For individuals aged 40 and older, the two most recommended generic calcium supplements are calcium carbonate and calcium citrate. Calcium carbonate is cost-effective and contains a high amount of elemental calcium, but it must be taken with food to absorb properly. Calcium citrate is absorbed well with or without food and is gentler on the stomach, making it ideal if you have sensitive digestion or take acid reducers. For the best results, choose a supplement that also contains Vitamin D3, which helps your body absorb the calcium. It is always best to consult your doctor to determine the safest dose for your specific needs.