Iron supplements can be known for rather unpleasant side effects. 8/10 of people who take oral iron tablets report experiencing side effects, from nausea and upset stomachs to constipation and diarrhea.* Active Iron’s non-constipating formula is specially engineered to target the body’s natural site for iron absorption in the small intestine, decreasing the likelihood of side effects.

What are the side effects of iron pills?

The most common side effects of taking iron pills are:

  • Upset stomach
  • Nausea
  • Diarrhea
  • Constipation
  • Headache
  • Heartburn

Upset stomach

An upset stomach is one of the most common side effects of taking an iron supplement. The best absorption of iron is on an empty stomach, which can be especially difficult for sensitive stomachs. Those who take iron tablets can report cramps, pain, and soreness in the stomach. Active Iron’s kind & strong formula is gentle on the stomach and increases iron stores by 94%.


Nausea and vomiting are another category of common side effects of iron supplements. Olympic medallist Aifric Keogh reported having bouts of nausea due to her iron supplements. She switched to Active Iron, which is clinically proven to have 6X less gut irritation than other oral iron tablets on the market.


In some cases, iron tablets can cause diarrhea. In a survey of 2400 women, 13% reported having diarrhea due to their iron supplements. Eating certain foods can also hinder oral iron absorption, such as eggs, coffee, and milk, further increasing the likelihood of side effects.


During a survey conducted with 2400 women, 40% reported experiencing constipation as a side effect of taking an iron supplement. Some doctors suggest taking iron pills with orange juice to help with the absorption process. Active Iron’s unique protein formula allows the iron to be absorbed in the body’s natural site for iron absorption in the small intestine, decreasing the likelihood of side effects.


Inadequate iron levels can sometimes lead to headaches, making it a cruel irony that some people also experience headaches from taking iron tablets. Luckily, this is a rare side effect. If you’re worried about headaches while taking oral iron, consult your GP.


Especially for those who already experience conditions like acid reflux, heartburn can be a side effect of iron tablets. Active Iron stays in an easy-to-absorb state all the way to the small intestine, the body’s natural site of absorption. Thanks to its particular whey protein layer, the iron is protected from stomach acid, helping to reduce gut irritation.

Side effects of liquid iron

Liquid iron supplements are an alternative to traditional iron supplements for people intolerant to conventional iron supplements, but they are not without side effects. One of the most common side effects of liquid iron is black stained teeth. Some doctors suggest taking liquid iron mixed with orange juice and taken through a straw, to avoid stained teeth. On top of this, those who take liquid iron might also experience:

  • Stained teeth
  • Nausea
  • Constipation/diarrhea
  • Black or dark stool

What are signs that your iron pills are not working?

If you continue to experience the effects of inadequate iron levels, such as tiredness and fatigue, it may be a sign that your iron supplements are not working (4).

Possible reasons include
• not taking the correct dose,
• not taking it regularly, or
• stopping before the benefits can be felt.

For optimum absorption, it is important to take an iron supplement daily. Active Iron is clinically proven to increase iron levels within six weeks, with the benefits felt after only three weeks.

Experiencing side effects is another one of the main reasons why people stop taking iron tablets, as they can be debilitating. By choosing an iron supplement that is gentle on your stomach, you can take your iron supplement daily, achieving optimum absorption, and thus ensuring they are working correctly. For more info, check out our complete guide to the signs your iron pills are working.


Do you know of an iron supplement without side effects?

When choosing an iron supplement, it is essential to choose one strong on absorption whilst gentle on the stomach.

Active Iron delivers 2X better absorption than standard ferrous sulfate with its ground-breaking protein formula, while its non-constipating formula makes it 6X less likely to cause gut irritation. (6) Active Iron targets the body’s natural site of iron absorption in the small intestine, bypassing the stomach where most oral irons are absorbed. Worldwide, Active Iron is trusted by consumers and recommended by pharmacists to increase iron levels by 94%.

Iron Supplement Side Effects – FAQ:


Do iron tablets cause diarrhoea?

Iron tablets can cause diarrhoea as a side effect. This can be caused by inadequate iron absorption, leading to oxidation and subsequent gut inflammation. These factors can contribute to gastrointestinal symptoms, including diarrhoea. Active Iron is highly absorbed compared to other iron supplements, making it gentle on the stomach and clinical results have shown that it increases iron levels by 94%.

Do iron supplements cause heartburn?

Iron supplements can cause upper gastrointestinal symptoms including heartburn. However, Active Iron, a highly absorbed iron supplement, is known to be gentle on the stomach.

Do iron supplements cause nausea?

Iron supplements can cause some people to feel nauseous, especially when taken on an empty stomach. Active Iron is so gentle, that it can be taken on an empty stomach.

Do iron pills cause constipation?

Iron pills can cause constipation. Active Iron’s groundbreaking formula is clinically proven to be gentle on the stomach, helping to avoid constipation.

Do iron pills cause upset stomach?

Iron pills can cause upset stomach. This is due to poor absorption, which in turn causes oxidation and inflammation in the gut. Taking your iron with orange juice can help aid absorption. Active Iron is an iron supplement that is highly absorbed compared to other iron supplements, and is so gentle it can be taken on an empty stomach.