Iron Supplements & Gut Health

Iron is essential for energy, oxygen transport, and overall health. But not all iron supplements are created equal, especially when it comes to your gut. Some forms of iron can cause constipation, nausea, bloating, or even gut irritation, while others are gentler and more absorbable.

If you’ve ever felt uncomfortable after taking iron, you’re not alone. Studies show that up to 30% of people experience digestive side effects from iron supplements, leading many to abandon them altogether, even when they desperately need the nutrient. Today, we will go through different types of iron supplements, and what we recommend.

Why Does Iron Affect the Gut?

Iron is a reactive mineral, it can oxidize in the gut, leading to:

• Inflammation (especially in people with sensitive stomachs or conditions like IBS)

• Constipation (iron slows down gut motility)

• Nausea & cramping (from irritation of the stomach lining)

• Bloating & gas (due to changes in gut bacteria)

By choosing the right type of iron supplement, you can minimise these symptoms!

Types of Iron Supplements

Ferrous Sulfate — the most common

• Best for people who need fast iron correction

• Absorption rate: ~20-30% (one of the highest).

• Gut impact: High risk of side effects (constipation, nausea, dark stools)

Ferrous Gluconate — a gentler option

• Best for people who can’t tolerate ferrous sulfate but still need a strong dose.

• Absorption rate: ~15-20%.

• Gut impact: Moderate risk of side effects (less constipating than sulfate).

Ferrous Bisglycinate — the gut-friendly champion

• Best for anyone with a sensitive stomach, IBS, or digestive issues.

• Absorption rate: ~20-30% (as effective as ferrous sulfate but gentler).

• Gut impact: Lowest risk of side effects (no constipation, less nausea).

We recommend the Metagenics Hemagenics Iron Advanced, an iron bisglycinate supplement we stock right here in the clinic. Ask your dietician or contact reception if you’re interested!

How to Take Iron Supplements Without Upsetting Your Gut

Do:

• Take it with vitamin C to boost absorption and reduce oxidative stress in the gut.

• Split your dose (e.g., 30mg in the morning, 30mg at night) to reduce nausea.

• Take it with food (but avoid calcium-rich foods like dairy, which block absorption).

Avoid:

• Taking iron with coffee, tea, or calcium supplements (they inhibit absorption).

• Ferrous sulfate on an empty stomach (it’s the most likely to cause nausea).

• High doses at once (stick to ≤ 60mg elemental iron per dose unless prescribed).

If you’re struggling with the gut symptoms from iron supplements, have a chat with one of our dieticians and browse our in-clinic range of recommended supplements!