I have a pharmacist specialist that calls me every six months from my medical team. The first thing she told me was stop taking the calcium I was taking and start taking calcium citrate. It works much better with the drugs we are on.

Now for some technical reasons.

Calcium citrate's main benefits over other forms, like calcium carbonate, are its better absorption regardless of stomach acid levels (making it ideal for older adults or those on certain medications) and its inability to increase kidney stone risk. It is also absorbed well with or without food and may be less likely to cause gastrointestinal side effects like gas and bloating.

Here is a link to more information
https://ods.od.nih.gov/factsheets/Calcium-Consumer/#:~:text=Check%20the%20Supplement%20Facts%20label,form%20of%20calcium%20you%20take.

@jasonnyc When I started ADT (*) in late 2022 a nurse practioner mentioned that Calcium Citrate is recommened IF you take stomach acid reducers such as Zantac, Priosec, Nexium, etc.

Otherwise, any type of Calcium Carbonate can be used.

(*) I've been on Firmagon (Degarelix) and Nubeqa (Darolutamide) for stage 4 CSPC since late 2022.