Iron Tablets Upsetting Your Stomach? Why Gentle Iron Bisglycinate Is Worth Considering

You know why you're taking iron. A GP, midwife or pharmacist has recommended it, and you're trying to follow that advice. But then comes the queasy feeling after breakfast, the stomach cramps at work or another few days of constipation. It's enough to make you dread the next tablet, even when you want to keep going. If that sounds familiar, you're not being fussy. At Healthy, we stock Xcel Health Superior Iron, one option worth knowing about when digestive comfort is part of the conversation.

Iron tablets can upset your stomach because oral iron sometimes irritates the digestive system, leading to nausea, abdominal discomfort or changes in bowel habits. Iron bisglycinate is a form worth asking your pharmacist or clinician about if standard iron tablets are difficult to tolerate, although it isn't a guaranteed fix.

Why an iron tablet can leave your stomach unsettled

Iron in a tablet or capsule is more concentrated than the iron in food. Some can remain in the digestive tract, contributing to irritation.

For some people, the first sign is nausea shortly after taking a tablet. Others notice a heavy, uncomfortable stomach, constipation or, less often, diarrhoea. Iron can also make your stools darker. That colour change is often expected, though you should get advice if you're worried it could be something else.

There may be ways to make taking iron more manageable, depending on the preparation and your healthcare advice.

Mild nausea or constipation can be a known side effect. Severe pain, repeated vomiting, a possible allergic reaction or symptoms that feel unusual deserve prompt medical advice rather than another attempt to push through.

Is it the iron, the timing or something else?

Picture taking your iron first thing in the morning, then rushing out the door before you've eaten. An empty stomach can help your body absorb iron, but it can also be when nausea hits hardest. So the timing that looks ideal on paper isn't always the timing your stomach likes.

Now picture a different morning. You take your iron alongside a cup of tea and a multivitamin because it's easier to remember everything at once. That feels convenient, but tea and coffee can reduce iron absorption. Calcium in dairy foods or supplements can interfere too, and some multivitamins contain minerals that need to be separated from iron.

If your stomach is upset, ask your pharmacist whether food or timing might help. Don't change a prescribed dose yourself.

If you're exploring iron supplements at Healthy, keep the form you've been advised to use in mind.

Where iron bisglycinate enters the conversation

You'll often hear iron bisglycinate called gentle iron. It is iron bound to two molecules of glycine, an amino acid. This is known as a chelated form of iron. In everyday terms, the iron is attached to a carrier rather than being supplied as a more familiar iron salt, such as ferrous sulphate.

Some people find bisglycinate easier to tolerate. It's worth discussing if nausea or constipation makes your current tablets hard to take.

There is encouraging research, with an important limit. A 2023 systematic review found fewer reported digestive side effects with ferrous bisglycinate than with other iron supplements in a group of studies involving pregnant women. The researchers also noted substantial differences between studies and very low certainty for the side-effect evidence. We can't assume the same result for every adult or every product.

So if you're looking for gentle iron for a sensitive stomach in NZ, bisglycinate deserves a closer look, not an automatic promise of no side effects.

What We Like About Superior Iron's Bisglycinate Formula

We stock Xcel Health Superior Iron because it gives you a clearly identified iron form and a straightforward combination of companion nutrients. It's made in New Zealand and comes in a pack of 30 vegetarian capsules.

Each capsule provides 24 mg of elemental iron as iron bisglycinate. That wording matters: elemental iron tells you the actual amount of iron in the capsule, while bisglycinate tells you which form it comes in.

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. Vitamin C is involved in iron absorption, while B12 and folate have roles in normal red blood cell formation. Having them clearly specified in one capsule is part of the formula's appeal.

We like knowing exactly which iron form you're getting. That gives you something specific to discuss with your pharmacist. The added vitamins aren't proof of gentleness.

The adult label says to take one capsule in the morning, but your own healthcare directions come first. And while the product is labelled as suitable during pregnancy, we'd always recommend checking with your midwife or clinician before taking it when pregnant.

If you've been advised to take iron, we think this formula is well worth considering.

A few everyday details that may help you tolerate iron

Health New Zealand advises taking iron with food if it upsets your stomach. Absorption may be better on an empty stomach, so check with your pharmacist how best to balance comfort and absorption.

It's also worth looking at what you drink around the time you take iron. Your morning tea or flat white isn't something you necessarily need to give up. You may just need to have it at a different time. Milk, yoghurt and calcium supplements can also affect absorption, and antacids or certain medicines need special attention. Ask a pharmacist about the right spacing for your situation rather than guessing.

If constipation is the biggest complaint, a few everyday habits can make things more comfortable. Drink enough water through the day, and keep fibre-rich foods such as kiwifruit, vegetables, wholegrain bread and oats on the menu. A gentle walk may help you feel more comfortable too, even if it doesn't solve an iron-related side effect on its own.

Notice when discomfort appears. That can help your pharmacist identify whether timing or the iron form is involved.

Don't halve doses, skip days or add constipation medicine without advice, especially with prescribed iron.

If your iron was prescribed, do not swap it on guesswork

It's tempting to see a gentler-sounding supplement and replace the tablets you've been given. But different iron products contain different amounts of elemental iron. The 24 mg in one Superior Iron capsule isn't automatically equivalent to a higher-dose prescription, even if you prefer the bisglycinate form.

Your GP, pharmacist or midwife can advise on another form, the right dose and any follow-up blood tests.

Check first if you're pregnant, take other medicines, have ongoing side effects or notice significant symptoms. Keep all iron supplements safely out of sight and reach of children. Taking extra iron without an established need isn't a harmless shortcut, either.

Common questions

Can gentle iron still cause constipation?

Yes. Bisglycinate may be easier for some people to tolerate, but gentle iron can still cause constipation, nausea or an unsettled stomach. If you're uncomfortable, speak with a pharmacist rather than assuming you need to stop iron altogether.

Is iron bisglycinate the same as ferrous sulphate?

No. Both supply iron, but they're different chemical forms. Bisglycinate is iron chelated with glycine, while ferrous sulphate is an iron salt. They can differ in elemental iron content and how people tolerate them, so they aren't interchangeable dose for dose.

Can taking iron with food help nausea?

It can. Taking iron with food may ease nausea, although food can also reduce how much iron is absorbed. If your iron was prescribed, ask your pharmacist which approach is appropriate before changing how you take it.

Can Superior Iron replace my prescribed iron tablets?

Not automatically. One capsule contains 24 mg of elemental iron, which may be different from your prescribed amount. Ask your prescriber or pharmacist whether the formula and dose are appropriate for your needs before switching.

Can I take Superior Iron with my multivitamin?

Check the multivitamin first. It may already contain iron, folate, B12 or minerals such as calcium and zinc that can affect iron absorption. A pharmacist can help you avoid doubling up and work out suitable timing.

When should I ask a pharmacist about iron side effects?

Ask if nausea, constipation, diarrhoea or stomach pain persists, makes you miss doses or is worrying you. Seek urgent medical help for severe symptoms or signs of an allergic reaction, such as swelling or trouble breathing.

Next steps

If iron tablets upset your stomach, ask whether bisglycinate could suit your needs. Bring the name and strength of your current iron product.

We'd be pleased to help you explore Superior Iron as an NZ-made bisglycinate option with vitamin C, active B12 and folate in one vegetarian capsule. Take a closer look at the formula, then check that it fits the advice from your healthcare professional.

References

• Health New Zealand | Te Whatu Ora. Low iron and iron deficiency anaemia.
• Healthify He Puna Waiora. Iron supplements taken by mouth.
• Healthify He Puna Waiora. Iron.
• Fischer et al. (2023). The effects of oral ferrous bisglycinate supplementation on hemoglobin and ferritin concentrations in adults and children: a systematic review and meta-analysis of randomized controlled trials.