Iron Bisglycinate vs Ferrous Sulphate: What Really Matters When Choosing an Iron Supplement?
You see iron bisglycinate on one label and ferrous sulphate on another. Are they two names for the same ingredient, or does the difference matter?
There is a difference. Ferrous sulphate is an iron salt, while iron bisglycinate is iron attached to the amino acid glycine. Both provide elemental iron, but the amount supplied, how well you tolerate it and the reason you need iron all matter. At Healthy, we stock Xcel Health Superior Iron, a bisglycinate option worth getting to know if you have an established need for iron.
Two ways of delivering iron
Ferrous sulphate has been used in oral iron medicines for many years. It is a straightforward iron salt, sometimes written as ferrous sulfate, and remains an established option when prescribed or recommended for a particular iron need.
Iron bisglycinate takes a different form. The iron is attached to glycine, an amino acid. You might see the word chelated on the packaging. In plain language, that simply means the iron is attached to another molecule, in this case glycine.
The names tell you which iron form is inside, but not whether the product is right for you. Dose and tolerability matter just as much.
Both have a place. Let's look at three common assumptions.
Does gentle always mean no side effects?
Bisglycinate attracts attention as a gentler iron option. We understand the appeal of a supplement that may be easier to tolerate.
The research offers encouragement. A 2023 review of 17 randomised trials found fewer reported digestive side effects with bisglycinate in pooled studies of pregnant women. That is promising, although it does not guarantee comfort.
The results varied considerably between studies, and the evidence for men and non-pregnant women was much more limited. Importantly, not every study used ferrous sulphate as the comparison. We would not turn those findings into a claim that bisglycinate is always gentler for every adult.
Both forms can cause constipation, nausea or stomach discomfort. If tolerance concerns you, discuss the form and dose with your pharmacist or GP.
Does better absorbed always mean better for you?
Absorption is another reason iron bisglycinate gets attention. It has been studied as an alternative to traditional iron salts, and some findings are promising. But there is no reliable rule that bisglycinate is always four times better absorbed, or that it is automatically the best answer for every adult.
For a confirmed iron need, the more useful question is which form and amount make sense for you.
Research in one group may not apply to everyone, and an absorption claim does not make a lower-dose supplement interchangeable with prescribed iron. Bisglycinate is worth exploring, with elemental iron still in view.
Does a smaller milligram number mean a weaker choice?
One label might show the weight of an iron compound. Another might state a smaller amount of elemental iron.
Elemental iron means the actual iron provided, rather than the total weight of the compound carrying it. The two numbers are not interchangeable. For instance, a label showing 325 mg of a ferrous sulphate compound does not mean it provides 325 mg of elemental iron.
A smaller number may be the clearer one. That is why we appreciate the straightforward 24 mg elemental iron declaration on Superior Iron.
The right amount still depends on your established need and professional advice.
A NZ detail worth knowing about ferrous sulphate
You may have heard that ferrous sulphate tablets changed in New Zealand. Pharmac delisted the funded long-acting Ferrograd ferrous sulphate tablets from 1 March 2026 and identified funded ferrous fumarate tablets as another option. That does not mean every ferrous sulphate medicine disappeared: ferrous sulphate oral liquid is still listed in Pharmac's October 2026 Hospital Medicines List. If a prescribed product is affected, ask your pharmacist or prescriber about your options rather than changing it yourself. You can read Pharmac's Ferrograd decision.
The 24 mg Detail We Want You to Notice About Superior Iron
We love a label that makes the important details clear. That is something we particularly like about Xcel Health Superior Iron. Each vegetarian capsule provides 24 mg of elemental iron as iron bisglycinate. The form and the elemental amount are both clear.
Superior Iron is made in New Zealand and comes in a pack of 30 vegetarian capsules. Alongside the iron, each capsule contains 123 mg vitamin C as calcium ascorbate, 50 mcg vitamin B12 as methylcobalamin and 300 mcg active folate as 5-MTHF. We also like the clear names for these companion nutrients.
For someone with a confirmed need for iron who is considering a bisglycinate supplement, this is an appealing, clearly labelled option. It brings together a specified iron form, a stated elemental amount and useful accompanying nutrients in one vegetarian capsule. The listed adult direction is one capsule in the morning, but the amount you personally need should follow professional advice, especially if you have already been prescribed iron.
That 24 mg is not a promise of the same clinical effect as a medicine supplying 65 mg, 100 mg or 105 mg of elemental iron. What we are recommending is taking a closer look at a well-defined formula, not swapping one dose for another.
Before changing an iron supplement someone has prescribed
If you have been prescribed iron, do not replace it just because another form sounds gentler. Different products can supply very different elemental amounts.
A pharmacist, GP or midwife can help you assess a change, especially during pregnancy or breastfeeding, with relevant medicines or when you also take a multivitamin containing iron.
Iron supplements are best taken for a confirmed need with professional advice. Too much iron can be harmful, and all iron products should be kept out of children's reach. Ferrous sulphate remains a valid, established choice when it fits your situation.
Common questions
Are iron bisglycinate and ferrous sulphate both forms of iron?
Yes. Both supply elemental iron, but they are different compounds. Ferrous sulphate is an iron salt, while iron bisglycinate has iron attached to the amino acid glycine. You may also see ferrous sulphate written as ferrous sulfate. The ingredient form matters, but so do the amount of elemental iron and the reason you are taking it.
Is iron bisglycinate gentler than ferrous sulphate?
It may be better tolerated by some people. A 2023 review found fewer reported digestive side effects with bisglycinate in pooled studies of pregnant women, although the studies varied considerably. That does not prove the same result for every adult. Both forms can cause side effects, so discuss concerns about tolerance and dose with a health professional.
Is iron bisglycinate always better absorbed?
No. Some research supports interest in bisglycinate, but the evidence does not show that it is always better absorbed or clinically superior for every adult. Absorption is only part of the picture. A suitable elemental iron amount and the reason you need iron matter too. Avoid relying on a simple absorption multiplier when comparing labels.
Can 24 mg of bisglycinate replace my prescribed iron dose?
Not automatically. Superior Iron provides 24 mg of elemental iron as bisglycinate per vegetarian capsule. That is a clearly stated supplement amount, not a direct replacement for a prescription containing a different quantity of elemental iron. If you are taking prescribed iron, ask your GP, pharmacist or midwife before changing the product or dose.
Can iron bisglycinate still cause constipation?
Yes. Iron bisglycinate may feel gentler for some people, but it cannot be described as constipation-free. Any oral iron supplement can cause digestive effects, including constipation or stomach discomfort. If side effects are bothering you, talk with your pharmacist or GP about the product and amount you are taking rather than assuming one form has no risks.
Is ferrous sulphate still available in New Zealand?
Yes, in some forms. Pharmac delisted the funded long-acting Ferrograd ferrous sulphate tablets from 1 March 2026, but its October 2026 Hospital Medicines List still includes ferrous sulphate oral liquid. Ferrous fumarate is another funded tablet option. Availability of a particular product can change, so check with a pharmacist if you need a prescribed iron medicine.
Next steps
If you have an established need for iron and are discussing which formulation might suit you, we would love you to explore Superior Iron. Its 24 mg elemental iron as bisglycinate, vegetarian capsule and clearly named companion nutrients make it a product we are happy to put in front of you. You can also browse our iron supplement collection, but if bisglycinate is what you are looking for, start with Superior Iron.