If you take a proton pump inhibitor like omeprazole, lansoprazole or esomeprazole for reflux or stomach protection, the supplement story is less about dangerous interactions and more about absorption. These medicines reduce stomach acid, and stomach acid is part of how the body takes up several nutrients. Over the long term, that changes what is worth supplementing and which form to choose.
What long-term acid reduction affects
Three nutrients are worth knowing about. Vitamin B12 needs stomach acid to be released from food, so long-term PPI use can lower it, particularly in people over 50. Magnesium levels can drift down with extended use. And non-haem iron (the form in plants and most supplements) is absorbed less efficiently in a less acidic stomach. None of these is an emergency, but all are worth knowing if a daily PPI is part of your life.
What that means in practice
If you have been on a daily PPI for a year or more, it is reasonable to have B12 checked, and to top it up if it is low. If magnesium runs low on a blood test, repletion is straightforward. And if you need iron, the form matters more than usual here: iron bisglycinate is less dependent on stomach acid than ferrous sulphate, so it tends to be the better choice for someone on a PPI. This is another case where the form on the label does real work.
A note on timing
Calcium absorption can also shift on a PPI, and calcium carbonate in particular relies on stomach acid, so calcium citrate is the more reliable form if you supplement it. As with several supplements, when you take things relative to each other can matter as much as what you take.
The simple version
On a long-term PPI, watch B12 and magnesium, and choose the acid-independent forms of iron and calcium if you need them. None of this means stopping a medicine you need. To check a specific supplement against your PPI, the free checker will show you the call and the reasoning.