What does this mean in practice?

For women with low iron stores, the "gentle" iron supplement may not be raising ferritin effectively. The body absorbs ferrous sulphate far more readily than iron polymaltose.

What should you do next?

Choose ferrous sulphate over iron polymaltose if you need to raise low iron stores. The difference in effectiveness was large in this trial. Take it with vitamin C (such as a glass of orange juice) to boost absorption—this mirrors how the supplement was given in the study.... If stomach issues are severe, ask your doctor about taking it every other day rather than switching to a less effective form.

Ferrous Sulphate vs. Iron Polymaltose: A Small Trial Shows a Large Difference for Women

You've been told you're low in iron. You pick up a "gentle" iron supplement from the pharmacy because you've heard the regular kind causes stomach issues. Twelve weeks later, your levels haven't changed. A recent study explains why—and which form may work better.

Ferrous sulphate more than doubled iron stores in 12 weeks. The "gentle" alternative produced almost no change.

Key Findings

Researchers gave 57 women with low iron stores—measured by ferritin, a blood marker of stored iron—one of two common supplements for 12 weeks. Half took ferrous sulphate paired with vitamin C to aid absorption, the traditional, inexpensive option. Half took iron polymaltose complex, marketed as gentler on the stomach.