Our bodies require magnesium for over 300 biochemical reactions in the body. But if we take magnesium supplements, will we experience side effects? Our experts answer your magnesium side effects questions here.


Gastrointestinal distress is the number 1 reported magnesium side effect. That distress can include nausea, cramps, and diarrhea. But did you know, your distress might simply be caused by the type or volume of magnesium you're taking?

Digestive Side Effects from Types of Magnesium Supplements

Magnesium oxide and magnesium citrate are typically used to combat occasional constipation. And they each have a different way of working to keep your bowels moving.

Magnesium Oxide

In published studies, researchers have shown that the body does not easily absorb magnesium oxide. While our bodies extract and use 30% - 40% of the magnesium we eat, we only absorb about 4% of magnesium oxide supplements. And that means your digestive system gets moving to process the waste.

Magnesium Citrate

Magnesium citrate supplements have slightly more bioavailability. Our bodies absorb about 8% of this type of magnesium. But it also has a few mechanisms that help your bowels move things along as well. 

  1. high doses can increase some intestinal peptides that have a laxative effect;
  2. magnesium citrate produces a relaxing effect on your intestines; 
  3. it pulls water into your intestine to soften your stool and make it easier to pass.

But what if you don't have constipation? If you take these two forms of magnesium without having constipation symptoms, you could end up causing yourself digestive issues, including diarrhea.

While nausea and cramping are no fun, diarrhea can lead to dangerous issues with dehydration and other health complications. So, if you experience diarrhea (or other digestive issues) when taking magnesium oxide or citrate, try switching to a different type of magnesium like magnesium malate, aspartate or escorbate.

Magnesium Side Effects Caused by Intake Level

Magnesium is one of the top supplements we believe everyone needs. That's because most experts agree that over half of the US population is deficient in magnesium. Nutrition World's founder Ed Jones estimates about 85% of us don't have enough magnesium from our diets alone.

However, when starting to supplement with magnesium, we believe it's best to start slow and increase how much you take over time. Because of the relaxing effects of magnesium on our intestines (not to mention the rest of the body), it's not unusual to experience some digestion issues as our bodies adapt to a new level of this micronutrient.

It can take our bodies a few weeks to get used to new nutrients. So, if you experience diarrhea or other side effects, we have 2 recommendations.

  1. lower your daily intake slightly to allow your body to adapt, and
  2. with mild cramps, give yourself a couple of weeks to adjust.

As we mentioned, regular bouts of diarrhea can be dangerous for your health. So, if you experience diarrhea more than once or twice, you should discontinue your magnesium supplementation immediately, and seek medical advice.

Disclaimer. The information on this website and the topics discussed have not been evaluated by the FDA. Or, any one of the medical profession. And it is not aimed to replace any advice you may receive from your medical practitioner. Nutrition World assumes no responsibility or liability whatsoever on the behalf of any purchaser or reader of any of these materials. Nutrition World is not a doctor, nor does it claim to be. Please consult your physician before beginning any health regimen. If you are being treated for any medical illness, check with your medical professional before starting any protocol