15/05/2025
Let’s Clear Up the Calcium + Iron Confusion👩🏻⚕️
In an earlier post, I mentioned that calcium interferes with iron absorption - and I’ve had a few questions come in, especially about supplements that contain a small amount of calcium alongside iron. Let’s break this down a bit further.
Yes, it’s true that calcium and iron compete for absorption in the gut. But this effect is dose-dependent. Most studies suggest that it takes 300mg or more of calcium at the same time as iron to significantly interfere.
So what about supplements that include a tiny amount of calcium - like calcium citrate at 10–20mg per capsule?
Here’s the deal:
→ Small amounts like this are added to help stabilise the formula and balance pH - not to act as a nutrient.
→ These amounts are far too low to block iron absorption and are considered safe to take with iron.
For context:
• A 250ml cup of milk contains roughly 300mg of calcium.
• A standard calcium supplement contains around 500mg or more.
• Your iron supplement with 13mg of calcium citrate? Nowhere near interfering.
And what about tea?
Another good question - tea contains tannins, which can bind to iron and reduce its absorption. If you add milk to your tea, you’re also introducing a little calcium. But again, this depends on:
• How much milk you’re using
• How soon after iron you’re having it
• Whether you’re in a phase of active deficiency or maintenance
If you’re severely iron deficient, even small things like tea with a dash of milk soon after your iron dose could have a minor effect. And if you’re trying to correct deficiency fast, it’s best to avoid all potential blockers.
But if you’re already in a rebuilding or maintenance phase, the odd cup of tea with a splash of milk an hour after your iron? Probably fine.
Bottom line:
Sometimes it’s not that the iron supplement isn’t working - it’s what’s happening around it that’s affecting how well it absorbs.
📍Book a 1:1 consult if you want clarity on what your body actually needs.
