Nausea from prenatal vitamins may be tied to the iron or the size of the pill, though the trials are small. Taking it with food can help, since taking iron with food can ease its stomach side effects. Don't quit on your own. Ask your OB, midwife, or pharmacist about a smaller or lower-iron pill, because the folic acid in it matters most in the first weeks of pregnancy.
You're not imagining it. A 2008 paper from Toronto's Motherisk program says pregnant women "may experience gastrointestinal (GI) symptoms, particularly 'morning sickness', aggravated by the iron content or swallowing a large tablet," and that this "can deter pregnant women from starting or continuing to take prenatal multivitamins" (Nguyen et al., 2008). The same paper puts some nausea or vomiting at about 80% of pregnancies.
This article provides general information about medication management and is not a substitute for professional medical advice. Always consult your doctor or pharmacist before making changes to your medication schedule. Consult your doctor or pharmacist for advice specific to your medications.
Why Do Prenatal Vitamins Make You Nauseous?
One suspect is iron. The NIH Office of Dietary Supplements says high doses of supplemental iron, 45 mg a day or more, "may cause gastrointestinal side effects, such as nausea and constipation" (NIH ODS, Iron fact sheet). Its consumer page adds that this happens "especially on an empty stomach" (NIH ODS, Iron consumer fact sheet).
ACOG says you need 27 milligrams a day in pregnancy to make extra blood (ACOG, Healthy Eating During Pregnancy). That need is below the 45 mg level the NIH ties to stomach side effects. Brands put in different amounts, so check the iron line on your label before blaming the iron.
The second suspect is the pill itself.
Prenatal Vitamins Without Iron vs. a Smaller Pill: What the Trials Found
Two small trials from Toronto's Motherisk group compared lower- and higher-iron prenatals, and a 2006 Motherisk update summarized them. Duchesnay, maker of one product tested, funded both trials, so treat them as leads, not the final word.
Study 1: one product change, less constipation. A 2006 crossover trial had 138 pregnant women try two prenatals: a small, twice-daily pill with 35 mg of iron and calcium split off, and a large, once-daily pill with 60 mg of iron. Constipation was lower on the first (22.5% vs. 34.8%). Nausea rates were about the same (41% vs. 46%). The worse a woman's nausea, the less reliably she took the large pill. Because the pills differed in size, schedule and iron, the trial can't say which change did it.
Study 2: both pills small, iron dose didn't matter. A 2008 randomized trial assigned 167 pregnant women to small tablets with either 35 mg or 60 mg of iron. Among the women who started their pill, nausea or vomiting showed up in 21% (12 of 57) and 19% (9 of 47). Constipation didn't differ either (23% vs. 21%). Twenty of the 21 women who reported nausea already had it before they started.
What the team concluded. In a 2006 update, the same group wrote that "both tablet size and high iron content" were linked to lower use in women with morning sickness, and that "tablet size is more likely to affect compliance." Citing early results from the 2008 trial, it pointed to tablet size, not iron content, as the bigger barrier.
Neither trial found that the iron amount changed how many women felt sick. The pill-size idea comes from comparing across studies, not from a head-to-head test.
How to Reduce Nausea From Prenatal Vitamins
| What to try | Why it might help | Can you do it yourself? |
|---|---|---|
| Take it with a meal or snack | NIH ODS says taking iron with food can help cut stomach side effects | Yes |
| Move it to dinner or a bedtime snack | A common tip so you sleep through any queasiness. Not tested in a study | Yes, if you still take it every day |
| Ask about a smaller pill | Motherisk researchers point to tablet size as a barrier, based on early results | Ask your pharmacist |
| Ask about a lower-iron formula | One trial found less constipation with a smaller, split-dose, lower-iron product | Ask your OB or midwife |
| Ask about a gummy | May be easier to get down, but gummies hold less iron, per ACOG | Ask first, you may need extra iron |
| Ask about vitamin B6 or ginger | ACOG lists both for nausea of pregnancy | Ask first, no self-dosing |
Food is the easy place to start. ACOG's nausea advice is built around never letting your stomach go empty, with "five or six 'mini meals' a day" (ACOG, Morning Sickness). Pair your prenatal with one of them. More on iron and meals in our iron supplement timing guide, and if you also take calcium, see vitamins not to take together.
On B6, ACOG says "Vitamin B6 is a safe, over-the-counter treatment that may be tried first for nausea and vomiting of pregnancy." That comes after other causes are ruled out. ACOG also says ginger "can help settle your stomach" (ACOG). The NIH says pregnant women "should consult a physician" before taking B6, because doses could approach the upper limit (NIH ODS, Vitamin B6).
Is It Safe to Skip Prenatal Vitamins Due to Nausea?
Please don't decide this alone.
The big reason is folic acid. The CDC says it "is the only type of folate shown in studies to help prevent serious birth defects called neural tube defects." Those defects "happen in the first few weeks of pregnancy, often before you know you are pregnant." The CDC advises 400 mcg of folic acid daily for anyone who could become pregnant. That window overlaps with nausea, which ACOG says usually starts before 9 weeks. More in folate vs. folic acid for pregnancy.
Second, ACOG's own answer to "Should I take vitamins?" is "Yes, take a prenatal vitamin." It adds that "taking a vitamin supplement before and during pregnancy reduces the risk of having severe nausea and vomiting of pregnancy" (ACOG).
If you've been skipping, tell your care team so they can help you find a version you keep down. Don't catch up by doubling: ACOG warns that vitamin A "can cause birth defects if you double or triple the dose" (ACOG). If you also take a separate iron pill and missed it, see what to do if you forgot your iron supplement.
Prenatal Vitamins Making Morning Sickness Worse, or Is It Something Else?
Sometimes the vitamin isn't the problem. ACOG says an ulcer, food-related illness, or thyroid or gallbladder disease can also cause nausea in pregnancy (ACOG). Tell your provider if you have:
- Nausea and vomiting that starts for the first time after 9 weeks of pregnancy
- Belly pain or tenderness
- Fever
- Headache
- Swelling in the front of your neck
Prenatal Vitamins Making You Throw Up? When to Call Your OB
Most morning sickness is miserable but not dangerous. The severe form is called hyperemesis gravidarum, and ACOG says it "occurs in up to 3 percent of pregnancies." Call your OB or midwife if you notice signs of dehydration (ACOG):
- A small amount of dark urine, or you can't urinate
- You cannot keep down liquids
- You feel dizzy or faint when you stand up
- Your heart is racing or pounding
MedlinePlus adds a few more reasons to contact your provider: you can't keep any fluids down for over 12 hours, there is blood in your vomit, you have belly pain, or you have lost more than 5 pounds (MedlinePlus).
ACOG notes that experts "recommend early treatment so that it does not become severe."
Does Nausea From Prenatal Vitamins Go Away?
We found no study that tracks how long vitamin-triggered nausea lasts. For pregnancy nausea overall, ACOG says that "for most women, it goes away by 14 weeks of pregnancy," though for some it lasts longer (ACOG).
Nausea From Prenatal Vitamins When You're Not Pregnant
If you're trying to conceive and the nausea is new, take a pregnancy test and tell your clinician. MedlinePlus lists nausea and vomiting among the common signs of early pregnancy. Otherwise, taking it with food is the one tip here that doesn't depend on pregnancy, and your pharmacist can suggest a smaller or lower-iron option.
How Pillo Helps
Once you find a time your stomach tolerates, the hard part is doing it daily while you feel lousy. Pillo's reminders are persistent. They keep going until you deal with them, which makes it harder for one queasy evening to turn into a skipped week.
Add a dose note like "take after food" or the name of the formula your pharmacist suggested. Your history shows which days you took it. Download Pillo on Google Play.
FAQ
Can I stop taking prenatal vitamins because of nausea?
Talk to your OB, midwife, or pharmacist before stopping. The CDC says folic acid is the only form of folate shown to help prevent neural tube defects, which form in the first few weeks of pregnancy. Your care team can help you switch to a version you tolerate.
I threw up after taking my prenatal vitamin. Should I take another one?
We didn't find guidance on re-taking a prenatal after vomiting, so call your pharmacist before taking a second one. ACOG does warn against taking more than the recommended amount of your prenatal each day, because vitamin A can cause birth defects at double or triple doses (ACOG). Our vomiting after medication guide covers prescription drugs, not prenatals.
Does taking prenatal vitamins at night help with nausea?
No study we found has tested it. Many people take it with dinner or a bedtime snack so it's never on an empty stomach, which NIH ODS says can make high-dose iron harder on the stomach. Pick a time you can keep every day. Our best time to take vitamins guide covers the general rules.
Are gummy prenatal vitamins better for nausea?
They may be easier to get down, but ACOG says gummies can't hold as much iron as regular prenatals, so you may need a separate iron supplement (ACOG). Ask your OB first. For how iron amounts compare, see is 65 mg of iron too much.
Does vitamin B6 help with nausea while taking prenatals?
ACOG says vitamin B6 may be tried first for nausea and vomiting of pregnancy once other causes are ruled out (ACOG). The NIH advises pregnant women to consult a physician before taking it (NIH ODS). Your prenatal should already contain B vitamins, so ask whether more is right for you.
This article is for informational purposes only and does not constitute medical advice. Always consult your doctor or pharmacist before making any changes to your medication routine. If you are pregnant or trying to conceive, check with your OB, midwife, or pharmacist before changing or stopping your prenatal vitamin.
