The issue of how much, if any,  supplemental calcium you should take is unknown at this point in time. What is known is that there are many different uses, types, dosages, and risks of which the general public is shockingly unaware.

For instance, supplemental calcium may play a role in weight loss, possibly controlling lipids (fats in the blood like cholesterol and triglycerides), blood pressure and, of course, in maintaining healthy bones. However, in a number of studies taking more than approximately 800 mg of elemental calcium daily could increase the risk of a heart attack by 30%.

It is very important to specify that I am referring to elemental calcium because many people are unaware how much actual calcium is in various supplements. Calcium citrate- like Citracal or chewable O Purity- is only 21% elemental calcium. So, 1,000 mg of Citracal contains about 210 mg of elemental calcium. Calcium carbonate- like Tums, Caltrate or Caltrate Chewable contains about 40% elemental calcium. So, 1,000 mg of Caltrate contains approximately 400mg of elemental calcium. Calcium Phosphate, Calcium Lactate, and Calcium Gluconate are sources with VERY LITTLE elemental calcium and are pretty much a waste as far as I am concerned because you need to take too many to reach any reasonable level of supplemental elemental calcium.

It is important to note there is NO advantage to coral calcium and there have been reports of lead contamination. Coral calcium comes from limestone and is calcium carbonate.If you do decide to take calcium carbonate, then take it with a meal because it requires much more stomach acid to be digested than calcium citrate.  I think calcium citrate is best for anyone and certainly for those above 40 because stomach acid begins to decrease at this point.

In addition to the calcium you get from supplements, it is important that you are getting enough calcium from your diet:
8 oz Milk & Yogurt 300- 450 mg elemental calcium 3 oz Cheese 300- 450 mg elemental calcium 3 oz Bones in Canned Sardines and Salmon 181- 315 mg elemental calcium 8 oz calcium Fortified Foods (OJ, Soy Milk) 200- 300mg elemental calcium 1 cup Dark green, leafy vegetables 100- 200 mg elemental calcium
Your body absorbs calcium less efficiently as your intake increases, therefore it is best to take your calcium in smaller doses throughout the day to aid absorption. You should not take more than 500 milligrams of elemental calcium at one time and allow 4 to 6 hours between doses.
If you have osteopenia or osteoporosis or have a high risk you should take elemental calcium. However, taking higher amounts then I recommend have not necessarily shown to incrementally decrease your risk of fracture!.Long term use of medications, such as corticosteroids, and anti-convulsants can be damaging to bone. These medications are used for chronic conditions such as asthma, rheumatoid arthritis, and psoriasis. If you need to take these medications for extended periods of time you may need to increase your intake of calcium with supplements.If you rely on laxatives , the transit time in your bowel increases and may leave enough time for calcium to be absorbed in which case you should discus with your physician taking supplemental calcium.Ditto for those who take a lot of fiber. I would take no more than 800 mg of elemental calcium daily because cardiovascular risk increases above this amount according to the data so far. If you are pre, peri, menopausal or post menopausal and your bone density is normal, then I would not take supplemental calcium. Much the same applies to men (do not forget that 10% of osteoporosis is in males). Unless you are at high risk or already have an issue with your bone density, I would rely on a good dietary intake of calcium.
The issue here is that the National Institute of Health Consensus Conference and The National Osteoporosis Foundation support a higher calcium intake of 1,500 elemental milligrams per day of calcium for postmenopausal women not taking estrogen and adults 65 years or older.However, they have NOT yet accounted for the cardiovascular risk which I think is considerable.
NEVER forget to take an adequate amount of Vitamin D regardless of the path you choose with calcium.