concluded there wasn’t enough evidence to recommend testing every pregnant woman for vitamin D deficiency, partly because there’s no agreed-upon best vitamin D level for pregnancy. For women at higher risk, ACOG said a blood test can be useful, as summarized by the American Academy of Family Physicians. If you have any of the risk factors above, ask your provider whether you should be tested.

The test. The best measure of your vitamin D status is a blood test for 25-hydroxyvitamin D, also written 25(OH)D, according to MedlinePlus. Labs report results in one of two units:

Result ng/mL nmol/L
Too low for bone and overall health Below 12 to 20 Below 30 to 50
Enough for most people 20 or above 50 or above
Probably too high Above 50 Above 125

Source: MedlinePlus. These cutoffs apply to the general population; experts haven’t agreed on a specific target for pregnancy.

What low vitamin D can mean

For you. Without enough vitamin D, your body can’t absorb enough calcium, which over time can weaken bones, according to MedlinePlus.

For your baby. ACOG notes that severe vitamin D deficiency in pregnancy has been linked to problems with a newborn’s bone development, including rickets and fractures.

Pregnancy complications. Some studies have linked low vitamin D to preeclampsia, gestational diabetes, and low birth weight. But a 2024 Cochrane review of the clinical trials found the evidence is uncertain on whether taking vitamin D prevents these problems, according to Cochrane. ACOG has likewise said there isn’t enough evidence to recommend vitamin D to prevent preterm birth or preeclampsia.

Treatment

If a test shows you’re low, ACOG’s guidance is that 1,000 to 2,000 IU of vitamin D a day is generally considered safe during pregnancy, as summarized by the AAFP. Your provider will choose the dose based on your level and may recheck it later in pregnancy.

A few practical points:

  • Take the dose your provider recommends, and count the vitamin D in your prenatal too.
  • Don’t go above 4,000 IU a day on your own; that’s the upper limit for teens and adults, including in pregnancy.
  • Keep eating vitamin D foods like fortified milk and salmon.
  • After your baby is born, ask the pediatrician about vitamin D for your baby, especially if you’re breastfeeding.

What to do now

  • Check the risk factors above. If any apply, ask your provider whether you should have a vitamin D blood test.
  • Check how much vitamin D your prenatal vitamin has. See Vitamin D Supplements in Pregnancy.
  • If you’re tested, ask for your number and which unit it’s in (ng/mL or nmol/L).
  • For how much you need and where to get it, see Vitamin D in Pregnancy.

Related reading

Sources

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