Comparing Amino-Iron To Ferrous Sulfate

In our latest question and answer, the pharmacist compares two different forms of supplemental iron, ferrous sulfate and Amino-Iron.


Hi, I used to take ferrous sulfate (iron tablets), and last time I went to buy them I saw another iron supplement called Amino-Iron 18mg. Does the Amino-iron provide the same benefit as the ferrous sulfate tablets? Is one recommended over the other? Does an 18mg tablet of Amino-iron equal a certain dosage of ferrous sulfate?

Asked by rt9127 On Feb 16, 2019

Answered by
Medical Content Reviewed By PharmacistAnswers Staff

On Feb 16, 2019
Iron Blister Pack And Loose Tabs

There are a number of iron supplements on the market which can make it confusing when trying to compare them in terms, effectiveness, tolerability and the actual amount of elemental iron they provide.

While 'iron salts', like ferrous sulfate and ferrous gluconate are the most commonly recommended and purchased, different formulations, such as iron amino-acid chelates, are gaining in popularity.

It is important to understand the specific characteristics of the iron supplement you are considering as they differ in many areas, most notably the amount of elemental iron they provide.

Below, I discuss the two types of iron you inquired about, ferrous sulfate and Amino-Iron (amino acid chelate).

Ferrous Sulfate

Pile Of Loose Ferrous Sulfate Tabs

Ferrous sulfate is often the iron supplement of choice for the treatment of iron deficiency as it is effective, inexpensive and relatively well-tolerated.

Ferrous sulfate supplements contain 20% elemental iron by weight. You may see supplement labels list both the amount of ferrous sulfate used, as well as the elemental iron provided.

Here is an example product that contains 325 mg of ferrous sulfate, which translates to 65 mg of elemental iron (20% of 325 mg):

naturemade iron front


Douglas Labs Amino-Iron Front

Amino-Iron, manufactured by Douglas Labs, contains a specific type of iron known as 'iron bis-glycinate'. One tablet of Douglas Labs Amino-Iron contains 18mg of elemental iron.

Unlike the more common salt forms of supplemental iron (e.g. ferrous sulfate, ferrous gluconate), iron bis-glycinate is simply iron that is bound to two glycine molecules:

Iron Bisglycinate Molecular Structure

Iron bisglycinate is a 'chelated' form of iron, which has purported advantages over types of iron, like ferrous sulfate. These advantages include:

  • Fewer drug interactions
  • Greater bioavailability (i.e. increased rate and extent of absorption)
  • Better tolerated

Unlike ferrous sulfate products, most iron bis-glycinate products only list the amount of elemental iron provided. The vast majority contain either 18 mg or 27 mg of elemental iron. Amino-Iron, as stated, contains 18 mg per dose.

Amino Iron Label

Since Amino-Iron contains only 18 mg of elemental iron per dose, most ferrous sulfate products will provide more, as 325 mg of ferrous sulfate (65 mg of elemental iron) is the most common strength available.

Ferrous Sulfate; Amino-Iron Differences

Even though most ferrous sulfate products will contain more elemental iron per dose than Amino-Iron, there is more to consider.

We wrote a fairly extensive piece detailing the unique characteristics of iron bis-glycinate, which can be found on this site, but below is a general overview:

  • Iron bis-glycinate is better absorbed than ferrous sulfate. One study found that, on average, it has over three-fold greater absorption.
  • Iron bis-glycinate, being a chelated iron, will have less drug interactions than ferrous sulfate. Ferrous sulfate will itself chelate to a variety of other drugs, inactivating them. Since iron bis-glycinate is already chelated, it binding to other drugs isn't of concern.
  • As iron bis-glycinate is better absorbed, we would assume that lower doses can raise iron levels in the blood more efficiently than ferrous sulfate. A variety of studies have shown this to be the case. For example, one study found that 25 mg of iron bis-glycinate was comparable to 50 mg of ferrous sulfate.
  • It may be slightly less likely to cause gastrointestinal side effects than iron salts and may be safer in cases of accidental overdose.

Switching Between Ferrous Sulfate And Iron Bisglycinate

Switching Drug Arrows

There is no conversion factor if you want to switch between ferrous sulfate and iron bisglycinate supplements, like Amino-Iron. When doing so, you can, however, compare the amounts of elemental iron they both provide.

For example, since one Amino-Iron tablet contains 18 mg of elemental iron, you would need around 3.6 tablets to equal one ferrous sulfate 325 mg (65 mg elemental iron) tablet.

As described above, however, iron bis-glycinate has far better absorption than ferrous sulfate and you likely would need to take less to have a similar effect in regard to raising iron levels in your body.

You should speak to your doctor for advice on how much iron you need to be taking and whether or not supplementation is necessary.

The RDA (Recommended Dietary Allowances) for iron for adults aged 19–50 years:

  • 8 mg for males
  • 18 mg for females (pregnant females is 27 mg)

So, If you are simply looking for a daily iron supplement to take, you most likely can't go wrong with taking one ferrous sulfate dose or one Amino-Iron.

If you are treating anemia, you may need more and your doctor should give you a recommendation on how much iron to take. Amino-Iron is a good source of supplemental iron, but again, you likely don't need to take it in equivalent amounts as ferrous sulfate to have the same effects.

Additional Information

I want to answer each of the questions you mentioned specifically:

Does Amino-Iron Provide The Same Benefit Of Ferrous Sulfate?

They both provide elemental iron, so yes, they both can help to treat anemia and can be used as a daily iron supplement. As discussed above, even though Amino-Iron has less elemental iron per dose, it may have certain advantages (e.g. increased absorption and may be better tolerated).

Is One Recommended Over The Other?

Not necessarily. You will certainly hear ferrous sulfate 'recommended' more commonly as it is better known, inexpensive and it works. Nevertheless, those who are well-versed on iron supplements generally recommend Amino-Iron (or other products containing iron bisglycinate) due to its advantages.

In a clinical setting, such as a hospital, ferrous sulfate would likely be the oral iron of choice due to the low cost and data behind its effectiveness.

Is 18 mg of Amino-Iron Equivalent To A Certain Ferrous Sulfate Dose?

If we are simply comparing elemental iron content, most ferrous sulfate supplements have more than 18 mg (most have 65 mg). Nevertheless, Amino-Iron is far better absorbed and smaller doses are likely needed to have similar effects to higher doses of ferrous sulfate (I discussed above how one study found 25 mg of iron bisglycinate was just as effective as 50 mg of ferrous sulfate in raising iron levels in the body).

  • Elsevier ClinicalKey: Iron Salts (Accessed 2/16/19)
  • Albion Ferrochel Manufacturer Site
  • Ferrous bisglycinate 25 mg iron is as effective as ferrous sulfate 50 mg iron in the prophylaxis of iron deficiency and anemia during pregnancy in a randomized trial. Semantic Scholar
  • Safety evaluation of ferrous bisglycinate chelate. PubMed
  • National Institute of Health Iron Fact Sheet. NIH

About the Pharmacist

Dr. Brian Staiger Pharm.D

Dr. Brian Staiger is a licensed pharmacist in New York State and the founder of He graduated from the University At Buffalo with a Doctor of Pharmacy degree in 2010. He has been featured in numerous publications including the Huffington Post as well as a variety of health and pharmacy-related blogs. Please feel free to reach out to him directly if you have any inquiries or want to connect! He's answered thousands of medication and pharmacy-related questions and he's ready to answer yours! Office: 716-389-3076

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