Can My Prenatal Vitamin Cause Side Effects?

AndieM.Ed., RD, LDN, CLC, RYT-200

Read time: 3 minutes

What to know about prenatal vitamins and how they affect nausea and constipation

  • Considerations for finding a suitable prenatal vitamin

  • Solutions to ease digestibility and improve tolerance of prenatal vitamins

Prenatal vitamins are recommended for most pregnant women.3,4 But supplements may sometimes cause pregnancy symptoms such as nausea and constipation to get worse in the short term.1,2,5

The good news is that research shows taking prenatal vitamins in the pre-conception and early pregnancy period actually reduces the overall risk of nausea during pregnancy.1,6

Potential side effects of taking prenatal vitamins

Some people have no problem at all taking their prenatal supplement, while others may experience one or more of the following side effects:

Nausea. If you experience nausea, taking your vitamin with food or right before bed may help.1 If your nausea is severe, your doctor may have you explore other options, such as a children’s multivitamin plus folic acid for the first trimester and then continuing with a regular prenatal later.

Difficulty swallowing. Prenatal vitamins can be quite large. Certain brands split the dose over 2 smaller pills to combat this problem. Other options include pills with a slicker coating or even liquid, powder, or chewable supplements.1,7

Constipation. The iron found in most prenatal vitamins is often the culprit for constipation or GI cramping.1,8

Share any discomforts you may be experiencing with your health care provider so they can help you find an option that works best. Do not make any changes to your supplement routine without the guidance of your health care provider.

Read more:

Dealing With the Physical Discomforts of Pregnancy

Strategies for Managing Morning Sickness

Tips to help combat the side effects caused by prenatal vitamins

Alert your healthcare provider about any discomforts you are experiencing

Keep your healthcare provider apprised of any changes you are thinking of making to your supplements. This will help ensure you’re receiving the proper dosage of important nutrients while pregnant.

Our team of registered dietitians can also help you with questions and ideas about your dietary needs during pregnancy. They’re here to help on our free to live chat from Monday – Friday 8am - 6pm (ET), and Saturday – Sunday 8am - 2pm (ET). Chat Now!

Take your vitamin with food

Taking your prenatal vitamin on an empty stomach may contribute to your discomforts. Making sure you eat something before taking it can help ward off any unwelcome nausea or stomach upset.3

Read about: Meal Plan to Help Manage Morning Sickness

Combat constipation

If you are experiencing constipation, make sure to drink plenty of fluids and eat fiber-rich foods.10 Other foods that may help relieve constipation include dried prunes, prune juice, pears, or pear juice.11 Physical activity can also help you stay regular.3

Foods that contain fiber include: Whole grains, vegetables, fruit, nuts, seeds, and beans.12

If you still cannot relieve your stomach discomfort, consider talking to your doctor about alternative supplements like a pill without iron, or a separate iron preparation that dissolves in the intestines rather than in the more sensitive stomach, or one that is slow-release.9

Read more:

6 Tips to Help Manage Prenatal and Postpartum Constipation

Meal Plan for Constipation Relief During Pregnancy

Go To Exercises During Pregnancy

Follow the instructions and dosage recommendations

More isn’t better when it comes to vitamins. Take the recommended dose and talk to your doctor about other supplements you are taking or planning to take, including herbal supplements or naturopathic treatments, in addition to other vitamins.

Read more: The Risks of Taking Too Many Supplements

Try to take your vitamin at the same time every day, to help your body adjust to it

Some women seem to better tolerate their vitamin when they take it before bed with a small snack.

Let's Chat!

We know parenting often means sleepless nights, stressful days, and countless questions and confusion, and we want to support you in your feeding journey and beyond.

Our Happy Baby Experts are a team of lactation consultants and registered dietitians certified in infant and maternal nutrition – and they’re all moms, too, which means they’ve been there and seen that. They’re here to help on our free, live chat platform Monday - Friday 8am - 6pm (ET), and Saturday - Sunday 8am - 2pm (ET).Chat Now!

Read more about the experts that help write our content!

For more on this topic, check out the following articles:

Meal Plan: How to Eat More Fruits and Vegetables

Meal Plan with Iron Rich Foods for Pregnancy

Include More Whole Grains in Your Daily Diet

How Much Should I Eat While Pregnant?

Which Nutrients Do I Need During Pregnancy