What Are the Side Effects of Prenatal Vitamins?

If your prenatals are making you sick, talk to your doctor about finding a supplement that doesn't cause as many side effects.
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Your growing baby requires a lot of nutrients, which you may not be able to supply through diet alone. Prenatal vitamins ensure that you and your baby are getting the nourishment you need. Most people take these supplements with few problems, but some do experience prenatal vitamins' side effects.


That said, while there can be side effects to prenatal vitamins, it's still important to take them. These supplements provide your baby with the nutrients it needs to develop properly and can help prevent certain birth defects, so not taking prenatal vitamins isn't advised, according to the Mayo Clinic.

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With that in mind, here are the side effects of prenatal vitamins to be aware of.


Talk to your doctor if you experience any prenatal side effects, and they can help you address the issue and find the best prenatal vitamins for you, per the Mayo Clinic.


Getting enough iron is extremely important when you're pregnant because it helps your body make more blood to carry oxygen to your baby to support its development, according to the Mayo Clinic. It also helps prevent iron-deficiency anemia, which is linked to an increased risk for low birth weight and preterm delivery.

That's why most prenatal vitamins contain solid doses of the mineral. But these higher doses of iron can lead to bowel issues — most commonly, constipation, per the Mayo Clinic.


If you're experiencing this prenatal vitamin side effect, here are some tips to help you cope:


Constipation isn't the only poop-related problem you might experience — prenatal vitamins can cause diarrhea, too.


Prenatals can cause diarrhea due to the supplements' higher doses of certain nutrients like magnesium and myo-inositol, according to October 2020 research in ‌Nutrition Reviews.

If you experience prenatal vitamins' diarrhea, talk to your doctor about the best way to address the issue. They can help you find a pill that works better for you.


Changes in Stool Color

What color is your poop when pregnant? Well, that answer can change depending on the types and amounts of nutrients included in your prenatal supplement. So if you notice your pregnancy poop color has changed, don't worry — this is another common prenatal vitamin side effect.


Iron is often to blame for changes to poop color in pregnancy, according to the U.S. National Library of Medicine (NLM). The high doses of iron in prenatal vitamins can darken your pregnant poop color: Luckily, though, this typically isn't cause for concern.


You might also notice you're pregnant and have green poop. Green stool during pregnancy is often due to the high doses of iron in your prenatal supplement — this is likely the case if you have dark green pregnancy poop, per the Mayo Clinic.

However, if your stool looks tarry, has red streaks in it or you're experiencing cramping or sharp pain when you go to the bathroom, visit your doctor to make sure you aren't having a bad reaction to iron, according to the NLM.


You may also notice light-colored stool during early pregnancy. This can be a side effect to anti-diarrheal medication (which you may be taking to quell other prenatal vitamin side effects), per the Mayo Clinic.

It can also indicate liver problems, so if you experience light-colored stool along with symptoms like severe itching and jaundice, visit your doctor, per the University of Rochester Medical Center (URMC).


Pregnancy and Green Stool

You might also notice that your early pregnancy poop color is green more often than usual. This may be due to increased fiber intake or faster digestion, both of which can turn your stool green, per the Mayo Clinic.

Stomach Discomfort

Many pregnant people regularly experience nausea and vomiting. But can prenatal vitamins make you nauseous or sick?

Indeed, in some cases, prenatal vitamins can make you sick, per the ‌Nutrition Reviews‌ report. Symptoms may include:

  • Gas
  • Bloating
  • Nausea
  • Vomiting

While you might be able to deal with slight queasiness, if you find yourself throwing up regularly after taking your prenatal vitamin, your body probably isn't absorbing what it needs from the supplement. When prenatals make you this sick, taking your vitamin with food or at night right before bed may help minimize symptoms, according to the Mayo Clinic.


Some prenatal vitamins are better suited for sensitive stomachs — for instance, chewable or gummy versions of prenatal vitamins are often more easy on the stomach, per the Mayo Clinic.

Changes in Urine Color

Notice bright yellow pee in early pregnancy? This is another common side effect of your supplements, as some of the vitamins in prenatals — particularly B vitamins — can change your pregnancy pee color to bright yellow, according to the URMC.

Bright yellow urine in pregnancy is harmless, but discuss it with your doctor if you have any questions.

When You're Pregnant, What Color Is Your Pee?

Typically, urine color is anywhere from pale yellow to deep amber, according to the Mayo Clinic. If you have dark, orange or bloody urine, check in with your doctor.


Taking too high a dose of your prenatal vitamins can cause headaches, according to the American Pregnancy Association. If you've loaded up on prenatals and experience a headache, talk to your doctor to address the pain and settle on the best vitamin dose for you.

And if you're wondering why gummies give you a headache, the reason is the same: You may be taking too high a dose of your prenatal supplement.


Keep in mind that prenatal vitamins aren't the only cause of headaches everyday during pregnancy. For instance, changing hormone levels, increased blood volume, stress and caffeine withdrawal can all be reasons why you have a headache during pregnancy, per the American Pregnancy Association.

Skin Irritation

Vitamin A is an important nutrient for your growing baby. But in too high a dose, it can cause side effects like dry, itchy skin, according to the Mayo Clinic. Too much vitamin A can also contribute to symptoms mentioned previously like diarrhea, nausea and headaches.

If you notice this side effect, talk to your doctor about whether you should lower your dose of the nutrient. Excess vitamin A (which means taking 10,000 micrograms or more per day) has been linked to birth defects, so you want to be careful not to overdo it, per the Mayo Clinic.

Aches and Pains

Too much vitamin A can also lead to bone and joint pain, according to the Mayo Clinic.

You may also experience muscle pain or weakness if you overdose your prenatal vitamin, per the American Pregnancy Association. So if you notice this side effect, talk to your doctor to make sure you're taking your supplement in safe amounts.

Metallic Taste

Prenatal vitamins can contain metallic minerals like zinc and iron, according to the Cleveland Clinic. While the right doses of these nutrients are good for your developing baby, they can sometimes lead to a metallic taste in your mouth.

Staying hydrated, sucking on ice and maintaining good oral hygiene can all help ease this side effect.


Despite certain side effects, doctors typically recommend you only stop taking prenatal vitamins after you've finished breastfeeding your baby, per the Cleveland Clinic.




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