Why can prenatal vitamins make you feel nauseous? How to avoid this common problem

Strategies to make sure you can get the most out of your prenatal vitamins, and keep them down!
Written by
Sarah Stivens
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Last updated on
May 16, 2024
min read
Prenatal Vitamins Making You Feel Sick & Nauseous | Kin Fertility
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Pregnancy can be such a joyful time, but it's also okay if the beginning of your pregnancy journey feels daunting or confusing. There's lots of information to take in and advice to sift through — which cheese can you eat? Is coffee allowed?

And what the heck is a prenatal vitamin meant to do?

If you've made your way through those questions and are up to the 'researching which vitamins to buy' part, you may have heard that taking prenatal vitamins can sometimes cause nausea and other uncomfortable side effects.

The good news is, there are definitely ways to limit or get rid of prenatal vitamin side effects that make you feel unwell.

In this article, we'll explore the best strategies to make sure you can get the most out of your prenatal vitamins, and keep them down!

What are prenatal vitamins?

Prenatal vitamins are specially-formulated supplements that help women (and their babies) stay healthy during pregnancy. There's a huge range of pills on the market, but most prenatal brands contain a combination of vitamins and minerals that have been researched and proven to have benefits during pregnancy.

Because pregnancy involves so many changes to the body, it's important to make sure you're getting the right nutrients in as it'll make you'll feel better, and it helps meet the baby's needs as they grow.

You might be wondering, but what if I eat all the right foods? While eating well is still important, according to peer-reviewed studies, our modern diets just aren't enough.

Food nowadays tends to lack the recommended micronutrients — one study states that 33 per cent of the women interviewed were low in folate, 40 per cent were low in calcium, and more than 50 per cent were low in iron and zinc during their pregnancies.

Another study involving Canadian women also found that many of the participants had folate levels below the recommended amount. Basically, we can't rely on a healthy diet or food sources alone to get the right nutrients to the baby during pregnancy.

Why are prenatal vitamins important?

Aside from helping the baby grow and develop, prenatal vitamins have a number of other health benefits, such as:

  • Decreased risk of low birth weight
  • Decreased risk of birth complications such as preeclampsia, unplanned caesarean deliveries, and premature birth
  • Increased healthy blood volume/red blood cell mass
  • Improved health of the placenta
  • Improved mood and prevention of postpartum depression
  • Reduced likelihood of neural tube defects and other birth defects
  • Reduced risk of some paediatric cancers (1)

The dosage and type of prenatal vitamins you need to take can be really individual — depending on your health history.

For example, women with a family history of neural tube defects, diabetes, or epilepsy might need a more tailored dose (2). It's always best to ask your doctor before starting any new medications.

But what if you've done the research, been to the appointments, started your vitamins... and they're not agreeing with you?

Why do prenatal vitamins make you feel sick?

Most women experience morning sickness during their pregnancy — it usually peaks between weeks four to nine. Unfortunately, some types of prenatal supplements have been known to worsen morning sickness or trigger nausea. But why does this happen?

A lot of prenatal vitamins contain iron (important for the baby's health) which can cause stomach irritation and make you feel unwell. Some women might be more prone to feeling sick if they have a history of certain health conditions such as acid reflux, migraines or thyroid disorders (1).

Other studies have shown that tablet size might also have an effect on nausea symptoms — the bigger the tablet, the worse you may feel.

While nausea is the main side effect people report when they start taking a prenatal vitamin, some women may also experience constipation and other gastrointestinal problems.

It's easy to be put off by the idea of side effects and supplements making you feel worse, but it's important not to cease taking your prenatal vitamin. Instead, you can learn how to manage or get rid of these side effects, while still making sure you and your baby are healthy.

How do you stop nausea from prenatal vitamins?

If you're feeling sick after taking your prenatal vitamin, you don't have to keep spending your days close to the bathroom. According to the experts, there are a few tips that might help improve nausea and other symptoms:

Change the timing

If you normally take your tablet in the morning, it could be worth switching to taking it at night (with a snack).

It's called morning sickness for a reason — taking a prenatal vitamin early in the day or on an empty stomach could mean you're more likely to feel sick (3).

Change the tablet

If changing the timing of your prenatal vitamin doesn't seem to help, it might be time to reconsider the type or brand of tablet you're taking.

You could give Kin's Prenatal a try. It's formulated with your wellness in mind — the ingredients are ones your body can use while also being easier on the stomach than other supplements.

The capsules are broken up into two doses per day; smaller tablets = feeling less sick!

Start taking vitamins sooner

Some evidence suggests that beginning prenatal vitamins before conception can help you tolerate them during the early stages of pregnancy (3). If you take your prenatal vitamin before conceiving, it also benefits the baby — their development starts really early, sometimes before you even know you're pregnant.

Having the right nutrients on board gives them the best chance at growing in a healthy way.

What happens if I don't take prenatals during pregnancy?

We've already covered why taking a prenatal vitamin is important, and how to get the most out of them without battling too many side effects. But what actually happens if you don't take any prenatal vitamins at all?

In a nutshell, taking a prenatal vitamin means you have a better chance of avoiding adverse health outcomes (1). If your body doesn't have the right nutrients to support you and the baby, there can be a danger of complications like hypertension, gestational diabetes and even miscarriage.

For the baby, missing out on prenatal vitamins can have serious side effects— like poorer neuro-cognitive development, increased chance of congenital disorders, and birth defects.

Having the right vitamins and minerals in your system is particularly important when the baby's neural tube (the part that turns into the brain and spinal cord) is about to close (2).

This happens in the first trimester at about 28 days of gestation, which is why doctors recommend starting prenatal vitamins early.

Studies also suggest that iron is important during the second and third trimesters, so looking for a supplement with the right amount of iron for you is a good idea. Like with all medications, you should never take more than the recommended dose.

Over nutrition can also be harmful. That's why it's always best to ask your doctor before starting, and follow up with them if you experience any side effects (4).

Best prenatal vitamins that don't cause nausea

Finding the right prenatal vitamin for you can be half the battle in controlling nausea and other side effects. There are a lot of options on the market, but deciding doesn't have to be overwhelming.

As a starting point, the main vitamins your prenatal should contain are iron, folate or folic acid, iodine and vitamins that help with calcium absorption such as vitamin D (4).

But some of these ingredients, such as iron and folic acid can be the cause of stomach irritation— especially if the tablet contains too much iron, or is too large.

Introducing Kin's Prenatal range

After doing the research, Kin's Prenatal was created to help women to have the best experience possible when taking prenatal vitamins. It's a smaller pill that you take twice a day, instead of one large tablet making you feel sick.

The ingredients we've included are the real difference. While most vitamin brands use synthetic ingredients, Kin's Prenatal includes bioavailable ingredients, like methylated folate, instead.

We've created the vitamin this way so that your body can better absorb the nutrients it needs, while being gentle on your stomach. The other advantage of The Prenatal by Kin is that it's unflavoured and easy to swallow — you won't have to hype yourself up to take it every time.

You deserve to feel as well as possible during your pregnancy, so order your first dose here.


  1. S. K. Gill, C. Maltepe & G. Koren (2009) The effectiveness of discontinuing iron-containing prenatal multivitamins on reducing the severity of nausea and vomiting of pregnancy, Journal of Obstetrics and Gynaecology, 29(1), 13-16.
  2. Ahn, E., et al., (2004) Multivitamin supplements for pregnant women. New insights. Canadian Family Physician, 50 (5), 705-706;
  3. Crowley, K., & Martin, K.A., (2022) Patient education: Nutrition before and during pregnancy (The Basics), UptoDate. Retrieved March 9, 2022 from https://www.uptodate.com/contents/nutrition-before-and-during-pregnancy-the-basics?csi=e9e1d0fb-73d5-4054-a248-25b9f1ac2bc5&source=contentShare
  4. Garner, C., et al., (2022) Nutrition in pregnancy: Dietary requirements and supplements. UptoDate, Retrieved March 9, 2022 from https://www.uptodate.com/contents/nutrition-in-pregnancy-dietary-requirements-and-supplements#H3055186032
  5. Scholl, O.T, et al., (1997) Use of Multivitamin/Mineral Prenatal Supplements: Influence on the Outcome of Pregnancy, American Journal of Epidemiology, 146( 2), 134–141.
  6. Burris, H. H., et al., (2015). Prenatal vitamin use and vitamin D status during pregnancy, differences by race and overweight status. Journal of Perinatology, 35(4), 241-245.
  7. Nguyen, P., Thomas, M., & Koren, G. (2009). Predictors of Prenatal Multivitamin Adherence in Pregnant Women. The Journal of Clinical Pharmacology, 49(6), 735–742.
  8. Sfakianaki, A.K, (2013). Prenatal vitamins: A review of the literature on benefits and risks of various nutrient supplements. Formulary, 48(2), 77-82.
  9. Koren G., & Pairaideau, N., (2006). Compliance with prenatal vitamins, Patients with morning sickness sometimes find it difficult, Canadian Family Physician, 52, 1392-1393.
  10. Smith, J.A., et al., (2022) Nausea and vomiting of pregnancy: Treatment and outcome, UptoDate. Retrieved March 9, 2022 from https://www.uptodate.com/contents/nausea-and-vomiting-of-pregnancy-treatment-and-outcome?csi=c406bcb6-f5e9-49a6-b811-2b350a755248&source=contentShare
  11. Nguyen, P., et al., (2008) Effect of iron content on the tolerability of prenatal multivitamins in pregnancy. BMC Pregnancy Childbirth 8 (17) .
  12. Brodeur-Doucet, A. (2021) Can there be side effects associated with prenatal multivitamins? Montreal Diet Dispensary. Retrieved March 11, 2022 from https://www.dispensaire.ca/en/posts/side-effects-associated-with-prenatal-multivitamins/
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