7 min

Iron Supplements, Absorption, Cautions Breaking Down Nutrition for Medical Professionals

    • Nutrition

The other day at the grocery store I ran into an acquaintance who said ‘may I ask you a question’? This happens to you too right? All the time. She found out she was anemic, bought the first iron supplement on the shelf and took it.

But her lab tests showed no improvement. Then she said that her stomach had started hurting so she just stopped taking it. Did she have the right form? Dose? Just ahead let’s talk about the many iron supplement forms available, absorption rates and cautions and concerns.

When we hear the words iron supplements, we tend to think anemia in women and children but iron supplements have multiple uses such as for regular blood donors to recover their hemoglobin and ferritin levels, to reduce unexplained fatigue in women of child-bearing age, in some restless leg syndrome cases with low ferritin levels and to possibly help reduce the dry cough caused by drugs in the angiotensin-converting enzyme inhibitor family or we know as ACE inhibitors.

But which iron supplement is best?



Consider these 4 points in deciding…

#1. the supplement should provide the right dose of iron for the therapeutic use. The amount of elemental iron per milligram of iron compound really varies supplement to supplement so be sure the product contains the therapeutic dose you’re recommending.

#2. the supplement should provide the right form of iron for good absorption but least likely to cause gastrointestinal side effects such as constipation or gastric irritation.

#3. good quality: tested by companies like Consumer Labs or carries the USP seal

#4 value…your patients can afford it.

Ferrous sulfate, ferrous fumarate and ferrous gluconate are three very common supplement forms taken with water for greatest absorption and are inexpensive. However, many patients complain of stomach pain so an alternative is ferrous bis-glycinate which can be taken with food or within an hour of eating. This ferrous bis-glycinate form of iron has been shown to be absorbed two to four times better than ferrous sulfate when taken with food.

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Generally, taking iron with food will help reduce GI discomfort. Oh and for your patients who want vegetarian capsules, the ferrous bis-glycinate form is available. In fact, a Consumer Labs recent Top Pick among iron supplements is called NOW Iron, a vegetarian capsule in the ferrous bisglycinate form. Both Nature’s Bounty and Solgar also make bisglycinate formulas with some being vegetarian and kosher.

What about a timed- release or slow release formula? While these may reduce gastric irritation, there’s concern that less iron may be available in the small intestine where iron is absorbed due to the slower release so may not be a wise choice for anemia but studies suggest could be a choice for unexplained fatigue in women who are not anemic but have low ferritin levels.

Other supplement forms contain heme-iron polypeptide abbreviated HIP which may be better tolerated with less gastric irritation and constipation than iron salts like ferrous sulfate.

Let’s look quickly at the flip side for iron supplements, cautions and concerns.

First antacids and this includes proton pump inhibitors or PPIs.The dose and length of time taken may increase risk of iron deficiency. Antacids can also decrease iron absorption.

Iron absorption can be reduced by high doses of other minerals such as calcium, zinc, manganese, magnesium or copper. A two hour period is suggested between consuming one of these high-dose mineral supplements and an iron supplement. Be aware that some multis for women who haven’t gone thru menopause and who may still be at risk for iron deficiency can contain 500 mg of calcium.

The other day at the grocery store I ran into an acquaintance who said ‘may I ask you a question’? This happens to you too right? All the time. She found out she was anemic, bought the first iron supplement on the shelf and took it.

But her lab tests showed no improvement. Then she said that her stomach had started hurting so she just stopped taking it. Did she have the right form? Dose? Just ahead let’s talk about the many iron supplement forms available, absorption rates and cautions and concerns.

When we hear the words iron supplements, we tend to think anemia in women and children but iron supplements have multiple uses such as for regular blood donors to recover their hemoglobin and ferritin levels, to reduce unexplained fatigue in women of child-bearing age, in some restless leg syndrome cases with low ferritin levels and to possibly help reduce the dry cough caused by drugs in the angiotensin-converting enzyme inhibitor family or we know as ACE inhibitors.

But which iron supplement is best?



Consider these 4 points in deciding…

#1. the supplement should provide the right dose of iron for the therapeutic use. The amount of elemental iron per milligram of iron compound really varies supplement to supplement so be sure the product contains the therapeutic dose you’re recommending.

#2. the supplement should provide the right form of iron for good absorption but least likely to cause gastrointestinal side effects such as constipation or gastric irritation.

#3. good quality: tested by companies like Consumer Labs or carries the USP seal

#4 value…your patients can afford it.

Ferrous sulfate, ferrous fumarate and ferrous gluconate are three very common supplement forms taken with water for greatest absorption and are inexpensive. However, many patients complain of stomach pain so an alternative is ferrous bis-glycinate which can be taken with food or within an hour of eating. This ferrous bis-glycinate form of iron has been shown to be absorbed two to four times better than ferrous sulfate when taken with food.

Shop Products We Love (mentioned in the podcast)









Generally, taking iron with food will help reduce GI discomfort. Oh and for your patients who want vegetarian capsules, the ferrous bis-glycinate form is available. In fact, a Consumer Labs recent Top Pick among iron supplements is called NOW Iron, a vegetarian capsule in the ferrous bisglycinate form. Both Nature’s Bounty and Solgar also make bisglycinate formulas with some being vegetarian and kosher.

What about a timed- release or slow release formula? While these may reduce gastric irritation, there’s concern that less iron may be available in the small intestine where iron is absorbed due to the slower release so may not be a wise choice for anemia but studies suggest could be a choice for unexplained fatigue in women who are not anemic but have low ferritin levels.

Other supplement forms contain heme-iron polypeptide abbreviated HIP which may be better tolerated with less gastric irritation and constipation than iron salts like ferrous sulfate.

Let’s look quickly at the flip side for iron supplements, cautions and concerns.

First antacids and this includes proton pump inhibitors or PPIs.The dose and length of time taken may increase risk of iron deficiency. Antacids can also decrease iron absorption.

Iron absorption can be reduced by high doses of other minerals such as calcium, zinc, manganese, magnesium or copper. A two hour period is suggested between consuming one of these high-dose mineral supplements and an iron supplement. Be aware that some multis for women who haven’t gone thru menopause and who may still be at risk for iron deficiency can contain 500 mg of calcium.

7 min

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