I recently switched from calcium carbonate to calcium citrate as it appears that carbonate needs to be taken with food to be absorbed and citrate does not. Per another posters comment I purchased the supplement from Walmart because of price. I do try to get my calcium from food sources as much as possible. I am going to try to provide a link to an excellent article from the NYTimes. I hope it isn't behind a payroll as I used the "gift" option when copying. Here goes.
https://www.nytimes.com/2024/07/22/well/eat/bones-strength-calcium-vitamin-d.html