Iron Supplements Are Known For Causing GI Issues — Not This One

As a dietitian, I hear all too often about people’s negative experiences1 with iron supplements. “They upset my stomach.” Or, “They changed my bathroom schedule.” This side effect is typically enough to sour someone’s perception towards these beneficial supplements and make them stop use altogether. 

And that’s really concerning to me! Because many people take iron supplements after talking with a healthcare professional and/or getting bloodwork done that shows low iron status. In fact, approximately 10 million Americans are deficient in iron2 – and it's one of the most common nutritional deficiencies worldwide.

Iron is an absolutely essential mineral. It’s responsible for making two oxygen-carrying proteins (hemoglobin and myoglobin), so low iron levels often make you feel dizzy and tired (and impact your immune health.)

Without getting too much into the science here, these names refer to different chemical structures that deliver elemental iron into your system.

Research shows that chelated forms of iron (iron attached to an amino acid) are linked to fewer digestive side effects3 than other types of iron. (Oh, and ferrous forms tend to be more easily absorbed by the body.) 

How much iron you take at a time has also been shown to impact the GI system. An incorrect dose may lead some people to feel queasy or blocked up.

The Tolerable Upper Limit Level (UL) for supplemental iron is 45 milligrams4. Above this threshold, some individuals might experience these unwanted side effects (think: not pooping as much).

That’s pretty high considering the daily recommended amount of iron for men and women ranges from 8 to 18 milligrams daily—with women encouraged to reach the higher end of that range. Pregnant women need even more (27 milligrams daily) because of the significant increase in blood volume during this time. 

But if you’ve had insufficient or deficient iron levels or other indicators of low iron (e.g., hemoglobin, hematocrit, ferritin, etc.), there’s a decent chance a healthcare professional recommended taking a high dose approach. For example, a healthcare professional may recommend 325 mg of ferrous sulfate (which delivers 65 milligrams of elemental iron, which is the the clinical consensus dose for correcting truly low iron) for the short-term until sufficiency is achieved and then a lower maintenance dose after that.

In these scenarios when a higher dose may be recommended, consider starting with a lower amount and slowly increasing it to figure out your threshold. 

Many multivitamins exclude iron (and other minerals like calcium and magnesium) purely because the ingredients themselves take up a lot of space in capsules and can be expensive when premium chelated ingredients are used. 

Multivitamins also don’t always have a positive reputation for being gentle on the stomach (due to potent doses of multiple ingredients that aren't in their most gentle form).

“I love this vitamin because it doesn't upset my stomach when I take it on an empty stomach which many vitamins do!”

“I am so happy I tried this vitamin. It is easy on the stomach and I combine it with other vitamins and feel the difference. Will be ordering them again.”*

“What I really like about these is that even though they are bigger capsules they for me are easy to swallow. They are also very easy on my stomach!”

“I am extremely sensitive to multivitamins. I have not been able to tolerate any, and I have tried so many. Until now! I currently only take a half dose right now, but plan to progress and test a full dose later. I have absolutely no issue with the half dose which is a huge victory for me.” 

-Holly S

Iron can be a tricky mineral to supplement with, and many people have had not-so-great past experiences with it.